A 31-Tap Reconfigurable Analog FIR Filter Using Heterogeneously Integrated Polystrata Delay-Lines

This paper presents a 31-tap analog finite impulse response (FIR) filter capable of synthesizing bandpass, bandstop, and multi-null filter responses with continuous center frequency and bandwidth tuning from less than 1 to 20 GHz. The FIR filter delay-lines are realized using Polystrata 3D air-metal-dielectric technology and are heterogeneously integrated directly on top of a CMOS die using 100 um diameter Sn63Pb37 solder bumps. The CMOS chip contains 7-bit programmable weighting circuits at each delay-line tap to allow synthesis of arbitrary frequency responses limited only by the Q-factor of a 31-tap FIR filter and dynamic range of the weighting elements. The final assembly is 5.04 × 3.85 × 3.64 mm³, consumes 200–350 mA from a 1.8 V supply, and shows good repeatability between measured samples.