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Mitigating Thermal & Power Limitations to Enable 5G
Presented By –Doug Kirkpatrick, CEO
Eridan Communicationsdkirkpatrick@eridancommunications.com
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ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.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
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• 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
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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
ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
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%
ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
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
ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
• 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
= ⋅+
ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
• 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
ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
• 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
= ⋅+
ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
• 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
ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
-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
ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
• 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
ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
• 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
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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
ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
• 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
ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
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
ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
Thanks a lot for your time and attention!
Any questions and/or comments?
18
Q & A
ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
• Backup slides
ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
• 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
ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
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
ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
• 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
ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
• “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
ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
• 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
24
11% Efficiency
ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
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
25
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
ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
Modulated Efficiency across Frequency
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