1 IEEE Energy Efficiency Tutorial · 14/09/2018 · •5G New-Radio modulation •Heat flows in...

Mitigating Thermal & Power Limitations to Enable 5G

Presented By –Doug Kirkpatrick, CEO

Eridan [email protected]

1st IEEE Energy Efficiency Tutorial:

Wednesday, September 19, 2018

ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.

• 5G New-Radio modulation• Heat flows in Transmitters and Arrays• Physically available options• Where we are now• Paths forward

OVERVIEW

2


• It is well known that linear amplifiers operate with low efficiency on OFDM-style signals

• The scale of 5G is unprecedented• An inefficient network may be unsustainable• The solution is to use sampling theory instead of linear

network theory

We are here because…

3


1%

10%

100%

0 2 4 6 8 10 12 14

Effic

ienc

y

Signal PAPR (dB)

Linear PA Efficiency: Business Impact

5G-NR

2G

LTE-UL3G2.5G

0

1

2

3

4

5

6

7

8

9

10

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Pow

er /

Outp

ut p

ower

(Nor

mal

ized)

Circuit Energy Efficiency

Input Power

Power Dissipation

Power supply size

TX powerHeatsink

size

5G-NR

2G

LTE

3G2.5G

COST

Efficiency vs. PAPR Cost vs. Efficiency

• Signal design progression forces linear PA efficiency to decrease• First cost and operating costs increase

Higher input power is required (larger power supply) Thermal management of the PA heat (larger heatsink)

• Preferred efficiency range by industry: between 40 to 70 %• 5G must be profitable to build and operate – or it will fail

4

LTE-DL

Target zone

Linear PA upper limit


0

0.005

0.01

0.015

0.02

0.025

0.03

0 0.5 1 1.5 2 2.5 3 3.5

I C(A

)

VCE (V)GaAs HBT

Envelope PDF

Signal envelope

• Entire output signal –peak to peak – must fit within the linear PA load line

• PA is scaled for signal peak power

• Signal average power sets communication range

• Low average power increases PA heat Remains near the maximum

power dissipation

Linear PA Efficiency Ceilings

5

for 5G-NR

Power dissipation contours

5G-NR best linear PA efficiency is 10.6%


HEAT• Outer transmitters are

“electric blankets” to the inner transmitters

• Center elements get very hot• Constrains the achievable

size of active antenna arrays

Active Antenna Array Challenge

6


• Actual transmitter objective: modulation accuracy at-power

• Traditional approach: Linear Network TheoryModulate at small signal levels Increase signal power with linear amplifiersMaintains modulation accuracy, as long as all amplifiers

remain linear (mathematical sense)

• Alternative approach: Sampling Theory

Options – Look to Physics

7

VDD

VIN

RL

POUT

out D LV I R= ⋅

VDD

Large VIN

RL

PSAT

RON

SUPPLYout L

L ON

VV RR R

= ⋅+


• Nyquist showed how sampling is used to maintain waveform accuracy

• Sampling circuitry is inherently nonlinear Exactly what Ohm’s Law requires to achieve energy efficiency

• Fourier theory still applies Circuit speed must be sufficiently fast to properly resolve the samples

Sampling Theory in Transmitters

8


• Phase modulated carrier samples the signal envelope

• Dynamic Power Supply (DPS) sets the instantaneous envelope value

• Switch-mode mixer modulator (SM3) does the sampling at-power

• Switching forces use of polar signal processing

Sampling Transmitter Operation

9

( )( )( )cosA t t tω φ+

)(tA

SM3

DPS

VSUPPLY

Envelope

Phase Modulated RF

( )( )cos t tω φ+

0 0.5 1 1.5 2 2.5 3 3.50

0.2

0.4

0.6

0.8

1

VDS (V)

Dra

in C

urre

nt (A

)

Dynamic Power Supply

SUPPLYout L

L ON

VV RR R

= ⋅+


• DPS has a DC-DC converter and linear regulator (LAM) in series

• LAM stays efficient because the voltage drop across it remains very small

Sampling TX In Action

10


-70

-60

-50

-40

-30

-20

-10

0

10

780 785 790 795 800 805 810 815 820

• Use of switching circuitry greatly improves measured efficiency

• Modulation accuracy is maintained

• Modulation generality is not compromised

• Reported efficiency is fully linearized

Measured Efficiency vs. Signal PAPR

11

16384 QAM LTE Downlink 5G-NR

-51dB ACLR

0%

10%

20%

30%

40%

50%

60%

70%

0 2 4 6 8 10 12 14

Stac

k Effi

cienc

y

Signal PAPR (dB)

5G NR

LTE DL

LTE UL

3G

QAMs

EDGE

GSM-CE

Keysight measurement


• 0.72% EVM• -54 dB ACLR• 43.3% Efficiency

inclusive of linearizer Improves with CFR

• 2.5W Peak envelope power

• 10.0 dB PAPR Innate signal used here

LTE using 256-QAM: Downlink

0%

10%

20%

30%

40%

50%

60%

70%

0 2 4 6 8 10 12 14St

ack

Effic

ienc

ySignal PAPR (dB)

5G NRLTE DLLTE UL3GQAMsEDGEGSM-CEmodelMAEE

LTE-256 DL

PSD

(dB

)

Frequency (MHz)

12


• Traditional power amplifier must achieve all required parameters• Spreading the precision driver points improves options for local and

global optimization

Spreading the Key Performance Points

13

Traditional Linear Amplifier Direct Polar SM3

Critical Design ParameterFrequency Agility

Modulation AccuracyOutput Power

Power Efficiency

BUT:Need Δt ≤ 100ps


Architecture Trade-offsTraditional Linear Amplifier Direct Polar SM3

Feature Linear TX Doherty TX MIRACLE TXTuning range (fhigh : flow) 1.22 : 1 1.22 : 1 50 : 15G signal efficiency 9% 22% 43%Data density (max) 6 bps/Hz 6 bps/Hz >14 bps/HzPower supply (W) 1x (normalized) 0.4x 0.2xHeat absorber (m3) 8.4x 2.5x 1x (normalized)Maximum frequency ft / 3 ft / 6 ft / 10

Comparison is at the dashed outline

14


• Sampling based transmitter; measured efficiency • Costs fall for all of the present modulations

Input power is reduced by 2x to 6x Heatsink size drops by 3x to 7x

• All signal types are in the industry-preferred efficiency range : 40 to 60 %• 5G can now be profitable to build and operate

Net Business Impact

15

1%

10%

100%

0 2 4 6 8 10 12 14

Effic

ienc

y

Signal PAPR (dB)

Efficiency Target zone


This is real – Hardware is here now

140nm GaN SM3 MMIC

140nm GaN DPS MMIC

16384-QAM output signal measurement

ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.17

Conclusions

• Generating 5G-NR and LTE-256 signals with simultaneous• 43% / 47% fully-linearized TX energy efficiency• ACLR: -54 dB (LTE-256 signal) ; -52 dB (5G-NR signal) • 0.7% EVM (LTE-256 signal)

• Use sampling theory, not linear network theory• Modulation agnostic: fully backward compatible• Also forward compatible:

• Keysight lab validated 16,384-QAM with 0.4% EVM


Thanks a lot for your time and attention!

Any questions and/or comments?

18

Q & A


• Backup slides


• Now have >80dB direct envelope control Prior polar controlled envelope

dynamic range was ∼35 dB Path to 130dB

• “Good enough” ρ(t) = 0 Enables QAM & LTE Enables very high order QAM & LTE

Keys to Success: Magnitude Dynamic Range


Keys to Success: Drain-lag Solved

• Both long-term and short-term effects are moved outside of the SM3 operating area

• Required modification of the FET devices

21

Repetition period: 0.051 s

Peak power is 2.5 W


• Extremely reliable SM3 device timing is critical Ron vs. Vgs uniformity Proper foundry process is key Switch based design also key

• It exists – proof is in handMultiple devices from multiple wafers

with no change to calibration tables

Keys to Success: Switch Resistance Consistency


• “Conservation of Power” actually models Conservation of Energy

• Output power is specified Normalize to POUT

• Power dissipation (PD) is not wanted

• Design to minimize PD

Power Flow in Transmitters

Power Dissipation (heat)(bad)

Power In

Signal Power Out(good)

Signal Power In

PIN

PDC

POUT

PD

DC IN OUT DP P P P+ = +

1 for small OUT DIN

DC IN DC

P P PP P P

η ≡ −+

0

1

2

3

4

5

6

7

8

9

10

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Pow

er /

Outp

ut p

ower

(Nor

mal

ized)

Circuit Energy Efficiency

Input Power

Power Dissipation

Power supply size

TX powerHeatsink

size27%

70%

Conservation relation

Minimize PD for best efficiency

23

PDC

PINPOUT

PD

PDC

PINPOUT

PD

Efficiency

Efficiency


• Improve transmitter efficiency reduce size (and cost) of the

power supply reduce size (and cost) of the

heatsink

LTE Downlink Case (to scale)Power In

PDC

Signal Power Out(good)

Power Dissipation (bad)

Signal Power In

PIN

POUT

PD

Thermal Resistance (deg C/watt)

HeatsinkAmbient temperature

Temperature rise (deg C)

Linear Transmitter Efficiency < 11% by the design of the LTE signal

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11% Efficiency


Linear Operation• Output range is bounded

by the knee voltage• Signal always stays on the

load line

Switching Operation• Output range is bounded

by the ON resistance• Circuitry operates at the

endpoints of the load line• Efficiency increases

Implementation Differences

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0 0.5 1 1.5 2 2.5 3 3.50

0.2

0.4

0.6

0.8

1

VDS (V)

Dra

in C

urre

nt (A

)

0

0.005

0.01

0.015

0.02

0.025

0.03

0 0.5 1 1.5 2 2.5 3 3.5

I C(A

)

VCE (V)

ON state

OFF state

VDD

Large VIN

RL

PSAT

RON

VDD

VIN

RL

POUT


Modulated Efficiency across Frequency

1 IEEE Energy Efficiency Tutorial · 14/09/2018 · •5G New-Radio modulation •Heat flows in...

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Transcript of 1 IEEE Energy Efficiency Tutorial · 14/09/2018 · •5G New-Radio modulation •Heat flows in...