Convolvers for DPSK Demodulation of Spread Spectrum Signals.

摘要

Details are presented on the design and performance of acoustoelectric convolvers developed for decoding differential-phase-shift-keyed data at a 100 Kbit/s rate. The data is encoded on a 100-M-chip/s pseudo-noise spread-spectrum carrier. A 20-microsecond convolver, segmented at its center, acts as an electronically programmable matched filter, providing simultaneous correlation spikes for two adjacent 10-microsecond bit waveforms. Subsequent comparison using a sum-difference hybrid and envelope detectors allows for a decision as to the presence of a phase-reversal between two bits. Packaging techniques will be described which improve both the electrical and mechanical performance of acoustoelectric convolvers. Indium bonding of silicon to Kapton sheets allows the end to end placement of two 35-mm by 0.76-mm silicon strips over the same 0.76-mm-wide acoustic beam path. This results in a stable phase relationship between the two convolver segments. Kapton microstrip circuits provide improved rf connections to the silicon. A spring arrangement is incorporated to stabilize the Si-LiNbO3 air gap over a 75 deg C temperature range. (Author)