A 32 tap digitally controlled programmable transversal filter using LSI GaAs ICs (and SAW delay line)

A digitally controlled programmable transversal filter (DCPTF) is described that uses a LiNbO/sub 3/ surface-acoustic-wave (SAW) delay line and two GaAs large-scale-integrated (LSI) circuits to control magnitude and sign of the 32 tap weights. A radio-frequency (RF) signal is applied to an input transducer, which generates a surface acoustic wave that propagates down the LiNbO/sub 3/ substrate to an array of output electrodes. Each output electrode detects the electrical signal associated with the acoustic wave. Because of the delay between output electrodes, each electric signal is a delayed copy of the original output. The signal then flows into the RF tap-weighting-amplifier input. The amplifier outputs of each phase are connected to their respective summing buses. Negative tap weights are generated with an external 180 degrees hybrid. The DCPTF constitutes a significant reduction in size over previously reported PTFs with little sacrifice in performance. The filter is completely programmable and is constrained only by the bandwidth (100 MHz centered at 300 MHz) and the number of taps.<>