Application of the PSK Diode-Correlator for Programmable Frequency Filtering.

Abstract : This report describes an experimental and theoretical study of nonlinear tapped delay lines for use as an electronically programmable amplitude and phase weighted transversal filter. The Surface Acoustic Wave (SAW) delay line device studied here, which is called the Programmable Frequency Filter Module (PFFM), is a hybrid, integrated circuit device which utilizes SAW taped delay lines and attached microelectronic diode and resistor arrays. The PFFM is based on the UTRC PSK Diode Correlator which underwent basic development as a 128 tap Phase Shift Key (PSK) signal encoder and correlator under NESC Contract N00014-75-C-0978. While the signal processing capabilities of the single acoustic channel PSK Diode Correlator rely on discrete tap programming in 0 and 180 degree relative phase increments, the dual acoustic channel PFFM described here utilizes continuous tap programming in both amplitude and phase. Each acoustic channel of the device consists of a P diode-tapped signal processing region and two input transducer ports. The input signal and CW reference voltages are applied to the input ports at center frequency F(1) and f(2), respectively. A low power, wide bandwidth nonlinear mixing process occurs at each diode tap, and the difference frequency signals from all taps are summed at a common electrode comprising the filter output port. Rapid tap amplitude an biphase coding is achieved by controlling magnitude and polarity applied to the diode mixer located at each delay line tapping transducer.