GaN HPA optimized for telecom - Linearity results & DPD assessment March 2017

Transcription

1 GaN HPA optimized for telecom - Linearity results & DPD assessment March 2017 christophe.auvinet@ums-gaas.com

2 GaN technology toward 5G 1. Toward 5G with GaN 2. AB class HPA optimization 3. Doherty linearity assessment 4. Conclusion Date / Ref doc 2

3 GaN technology toward 5G 1. Toward 5G with GaN 2. AB class HPA optimization 3. Doherty linearity assessment 4. Conclusion Date / Ref doc 3

4 Toward 5G with GaN Fixed-Wireless What is the need? Fixed-wireless access as the first phase of 5G deployments AT&T, Verizon, Nokia trials in the US mmwave spectrum: / GHz / / GHz Qualcomm Snapdragon X50 5G modem (800 MHz / 28GHz 5Gb/s) Maxlinear (former Broadcom) BCM85100 (FDD / 60 GHz 10 Gbps) wwwave ICs suitable for 5G fixed-wireless access Date / Ref doc 4

5 Toward 5G with GaN TRx for Phase Array Front-end technology? 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 Phase array antenna TRx device TRx Half-duplex architecture Key parameters: PS PA Efficiency Dimension, Integration SW PS LNA SW Cost Linearity Broad bandwidth GaN technology is offering High Power Density & High PAE Date / Ref doc 5

6 Toward 5G with GaN Design & Challenges Application requires linearity 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) PAE vs Output Average Power TX chain to be compatible with Digital Pre-Distorsion system System validation required DPD to be implemented Generation of RF vector Signal Test Bench Synoptic DRV DPD Loop DUT Sampling, Demodulation & Analysis Date / Ref doc 6

7 Toward 5G with GaN Design & Challenges New approach for circuit design 2 Tones Load-pull on GH25 Tr GaN / 10W Run#1 Goals: Demonstrate high linearity on GH25 Provide HPA compatible with DPD Simu vs Meas. Challenges: Modeling accuracy Memory effects (traps, decoupling circuit, ) Unbalanced spectrum GaN / 10W Run#1 GaAs / CHA6552-QJG GaN / 10W Run#1 Date / Ref doc 7

8 GaN technology toward 5G 1. Toward 5G with GaN 2. AB class HPA optimization 3. Doherty linearity assessment 4. Conclusion Date / Ref doc 8

9 AB class HPA GH25 Example Main Features GHz Psat > 39dBm Gain = 18dB C/I3 = back-off MER wodpd = MER withdpd < DC bias: Vd = 25V / IdQ = 340mA UMS GaN 0.25um / QFN 6x5 / MSL MER& ACPR (db) versus Output Power (dbm) Vd=25V, IdQ1=220mA / IdQ2=200mA QAM256 / CS=56MHz / RRC=0.2 MER & ACPR (db) MER w/o DPD MER with DPD ACPR w/o DPD ACPR with DPD >20dB Date / Ref doc Average Output power (dbm) GaN HPA compatible with low consumption DPD 9

10 AB class HPA Way to design RUN1: Classical trade-off Pout/PAE PSAT > 3W/mm PAEmax # 35% High Linear Gain # 22dB Smooth compression Wide band Run1 C/I3 improved & flattened Linear Gain & Frequency Band reduced RUN2: Linearity oriented Run2 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 Date / Ref doc 10

11 AB class HPA Designs Comparison IMD3 vs Pout IMD3 vs Pout IMD3 (dbc c) At nominal biasing IMD3_Low IMD3_High IMD3_LOW IMD3_High Output Power DCL (dbm) IMD3 (dbc c) Date / Ref doc At optimum biasing IMD3_Low Run#1@Optimum IMD3_High Run#1@Optimum IMD3_LOW Run#2@Optimum IMD3_High Run#2@Optimum Output Power DCL (dbm) IMD3 improvement at 30dBm (# 10 B.O.) Linearity better around average power for a 256QAM signal

12 AB class HPA Enhanced decoupling ) IMD3 (dbc) IMD3 vs Pout Run# F = 10 khz to 40MHz Un-balanced tones at 10KHz Fully balanced tones from 100kHz to 40MHz Output Power DCL (dbm) Spectrum Run#2 P AVG =30dBm / I DQ nom QAM256 / CS=56MHz / Poly-DPD ACPR # 34dB Fully balanced spectrum each side of 56MHz signal bandwidth Date / Ref doc Enhanced decoupling from khz to MHz ensure balanced spectrum in modulation 12

13 AB class HPA Spectrum with & w/o DPD Run#1 F=7GHz / Pout AVG =30dBm / I DQ nom QAM256 / CS=56MHz / Poly-DPD Run#2 FRF=7GHz / Pout AVG =30dBm / I DQ nom QAM256 / CS=56MHz / Poly-DPD ACPR withdpd ACPR w/odpd # 5dB ACPR withdpd ACPR w/odpd # 20dB Intrinsic ACPR improvement and balanced correction on Run#2 Run#2 design easily linearizable with DPD Date / Ref doc 13

14 AB class HPA Constellation with DPD Run#1 F=7GHz / Pout AVG =30dBm / I DQ nom QAM256 / CS=56MHz / Poly-DPD MER = -33dB (with DPD) Run#2 FRF=7GHz / Pout AVG =30dBm / I DQ nom QAM256 / CS=56MHz Poly-DPD MER = -57dB (with DPD) Constellation with DPD Date / Ref doc 14 Constellation with DPD Less distortion, dynamic effects and noise on Run#2 Better Modulation Error Ratio

15 GaN technology toward 5G 1. Toward 5G with GaN 2. AB class HPA optimization 3. Doherty linearity assessment 4. Prospects Date / Ref doc 15

16 Doherty Suitable for high PAR Doherty is very suitable for application with PAR providing constant PAE at back-off AB/B class PAE & PDF vs P AVG Doherty PAE & PDF vs P AVG PDF PAE PDF PAE PAE Souhaitée PAE Classe B Pout dbm Pout dbm Pout(t) Pout(t) Date / Ref doc 16

17 Doherty Linearity is a challenge 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 Main (AB/B class) Zc, λ/4 Example of AM/AM & AM/PM vs biasing 90 PAE Peak (C class) PAE Main PAE Doherty PAE Peak P OBO P SAT Pout Date / Ref doc 18

18 Doherty GH25 Q-MMIC Example Main Features 7-8 GHz Psat > 42dBm Gain > 18dB C/I3 > back-off MER wodpd = MER withdpd = PAE > UMS GaN 0.25um / QFN 8x GHz 7.5 GHz MER & ACPR (db) MER w/o DPD MER with DPD ACPR w/o DPD ACPR with DPD # 14dB PAE (%) GHz PAE >24% Average Output power (dbm) DPD able to linearize Doherty PA Date / Ref doc Output power (dbm)

19 Doherty Spectrum with & w/o DPD Doherty with & w/o DPD F=7.3GHz / Pout AVG =32dBm / I DQ opt QAM256 / CS=28MHz / Poly-DPD Doherty with DPD F=7.3GHz / Pout AVG =32dBm / I DQ opt QAM256 / CS=28MHz / Poly-DPD MER = -48dB (with DPD) ACPR withdpd ACPR w/odpd # 15dB Significant ACPR improvement with DPD. Low dynamic effects. DPD capability demonstrated with Doherty PA Date / Ref doc 19

20 System Validation Modulation & DPD Synthesis w/o DPD DPD w/o memory DPD with memory Run#1 ACPR=-30dBc MER=-26dB ACPR=35dBc MER=-33dB ACPR=39dBc MER=-34dB Run#2 ACPR=-35dBc MER=-28dB ACPR=57dBc MER=-55dB ACPR=60dBc MER=-57dB Doherty ACPR=-28dBc ACPR=-52dBc ACPR=-56dBc MER=-24dB MER=-48dB MER=-50dB AB class Run#2 significant improvement vs Run#1 Doherty promising results Date / Ref doc 20

21 GaN technology toward 5G 1. Toward 5G with GaN 2. AB class HPA optimization 3. Doherty linearity assessment 4. Conclusion Date / Ref doc 21

22 Conclusion Linear HPA can be achieved with GaN Technology 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 22

23 THANK YOU Date / Ref doc 23