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Digital Audio Broadcasting

Supplementary Analog SCA Compatibility Tests

Test Plan and Procedures

Document No. 02-15

April 2002

Advanced Television Technology Center1330 Braddock, Suite 200

Alexandria, VA 22314-1650(703) 739-3850

(703) 739-3230 (Fax)www.attc.org

©2002 ATTC, Inc.

Advanced Television Technology Center

©2002 ATTC, Inc. i

Table of Contents

1 INTRODUCTION 1

1.1 BACKGROUND 11.2 DOCUMENT SCOPE 11.3 DOCUMENT STRUCTURE 11.4 RELATED DOCUMENTS 1

2 TEST OVERVIEW 3

2.1 OBJECTIVES 32.2 METHODOLOGIES 32.3 TEST CONDITIONS 32.4 EVALUATION METHODS 3

3 SIGNAL DESCRIPTIONS 4

3.1 RF SIGNALS 43.1.1 DESIRED ANALOG – TYPE I 43.1.2 DESIRED ANALOG – TYPE II 43.1.3 DESIRED ANALOG – TYPE III 53.1.4 DESIRED HYBRID – TYPE I 53.1.5 DESIRED HYBRID – TYPE II 53.1.6 DESIRED HYBRID – TYPE III 63.1.7 UNDESIRED ANALOG 63.1.8 UNDESIRED HYBRID 63.1.9 ADDITIVE WHITE GAUSSIAN NOISE 73.2 STEREO CLIPPED USASI NOISE 73.2.1 INTRODUCTION 73.2.2 USASI NOISE SOURCE CHARACTERIZATION 73.2.3 RECORDING PROCESS AND CHARACTERIZATION 103.2.4 SURVEY OF “REAL-WORLD” BROADCAST STATIONS 113.2.5 MODULATED SPECTRUM CHARACTERIZATION 14

4 STANDARD METHODOLOGIES 17

4.1 FM BAND AND RF MEASUREMENTS 174.1.1 FM ANALOG POWER 174.1.2 IBOC HYBRID MODE POWER 184.1.3 POWER IN THE PRESENCE OF MULTIPATH 194.1.4 RATIO OF ANALOG TO DIGITAL POWER (IBOC HYBRID MODE) 204.1.5 ADDITIVE WHITE GAUSSIAN NOISE POWER 214.1.6 DEVIATION AND CHANNEL CONFIGURATION 244.2 BASEBAND AUDIO MEASUREMENTS 264.2.1 SIGNAL-TO-NOISE RATIO (SNR) 26


©2002 ATTC, Inc. ii

5 TEST PROCEDURES 28

5.1 SCA RECEIVER PERFORMANCE IN THE PRESENCE OF ANALOG AND IBOC ADJACENT

CHANNELS 285.2 SCA RECEIVER PERFORMANCE IN THE PRESENCE OF AN ANALOG OR IBOC HOST 305.3 SCA RECEIVER PERFORMANCE IN THE PRESENCE OF AN ANALOG OR IBOC HOST IN

MULTIPATH CONDITIONS 32

6 - APPENDIX A - LIST OF RECEIVERS UNDER TEST 34

7 - APPENDIX B - MULTIPATH PROFILES 35

7.1 CHARACTERIZATION OF STATIC MULTIPATH PROFILES 357.2 MULTIPATH PROFILES - STATICMP1 407.3 MULTIPATH PROFILES – STATICMP2 437.4 MULTIPATH PROFILES – STATICMP3 45


©2002 ATTC, Inc. 1

1 Introduction

1.1 BackgroundThe Advanced Television Technology Center (ATTC) has conducted an extensive DAB testprogram over the course of the past two years. This program has primarily focused onfulfilling the laboratory test requirements of the National Radio System Committee’s(NRSC) DAB Subcommittee in evaluating iBiquity Digital’s IBOC system. As such, manyof the test program objectives, methodologies, and test conditions have been well defined bythe various NRSC Working Groups.

However, other parties have recently expressed an interest in conducting IBOC DAB teststhat are outside the scope of the NRSC process, in order to examine certain aspects of IBOCcompatibility in more detail than originally required by the NRSC. In particular, NationalPublic Radio (NPR) and the International Association of Audio Information Services(IAAIS) are interested in further evaluating the compatibility of FM IBOC with existinganalog SCA services (e.g. “Reading For The Blind” SCA services).

This test plan is a result of a collaborative effort between iBiquity, NPR, IAAIS, and ATTCto develop test procedures that are appropriate for examining IBOC compatibility with67kHz and 92kHz analog audio SCA services. In addition to greatly expanding the testconditions of the original NRSC tests, the field of SCA receivers under test has beenexpanded to encompass a wider variety of models and manufacturers. Multipath testconditions have also been added to the program to gauge the effect of multipath on IBOCcompatibility with host SCA services.

1.2 Document ScopeThis document contains the laboratory plan and procedures to be utilized for theSupplementary Analog SCA Compatibility Tests of the iBiquity Digital In-Band On-Channel (IBOC) Digital Audio Broadcasting (DAB) System.

1.3 Document StructureThis document is written in such a way that signal types and measurement methodologiesused repeatedly throughout testing are defined once. Prior to defining the test proceduresthere are sections dedicated to the defining signals and measurement methodologies(Sections 3 and 4 respectively). When the test procedures call for a specific signal ormeasurement, the reader should refer to the appropriate section for the complete definition.

1.4 Related DocumentsFor a detailed description of the physical test platform that will be used duringsupplementary analog SCA compatibility testing refer to the following ATTC documents:

ATTC Document No. 01-20, Digital Audio Broadcasting, Test Bed Proof of PerformancePlan, Revision 2.0, November 2001ATTC Document No. 01-01, Digital Audio Broadcasting, Test Bed Proof of PerformanceRecord, Revision 2.0, November 2001


©2002 ATTC, Inc. 2

ATTC Document No. 01-16, Digital Audio Broadcasting, Test Bed Daily CalibrationProcedure, Revision 4.0, October 2001Digital Audio Broadcasting, Test Bed Daily Calibration Record of Test Results”(open ATTCDocument)

The previous (NRSC specified) analog SCA compatibility test procedures and results aredetailed in the following ATTC documents:

ATTC Document No. 01-03, Digital Audio Broadcasting, IBOC Laboratory Test Procedures– FM Band, Revision 4.2, August 2001ATTC Document No. 01-16B, Digital Audio Broadcasting, SCA Compatibility of the IBOCSystem in the FM Band, Summary of Test Results, October 2001


©2002 ATTC, Inc. 3

2 Test Overview

2.1 ObjectivesThe test procedures described in this document have one main objective, to quantify theimpact of IBOC on existing SCA services. This is known as Compatibility testing. Incompatibility testing various adjacent channel and multipath conditions are simulated inthe laboratory. For each channel condition, tests will be conducted to determine the impactof IBOC, if any, on SCA services.

2.2 MethodologiesTo meet the objective described in the previous section, a series of controlled laboratorytests will be conducted. Each of these tests will include some channel impairment that iscommonly observed in the FM broadcast band. These interference scenarios will be createdin the laboratory, and the performance of certain commercially available SCA receivers 1will be evaluated. The receivers will be tested under these conditions in the presence andabsence of an IBOC signal on either the “host” or adjacent channel station.

2.3 Test ConditionsBelow is a list of the test conditions to be utilized during the testing process:

1. First adjacent channel interference2. Second adjacent channel interference3. “Host” channel interference4. “Host” channel interference in the presence of multipath

NPR, the IAAIS, iBiquity Digital, and the ATTC developed the test scenarios outlined inthis document.

2.4 Evaluation MethodsThe performance of the SCA receivers will be determined objectively. Objective evaluationof an SCA receiver requires the use of standard audio test equipment to measure andobjectively quantify audio quality in an accurate and repeatable manner. Audio quality willbe measured in terms of the audio signal-to-noise ratio (SNR).

1 NPR and the IAAIS have chosen the SCA receivers to be tested. For a list of these receivers refer tosection 6 of this document.


©2002 ATTC, Inc. 4

3 Signal DescriptionsThe purpose of this section is to define all of the signals (RF and audio) to be usedthroughout testing. Later sections of this test plan may refer to a “Desired Hybrid Type I”,for example, the definition of which can be found in this section.

3.1 RF Signals

3.1.1 Desired Analog – Type IA desired analog Type I signal is designed for use in tests of analog host compatibility withmultipath. This type of signal shall be used in the tests of both 67kHz and 92kHzsubcarriers. The injection of both subcarriers for this type of signal is 10% regardless ofwhich SCA is being tested. However, the audio only modulates the SCA being evaluated.When the 67kHz SCA is being tested, for example, there will be no audio present on the92kHz SCA (resulting in 0kHz Deviation). This signal type will yield a total channelmodulation of 110% when configured as shown in Table 3-1.

Table 3-1 - Desired Analog – Type I Signal Characteristics

Main Channel Main ChannelAudio

Power 67kHz Subcarrier 92kHz Subcarrier

1) 97.9MHz

2) Stereo Transmission

3) 10% Pilot Injection

4) 75µs Pre-emphasis

5) Total Modulation =110%

Clipped USASIwith peaks equal80% modulation(60kHz PeakDeviation)

Moderate(-62dBm)

1) 10% injection

2) 150µs pre-emphasis

3) 6kHz PeakDeviation with a400Hz Tone – 0kHzwith Silence

4) Test DependentAudio – 400HzTone or Silence

1) 10% injection


3) 7kHz PeakDeviation with a400Hz Tone –0kHz with Silence


3.1.2 Desired Analog – Type IIA desired analog Type II signal is designed for use in first adjacent interference tests,second adjacent interference tests, and analog host compatibility with no multipath. Whenusing this type of signal, keep in mind that the injection of the SCA being evaluated is to be10% while the other SCA should be turned off (0% injection). This configuration will yield atotal channel modulation of 105% when configured as shown in Table 3-2.

Table 3-2 - Desired Analog – Type II Signal Characteristics



1) 97.9MHz



Clipped USASIwith peaks equal85% modulation(63.75kHz PeakDeviation)

Moderate(-62dBm)

1) 10% injection or Off


1) 10% injection or Off



©2002 ATTC, Inc. 5



3) 6kHz PeakDeviation with a400Hz Tone


3) 7kHz PeakDeviation with a400Hz Tone


3.1.3 Desired Analog – Type IIIThe Desired Analog Type III signal is the same as a Desired Analog Type I signal, exceptthat a Type III signal calls for no modulation on the main (host) carrier. This signal shallalso be used in tests of analog host compatibility with multipath. The injection of bothsubcarriers for this type of signal is 10% regardless of which SCA is being tested. However,the audio only modulates the SCA being evaluated. When the 67kHz SCA is being tested,for example, there will be no audio present on the 92kHz SCA (resulting in 0kHzDeviation). This type of signal yields a total channel modulation of 30%. A Type III signalwill have the characteristics listed in Table 3-3.

Table 3-3 - Desired Analog – Type III Signal Characteristics



1) 97.9MHz





None Moderate(-62dBm)

1) 10% injection




1) 10% injection




3.1.4 Desired Hybrid – Type IThis signal shall be defined as the spectral sum of an analog desired signal Type I (asdefined in section 3.1.1) and the digital carriers as generated by an iBiquity Digital IBOCexciter in hybrid mode. The digital carriers utilize OFDM modulation. The power sum ofall digital carriers in the hybrid signal has an average power that is 20dB less than theaverage power in the analog carrier.

3.1.5 Desired Hybrid – Type IIA desired hybrid Type II signal shall be defined as the spectral sum of an analog desiredsignal Type II (section 3.1.2) and the digital carriers as generated by an iBiquity DigitalIBOC exciter in hybrid mode. The digital carriers utilize OFDM modulation. The powersum of all digital carriers in the hybrid signal has an average power that is 20dB less thanthe average power in the analog carrier.


©2002 ATTC, Inc. 6

3.1.6 Desired Hybrid – Type IIIA Type III desired hybrid signal is defined as the spectral sum of an analog desired signalType III (section 3.1.3) and the digital carriers as generated by an iBiquity Digital IBOCexciter in hybrid mode. The digital carriers utilize OFDM modulation. The power sum ofall digital carriers in the hybrid signal has an average power that is 20dB less than theaverage power in the analog carrier.

3.1.7 Undesired AnalogAn undesired analog interferer signal is designed for adjacent channel interference teststhat employ objective evaluation. Such a signal shall have the following characteristics:

Table 3-4 - Undesired Analog Signal Characteristics



1) Frequency:a) Upper First:98.1MHzb) Lower First:97.7MHzc) Upper Second:98.3MHzd) Lower second:97.5MHz

2) Stereo Transmission3) 10% Pilot Injection4) 75µs Pre-emphasis5) Total Modulation =100%

Clipped USASINoise with peaksequal 90%modulation(67.5kHz PeakDeviation)

Variable Off Off

3.1.8 Undesired HybridAn undesired hybrid interferer is designed to be used in adjacent channel interference teststhat employ objective evaluation.

This signal shall be defined as the spectral sum of an analog undesired signal and thedigital carriers as generated by an iBiquity IBOC exciter in hybrid mode. The digitalcarriers utilize OFDM modulation; further details are proprietary to iBiquity.

The analog portion of the signal shall be defined as in section 3.1.7.

The sum of all digital carriers in the hybrid signal shall have an average power that is 20dBbelow the average analog power. The measurement method for setting and verifying thispower ratio is outlined in section 4.1.4.

The digital carriers may or may not be modulated by audio. Due to the randomizationprocess of the audio, it is not expected that modulation of the digital carriers will affect testresults in any manner.


©2002 ATTC, Inc. 7

3.1.9 Additive White Gaussian NoiseWhere AWGN noise is specified, a broadband noise signal shall be added to the spectrum atthe specified power level. This noise shall have flat spectral characteristics between 88MHzand 108MHz. Beyond these frequency limits, the noise shall be sharply attenuated with abandpass filter. The peak amplitude excursions of the noise signal shall have a Gaussianprobability distribution.

Section 4.1.5 describes the procedure used to determine and set the power level of thisadditive white Gaussian noise.

3.2 Stereo Clipped USASI Noise

3.2.1 IntroductionIn order to simulate real world conditions in the laboratory, the FM signals (undesired aswell as desired) must be modulated with a signal that simulates typical broadcastingprogram material. This need for a standard audio signal lead to the generation of a ClippedUSASI Interferer.

USASI noise, developed by the United State of America Standards Institute, is designed tosimulate the spectra of typical audio programming over a long period of time. USASI noiseis created by passing the output of a white noise source through a network of filters. Thisnetwork consists of a 100Hz high pass filter and a 320Hz low pass filter, both with a6dB per octave roll off.

For these tests, a simulation of the frequency spectrum of a typical FM rock station isrequired. Rock stations in the FM band often broadcast highly processed audio. This highdegree of processing can result in clipping of the audio signal. To accurately simulate theseconditions for laboratory tests, the USASI noise interferer also needs to be clipped.

Also, for these tests to be repeatable, it must be possible to recreate the modulating audiosignal. To ensure that the exact audio signal could be recreated, a recording of this signalwas made.

A number of steps were involved in the creation of this interferer. Initially, the output ofthe noise generator had to be verified as USASI noise. Next, a recording of the noise wasmade. Verification that the recording process did not have a significant impact on the noisesignal was performed. Finally the signal was clipped, using Cool Edit Pro software, tosimulate processed rock. These steps are detailed below.

3.2.2 USASI Noise Source CharacterizationThe USASI noise signal to be used for tests was generated by a Delta Electronics SNG-1Stereo Noise Generator. The Delta noise generator noise mode called “NRSC” was usedbecause in this mode, the unit generates stereo USASI noise. To verify that the noisegenerator was truly generating USASI noise a series of characterization tests wereconducted. The Delta noise generator was configured as shown in Table 3-5 and the outputwas connected either to a Tektronix Oscilloscope or an Audio Precision AP-1. The results ofthis characterization are illustrated in the following sections.


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Table 3-5 – Delta SNG - 1 Setup

Parameter DescriptionNoise Select USASINoise Mode CWOutput Select NRSCOutput Level +4dBu RMS

Probability Distribution of Noise AmplitudesThe plots included in this section illustrate the statistical data and average values of thevoltage levels as seen at the output of the Delta noise generator. One of the specificationsof USASI noise is that the voltage level distribution over time is Gaussian. The figurebelow illustrates a perfectly Gaussian probability distribution.

68%

95%

99%

µ - 3σ µ - 2σ µ - 1σ µ µ + 1σ µ + 2σ µ + 3σ

Figure 3-1 - Gaussian Probability Distribution

By comparing the ideal curve and values of Figure 3-1 to the values on the right and thedistribution curve on the left side of Figure 3-2 it can be seen that the distribution ofvoltage levels at the output of the Delta noise generator is very nearly Gaussian.


©2002 ATTC, Inc. 9

Figure 3-2 – Statistical plot of the Delta Electronics Noise Generator output

Frequency ResponseThe plot below is an averaged fast Fourier transform of the output of the Delta noisegenerator. This plot shows that the Delta noise generator output does roll off as dictated bythe definition of USASI noise.

-45

-5

-40

-35

-30

-25

-20

-15

-10

dBu

0 20k2.5k 5k 7.5k 10k 12.5k 15k 17.5k

Hz

Figure 3-3 – Averaged FFT of Delta noise generator output

ProbabilityDistribution

Percentage ofTotal Powerwithin the RangeIndicated

Maximum andMinimum VoltageLevels


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3.2.3 Recording Process and CharacterizationAs stated in section 3.2.1, there is a need to record the USASI noise signal in order toensure the repeatability of these tests. However, this recording process must notsignificantly affect the noise signal. A digital recording of the Delta noise generator wasproduced using the setup shown in Figure 3-4.

Delta SNG-1 NVisionNV 1035A to D

Digital AudioWork Station

L

R

AESAudio

Figure 3-4 – Device setup used to make digital recording of Delta noise generator

The Delta was configured as in Table 3-5. The A-to-D converter was used to convert theDelta outputs (left and right analog) to an AES audio signal. This was then recorded at a44.1kHz sampling rate, with 16 bits of resolution. The following subsections detail thecharacterization of this recording.

Probability Distribution of Noise AmplitudesThe plots included in this section illustrate the statistical data and average values of thevoltage levels seen when the recording of the output of the delta noise generator is playedback.

Figure 3-5 - Statistical plot of the recording of the Delta Electronics NoiseGenerator output

ProbabilityDistribution

Percentage ofTotal Powerwithin the RangeIndicated

Maximum andMinimum VoltageLevels


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Frequency ResponseFigure 3-6 shows FFT’s of the Delta Noise Generator output and the recording of the outputoverlaid.

-45

-5

-40

-35

-30

-25

-20

-15

-10

dBu

0 20k2.5k 5k 7.5k 10k 12.5k 15k 17.5k

Hz

Figure 3-6 - FFT of outputs of Delta noise generator overlaid with FFT of Left andRight channels of the USASI noise recording

ClippingThe next step in the development of the USASI interferer was to clip the signal. The signalwas clipped by 3dB using Cool Edit Pro software. To do this the following steps wereperformed:

1. Select the entire waveform.2. Under the Transform menu select Amplify.3. In the Normalization box enter 0dB in the Peak Level field and press Calculated Now.

This calculates the amplification required to normalize the signal to 0dBFS and placesthe value in the Amplification field.

4. Press the OK button. This will normalize the peaks to 0dBFS.5. Under the Transform men select Hard Limiting.6. Set the Max Amplitude field to 0dB, the Boost field to 3dB, the Look Ahead Time to 0,

and the Release time to 100.7. Press the OK button.

Bit Error Rate ValidationFor information regarding the Bit Error Rate validation please see the Proof ofPerformance Test Plan and sections 3.7 and 3.8 of the Proof of Performance Results asreferenced in section 1.4 of this document.

3.2.4 Survey of “Real-World” Broadcast StationsTo verify that the interferer developed actually did simulate real world conditions; a surveyof some local (Washington D.C. metro area) radio stations was performed. Examination of


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Off-Air radio stations operating in the FM broadcast band revealed a wide variety ofstations utilizing many different degrees of audio processing.

Examples of some of the different types of radio stations are shown in the plots of thissection. The first two plots below (Figure 3-7 and Figure 3-8) show the RF spectrum anddemodulated baseband of a local station operating at 107.3MHz; this is an example of astation that is broadcasting heavily processed program material. The next two plots(Figure 3-9 and Figure 3-10) are of a public station operating at 90.9MHz. This is anexample of a station broadcasting lightly processed material. The last two plots (Figure3-11 and Figure 3-12) of this section are of a good example of a station broadcastingmoderately processed program material, a local rock station operating at 101.1MHz.

Figure 3-7 - Max Hold and Averaged Traces of 107.3MHz local radio station

Figure 3-8 – Averaged Trace of 107.3MHz local radio station baseband


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Figure 3-9 - Max Hold and Averaged Traces of 90.9MHz local radio station



©2002 ATTC, Inc. 14

Figure 3-11 – Max Hold and Averaged Traces of 101.1MHz local radio station


3.2.5 Modulated Spectrum CharacterizationThis section contains a comparison of the Standard interferer develop and an off-air radiostation. It was decided by the IAAIS and NPR that the “middle of the road” amount ofprocessing would be sufficient for these tests. Therefore, it was decided that the standardinterferer would be modeled after the local Washington DC station operating at 101.1MHz.The plots of this section illustrate this.


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Figure 3-13 – Averaged Traces of 101.1MHz Off-Air overlaid with the desiredchannel Modulated with 3dB Clipped USASI

Figure 3-14 – Max Hold Traces of 101.1MHz Off-Air overlaid with the desiredchannel Modulated with 3dB Clipped USASI


©2002 ATTC, Inc. 16

Figure 3-15 - Averaged Trace desired channel modulated with 3dB Clipped USASIbaseband


©2002 ATTC, Inc. 17

4 Standard MethodologiesThe purpose of this section is to describe the methods by which all measurements will beobtained. The methodologies described here will be used repeatedly throughout the testingprocess. Each procedure described in the following subsections is standardized for all tests.

4.1 FM Band and RF MeasurementsThis section details the methodologies that will be used to make RF measurements in theFM band.

4.1.1 FM Analog PowerMethodologyThis procedure specifies the method for measuring analog FM power. FM signals have therather unique characteristic of constant power regardless of the content or amplitude of themodulating signal. Therefore, power can be measured with or without a modulating signalpresent.

If a modulating signal is present, then the power across the entire channel is integrated inorder to determine overall power. Traditionally, there are three common laboratorymethods of performing this integration:

1) Numerically, by utilizing a DSP based Vector Signal Analyzer (VSA) or through the useof band power markers on a spectrum analyzer

2) Physically, by detecting heat in a thermal sensor3) Electrically, by using a diode to rectify the signal and take advantage of a diode’s

“square-law” region of operation

For our testing purposes, we shall use method (3) in conjunction with an average powermeter and RMS responding diode detector.

SetupThe measuring instrument shall be an HP437B average power meter with an 8481D diodedetection sensor, and will be configured as shown in Table 4-1.

Table 4-1 - HP 437B Setup – Analog FM Power

Parameter DescriptionSensor Type HP 8481D (diode detector)Limit Checking OnLow Limit -70dBmHigh Limit -20dBmCal. Factor 98.5%Note: “Preset” first, and then set above parameters

Usage of the HP437B must take into consideration the dynamic range of the diode detector.Under no circumstances shall a measurement be taken outside the sensor’s measurementrange. In addition, extra care must be taken during IBOC measurements due to the high


©2002 ATTC, Inc. 18

peak-to-average ratio of OFDM. Therefore, measurements with an IBOC signal mustmaintain 10dB of “headroom” below the sensor’s peak range.

In addition, note that measurements must be made under conditions with no interfererspresent since any out of band signal will artificially increase readings on the power meter.

Procedure1) Configure the instrument according to the table found in the “Setup” section above.2) The analog carrier can be either modulated or unmodulated. There is no procedural

change for either case.3) The power level shall be observed and the instantaneous reading recorded.

Presentation of DataThe resulting measurement shall be expressed in dB units with a precision of 0.01dB

4.1.2 IBOC Hybrid Mode PowerMethodologyThis procedure specifies the method for measuring the power of an IBOC signal in hybridmode. A hybrid signal is the spectral sum of a traditional analog FM signal and OFDMdigital carriers at the channel edges.

The true average power of this signal may be determined by integrating over the entirechannel, using an average power meter or vector signal analyzer, as discussed in 4.1.1above. However, the resulting number would not be easily related to traditional analogpower measurements. For comparison purposes, we would like to be able to say that a−30dBm hybrid signal has the same amount of analog energy as a traditional –30dBm FMsignal.

For this reason, all references to the power of a hybrid signal will actually be specifyingpower in the signal that results from a traditional analog FM signal. In other words, a−30dBm hybrid signal will actually have –30dBm of analog FM energy plus the energyresulting from the digital carriers.

Consequently, in order to exclude the digital energy from our measurements, it is notpossible to directly measure hybrid mode power using a traditional average power meter (atleast not without an impracticably steep bandpass filter). Therefore, there are threepractical measurement methods that can be employed:

1) Remove digital sidebands and measure remaining analog power with a traditionalaverage power meter or Vector Signal Analyzer

2) Use a Vector Signal Analyzer to numerically integrate over analog bandwidth3) Use spectrum analyzer to measure power of the unmodulated analog carrier.

For our purposes, we will utilize the first method using an HP437B average power meter.This is facilitated by the fact that the test bed has electromechanical RF switches, whichcan readily switch the digital carriers in and out of the spectrum. In addition, the removalof the digital sidebands increases measurement accuracy.


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SetupThe measuring instrument shall be an HP437B average power meter with an RMSresponding sensor, and will be configured as shown in Table 4-2.

Table 4-2 - HP 437B Setup – Hybrid Mode Power


Usage of the HP437B must take into consideration the dynamic range of the diode detector.Under no circumstances shall a measurement be taken outside the sensor’s measurementrange. In addition, note that measurements must be made under conditions with nointerferers present since any out of band signal will artificially increase readings on thepower meter.

Procedure1) Configure the instrument according to the tables found in the “Setup” section above.2) The analog carrier can be either modulated or unmodulated. There is no procedural

change for either case.3) The digital carriers shall be removed by opening the appropriate electromechanical RF

switch. The remaining energy will be purely analog FM.4) The power level shall be observed and the instantaneous reading recorded.

Presentation of DataThe resulting measurement shall be expressed in dBm, and rounded to the nearest tenth ofa decimal place. It should be made clear that this power refers to the analog energy anddoes not represent the average power level of the entire hybrid signal (as discussed above).

4.1.3 Power in the Presence of MultipathMethodologyThis procedure defines the method that shall be used for determining the power of analogand hybrid signals in the presence of multipath. For a detailed discussion of the multipathscenarios to be used in testing refer to section 7 of this document.

Each multipath profile that will be used consists of a main path and one echo with a rangeof phase offsets. As the phase offset of the echo component is varied, the total envelopepower of the signal will also change due to the constructive or destructive vector addition ofthe main path and the echo path.

If one wished to maintain a constant envelope power level at the receiver input terminals,the transmitted power level would have to be adjusted differently for each multipath echophase offset. If one were to adopt this approach, the phase offset of the echo would no


©2002 ATTC, Inc. 20

longer be the only variable in each test. In addition, it would no longer be possible tocorrelate received signal power with geographical distance from a theoretical transmitter.

Since each test is designed to investigate the impact of only one variable (multipath), andthe test results will ultimately be used in conjunction with geographical station coveragemaps, the power of the desired signal will not be adjusted to compensate for a destructiveecho phase. The power of a multipath-impaired signal will be expressed in terms of thepower in the unimpaired main path only.

SetupThe “bypass” multipath profile is used during this measurement. This consists of a singlepath with no loss.

Procedure1) Load the bypass profile into the multipath simulator2) Start the simulation3) Disable any AGC functionality, or set AGC to “hold”.4) For an analog signal, measure the power according to section 4.1.1. For a hybrid signal,

measure the power according to section 4.1.2.5) Load the multipath profile for the desired test (such as StaticMP1), but make no

additional adjustments (such as AGC settings) to the simulator.

Presentation of DataThe resulting power measurement shall comply with the format outlined in sections 4.1.1 or4.1.2 of this document.

4.1.4 Ratio of Analog to Digital Power (IBOC Hybrid Mode)MethodologyThis procedure specifies the method used to determine the ratio of analog to digital powerin a hybrid mode signal. In practice, the ratio of analog to digital power does not vary, andis not a user-defined parameter. It is a fixed parameter that is defined in the specificationsand describes any hybrid mode signal. This measurement will therefore be performedperiodically (during daily calibration) in order to verify that the test system is setupaccording to the definition of an iBiquity hybrid mode signal.

iBiquity Digital Corporation has specified that the average digital power shall be 20dBbelow the average analog power. It should be emphasized that this is the average power ofthe digital carriers, not the peak power.

The procedure is very similar to that discussed in 4.1.2. Electromechanical RF switches areused to separate the digital subcarriers from the analog energy. The digital energy isswitched out, and the analog power is measured according to section 4.1.1. Next, the digitalenergy is switched in and the analog switched out. The average digital energy is measuredusing an average power meter. The difference between these two measurements is verifiedto be 20dB.


©2002 ATTC, Inc. 21

SetupThe measuring instrument shall be an HP437B average power meter with an RMSresponding sensor, and will be configured as shown in Table 4-3. The HP437B provides ahigher level of accuracy than the VSA, and as such is the preferred instrument for analog-to-digital ratio measurements.

Table 4-3 - HP 437B Setup – Analog-to-Digital Ratio


Usage of the HP437B must take into consideration the dynamic range of the diode detector.Under no circumstances shall a measurement be taken outside the sensor’s measurementrange. In addition, extra care must be taken during IBOC measurements due to the highpeak-to-average ratio of OFDM. Therefore, measurements with an IBOC signal mustmaintain 10dB of “headroom” below the sensor’s peak range.

Procedure1) This measurement shall be made under conditions where no interferers are present

since any out-of-band signal will artificially increase readings on the power meter.2) The analog carrier can be either modulated or unmodulated. There is no procedural

change for either case.3) Remove the digital carriers by opening the appropriate electromechanical RF switch.

The remaining energy will be purely analog FM.4) Put the HP437B into “Relative” mode.5) Remove the analog energy and re-insert the digital carriers via the electromechanical

RF switches.6) Record the “relative reading” on the HP437B. This is the ratio of analog-to-digital

power.

Presentation of DataThe measurement resulting from step six (6) shall be expressed in dB units with a precisionof 0.1dB.

4.1.5 Additive White Gaussian Noise PowerMethodologyThis subsection describes the methods which shall be used to measure the average power ofan Additive White Gaussian Noise (AWGN) signal.

There are several ways to express the power level of a noise signal such as Additive WhiteGaussian Noise (AWGN). The first method is bandwidth independent, and has units equalto degrees Kelvin. If an AWGN signal has a power that is said to be 30,000K, then it has


©2002 ATTC, Inc. 22

the same amount of noise power as a theoretical resistor would at a physical temperature of30,000 Kelvin. The second method is bandwidth dependent, and has units equal to Powerper Unit Bandwidth. For our purposes, we need to measure noise power in a givenbandwidth. Therefore, we shall use the latter method, and express our results in dBm/Hz.

Unfortunately, the measurement of noise power in dBm/Hz units requires some ratherspecialized procedures and/or equipment. There are two well-known methods used tomeasure the power level of AWGN in bandwidth dependent units.

The first method is informally referred to as the “ENB Method”. ENB is an abbreviation forEquivalent Noise Bandwidth. In reality, ENB is a property of a bandpass filter. Anybandpass filter has a passband with a finite bandwidth, which may be measured andcharacterized using network analyzers or similar instrumentation. This characterizationmay also involve the calculation of an ENB value for the filter (The details of ENBcalculation are beyond the scope of this test procedure). This ENB calculation may then beused as a conversion factor to convert absolute power units (dBm) into power per unitbandwidth units (dBm/Hz). Using this methodology, one can band-limit AWGN noise usingan ENB calibrated filter, and measure the resultant power in absolute units (usingstandard instrumentation such as a thermal power meter). These dBm units may then beconverted to dBm/Hz units using the ENB conversion factor as follows:

dBm/Hz = dBm - 10log(ENB)where ENB is the bandpass filter’s Equivalent Noise Bandwidth, given in Hz units

The setup and procedures for performing a measurement using the ENB method are givenin the sections below.

The second method of measuring noise power in dBm/Hz units employs an HP VectorSignal Analyzer (VSA). The VSA is a very sophisticated and rather unique device, becauseit is fundamentally a time domain device that performs rapid FFT’s for spectrum analysis.This architecture allows one to easily measure Power Spectral Density (PSD) without thenormal spectrum analyzer concerns of calibrated resolution bandwidth filters. Since thePSD measurement provides results in dBm/Hz units, noise power density can also bedirectly measured in dBm/Hz units. The setup and procedures for this measurementmethodology are also given below.

Unfortunately, both of these measurement methodologies (ENB and VSA) arefundamentally limited by the low level sensitivity of the instrumentation (either the powermeter or the VSA). For example, a 30,000K noise signal has a power level which is rapidlyapproaching the inherent noise floor of the VSA, and is also significantly below the limits ofany thermal power sensor. In order to overcome this limitation, noise power is measured ata much higher power level. Then, in order to achieve lower noise power levels, aknown/calibrated attenuator is inserted in-line with the high level noise source. (Insertionof this inline attenuation is facilitated by our noise generation instrument, which containsprecision attenuators installed internally).


©2002 ATTC, Inc. 23

Setup (ENB Method)The power measuring instrument shall be an HP437B average power meter with an 8481Ddiode detection sensor, and will be configured as shown in Table 4-4.

Table 4-4 - HP 437B Setup – Analog FM Power

Parameter DescriptionSensor Type HP 8481D (diode detector)Limit Checking OnLow Limit -70dBmFilter/Averaging AutoNote: “Preset” first, and then set above parameters

Because the AWGN noise will have a relatively high peak-to-average ratio, the powersensor must operate with at least 10dB of “headroom”. Therefore, this sensor may not beused to measure any AWGN noise power exceeding –30dBm.

Procedure (ENB Method)1) Set the noise generator’s output attenuator to 0.0dB, and enable the calibrated internal

FM Bandpass Filter (FM BPF).2) Remove all other bandpass filters from the noise signal path, and replace with a “barrel”

connector (Refer to the test bed schematics for locations of additional filters).3) Measure the absolute power of the noise, using the instrumentation described above,

and observing the appropriate power limits.4) Measure the insertion loss (at 97.9MHz) of any filters which may have been removed in

Step 2. Subtract the insertion loss of these filters from the measurement of Step 3.5) Convert the result of Step 4 from dBm to dBm/Hz units using the equation described in

the methodology section. Note that the ENB of the noise generator’s filter is availableon the unit’s calibration certificates.

6) Replace any bandpass filters which may have been removed in Step 2.

Presentation of Data (ENB Method)The result of Step 5, above, shall be given in dBm/Hz units and expressed with a precisionof 0.1dB.

Setup (VSA Method)The power measuring instrument shall be an HP89441A Vector Signal Analyzer (VSA), andwill be configured as shown in Table 4-5.

Table 4-5 - HP Vector Signal Analyzer Setup – Noise Measurements

Parameter SettingNote: “Preset” first, and then set parameters belowCenter Frequency 97.9 MHzSpan 1.0 MHzRange (sensitivity) Highest sensitivity before “over” LEDResolution Bandwidth 10kHz (auto-coupled)


©2002 ATTC, Inc. 24

Measurement Data PSD (Power Spectral Density)Averages 250Marker Frequency 97.9MHz

Procedure (VSA Method)1) Setup the HP 89441 VSA according to Table 4-5.2) Note that the marker must be positioned to take measurements at 97.9MHz3) Set the noise generator output attenuator to 0.0dB, and the FM bandpass filter

inline/enabled.4) Observe the power spectral density (PSD) marker reading on the VSA, ensuring that

the running average has reached at least 250.

Presentation of Data (VSA Method)The resulting measurement will be given in dBm/Hz units, and expressed with a precisionof 0.1dB.

4.1.6 Deviation and Channel ConfigurationMethodologyA typical broadcast FM signal has numerous configuration parameters, which need to beregularly monitored and verified. Some of these parameters include main channelmodulation, pilot injection, SCA injection and SCA modulation.

Throughout the testing process, there is a need to measure and verify these parameters. Inrecent years the market has seen the introduction of broadcast grade modulation monitorsthat utilize DSP technology for more accurate measurements. These units reducecalibration drift and uncertainty. In addition, the digital readouts remove much of theguesswork from directly reading an analog deflection meter. For these reasons, the testingprocess shall utilize broadcast grade DSP based modulation instruments to measure thevarious FM channel modulation parameters.

The modulation monitors to be used are a Belar FMMA-1 Modulation Analyzer, a BelarFMSA-1 Digital Stereo Monitor and a Belar SCMA-1 SCA Modulation Monitor inconjunction with a Belar RFA-4 Down Converter. The performance of these devices isdocumented in the proof of performance record, as referenced in section 1.4 of thisdocument. Further verification of the Belar FMMA-1 accuracy will be obtained throughcomparison with a Modulation Sciences Inc. FM Modulation Monitor.

SetupThe FM channel characteristics shall be measured using the instrumentation and setupshown in Figure 4-1. A complete listing of the setup of the Belar devices may be found inthe test bed proof-of-performance record of test results, as referenced above in section 1.4.


©2002 ATTC, Inc. 25

FMBandPassFilter

Splitter

AmpModulation SciencesFM Modulation Monitor

FMBandPassFilter

Belar RFA-4Down Converter

Belar FMMA-1 Mod.Analyzer (w/ Option 01)

Belar SCMA-1 SCA Mod.Mon. and Demodulator

Belar FMSA-1 StereoDemodulator

FromTest Bed

Figure 4-1 - Setup for Modulation & Configuration Readings

Notes:1) The bandpass filter between the splitter and the Belar down converter blocks the L.O.

signal, which would otherwise be conducted out of the RFA-4 input.2) The amplifier is necessary to achieve an appropriate operating power level for the

Modulation Sciences monitor.

ProcedureThe equipment configured as shown in Figure 4-1 shall be used to make measurements asfollows:

1) Total Peak Modulationa) Belar FMMA-1b) Modulation Sciences Inc. FM Modulation monitor

2) Pilot Injectiona) Belar FMSA-1b) Modulation Sciences Inc. FM Modulation monitor

3) Individual Left and Right Modulationa) Belar FMSA-1

4) Subcarrier Injectiona) Belar SCMA-1b) Modulation Sciences Inc. FM Modulation monitor

5) Subcarrier Percent Modulationa) Belar SCMA-1

The test engineer will verify that the Modulations Sciences Monitor and the Belar devicesdo not yield results that differ by more than a few percent when making the appropriatemeasurements (measurements 1, 2, and 4 listed above).

It is important to note that these measurements may only be performed on analog signals.In other words, all measurements must be made with the IBOC sidebands removed. Theseinstruments are not designed to provide accurate readings in the presence of IBOCsidebands, and erroneous readings will result if such a measurement is attempted.


©2002 ATTC, Inc. 26

Presentation of DataThe resulting data shall be expressed in percentage (%) units with a precision of 0.1%.

4.2 Baseband Audio MeasurementsThis section details the methodologies that will be used to make audio measurements.

4.2.1 Signal-to-Noise Ratio (SNR)MethodologyThis procedure defines the method for finding the SNR of demodulated analog audio, asseen at the output of an FM SCA receiver.

SNR is the ratio of some reference signal to the baseband noise floor of the Device UnderTest (DUT). In our case, the DUT is not only the receiver, but also the entire broadcastsystem and communications channel (including interferers). For our purposes, thereference signal is defined as the desired signal in the interference scenario under test.Refer to the subsections of 3.1 for the definitions of various desired signals.

The noise measurements shall comply with the ITU-R 468.4 standard2. This standarddefines the characteristics of a “quasi-peak” voltmeter to be used for detection, and also afilter that is used to weight the response. The weighting filter is an attempt to model thehuman auditory system. The human ear, for example, is not as sensitive to low frequencynoise as it is to mid frequency noise. Therefore low frequencies carry less weight in an SNRmeasurement that adopts the 468 method.

SetupThe measuring instrument shall be an Audio Precision System One, with the analyzerconfigured as shown in Table 4-6.

Table 4-6 Audio Precision Setup for S/N Measurements

Analyzer SettingsMeasure A AmplitudeRange AutoBP/BR Freq. AutoDetector Q-PeakBandwidth 10Hz 22kHzFilter CCIR-468Channel A Input 100kΩRange AutoChannel B Input 100kΩRange Auto

2 International Telecommunications Union, ITU Rec.468-4, “Measurement of Audio-Frequency NoiseVoltage Level in Sound Broadcasting”


©2002 ATTC, Inc. 27

Procedure1) Apply the desired signal to the receiver. This will be the reference signal for the SNR

measurement.2) Set up the Audio Precision analyzer according to Table 4-6.3) Use the Audio Precision analyzer to measure the value of the voltage generated across

the appropriate output of the receiver. Record this value for use in step 7.4) Remove modulating audio from the input to the SCA generator.5) Use the Audio Precision analyzer to measure the value of the voltage remaining at the

output of the receiver. Repeat this measurement until 40 readings are obtained.6) Find the statistical mean of the 40 readings.7) Find the ratio of the result from step 3 (in volts) to the result from step 6 (also in volts).

Presentation of DataThe ratio resulting from step 7 (above) is a unit-less quantity, which should be expressed indB. Since this ratio is derived from voltage units, the calculation shall be: 20*log(ratio).The result shall be rounded to the nearest tenth of a dB.


©2002 ATTC, Inc. 28

5 Test ProceduresThis section describes in detail, the test conditions that will be utilized during the testingprocess.

5.1 SCA Receiver Performance in the Presence ofAnalog and IBOC Adjacent Channels

ObjectivesCharacterize the performance of analog SCA receivers in the presence of both analog andhybrid adjacent channel interference. Quantify the difference between the impact of analogand hybrid interferers in various channel conditions.

MethodologyIn order to meet these objectives the test bed will be utilized to generate various adjacentchannel interference scenarios. The performance of SCA receivers will be evaluated foreach scenario with an analog and a hybrid adjacent channel interferer. For a list of thereceivers to be tested, refer to section 6 of this report.

Evaluation of performance will be measured in terms of the SCA receiver’s audio signal-to-noise ratio (SNR). For all of the adjacent channel interference scenarios the SNR of eachSCA receiver will be measured at varying adjacent channel power levels.

Upon completion of these tests, the test results data will be separated into cases withanalog interferers and cases with hybrid interferers. The difference between hybrid andanalog adjacent channel interference can then be objectively evaluated.

Test ConditionsTable 5-1 illustrates all of the test interference conditions under which the SCA receiverperformance will be tested in the presence of adjacent channel interference. The scenarioslisted were chosen by the IAAIS and NPR. The following information may be helpful inunderstanding the table:

1. Each row of the table represents one test, and each test is assigned a uniqueidentification number in the # column.

2. The Desired column indicates the mode, power level, and the SCA frequency to be testedon the desired channel. The SCA frequency to be tested is either 67kHz or 92kHz. Thedesired mode is Analog and the power level is Moderate (-62dBm) for all of these tests.

3. In the interferer columns, the mode of the interferer is indicated as Analog or Hybrid.Next to the mode of the interferer is the range of D/U to be used. D/U is the ratio of thepower in the desired signal to the power in the undesired signal. This value isexpressed in dB units.

4. The AWGN column indicates the presence or absence of a broadband noise floor in thetest scenario. If additional noise is present in a test, the absolute power level isindicated in Kelvin units.


©2002 ATTC, Inc. 29

Table 5-1 Adjacent Channel Interference Scenarios

# Lower 2nd adj. Lower 1st adj. Desired Upper 1st adj. Upper 2nd adj. AWGN 8001 Analog: +30à0 Analog: 67kHz: Moderate None 8002 Hybrid: +30à0 Analog: 67kHz: Moderate None 8003 Analog: +30à0 Analog: 67kHz: Moderate 30,000K 8004 Hybrid: +30à0 Analog: 67kHz: Moderate 30,000K 8005 Analog: 67kHz: Moderate Analog: +30à0 None 8006 Analog: 67kHz: Moderate Hybrid: +30à0 None 8007 Analog: 67kHz: Moderate Analog: +30à0 30,000K 8008 Analog: 67kHz: Moderate Hybrid: +30à0 30,000K 8009 Analog: 0à-42 Analog: 67kHz: Moderate None 8010 Hybrid: 0à-42 Analog: 67kHz: Moderate None 8011 Analog: 0à-42 Analog: 67kHz: Moderate 30,000K 8012 Hybrid: 0à-42 Analog: 67kHz: Moderate 30,000K 8013 Analog:67kHz: Moderate Analog: 0à-42 None 8014 Analog:67kHz: Moderate Hybrid: 0à-42 None 8015 Analog:67kHz: Moderate Analog: 0à-42 30,000K 8016 Analog:67kHz: Moderate Hybrid: 0à-42 30,000K 8017 Analog: +30à0 Analog: 92kHz: Moderate None 8018 Hybrid: +30à0 Analog: 92kHz: Moderate None 8019 Analog: +30à0 Analog: 92kHz: Moderate 30,000K 8020 Hybrid: +30à0 Analog: 92kHz: Moderate 30,000K 8021 Analog: 92kHz: Moderate Analog: +30à0 None 8022 Analog: 92kHz: Moderate Hybrid: +30à0 None 8023 Analog: 92kHz: Moderate Analog: +30à0 30,000K 8024 Analog: 92kHz: Moderate Hybrid: +30à0 30,000K 8025 Analog: 0à-42 Analog: 92kHz: Moderate None 8026 Hybrid: 0à-42 Analog: 92kHz: Moderate None 8027 Analog: 0à-42 Analog: 92kHz: Moderate 30,000K 8028 Hybrid: 0à-42 Analog: 92kHz: Moderate 30,000K 8029 Analog: 92kHz: Moderate Analog: 0à-42 None 8030 Analog: 92kHz: Moderate Hybrid: 0à-42 None 8031 Analog: 92kHz: Moderate Analog: 0à-42 30,000K 8032 Analog: 92kHz: Moderate Hybrid: 0à-42 30,000K

SetupPlease refer to the test bed schematics, located in the proof-of-performance record fordetails of the test platform setup. Note that SW7 through SW12 shall be set such that themultipath simulators are bypassed. SW1 through SW6 shall be used to set each channel toeither analog, hybrid or off mode. AT1 through AT3 shall be used to set D, U1 and U2signal power levels in 0.25dB increments. Noise power levels shall be set with the AWGNgenerator’s internal attenuator in 0.1dB increments.

Procedure1) All of the analog SCA receivers (see section 6) shall be used for this test series.2) Table 5-1 will be used as a guide for setting up each interference scenario. Each row of

this table shall be executed individually.3) Establish the noise floor according to the AWGN column of the test grid. Refer to

section 3.1.9 for a definition of AWGN noise, and 4.1.5 for the procedures of AWGNnoise power measurement.

4) Establish the signal strength, frequency, and mode of the desired signal as indicated inthe test grid. For a complete definition of the desired analog and desired hybrid signals,refer to sections 3.1.2 and 3.1.5, respectively. The procedures for measuring FM powermay be found in sections 4.1.1 and 4.1.2.


©2002 ATTC, Inc. 30

5) Establish the signal strength, frequency, and mode of the interfering signals asindicated in the test grid. For a complete definition of the undesired analog interfererand undesired hybrid interferer signals, refer to 3.1.7 and 3.1.8, respectively. Theprocedures for measuring FM power may be found in sections 4.1.1 and 4.1.2.

6) Modulate the desired main channel and the interferer with the appropriate CDrecordings of Clipped USASI (3.2).

7) Begin taking SNR measurements, as described in section 4.2.1, at the appropriate D/Ulevels.

Presentation of DataA plot of the SCA receiver SNR as a function of the ratio of the desired channel power levelto the undesired channel power level (D/U) will be generated.

5.2 SCA Receiver Performance in the Presence of anAnalog or IBOC Host

ObjectivesCharacterize the performance of analog SCA receivers in the presence of both analog andhybrid “Host” signals. Quantify the difference between the impact of analog and hybridhost signals in various channel conditions.

MethodologyIn order to meet this objective the test bed will be utilized to generate Analog and Hybridmain channel signals under various channel conditions. The performance of SCA receiverswill be evaluated for each condition. For a list of the receivers to be tested, refer to section6 of this report.

Evaluation of performance will be measured in terms of the SCA receiver’s audio signal-to-noise ratio (SNR). For all of the host compatibility channel scenarios the SNR of each SCAreceiver will be measured.

Upon completion of these tests, the test results data will be separated into cases where thehost was analog and where the host was a hybrid signal. The difference between hybridand analog host compatibility can then be objectively evaluated.

Test ConditionsTable 5-2 illustrates all of the test interference conditions under which the SCA receiverperformance will be tested for host compatibility. The scenarios listed were chosen by theIAAIS and NPR. The following information may be helpful in understanding the table:


2. The Desired column indicates the mode, power level, and the SCA frequency to be testedon the desired channel. The SCA frequency to be tested is either 67kHz or 92kHz. Thedesired mode is Analog or Hybrid and the power level is Moderate (-62dBm) for all ofthese tests.


©2002 ATTC, Inc. 31

3. Signal Type column indicates the signal type to be used for testing. For definitions ofthese signal types refer to sections 3.1.2 and 3.1.4.

4. The AWGN column indicates the presence or absence of a broadband noise floor in thetest scenario. If additional noise is present in a test, the absolute power level isindicated in Kelvin units.

5.

Table 5-2 Host Compatibility Scenarios

# Desired Signal Type AWGN 8101 Analog: 67kHz: Moderate Analog II None 8102 Hybrid: 67kHz: Moderate Hybrid II None 8103 Analog: 67kHz: Moderate Analog II 30,000K 8104 Hybrid: 67kHz: Moderate Hybrid II 30,000K 8105 Analog: 92kHz: Moderate Analog II None 8106 Hybrid: 92kHz: Moderate Hybrid II None 8107 Analog: 92kHz: Moderate Analog II 30,000K 8108 Hybrid: 92kHz: Moderate Hybrid II 30,000K

SetupPlease refer to the test bed schematics, located in the proof-of-performance record fordetails of the test platform setup. Note that SW7 thru SW12 shall be set such that themultipath simulators are bypassed. SW1 thru SW6 shall be used to set each channel toeither analog, hybrid or off mode. AT1 thru AT3 shall be used to set the Desired signalpower level in 0.25dB increments. Noise power levels shall be set with the AWGNgenerator’s internal attenuator in 0.1dB increments.

Procedure1) All of the analog SCA receivers (see section 6) shall be used for this test series.2) Table 5-1 will be used as a guide for setting up each interference scenario. Each row of

this table shall be executed individually.3) Establish the noise floor according to the AWGN column of the test grid. Refer to

section 3.1.9 for a definition of AWGN noise, and 4.1.5 for the procedures of AWGNnoise power measurement.

4) Establish the signal strength, frequency, subcarrier frequency and mode of the desiredsignal as indicated in the test grid. For a complete definition of the desired analog anddesired hybrid signals, refer to sections 3.1.2 and 3.1.5, respectively. The procedures formeasuring FM power may be found in sections 4.1.1 and 4.1.2.

5) Modulate the desired main channel with the appropriate CD recording of ClippedUSASI (3.2).

6) Begin taking SNR measurements, as described in section 4.2.1, at the appropriate D/Ulevels.

Presentation of DataThe SNR measurement data will be presented in tabular form with a precision of 0.1 dB.


©2002 ATTC, Inc. 32

5.3 SCA Receiver Performance in the Presence of anAnalog or IBOC Host in Multipath Conditions

ObjectivesCharacterize the performance of analog SCA receivers in the presence of both analog andhybrid “Host” signals under multipath impaired channel conditions. Quantify thedifference between the impact of analog and hybrid host signals in these channel conditions.

MethodologyIn order to meet this objective the test bed will be utilized to generate Analog and Hybridmain channel signals under multipath impaired channel conditions. The performance offour SCA receivers will be evaluated for each scenario.

Evaluation of performance will be measured in terms of the SCA receiver’s audio signal-to-noise ratio (SNR). For all of the host compatibility with multipath test conditions the SNRof four SCA receivers will be measured. For a list of the receivers to be subjected to thesetests, refer to section 6 of this report.

Upon completion of these tests, the test results data will be separated into cases where thehost was analog and where the host was a hybrid signal. The difference between hybridand analog host compatibility with multipath can then be objectively evaluated.

Test ConditionsTable 5-3 illustrates all of the test interference conditions under which the SCA receiverperformance will be tested for host compatibility. The scenarios listed were chosen by theIAAIS and NPR. The following information may be helpful in understanding the table:


2. The Desired column indicates the mode, power level of the desired channel. The desiredmode is Analog or Hybrid and the power level is Moderate (-62dBm) for all of thesetests.

3. Signal Type column indicates the signal type to be used for testing. For definitions ofthese signal types refer to sections 3.1.1, 3.1.3, 3.1.4, and 3.1.6.

4. The Multipath column indicates the multipath scenario that was used during testing.For a detailed description of the multipath scenarios used refer to section 7 of thisdocument.

5. The Echo Phase column indicates the range of phases to be tested. The phase will bestepped over the range indicated in steps of 45 degrees.

6. The SCA Under Test column indicates the subcarrier that is being evaluated (either67kHz or 92kHz).

Table 5-3 – Host Compatibility with Multipath Scenarios

# Desired Signal Type Multipath Echo Phase SCA Under Test8201 Analog: Moderate Analog III StaticMP1 -187 à -7 67kHz8202 Hybrid: Moderate Hybrid III StaticMP1 -187 à -7 67kHz8203 Analog: Moderate Analog I StaticMP1 -187 à -7 67kHz8204 Hybrid: Moderate Hybrid I StaticMP1 -187 à -7 67kHz


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8205 Analog: Moderate Analog III StaticMP2 -187 à -7 67kHz8206 Hybrid: Moderate Hybrid III StaticMP2 -187 à -7 67kHz8207 Analog: Moderate Analog I StaticMP2 -187 à -7 67kHz8208 Hybrid: Moderate Hybrid I StaticMP2 -187 à -7 67kHz8209 Analog: Moderate Analog III StaticMP3 -16 à -164 67kHz8210 Hybrid: Moderate Hybrid III StaticMP3 -16 à -164 67kHz8211 Analog: Moderate Analog I StaticMP3 -16 à -164 67kHz8212 Hybrid: Moderate Hybrid I StaticMP3 -16 à -164 67kHz8213 Analog: Moderate Analog III StaticMP1 -187 à -7 92kHz8214 Hybrid: Moderate Hybrid III StaticMP1 -187 à -7 92kHz8215 Analog: Moderate Analog I StaticMP1 -187 à -7 92kHz8216 Hybrid: Moderate Hybrid I StaticMP1 -187 à -7 92kHz8217 Analog: Moderate Analog III StaticMP2 -187 à -7 92kHz8218 Hybrid: Moderate Hybrid III StaticMP2 -187 à -7 92kHz8219 Analog: Moderate Analog I StaticMP2 -187 à -7 92kHz8220 Hybrid: Moderate Hybrid I StaticMP2 -187 à -7 92kHz8221 Analog: Moderate Analog III StaticMP3 -16 à -164 92kHz8222 Hybrid: Moderate Hybrid III StaticMP3 -16 à -164 92kHz8223 Analog: Moderate Analog I StaticMP3 -16 à -164 92kHz8224 Hybrid: Moderate Hybrid I StaticMP3 -16 à -164 92kHz

Procedure1) Four of the analog SCA receivers, chosen by the IAAIS and NPR, shall be used in this

test series. For a list of the receivers to be tested see section 6.2) Table 5-3 will be used as a guide for setting up each interference scenario. Each row of

this table shall be executed individually.3) Setup the multipath scenario that the test grid indicates.4) Establish the signal strength, frequency, subcarrier frequency and mode of the desired

signal as indicated in the test grid. For a complete definition of the desired analog anddesired hybrid signals, refer to sections 3.1.1, 3.1.3, 3.1.4, and 3.1.6 respectively. Theprocedures for measuring FM power may be found in sections 4.1.1 and 4.1.2.

5) Modulate the desired main channel with the appropriate CD recording of ClippedUSASI (3.2).

6) Adjust the phase offset of the echo.7) Take SNR measurements, as described in section 4.2.1.8) Repeat steps 6 and 7 until measurements have been taken over the entire range

indicated by the test grid.

Presentation of DataThe results of these tests will be present in a plot of SNR versus the phase offset of theEcho.


©2002 ATTC, Inc. 34

6 - Appendix A - List of Receivers Under Test

Table 6-1 – Receivers to be tested for Adjacent Channel Compatibility and HostCompatibility without Multipath.

Radio Make/Model No: Type Serial No:Dayton AF210 (REF) 67 kHz and 92 kHz Settings 2101341McMartin TR-E5/55M 67 kHz 286834Norver 67 kHz 67 kHz A0012461Dayton AF200 67 kHz 810239ComPol SCA-RLA 67 kHz 1004ComPol SCA-RLA 67 kHz 1005CozmoCom 92 kHz 92 kHz 0073696Dayton AF200 92 kHz 810238ComPol SCA-RLA 92 kHz 1006ComPol SCA-RLA 92 kHz 1007

Table 6-2 – Receivers to be tested for Host Compatibility with Multipath channelimpairments.

Radio Make/Model No: Type Serial No:McMartin TR-E5/55M 67 kHz 286834ComPol SCA-RLA 67 kHz 1005ComPol SCA-RLA 92 kHz 1006CozmoCom 92 kHz 92 kHz 0073696


©2002 ATTC, Inc. 35

7 - Appendix B - Multipath ProfilesThis appendix describes the multipath profiles that are to be used during the testingprocess.

7.1 Characterization of Static Multipath ProfilesSince signal-to-noise ratio measurement in the presence of dynamic multipath may not berepeatable without averaging the results of an impracticably large number ofmeasurements, the IAAIS and NPR agreed to the use of static multipath scenarios.

It was decided that there would be three static multipath scenarios developed for testing,each with one echo of varying phase offset. The echo was adjusted to have either 1.2µs or3µs of delay.

Figure 7-1 illustrates the device setup used to develop the multipath scenarios, and producethe plots in the following sections. The tracking generator of the spectrum analyzer wasamplified in order to simulate the power levels seen by the test bed during normaloperation.

SpectrumAnalyzer

TrackingGeneratorOutput

Test Bed

RF Input toTest Bed

RF OutputFrom Test bedRF Input

PadAmp

Figure 7-1 Device setup used to develop static multipath scenarios.

The plots on the following pages illustrate the frequency response of the channel with theworst case scenarios (echo with no attenuation) for both of the delays chosen. These plotsare overlaid with an unimpaired IBOC signal. The pathological phase offset is defined asthe phase offset that causes a null at 97.82MHz, which is between the lower sidebandscaused by the 92kHz and 67kHz subcarriers. Four other phase offsets were chosen suchthat the null is near enough, in frequency, to the subcarrier sidebands that someinterference is still discernable.


©2002 ATTC, Inc. 36

Figure 7-2 – Static Multipath, one echo, no attenuation, 1.2µµs delay, 173 degreesphase offset

Figure 7-3 – Static Multipath, one echo, no attenuation, 1.2µµs delay, -142 degreesphase offset


©2002 ATTC, Inc. 40



7.2 Multipath Profiles - StaticMP1StaticMP1 is designed to have one type echo, with 6dB of attenuation, 1.2µs delay and avarying phase offset. The plots of this subsection illustrate the frequency response of thechannel in the presence of this type of echo for all of the phase offsets to be used in testing.The frequency response is overlaid with an unimpaired IBOC signal.


©2002 ATTC, Inc. 43


7.3 Multipath Profiles – StaticMP2StaticMP2 is designed to have one type echo, with 10dB of attenuation, 1.2µs delay and avarying phase offset. The plots below illustrate the frequency response of the channel inthe presence of this type of echo for all of the phase offsets to be used in testing. Thefrequency response is overlaid with an unimpaired IBOC signal.



©2002 ATTC, Inc. 45



7.4 Multipath Profiles – StaticMP3StaticMP3 is design to have one type echo, with 10dB of attenuation, 3µs delay and avarying phase offset. The plots below illustrate the frequency response of the channel inthe presence of this type of echo for all of the phase offsets to be used in testing. Thefrequency response is overlaid with an unimpaired IBOC signal.