Power Reduction in RF

Power Reduction in RF SoC Architecture using MEMS Eric Mercier 1

RF domain overview Technologies Piezoelectric materials Acoustic systems Ferroelectric materials Meta materials Magnetic materials RF MEMS High-Q Passives RF switches Filters & Duplexer Time references Resonators RF module architecture MEMS & Si co-integration Digital-oriented RF design Opportunistic Radio Low power consumption xxparadigm RF CMOS design Ultra-Low Power RF for WSN mmw 60 GHz full-cmos High data rate contactless Impulse UWB 2

MEMS in RF front-end Possible technologies of interest Initially developped for telecom applications 802.15.4 / Zigbee, Bluetooth low energy. 3

AlN process - Packaging Initial uniformity = 0.4% Mo Kt² = 7.1% (state of the art) AlN 1µm Trimming of frequency σimprovement = 6X, f target < 1 MHz Mo Air cavity protected by SiO2 and BCB membranes Fréquence 25 20 15 10 5 0 Before P03 Target=2.11GHz σ = 15 MHz <2.025 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.1 2.11 2.12 Resonnant frequency >2.125 Fréquence After 100 90 80 70 60 50 40 30 20 10 0 <2.06 2.065 2.075 P03 Target=2.11GHz σ = 2,5 MHz 2.085 2.095 2.105 2.115 2.125 2.135 2.145 2.155 >2.16 Resonant frequency Overmolding Underfill BAW filter BGA substrate or IPD 4

SMR BAW filters 100Ω - 100Ω differential filter for WCDMA Rx 36 filters sampling on 200mm wafer containing 20 000 filters Packaging Resonator Quality factor = 1800 Trimming Piezo stack Bragg 200mm Si wafer 5

CRF Filters Filter 50 Ω sing / 50 Ω sing Filter 50 Ω sing /200 Ω diff 40 filters sampling on 200mm wafer containing 40 000 filters Top Piezo Filter 50 Ω diff / 12 Ω diff Coupl Bragg Bot Piezo Bragg Ability to design the filter for various impedance matching ESSDERC 09 6

BAW Duplexer / full-duplex communications Ensure a good rejection of TX band in RX mode High rejection of TX filter in RX band High rejection of RX filter in TX band to avoid saturation effect in RX chain helps power consumption reduction Low Insertion Losses Correct impedance matching on each side Overall filter response impacted by the matching Mismatch means less rejection / more insertion loss very encouraging first results Workshop IMS 09 7

Multi-frequency AlN patterning Process several frequency on a single wafer Approach investigated AlN patterning Workshop IMS 09 0.5 mm AlN Tx (1270 nm) AlN Rx (1110 nm) Bragg mirror 8

BAW VCO and filters Current L/C-based integrated VCO Low-Q / high current consumption for phase noise reduction Piezo-electric resonator High-Q / lower current consumption for better phase noise Passives : lower cost technology than advanced CMOS for passives High performance broad band BAW VCO for UMTS Increased tuning range thanks to negative capacitor Impedance FTR with Cneg ω 2 Shunt Co + Cm + Cneg = LmCm( Co + Cneg) Lm C0 BAW Cm Cneg Cvar ISSCC`08 2 x IMS `09 1 patent Q factor 700 600 500 400 300 200 100 2.8pF 160MHz 1.4pF resonator with Cneg 0.7pF 0.5pF 0.3pF 0.2pF resonator without Cneg 0.1pF 0pF 2.25 2.3 2.35 2.4 Frequency GHz Q series :700 Q shunt : 600 Q shunt : 220 Fseries Fshunt Frequency 9

Digital-oriented TX Architecture From analog to digital TX architecture Compatible with advanced CMOS technologies Easy reconfiguration for multi-standard purposes ANALOG RADIO SINGLE-STANDARD USAGE CogArt`08 VTC `09 2 x patents SIGNAL SOURCE DIGITAL RADIO DAC HIGH RESOLUTION LOW FSAMPLING DAC ANALOG RFIC BiCMOS OPPORTUNISTIC USAGE SAW PA DUPL. SIGNAL SPECTRUM BAW Filtering SIGNAL SPECTRUM SIGNAL SOURCE DIGITAL RFIC CMOS DIGITAL MODULATOR LO DAC DAC LOW RESOLUTION HIGH FSAMPLING BPF PA DUPL. -f S /2 0 (f CH ) f S /2 Freq. -f S /2 0 (f CH ) f S /2 Freq. Use of BAW to recombine the signals LINC architecture Filter out Σ DAC noise ULP RF under investigation 10

Linear Amplification using Non-Linear Components Non-linear PA Q s I (t) Whatever the modulation scheme Very interesting power reduction s I,1 (t) ϕ (t) θ (t) ϕ(t) s I,2 (t) I + SIGNAL SPECTRUM SIGNAL SPECTRUM I&Q SIGNAL: GSM/ EDGE/ WCDMA/ OFDM I Q I L I N C P P Q N I N Q Σ MOD Σ MOD Σ MOD Σ MOD D S P ANALOGUE PASSBAND FILTER ANALOGUE PASSBAND FILTER SAT. PA POWER CONTROL SAT. PA F I L T E R & C O M B I N E R A N T E N N A -f S /8 0 f S /8 -f S /8 0 SIGNAL SPECTRUM f S /8 Freq. -f S /2 0 f CH f S /2 Freq. SPECTRUM Sigma Delta Filter Bandwidth f C = R.f S /2 DIGITAL CIRCUIT PA MODULE f B1 Bandpass Filter Bandwidth f C f B2 TX Frequency. But still some limited bandwith issues ~ 5 % providing 80 MHz TX Band LINEAR PA NON-LINEAR PA 11

LAMB wave filters for channel filtering 1 st demonstration of BAW Lamb wave filter for IF use ESSDERC 07 f c = 156.5 MHz I.L. = -7,3 db Z 0 = 1 kω Coupling acoustic filter & air gap isolation Simulated Measured. 12

In progress on Lamb filters Synthesis of band pass filters Electrical connections between resonators 2 poles ladder filter 2 poles lattice filter Acoustic coupling between resonators 13

RX Intermediate Frequency Bulky external filter Good rejection but high cost / low integration Integrated Gm/C filters Good integration factor / power consumption but not sharp enough High input / output impedance Reduction of the power consumption at moderate frequencies High-Q channel filter Enhanced performance Relaxed linearity specifications Low cost technologies As low frequency as possible Sub-sampling process for digital-oriented architecture Much better performance with comparable power consumption Better scalability for power reduction improvement 14

Band-pass filtering ADC Interest in bringing the digital world towards the analog chain No compromise on quality of the filtering New architecture of ADC to limit the power consumption Digital robustness and technology scaling Small number of analog IC blocks to design fs = 4 x fc to simplify demodulation Multi-standard RF receiver for the 2.4-2.5 GHz band Co-existence of several standards : BT low energy, WiFi, ZigBee A 2 nd order band-pass Σ- BW = 25 MHz at 2.45 GHz carrier 15

Impedance matching in real time Mismatch between antenna and PA Optimum matching for maximum power transfer Compensate for hands effects on the antenna Result : some 100s µs process for 30 db improvement PA C Tunable maching network v1 C Z1 v2 Zant Attenuator RF LO Mixer Filter Processor Down conversion module more output power better power consumption MEMS use for better efficiency IF NEWCAS 08 v 1_ IF v 2 _ IF Registry control Magnitude calculator Phase calculator PROCESSOR Z1 impedance calculator Tunable Matching Network Matching Network controller Antenna impedance calculator Reset v mag v v arg v 1 _ IF 2 _ IF 1 _ IF 2 _ IF Z 1 Re ( Z ant ) Im ( Z ant ) Re( Z 1 ) Im ( Z 1 ) a b c d Z ant 16

BAW Reference frequency Miniaturization and integration issue Highly required for cost / integration improvements Temperature behavior of the resonator Predictive and reproducible Monotonic and low temperature drifts IMS `09 On-going design by STm, compensating for temperature drifts Actual compensation of the temperature Major improvement for use in wireless applications 17

MEMS in ULP RF front-end Conclusions on technologies of interest for ULP RF Some good results on frequency, Q, bandwidth, technologies Sampling architectures under study for RX Considerations on resonators for reference frequency Multi-standard also for WSN 802.15.4 / Zigbee, Bluetooth low energy. 18