Abstract: A Modem utilizing process technology compatible CCD and IGFET circuits and sub-systems incorporated on a single I.C. chip. CCD transversal filters are employed as bandpass filters, being tuned for different modes of operation by adjustment of the clock frequency. The bandpass filters are operated in conjunction with a charge amplifier to remove d.c. offset from the analog output of the filters. The demodulator section of the Modem also incorporates low-pass filter employing switched resistors. The modulator section includes waveform generators based on a digital-to-analog converter including switched capacitors having values selected such that a sine wave having minimal distortion is generated when switched in proper sequence. Provision is made for digital inputs to control the frequency and amplitude of the sine wave output. The Modem can be operated under control of a microprocessor.

Abstract: A one bit by N correlation digitally programmable filter comprising a multi-phase charge-transfer shift register whose phase are selectively clocked to achieve the programming. One phase is coupled to an integrator circuit that generates an output voltage proportional to the sum of the charged packets transferred. The clocking cycle is repeated sequentially to generate other selected summations. A plurality of correlators are utilized in parallel to perform an M bit by N correlation.

Abstract: An improved spread spectrum communication system having a transmitter subsystem and a receiver subsystem is disclosed. The transmitter subsystem comprises a data source of 50 bps rate which is modulo-2 added to a C/A (clear/acquisition) code of 1,023K chips/sec in an EXCLUSIVE OR gate, phase modulated on a carrier signal at about 154 f.sub.o where f.sub.o = 10.23 MHz in a phase shift keying modulator and transmitted.