proprietary statement: the information contained is this document is proprietary to drs...
TRANSCRIPT
PROPRIETARY STATEMENT: The information contained is this document is Proprietary to DRS Technologies, Inc.
“High Performance GNU Radio applications: Super or Zero? : A Trade-off Comparison of Superhet vs. Zero IF Radio Architectures in Real World Environments”
2Use or disclosure of data contained on this sheet is subject to the restrictions on the title page. Copyright © 2012, 2015 DRS Technologies, Inc. Proprietary information. .
A/DRF
ConverterGNUDSP
Antenna
In other words - Nasty radio
environments can produce an
undesirable output
3Use or disclosure of data contained on this sheet is subject to the restrictions on the title page. Copyright © 2012, 2015 DRS Technologies, Inc. Proprietary information. .
DRS Signal Solutions produces radios that meet GNU standards
Zero IF frequency conversion architectures have been proposed to meet the goal of a “radio on a chip” for receivers and transmitters.
This presentation examines zero IF and super-heterodyne approaches, comparing the strengths and weakness in dense signal environments. Particular attention is paid to size, weight, power, price and performance. Real-world operational examples are given to highlight the differences.
4Use or disclosure of data contained on this sheet is subject to the restrictions on the title page. Copyright © 2012, 2015 DRS Technologies, Inc. Proprietary information. .
Agenda
• Discussion of real world and crowded spectrum issues
• Review dynamic range terminology…NF, IP3, IP2 & NPR
• Super-heterodyne and Zero IF …The difference explained
• How the pros and cons could affect a GNU Radio application
• Testing and evaluation….On-the-Air vs NPR
• Conclusions
5Use or disclosure of data contained on this sheet is subject to the restrictions on the title page. Copyright © 2012, 2015 DRS Technologies, Inc. Proprietary information. .
The Real World Omni-directional Discone Antenna (30 to 1000 MHz) and Log
Periodic Array ( 1 to 3 GHz) 3 Miles South of Chicago
6Use or disclosure of data contained on this sheet is subject to the restrictions on the title page. Copyright © 2012, 2015 DRS Technologies, Inc. Proprietary information. .
Real World Spectrum Energy- Chicago
………………
7Use or disclosure of data contained on this sheet is subject to the restrictions on the title page. Copyright © 2012, 2015 DRS Technologies, Inc. Proprietary information. .
Multiple Signals Require Total Average Power and Crest Factor (CF) Considerations
05
10152025303540
1 10 100Number of Signals
Average PowerAve. Pow. + Theoretical PeakAve. Pow. + Statistical Peak
.…10Log(#Signals), 15Log(#Signals), or 20Log(#Signals)
8Use or disclosure of data contained on this sheet is subject to the restrictions on the title page. Copyright © 2012, 2015 DRS Technologies, Inc. Proprietary information. .
Simple and Complex Signals and Their Crest Factors (CF)
Tuner Sig Str (dBm)0
-10
-20
-30
-40
-50
-60
10 simple signals
Average power
Plus statistical peak
Complex signal
Example-TV
64 QAM DVT
Average power
Plus statistical peak
Example – FM signals
+10 dB
+10 dB+15 dB
ADC full scale! Needs IF/RF gain change
9Use or disclosure of data contained on this sheet is subject to the restrictions on the title page. Copyright © 2012, 2015 DRS Technologies, Inc. Proprietary information. .
Note!
Overload of the radio stages before the ADC may require RF/IF attenuation, but the radio control is usually limited to
seeing signals in the ADC IF bandwidth.
The ADC is blind to signals outside its IF spectrum!
What you can’t see can hurt you!
Simulate or calculate first!
10Use or disclosure of data contained on this sheet is subject to the restrictions on the title page. Copyright © 2012, 2015 DRS Technologies, Inc. Proprietary information. .
Calculating CF Signals at Different Levels and Types
Chicago South, Ill. FM Other significant signals (15Log#) Chicago, Ill. DTVSS -dBm PWR mW Total mW AverageCF total_dBm + 10 dB SS -dBm PWR mW Total mW AverageCF total_dBm SS -dBm PWR mW Total mW Avetotal_dBmCF (dBm + 15dB)
-20.3 9.33E-03 5.70E-02 -2.44 -23 5.01E-03 2.13E-02 -16.72 -15.40 2.88E-02 0.15 -8.38 6.62-21.5 7.08E-03 -21 7.94E-03 -16.40 2.29E-02-22.0 6.31E-03 -25 3.16E-03 -17.20 1.91E-02-22.5 5.62E-03 -23 5.01E-03 -17.70 1.70E-02-22.7 5.37E-03 -38 1.58E-04 -18.20 1.51E-02 FM + Other + DTV (mW) 5.180 mW-22.9 5.13E-03 -52 6.31E-06 -18.60 1.38E-02
-32.1 6.17E-04 2.13E-02 -21.10 7.76E-03 FM + Other + DTV (dBm) 7.14 dBm-23.4 4.57E-03 -21.60 6.92E-03-23.4 4.57E-03 -22.40 5.75E-03-23.7 4.27E-03 5.70E-02 -23.20 4.79E-03-23.8 4.17E-03 -25.00 3.16E-03
1.45E-01FM Crest Factor = Ave. Pwr + Stastical Peak; 20Log #Sig DTV Crest Factor = Ave. Pwr + Stastical Peak; 10Log #Sig + 15 dB
11Use or disclosure of data contained on this sheet is subject to the restrictions on the title page. Copyright © 2012, 2015 DRS Technologies, Inc. Proprietary information. .
Calculating CF on Cellular Spectrums
• From the above, note RF level and spectral BW of the down links (Cell towers)….about -33 dBm…. over 852 to 864 MHz ~ 22 MHz• TDMA signals are channel spaced at 200 KHz. 22 MHz/200KHz =
110 channels• About 80 % are occupied…88. 15 Log 88 = 29.2 dB• Add 29.2 dB to -33 dBm = -3.8 dBm statistical peak power –
What about other cell bands?
12Use or disclosure of data contained on this sheet is subject to the restrictions on the title page. Copyright © 2012, 2015 DRS Technologies, Inc. Proprietary information. .
DRS Signal Solution in Germantown….total signal power + crest factor
Germantown, MD FM Germantown, MD DTV Germantown Cell towerSS -dBm PWR mW Total mW CF total_dBm + 10 dB SS -dBm PWR mW Total mW total_dBmCF (dBm + 15dB) Total dBm + 10 dB CF= -3.5 dBm
-26.3 2.34E-03 1.32E-02 -8.78 -28.30 1.48E-03 8.36E-03 -20.78 -5.78 88 signals about -33 dBm-26.3 2.34E-03 -28.40 1.45E-03 -3.5-28.9 1.29E-03 -30.10 9.77E-04 FM + DTV + Cell(mW) 0.843 mW
-29.5 1.12E-03 -30.80 8.32E-04 FM + DTV + Cell (dBm) -0.74 dBm-29.9 1.02E-03 -31.30 7.41E-04-29.5 1.12E-03 -31.30 7.41E-04-29.7 1.07E-03 -31.40 7.24E-04-29.7 1.07E-03 -31.90 6.46E-04-31.8 6.61E-04 -33.40 4.57E-04-32.2 6.03E-04 -38.00 1.58E-04-32.3 5.89E-04 -38.00 1.58E-04
1.32E-02 8.36E-03
FM Crest Factor = Ave. Pwr + Stastical Peak; 20Log #SigDTV Crest Factor = Ave. Pwr + Stastical Peak; 10Log #Sig + 15 dB
13Use or disclosure of data contained on this sheet is subject to the restrictions on the title page. Copyright © 2012, 2015 DRS Technologies, Inc. Proprietary information. .
The Real World is Brutal
Multiple strong signals in an imperfect radio will create false “spurious” signals that will create useless clutter and interfere with the reception of the desired signal.
With many strong signals, the radio may be grossly overloaded and lose sensitivity.
14Use or disclosure of data contained on this sheet is subject to the restrictions on the title page. Copyright © 2012, 2015 DRS Technologies, Inc. Proprietary information. .
Traditional Dynamic Range Two Tone Tests
Sig Gen 1
Sig Gen 2
Noise Gen
Tuner under test
FFT Display
Sig 1 Sig 2
-IM 2 or 3 +IM 2 or 3
Noise
Tuner ADC
Typical Tests for Noise Figure, IP2, IP3, Phase Noise and Spurious Signals
Frequency
ADC Full Scale
Spurs
15Use or disclosure of data contained on this sheet is subject to the restrictions on the title page. Copyright © 2012, 2015 DRS Technologies, Inc. Proprietary information. .
Non-linearity in Radios Cause Spurious Issues…IP2 & IP3
Two signals in the non-linear portion of the transfer curve will cause IM2 & IM3 (Intermods)…If a mixer, the spurs can be (Harmonics of RF X LO)
16Use or disclosure of data contained on this sheet is subject to the restrictions on the title page. Copyright © 2012, 2015 DRS Technologies, Inc. Proprietary information. .
A Better DR Test for Tuners Working with Real World Signals (Used by the telephone companies for 75 years)
17Use or disclosure of data contained on this sheet is subject to the restrictions on the title page. Copyright © 2012, 2015 DRS Technologies, Inc. Proprietary information. .
Testing and Evaluation…Real World and Simulation
Real World RF Spectra – testing for intermodulation (IM) distortions (spurious signals)…IP2 ~ IM2, IP3 ~ IM3…etc. created by non-linearity in tuner.
Noise Power Ratio NPR testing – Substituting controlled noise for multiple signals and looking into the notch to measure IM’s created by non-linearity in tuner.
18Use or disclosure of data contained on this sheet is subject to the restrictions on the title page. Copyright © 2012, 2015 DRS Technologies, Inc. Proprietary information. .
Real World Spectrum…Detecting RF Intermods & (XRF times XLO) in Tuners
SignalGenerator
Power Splitter
Antenna
FFT
Tuner Under Test
ADC
Wanted Signal
?? ?
??
Step Attenuator
Amplitude test for real signals Attenuate antenna signals by 3 dB Did ? Signal drop by 3 dB If dropped by 6 dB then it is an IM2 If it dropped by 9 dB than it is an IM3
Frequency test for real signals Tune UUT by 1/10 th FFT bandwidth Did ? Signal move 1/10th
If moved 2X then it is an IM2 If moved 3X then it is an IM3
Note! 1X RF times LO harmonic spurs can only be detected by the frequency test
19Use or disclosure of data contained on this sheet is subject to the restrictions on the title page. Copyright © 2012, 2015 DRS Technologies, Inc. Proprietary information. .
Noise Power Ratio Testing Comparisons
1. Tune radio UUT #1 & #2 to middle of 1st notch2. Set SG frequency to tuned radio a level of 10 dB SNR3. Reduce attenuator (raise noise) until 7 dB SNR4. Switch out notch and measure noise5. NPR is difference between step 3 and 46. Move tuning to next notch and repeat
SignalGenerator
Power AmpLow Pass Filter
Noisey Resistor
UUT # 1
UUT # 2
Attenuator
-77 dB/Hz
-84 dBm/Hz into UUT
1000 MHz
Home Brew NPR Test Set
Power combiner and
splitter
-78 dB/Hz
(Max of +6 dBm@1GHz BW)
-174 dBm/Hz + R noise
20Use or disclosure of data contained on this sheet is subject to the restrictions on the title page. Copyright © 2012, 2015 DRS Technologies, Inc. Proprietary information. .
Causes of Out-of-Band Noise Inside Notch :
• Non-linear stages between antenna and mixer/IFA…….
• 1st and 2nd IF responses
• 1st and 2nd image responses
• All possible third order responses
• All possible second order responses
• Reciprocal mix of LO phase noise
• All M X N mixer combinations that make a 1st IF response
21Use or disclosure of data contained on this sheet is subject to the restrictions on the title page. Copyright © 2012, 2015 DRS Technologies, Inc. Proprietary information. .
Super-heterodyne Architecture
RFOutput
PostselectorPower amp
1st mixer2nd IF BPF2nd mixer1st IF IF amp DAC
1st LO synthesizer2nd LO
synthesizer
ADC clock
Data
Rx
Tx
22Use or disclosure of data contained on this sheet is subject to the restrictions on the title page. Copyright © 2012, 2015 DRS Technologies, Inc. Proprietary information. .
Zero IF Architecture
Optional BPF
Optional BPF
Rx
Tx Amp
DAC
ADC clock
Amp
DAC
RFOutput
Power amp
LO synthesizer
LPF
LPF
0
90
Powercombiner
“I” mixer
“Q” mixer
"Q”data
“I”data
23Use or disclosure of data contained on this sheet is subject to the restrictions on the title page. Copyright © 2012, 2015 DRS Technologies, Inc. Proprietary information. .
Super-heterodyne vs. Zero IF
Pros:• High quality fixed frequency IF
bandpass filtering• 1/f noise at IF is negligible• Good image and spurious signal
rejection• Good (Superior) dynamic range
Cons:• Higher complexity• Larger size• Higher cost• May be higher power
Pros:• Low cost, small• Simple receiver
architecture• Baseband filtering can
be done digitally or with active filters
Cons:• 1/f noise is amplified• DC offset spur caused by LO rectification
in mixer• Requires image rejecting mixer – Image
(false signal) Tx/Rx spurs about - 45 dB dBc (vs. superhets -90 dBc)
• Second order distortion, nonlinearity creates a signal at 2f.
• Both Rx & Tx respond/transmit LO harmonics
Superhet
Zero IF
24Use or disclosure of data contained on this sheet is subject to the restrictions on the title page. Copyright © 2012, 2015 DRS Technologies, Inc. Proprietary information. .
Types of Preselection to Reduce Out-of-Band (OOB) Interference
Antenna
Preamp
IP2, IP3 & NF Ultimate OOB rejection
Simple Preselection
Protect
200 to 350MHz
350 to 550MHz
550 to 850MHz
850 to 1500MHz
RF in RF
out
Low pass filter for image noise & LO rejection
IP2 , IP 3 & NF
I.L . IP2 , IP3 , Shape factor
Tracking Preselector
Switched Sub-octave Preselection
Number of Bands and IP2 Shape factor
1
2
3
Low pass filter for image noise & LO rejection
Ultimate OOB rejection
Least cost but no 2nd order protection and multiple signal overload issues
2nd order protection but loss problems…Higher Noise Figure
Most protection from OOB interferers & 2nd IMs but higher cost and PCB real estate
25Use or disclosure of data contained on this sheet is subject to the restrictions on the title page. Copyright © 2012, 2015 DRS Technologies, Inc. Proprietary information. .
Issues to Consider…
Product data sheets; general specifications do not adequately predict radio performance in the real world.
Which of the following matter for your specific application?
Cost: A simple lower cost product may fit the need for a specific requirement. – But even with limited frequency applications, zero IF requires a tight preselector BPF to reduce spurious
RF environment: Real world spectral evaluation and testing is essential to avoid damage from RF interferers. Many combinations of large signals can produce “Single Signal Spurious”.
Spurious signals: The presence unwanted signals in a crowded RF spectrum may result in false signals or interference with desired signals.
Performance: It is very difficult to define the metrics to determine “Good Enough” when each surveillance site has varying spectra. Knowledge is key
26Use or disclosure of data contained on this sheet is subject to the restrictions on the title page. Copyright © 2012, 2015 DRS Technologies, Inc. Proprietary information. .
Zero IF vs. Super-heterodyne: Tuners at low signal spectra (300 MHz) On-the-Air Intermod Spurs
A 3 dB change in antenna level resulted in a 6 dB drop in IM’s ….therefore IM2’s
SPURS
Zero IF Superhet
Signal
27Use or disclosure of data contained on this sheet is subject to the restrictions on the title page. Copyright © 2012, 2015 DRS Technologies, Inc. Proprietary information. .
Conclusions• GNU Radio provides a framework for very diverse RF application
development, including specialized, high-performance designs
• In high density signal environments, super-heterodyne Tx/Rx have higher dynamic range – Fewer IMs (Spurious signals)
• Both Zero IF and Superhets benefit from preselection filters that reduce the total number of signals
• In a low signal density environment, a Zero IF may be OK and less expensive but an RF bandpass filter is recommended
• On-the-Air testing for IMs is easy but difficult to quantify
• Noise Power Ratio testing gives the best indication on how radios perform in a high density signal environments vs IP2 and IP3 test
THANK YOU FOR YOUR ATTENTION