Application of PC Vias to Configurable RF Circuits March 24, 2008 Prof. Jeyanandh Paramesh Department of Electrical and Computer Engineering Carnegie Mellon University Pittsburgh, PA 15213
Ultimate Goal: Cognitive Radio A node in a cognitive radio network must Adaptively sense spectral environment Optimally set transmission parameters optimum modulation, frequency of operation, transmit power etc. Basic building block Reconfigurable RF front-end Universal Transmitter & Receiver
Wireless Communication Standards 1995 2000 2002 2005 2009+ RANGE/ MOBILITY IS-95 IS-136 CDMA 2000 W- CDMA EV-DO Cellular 4G GSM GPRS/ EDGE UMTS HSDPA 802.16c 802.16c 802.16e WWAN (WiMAX) 802.11b 802.11g 802.11n WLAN (WiFi) 802.11a 802.15.1 802.15.3 SPEED ZigBEE 802.15.4 (UWB) 60GHz UWB WPAN
Single-band RF Transceiver CMOS RF/Analog Chip CMOS Digital Chip ADC LNA ADC T/R Switch PLL Digital Signal Processor DAC PA DAC
Multi-band RF Transceiver Front-end Module CMOS RF/Analog Chip CMOS Digital Chip LNA ADC LNA LNA ADC LNA Configurable Digital Signal Processor PA PA DAC PA DAC PA
Low-noise amplifiers for GPS, WCDMA & WLAN Ref: Y. Xu, C. Boone, L. Pileggi, JSSC 8/2004
Digital Configuration Wideband LNA ADC Configurable DSP Software-defined Receiver Prohibitive requirements Extreme front-end bandwidth & dynamic range Extreme ADC resolution and sampling rate Impractical when power dissipation and weight are important Ref: J. Mitola
Factory Configuration Metal-mask Configuration Ref: Y. Xu, C. Boone, L. Pileggi, JSSC 8/2004
PC Via-Based RF/Analog Configuration LNA Low swing Low power, Low noise LNA 90 o VCO High-swing Low-power, Low noise MEMS Configuration PLL PA High-swing High-power, High-linearity PA 90 o Phase-change Configuration
T/R Switch TX RX For high T/R port Isolation, via must have Low Ron High Roff Low parasitic capacitance To Antenna Low loss in the RX path Power handling capability in TX Path
Configurable Low-Noise Amplifier Re-configurable transistor bank ~1.2V in 90nm CMOS 2.9nH 1.7nH 0.7nH Re-configure between 2.4GHz, 5.8GHz & 11.6GHz To be taped-out in IBM 90nm RF-CMOS process with PC BEOL in Sept 08 460u 220u 110u GeSb BEOL PC Via 280u 140u 70u 9.6nH 2.6nH 1.4nH 0.41nH 0.26nH 0.125nH
Configurable Voltage Controlled Oscillators Re-configure between 2.4GHz, 5.8GHz & 11.6GHz 2.9nH 1.7nH 0.7nH To be taped-out in IBM 90nm RF- CMOS process with PC BEOL in Sept 08 1/f noise of PC Vias GST 1/f noise high in amorphous (OFF) state GeSb 1/f noise characteristics unknown Re-configurable transistor bank
Challenges in High-Efficiency Transmitters Configuration of PA s very hard Non-linear PA s more efficient than linear PA s Non-linear PA s best for constant-envelope modulation (PM/FM) Linear PA s best for amplitude modulation Spectrally efficient modulation schemes use non-constant envelope signals Peak-to-average ratio determines required PA linearity High for QAM, even higher for OFDM Linear & non-linear PA s are topologically similar, but component requirements are vastly different
Configurable Multi-band Power Amplifiers Configurable matching network Configurable matching network Re-configurable device bank Configurable matching network
Configurable Matching Networks for PA s VDD Power Amplifier Tunable matching network Tune PA efficiency by tuning load see by PA PC Switch Array Adaptively tune out variations in antenna impedance Adaptively tune power supply voltages with output power
Electrical Properties of PC Via Ron/Roff (Q degradation) Parasitic Capacitances (Isolation) Flicker Noise Current/Voltage Handling Capability Switching Speed
Differential MEMS Probe RF Circuit Terminal #1 Cu3 PC Cu2 PC RF Circuit Terminal #2 Cu1
Electrical Configuration of PC Vias Cu3 PC b a TiW d e TiW Cu3 c PC f PC TiW i g h Cu2 Cu2 TiW TiW PC PC j Heater Cu1 Cu1 Sharing signal path with PC via configuration path problematic in some applications Can we use proximity heating to configure vias? Ref: T. E. Schlesinger & G. Fedder
Summary RF circuits impose a different set of requirements on the PC Vias compared to digital circuits Need to characterize via properties carefully Compact model for SPICE-level simulation required Many challenges in turning the vias on and off Dual-MEMS probes Electrical Switching