GaN HPA optimized for telecom - Linearity results & DPD ... Amplificateur... · GaN HPA optimized...

GaN HPA optimized for telecom -Linearity results & DPD assessmentMarch 2017 [email protected]

GaN technology toward 5G

1. Toward 5G with GaN

2. AB class HPA optimization

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Date / Ref doc 2

3. Doherty linearity assessment

4. Conclusion





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4. Conclusion

� Fixed-wireless access as the first phase of 5G deployments� AT&T, Verizon, Nokia trials in the US

� mmWave spectrum: 27.5-28.35 / 37-38.6GHz / 38.6-40 / 57-71 GHz

� Qualcomm Snapdragon X50 5G modem (800 MHz / 28GHz � 5Gb/s)

� Maxlinear (former Broadcom) BCM85100 (FDD / 60 GHz � 10 Gbps)

What is the need?

Toward 5G with GaN – Fixed-Wireless


Date / Ref doc 4

wwWave ICs suitable for 5G fixed-wireless access

� Phase Array antenna and massive MIMO techniques� Ericsson, Huwaei, NTT Docomo & Samsung trials

� User and Spatial multiplexing increasing bit rates

� Beamforming for propagation loss compensation

Front-end technology?

Toward 5G with GaN – TRx for Phase Array

Phase array antenna

TRx device


Date / Ref doc

� Key parameters:� Efficiency

� Dimension, Integration

� Cost

� Linearity

� Broad bandwidth

5

PA

LNAPS

PS

SWSW

GaN technology is offering High Power Density & High PAE

TRx Half-duplex architecture

� To pass spectrum requirement� System figure of merit to translate into component requirement

� Linked to “intrinsic linearity” of the HPA

� Performances defined at back-off vs Psat (due to PDF)

Application requires linearity

Toward 5G with GaN – Design & Challenges

PAE vs Output Average Power


Date / Ref doc

� TX chain to be compatible with Digital Pre-Distorsion system� System validation required

� DPD to be implemented

6

Generation of RF vector Signal

Sampling, Demodulation & Analysis

DPD Loop

DUTDRV

Test Bench Synoptic

� Goals:� Demonstrate high linearity on GH25

� Provide HPA compatible with DPD

� Challenges:� Modeling accuracy

Memory effects (traps, decoupling circuit, …)

New approach for circuit design

Toward 5G with GaN – Design & Challenges

GaN / 10W Run#1

GaN / 10W Run#1

2 Tones Load-pull on GH25 Tr

Simu vs Meas.


Date / Ref doc

� Memory effects (traps, decoupling circuit, …)

� Unbalanced spectrum

7

GaAs / CHA6552-QJGGaN / 10W Run#1





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4. Conclusion

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Main Features� 5.5- 7.5 GHz� Psat > 39dBm� Gain = 18dB� C/I3 = 34dBc @10dB back-off� MERwoDPD = -27dB @30dBm� MERwithDPD < -50dB @30dBm� DC bias: Vd = 25V / IdQ = 340mA� UMS GaN 0.25um / QFN 6x5 / MSL3

AB class HPA – GH25 Example

MER& ACPR (dB) versus Output Power (dBm)Vd=25V, IdQ1=220mA / IdQ2=200mA


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25 26 27 28 29 30 31 32 33 34 35 36

ME

R &

AC

PR

(dB

)

Average Output power (dBm)

MER w/o DPD

MER with DPD

ACPR w/o DPD

ACPR with DPD

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GaN HPA compatible with low consumption DPD

>20dB

Vd=25V, IdQ1=220mA / IdQ2=200mAQAM256 / CS=56MHz / RRC=0.2

� RUN1: Classical trade-off Pout/PAE� PSAT > 3W/mm (@8dBcomp)

� PAEmax # 35%

� High Linear Gain # 22dB

� Smooth compression

� Wide band

AB class HPA – Way to design

Run1


Date / Ref doc

� RUN2: Linearity oriented � Same output stage size

� Tighter AM/AM & AM/PM variation

� Optimum impedance & biasing for IM3

� Back-off between stages increased

� Enhanced on chip decoupling

� 2nd harmonic load

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☺ C/I3 improved & flattened� Linear Gain & Frequency Band reduced

Run2

AB class HPA – Designs Comparison

IMD3 vs PoutAt nominal biasing

IMD3 vs PoutAt optimum biasing

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IMD

3 (d

Bc)

IMD3_Low Run#1@NominalIMD3_High Run#1@NominalIMD3_LOW Run#2@NominalIMD3_High Run#2@Nominal

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IMD

3 (d

Bc)

IMD3_Low Run#1@Optimum

IMD3_High Run#1@Optimum

IMD3_LOW Run#2@Optimum

IMD3_High Run#2@Optimum


Date / Ref doc 11

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IMD

3 (d

Bc)

Output Power DCL (dBm)

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IMD

3 (d

Bc)


IMD3 improvement at 30dBm (# 10 B.O.)� Linearity better around average power for a 256QAM signal

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IMD

3 (d

Bc)

IMD3_LOW @10kHzIMD3_High @10kHzIMD3_Low @100kHzIMD3_High @100kHzIMD3_Low @1MHzIMD3_High @1MHzIMD3_Low @2MHzIMD3_High @2MHzIMD3_Low @5MHzIMD3_High @5MHzIMD3_Low @10MHzIMD3_High @10MHzIMD3_Low @20MHz

IMD3 vs Pout – Run#2∆F = 10 kHz to 40MHz

Spectrum – Run#2PAVG=30dBm / I DQnom

QAM256 / CS=56MHz / Poly-DPD

AB class HPA – Enhanced decoupling

ACPR # 34dB


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IMD

3 (d

Bc)


IMD3_Low @20MHzIMD3_High @20MHzIMD3_Low @30MHzIMD3_High @30MHzIMD3_Low @40MHz

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Enhanced decoupling from kHz to MHz ensurebalanced spectrum in modulation

Un-balanced tones at 10KHzFully balanced tones from 100kHz to 40MHz Fully balanced spectrum each side

of 56MHz signal bandwidth

Run#1F=7GHz / Pout AVG=30dBm / I DQnom


Run#2FRF=7GHz / Pout AVG=30dBm / I DQnom


AB class HPA – Spectrum with & w/o DPD


Date / Ref doc 13

Intrinsic ACPR improvement and balanced correction on Run#2� Run#2 design easily linearizable with DPD

ACPRwithDPD – ACPRw/oDPD # 20dBACPRwithDPD – ACPRw/oDPD # 5dB

Run#1F=7GHz / Pout AVG=30dBm / I DQnom


Run#2FRF=7GHz / Pout AVG=30dBm / I DQnom

QAM256 / CS=56MHz Poly-DPD

AB class HPA – Constellation with DPD

MER = -33dB (with DPD) MER = -57dB (with DPD)


Date / Ref doc 14

Constellation with DPD Constellation with DPD

Less distortion, dynamic effects and noise on Run#2 � Better Modulation Error Ratio





Date / Ref doc 15


4. Prospects

� Doherty is very suitable for application with PAR providing constant PAE at back-off

Doherty – Suitable for high PAR

AB/B class PAE & PDF vs P AVG Doherty PAE & PDF vs P AVG

PDF PAE PDF PAE


Date / Ref doc 16

Pout dBm

Pout(t)

Pout dBm

Pout(t)

PAE Classe BPAE Souhaitée

� Doherty behaviour difficult to predict� Modulation of the main amplifier drain load by the peak amplifier

� AM/AM & AM/PM sensitive to bias

� Compatibility with DPD to be assessed

Doherty – Linearity is a challenge

Zc, λ/4

90°

Main (AB/B class)

Example of AM/AM & AM/PM vs biasing


Date / Ref doc 18

90°

Peak (C class)

PAE Main

PAE Peak

PAE Doherty

Pout

PAE

PSATPOBO

35

40

7.1 GHz

7.5 GHz

Doherty – GH25 Q-MMIC Example

Main Features� 7-8 GHz� Psat > 42dBm� Gain > 18dB� C/I3 > 20dBc @10dB back-off� MERwoDPD = -24dB @32dBm� MERwithDPD = -48dB @32dBm� PAE > 24% @32dBm� UMS GaN 0.25um / QFN 8x8

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0

5

10

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25

30

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PAE

(%)

Output power (dBm)

7.5 GHz

7.9 GHz

18

DPD able to linearize Doherty PA

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ME

R &

AC

PR

(dB

)

Average Output power (dBm)

MER w/o DPD

MER with DPD

ACPR w/o DPD

ACPR with DPD

PAE >24%

# 14dB

MER = -48dB (with DPD)

Doherty – Spectrum with & w/o DPD

Doherty with & w/o DPDF=7.3GHz / Pout AVG=32dBm / I DQopt


Doherty with DPDF=7.3GHz / Pout AVG=32dBm / I DQopt



Date / Ref doc 19

Significant ACPR improvement with DPD. Low dynamic effects. � DPD capability demonstrated with Doherty PA

ACPRwithDPD – ACPRw/oDPD # 15dB

Synthesis

System Validation – Modulation & DPD

w/o DPD DPD w/o memory DPD with memory

Run#1 ACPR=-30dBcMER=-26dB

ACPR=35dBcMER=-33dB

ACPR=39dBcMER=-34dB

Run#2 ACPR=-35dBcMER=-28dB

ACPR=57dBcMER=-55dB

ACPR=60dBcMER=-57dB

Doherty ACPR=-28dBc ACPR=-52dBc ACPR=-56dBc


Date / Ref doc 20

MER=-24dB MER=-48dB MER=-50dB

AB class Run#2 � significant improvement vs Run#1Doherty � promising results





Date / Ref doc 21


4. Conclusion

Conclusion

Linear HPA can be achieved with GaN Technology


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Low consumption DPD able to linearize GaN HPA(AB class and also Doherty PA)

GaN a good candiate for future of telecom applications (PtP booster / 5G BTS TRx module)


Date / Ref doc 23

THANK YOU

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