a sige bicmos e-band power amplifier with 22% pae at 18dbm op1db and 8.5% at 6db back-off leveraging...

A SiGe BiCMOS E-Band Power Amplifier with 22% PAE at 18dBm OP1dB and 8.5%

at 6dB Back-Off Leveraging Current Clamping in a Common-Base Stage

J. Zhao1,2, E. Rahimi1, F. Svelto1, A. Mazzanti1

1University of Pavia, Pavia, Italy2HiSilicon-Technologies, Milan, Italy

Outline

• Motivations

• Current-clamping to improve back-off efficiency for

mm-Wave PAs

• Measurement Results

• Conclusions

2 of 20@ 2017 IEEE International Solid-State Circuits

Conference

2.6: A SiGe BiCMOS E-Band Power Amplifier with 22% PAE at 18dBm OP1dB and 8.5% at

6dB Back-Off Leveraging Current Clamping in a Common-Base Stage

Motivations

• 5G requires high-capacity, high-density, and low-cost backhaul

• 10 GHz spectrum available at E-band (71-76GHz, 81-86GHz)

• Silicon based transceivers reduce costs

[IEEE Network 2014]


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Average efficiency of PAs

4 of 20

𝑃𝐴𝐸 =𝑃𝑂𝑈𝑇 − 𝑃𝐼𝑁𝑃𝑆𝑈𝑃𝑃𝐿𝑌

=

1 −1

𝐺𝑃

𝑃𝑂𝑈𝑇𝑉𝑆𝑈𝑃𝑃𝐿𝑌 𝐼𝑆𝑈𝑃𝑃𝐿𝑌

@ 2017 IEEE International Solid-State Circuits

Conference



• Average efficiency is critical

• PAE at 6dB back-off in silicon E-band PAs is 1-3% only

• Can be improved by scaling supply voltage and

current with POUT

• Wideband voltage modulators are power hungry

• Current modulation is more suitable for mm-Wave

Supply current modulation

• Class-B features 𝐼𝑆𝑈𝑃𝑃𝐿𝑌 ∝ 𝐼𝑅𝐹, but suffers from low

gain and low linearity

• Current clamping is proposed for ISUPPLY modulation,

yielding superior gain, linearity and efficiency


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Clamping technique

Voltage clamping : 𝑉𝑎𝑣𝑒𝑟𝑎𝑔𝑒 ∝ 𝑉𝑅𝐹


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Current clamping


Current clamping is the dual


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Current clamping


Current clamping is the dual: 𝐼𝑎𝑣𝑒𝑟𝑎𝑔𝑒 ∝ 𝐼𝑅𝐹


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Current clamping in Common-Base

CBE = 0

LECBE=1/ω2


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Ipk

-Ipk

0

2IpkIE

IIN

IL

• Average current of Q1 tracks quickly the

envelope of IIN

• 50% supply current (and power) saving

compared to Class-A biasing

Current clamping with AM input


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fCarrier = 80GHz, fAM= 5GHz

I IN

an

d I

L(m

A)

Common-Base vs Common-Emitter

C.B. and C.E. configurations behave very differently

C.B. enjoys:

• higher breakdown voltage higher PSAT and efficiency

• flat curves and very linear current gain OP1dB near PSAT

@ 2017 IEEE International Solid-State Circuits

Conference


6dB Back-Off Leveraging Current Clamping in a Common-Base Stage11 of 20

1.6V

Common Emitter (C.E.)

VCE [V]

I C[m

A]

Common

Base (C.B.)

3.4V VCB [V]

I C[m

A]

Schematic of two-stage PA

• Common-Base output stage with current clamping

• Near 20dBm PSAT without power combining

• Cascode driver in Class-A for high linearity

• Inter-stage matching (T2) introduces ~x3 current-gain

2.3V 1.8V


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Chip photograph

ST SiGe BiCMOS 55nm with fT=320GHz, fMAX=370GHz


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S-Parameter measurements

• Peak gain = 21dB at 80GHz

• 3dB bandwidth from 71-86GHz

• Unconditionally stable

S11

S22

S21

S12


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Large-signal performances @ 80GHz


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• OP1dB=18dBm, only 1dB lower than PSAT=19dBm

• PAE @ OP1dB = 22% , PAE @ OP1dB-6dB = 8.5%

Gain

PAE

18dBm

0

20

40

60

80

100

120

140

0 5 10 15 20

DC

Cu

rre

nt

[mA

]

Output Power [dBm]

Large-signal measurements @ 80GHz

ISUPPLY of output stage tracks well Pout and reduces to half

from OP1dB to 6dB back-off

Output stage

DC current

Driver DC

current

∝ 𝐏𝐨𝐮𝐭

OP1dBOP1dB-6dB


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Large-signal performances over frequency

>17dBm OP1dB and >20% PAE from 70-90GHz


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Comparison with State-of-the-art

2× or higher efficiency, both at OP1dB and 6dB B.O.


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Conclusions

• Current-clamping in Common-Base is investigated

for ISUPPLY modulation, yielding PAE improvement at

back-off

• A two-stage E-band SiGe BiCMOS PA features

PSAT=19dBm with OP1dB=18dBm (only 1dB distance)

• PAE @ OP1dB = 22% , PAE @ OP1dB-6dB = 8.5%,

remarkably higher than previously reported silicon

PAs at E-band


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Acknowledgments

• Authors thank the RF Dept. of HiSilicon for

technical and financial support

• Authors thank the Huawei Milan - Italy for the

assistance with measurements.


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a sige bicmos e-band power amplifier with 22% pae at 18dbm op1db and 8.5% at 6db back-off leveraging...

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