doc.: ieee 802.11-09/1213r1 submission november 2009 vinko erceg, broadcomslide 1 60 ghz impairments...

November 2009

Vinko Erceg, Broadcom

Slide 1

doc.: IEEE 802.11-09/1213r1

Submission

60 GHz Impairments Modeling

Date: 2009-11-19

Authors:

Name Affiliations Address Phone Email

Vinko Erceg Broadcom San Diego 858 521-5885 [email protected]

Murat Messe Broadcom

Alireza Tarighat Broadcom

Michael Boers Broadcom

Jason Trachewsky Broadcom

Changsoon Choi IHP [email protected]

November 2009


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doc.: IEEE 802.11-09/1213r1

Submission

Revision History

• Rev1: Phase Noise and CMOS PA AM-AM model parameters were updated

November 2009


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doc.: IEEE 802.11-09/1213r1

Submission

Outline

• PA non-linearities (distortion) modeling• PA Output Backoff (OBO)• Phase noise modeling• Carrier frequency offset and symbol clock modeling• I/Q Imbalance modeling

November 2009


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doc.: IEEE 802.11-09/1213r1

Submission

PA Non-Linearities Modeling (1)

• Input signal x(t) to an amplifier produces output signal y(t):

PM)-(AM distortion phase theis ))((

AM)-(AM distortion (gain) amplitude theis )(

where

))(()(2cos)(

))(2cos()()(

tA

tAG

tAttftAGy(t)

ttftAtx

c

c

November 2009


Slide 5

doc.: IEEE 802.11-09/1213r1

Submission

PA Non-Linearities Modeling (2)

• Popular approaches to model G and are:– Saleh Model [1]

• Both amplitude and phase distortion are modeled• This model was originally developed for the Traveling Wave Tube Amplifiers

(TWTA)• For some parameter settings output power decreases as input power increases• May be used for some Solid State Power Amplifier (SSPA) applications

– Rapp model [2]• Originally developed to model only amplitude distortion• Suitable for SSPA modeling

– Modified Rapp Model [3,5]• Phase distortion modeling was added • Suitable for SSPA modeling

– Ghorbani model [4]• Both amplitude and phase distortion is modeled• Suitable for SSPA modeling

November 2009


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doc.: IEEE 802.11-09/1213r1

Submission

Ghorbani Model

• Both amplitude and phase distortions are modeled by 4 parameters:

A1

)(

A 1

)(

43

1

43

1

2

2

2

2

yAy

AyA

xAx

AxAG

y

y

x

x

November 2009


Slide 7

doc.: IEEE 802.11-09/1213r1

Submission

Rapp AM-AM Model

• Amplitude distortion (AM-AM) in Rapp model is modeled as:

level saturation theis

factor smoothness theis

signalgain small theis

where

1

)(2

12

sat

ss

sat

A

s

g

AgA

AgAG

November 2009


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doc.: IEEE 802.11-09/1213r1

Submission

Modified Rapp AM-PM Model

• See reference [3] for modified Rapp model that includes also phase distortion modeling

• Phase distortion (AM-PM) may be also modeled as:

• The above equation is used for our modeling purposes

2

1

1

)(q

q

A

AA

November 2009


Slide 9

doc.: IEEE 802.11-09/1213r1

Submission

802.11n PA Distortion Model [7] Example

IM1 PA non-linearity

Simulation should be run at an oversampling rate of at least 4x. Use RAPP power amplifier model as specified in document 00/294 with p = 3. Calculate backoff as the output power backoff from full saturation:

PA Backoff = 10 log10(Average TX Power/Psat).Total TX power shall be limited to no more than 17 dBm.Disclose: (a) EIRP and how it was calculated, (b) PA Backoff, and (c) Psat per PA.Note: the intent of this IM is to allow different proposals to choose different output

power operating points.Note: the value Psat = 25dBm is recommended.

Note: AM-PM is not modeled

November 2009


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doc.: IEEE 802.11-09/1213r1

Submission

GaAs PA Model (1)

• GaAs PA Model– In [5], a 802.15.3c PA distortion model was proposed based on the

GaAs pHEMT 60GHz HPA measurements from NEC– The NEC GaAs PA characteristics seem to have similar trend to other

published/measured amplifier characteristics in this class• Characteristic AM-AM and AM-PM curves• Modified Rapp or Ghorbani models may be used for fitting the AM-AM

and AM-PM experimental data points• We use modified Rapp model

– Least squares fitting function– Voltage is rms– Highest voltage AM-PM point was not included in the modeling (does not

follow trend)

November 2009


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doc.: IEEE 802.11-09/1213r1

Submission

GaAs PA Model (2)

November 2009


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doc.: IEEE 802.11-09/1213r1

Submission

GaAs PA Model (3)

November 2009


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doc.: IEEE 802.11-09/1213r1

Submission

GaAs PA Model (4)

• Modified Rapp model parameters for NEC GaAs PA– AM-AM parameters

• g = 19

• Asat = 1.4

• s = 0.81

– AM-PM parameters• = - 48000

• = 0.123

• q1 = 3.8

• q2 = 3.7

November 2009


Slide 14

doc.: IEEE 802.11-09/1213r1

Submission

CMOS PA Model (1)

• We use the measured data from a 65 nm CMOS 60 GHz PA in reference [6]– Modified Rapp or Ghorbani models may be used for fitting the AM-

AM and AM-PM experimental data points

– We use modified Rapp model• Least squares fitting function

• Voltage is rms

• AM-PM response was normalized so that the first point has Phase = 0o

November 2009


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doc.: IEEE 802.11-09/1213r1

Submission

CMOS PA Model (2)

November 2009


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doc.: IEEE 802.11-09/1213r1

Submission

CMOS PA Model (3)

November 2009


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doc.: IEEE 802.11-09/1213r1

Submission

CMOS PA Model (4)

• Modified Rapp parameters for CMOS PA– AM-AM parameters

• g = 4.65

• Asat = 0.58

• s = 0.81

– AM-PM parameters• = 2560

• = 0.114

• q1 = 2.4

• q2 = 2.3

November 2009


Slide 18

doc.: IEEE 802.11-09/1213r1

Submission

PA Output Backoff (1)

• PA Output Backoff (OBO) may be defined as:

where P is either PA saturation point or 1 dB PA compression point

• OBO is related to:– Meeting spectrum mask requirements

– Increasing modulation accuracy (reducing EVM)

– Reducing Adjacent Channel Interference (ACI)

P

PowerTXAverageOBO

__log10 10

November 2009


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doc.: IEEE 802.11-09/1213r1

Submission


• OBO values for OFDM system reported in [9-11] relative to the 1 dB PA compression point are approximately 6 dB for 64 QAM modulation with R = ¾ coding

• OBO value for OFDM system reported in [10] relative to the PA saturation point is approximately 9 dB for 64 QAM modulation with R = ¾ coding

• OBO values for OFDM system reported in [11] relative to the 1 dB PA compression point are approximately 4.5 dB for 16 QAM modulation with R = ¾ coding (performance degradation of 1.5 dB)

• Theoretical OBO value for Single Carrier (SC) GMSK modulation is 0 dB– OBOSC_GMSK = 0.5 dB may be used

November 2009


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Submission


Modulation Accuracy (dB)EVM

OBO (dB) Spectrum Mask Requirements

Mod. Accuracy Requirements

OBO Requirement

November 2009


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doc.: IEEE 802.11-09/1213r1

Submission

Phase Noise Model (1) • Phase noise may be reasonably modeled by a two pole –

one zero model

• We propose the following parameters of the model:– PSD(0) = -90 dBc/Hz

– Pole frequency fp = 1 MHz

– Zero frequency fz = 100 MHz

– PSD(infinity) = -130 dBc/Hz

))/(1

)/(1)0()(

2

2

p

z

ff

ffPSDfPSD

November 2009


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doc.: IEEE 802.11-09/1213r1

Submission

Phase Noise Model (2)

November 2009


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doc.: IEEE 802.11-09/1213r1

Submission

Frequency Offset/Symbol Clock Accuracy

• Symbol clock frequency tolerance in most systems is specified at +/- 20 ppm– Reasonable cost/performance tradeoff

• Frequency offset of –13.675 ppm at the receiver, relative to the transmitter may be used [7]

• The symbol clock of the same relative offset as the carrier frequency offset may be used

November 2009


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doc.: IEEE 802.11-09/1213r1

Submission

I/Q Imbalance Modeling (1)

• Following model may be used for I/Q imbalance modeling [8]:

where y(t) is the ideal complex transmit signal, yd(t) is the distorted complex signal, and distortion coefficients are given as

where θ and α are phase and gain imbalances, respectively

)(*)()( tytyty rrd

)2/sin()2/cos(

)2/sin()2/cos(

rrrr

rrrr

jv

j

November 2009


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doc.: IEEE 802.11-09/1213r1

Submission


0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.515

20

25

30

35

40

45

50

55

IQ gain imbalance (dB)

TX

EV

M (

dB)

TX EVM vs. flat TX IQ imbalanace (with no pre-compensation), TX Floor SNR of 50dB

Phase imb. =0

Phase imb. =1

Phase imb. =2

Phase imb. =3

Phase imb. =4

Phase imb. =5

Phase imb. =6

Tx

EV

M (

-dB

)

November 2009


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doc.: IEEE 802.11-09/1213r1

Submission


• We propose that including I/Q imbalance in the simulations be optional

• Slides presented here regarding I/Q imbalance may serve as a reference

November 2009


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doc.: IEEE 802.11-09/1213r1

Submission

Conclusion

• We propose the following impairments/parameters to be included in the simulations:– PA distortion

– OBO

– Phase noise

– Frequency/Symbol Clock offset

• We propose that inclusion of the I/Q imbalance impairment is optional

November 2009


Slide 28

doc.: IEEE 802.11-09/1213r1

Submission

References• [1] A.A.M. Saleh, "Frequency-independent and frequency-dependent nonlinear

models of TWT amplifiers," IEEE Trans. Communications, vol. COM-29, November 1981, pp.1715-1720.

• [2] C. Rapp, "Effects of HPA-Nonlinearity on a 4-DPSK/OFDM-Signal for a Digital Sound Broadcasting System", in Proceedings of the Second European Conference on Satellite Communications, Liege, Belgium, Oct. 22-24, 1991, pp. 179-184.

• [3] M. Honkanen and Sven-Gustav Haggman, “New Aspects on Nonlinear Power Amplifier Modeling in Radio Communication System Simulations”, Proc. IEEE Int. Symp. On Personal, Indoor, and Mobile Comm, PIMRC ’97, Helsinki, Finland, Sep.1-4, 1997, pp. 844-848.

• [4] A. Ghorbani, and M. Sheikhan, “The effect of Solid State Power Amplifiers (SSPAs) Nonlinearities on MPSK and M-QAM Signal Transmission”, Sixth Int'l Conference on Digital Processing of Signals in Comm., 1991, pp. 193-197.

• [5] IEEE Document 15-06-0477-01-003c-rf-impairment-models-60ghz-band-sysphy-simulation.pdf.

• [6] Mikko Varonen, et. al. “Millimeter-Wave Amplifiers in 65-nm CMOS”. ESSCIRC 2007. 11-13 Sep. 2007. pp. 280-283.

• [7] IEEE Document 11-03-0814-31-000n-comparison-criteria.doc.• [8] Alireza Tarighat, and Ali H. Sayed, “Joint Compensation of Transmitter and

Receiver Impairments in OFDM Systems,” IEEE Transactions on Wireless Communications, VOL. 6, NO. 1, January 2007, pp. 240-247.

November 2009


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doc.: IEEE 802.11-09/1213r1

Submission

References• [9] Yongwang Ding and Ramesh Harjani, “A High-Efficiency CMOS +22-dBm

Linear Power Amplifier,” IEEE Journal of Solid-State Circuits, VOL. 40, NO. 9, September 2005, pp. 1895-1900.

• [10] Mostafa Elmala, Jeyanandh Paramesh, and Krishnamurthy Soumyanath, “A 90-nm CMOS Doherty Power Amplifier With Minimum AM-PM Distortion,” IEEE Journal of Solid-State Circuits, VOL. 41, NO. 6, June 2006, pp. 1323-1332.

• [11] Mathias Pauli, Udo Wachsmann, Magnus Sundelin, and Peter Schramm, “Transmitter Impairments in OFDM-Based Wireless LAN,” Vehicular Technology Conference, 53rd VTC 2001 Spring, VOL 1, 6-9 May 2001, pp. 692 – 696.

doc.: ieee 802.11-09/1213r1 submission november 2009 vinko erceg, broadcomslide 1 60 ghz impairments...

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