1 st IEEE Energy Efficiency Tutorial: Mitigating Thermal & Power Limitations to Enable 5G Presented By – Doug Kirkpatrick, CEO Eridan Communications dkirkpatrick@eridancommunications.com Wednesday, September 19, 2018
OVERVIEW • 5G New-Radio modulation • Heat flows in Transmitters and Arrays • Physically available options • Where we are now • Paths forward 2 ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
We are here because… • 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theory instead of linear network theory 3 ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
Linear PA Efficiency: Business Impact 5G-NR Cost vs. Efficiency Efficiency vs. PAPR 100% Target zone 10 Power / Output power (Normalized) 2G 9 Input Power Power supply size Linear PA upper limit 2.5G 8 3G Power Dissipation LTE-UL COST Efficiency 7 LTE 5G-NR LTE-DL 6 10% 5 3G2.5G 4 TX power 3 2G Heatsink 2 size 1% 1 0 2 4 6 8 10 12 14 0 Signal PAPR (dB) 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Circuit Energy 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to build and operate – or it will fail 4 ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
Linear PA Efficiency Ceilings for 5G-NR Envelope PDF • Entire output signal – 5G-NR best linear PA efficiency is 10.6% peak to peak – must fit Signal envelope within the linear PA load line • PA is scaled for signal peak power • Signal average power 0.03 0.025 sets communication range 0.02 I C (A) • Low average power 0.015 0.01 increases PA heat Remains near the maximum 0.005 power dissipation 0 0 0.5 1 1.5 2 2.5 3 3.5 GaAs HBT V CE (V) Power dissipation contours 5 ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
Active Antenna Array Challenge HEAT • Outer transmitters are “electric blankets” to the inner transmitters • Center elements get very hot • Constrains the achievable size of active antenna arrays 6 ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
Options – Look to Physics V = I ⋅ R • Actual transmitter objective: modulation out D L V DD accuracy at-power R L • Traditional approach: Linear Network Theory Modulate at small signal levels P OUT V IN Increase signal power with linear amplifiers Maintains modulation accuracy, as long as all amplifiers V DD remain linear (mathematical sense) V SUPPLY V = ⋅ R R L out L R + R L ON P SAT • Alternative approach : Sampling Theory Large V IN R ON 7 ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
Sampling Theory in Transmitters • 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 8 ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
Sampling Transmitter Operation V SUPPLY V = ⋅ R out L R R + L ON 1 • Phase modulated carrier samples the signal envelope 0.8 • Dynamic Power Supply (DPS) Drain Current (A) sets the instantaneous 0.6 envelope value • Switch-mode mixer modulator 0.4 V SUPPLY (SM 3 ) does the sampling at- 0.2 power ( t ) A Envelope DPS 0 0 0.5 1 1.5 2 2.5 3 3.5 • Switching forces use of polar V DS (V) cos ( ) ( ) ω t + φ t ( )cos ( ) signal processing ( ) A t ω t + φ t Dynamic Power Supply Phase SM 3 Modulated RF 9 ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
Sampling TX In Action • DPS has a DC-DC converter and linear regulator (LAM) in series • LAM stays efficient because the voltage drop across it remains very small 10 ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
Measured Efficiency vs. Signal PAPR • Use of switching circuitry 70% greatly improves 60% measured efficiency 5G NR 50% Stack Efficiency • Modulation accuracy is LTE DL 40% LTE UL maintained 30% 3G • Modulation generality is QAMs 20% not compromised EDGE 10% GSM-CE • Reported efficiency is 0% fully linearized 0 2 4 6 8 10 12 14 Signal PAPR (dB) 10 5G-NR 16384 QAM LTE Downlink 0 -10 -20 Keysight -30 measurement -51dB ACLR -40 -50 -60 -70 780 785 790 795 800 805 810 815 820 11 ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
LTE using 256-QAM: Downlink 70% 5G NR LTE-256 DL LTE DL LTE UL 60% 3G QAMs EDGE 50% Stack Efficiency • 0.72% EVM GSM-CE PSD (dB) model 40% MAEE • -54 dB ACLR 30% 20% • 43.3% Efficiency 10% inclusive of linearizer 0% Frequency (MHz) 0 2 4 6 8 10 12 14 Improves with CFR Signal PAPR (dB) • 2.5W Peak envelope power • 10.0 dB PAPR Innate signal used here 12 ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
Spreading the Key Performance Points Direct Polar SM 3 Traditional Linear Amplifier Critical Design Parameter BUT : Frequency Agility Need Δ t ≤ 100ps Modulation Accuracy Output Power Power Efficiency • Traditional power amplifier must achieve all required parameters • Spreading the precision driver points improves options for local and global optimization 13 ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
Architecture Trade-offs Traditional Linear Amplifier Direct Polar SM 3 Comparison is at the dashed outline Feature Linear TX Doherty TX MIRACLE TX Tuning range ( f high : f low ) 1.22 : 1 1.22 : 1 50 : 1 5G signal efficiency 9% 22% 43% Data density (max) 6 bps/Hz 6 bps/Hz >14 bps/Hz Power supply (W) 1x (normalized) 0.4x 0.2x Heat absorber (m 3 ) 8.4x 2.5x 1x (normalized) f t / 3 f t / 6 f t / 10 Maximum frequency 14 ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
Net Business Impact 100% Efficiency Target zone Efficiency 10% 1% 0 2 4 6 8 10 12 14 Signal PAPR (dB) • 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 15 ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
This is real – Hardware is here now 16384-QAM output signal measurement 140nm GaN SM 3 MMIC 140nm GaN DPS MMIC ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
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 17 ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
Q & A Thanks a lot for your time and attention! Any questions and/or comments? 18 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.
Keys to Success: Magnitude Dynamic Range • 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 ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
Keys to Success: Drain-lag Solved Peak power is 2.5 W Repetition period: 0.051 s • Both long-term and short-term effects are moved outside of the SM 3 operating area • Required modification of the FET devices 21 ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
Keys to Success: Switch Resistance Consistency • Extremely reliable SM 3 device timing is critical R on vs. V gs uniformity Proper foundry process is key Switch based design also key • It exists – proof is in hand Multiple devices from multiple wafers with no change to calibration tables ALL INFORMATION SHALL BE CONSIDERED SPEAKER PROPERTY UNLESS OTHERWISE SUPERSEDED BY ANOTHER DOCUMENT.
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