Abstract: A photoconductive spread-spectrum communications system that includes a tsmitter and a receiver. The transmitter includes an oscillating laser, a Pockels' cell, a delay cell, a photoconductive switch, and an antenna for transmitting an electromagnetic spread-spectrum signal. The receiver includes an oscillating laser, a Pockels' cell, an antenna for receiving a spread-spectrum signal, a photoconductive switch, a filter, and a threshold detector for regenerating the signal contained within the spread-spectrum transmission.

Abstract: A device for converting DC to RF has a monolithic PIN diode adapted to be coupled to a DC supply. The diode receives light switching pulses and is coupled to a monolithic resonator. The monolithic form provides compactness and reliability, while the diode, which is reversed biased when OFF, prevents substrate leakage currents. The diode and the resonator can be made in a single substrate, e.g., silicon, or in different substrates, e.g., silicon for the diode to obtain a long carrier lifetime and, thus, minimize the light pulse repetition rate, and GaAs for the resonator to obtain a high Q. The resonator can also act as an impedance transformer.

Abstract: Locations of a desired number of signal points for a double side band-quadrature carrier modulation system occupy the inner intersections of a multiplicity of concentric rings with a triangular grid. The signal point locations of the desired number on the outer partially occupied ring are provided with additional signal points at positions selected to provide that the centroid of the set of locations is at the center of the rings.

Abstract: A sinusoidal component of phase jitter in a communications channel is reduced by apparatus including means providing an oscillator signal at the receiver and modifying the received signal phase in accord therewith. Decision means determine the probable transmitted signal and the signals at the input and output of the decision means are compared to determine the residual phase jitter. The residual phase jitter is compared with a suitably delayed oscillator signal and the results of the comparison are used to alter the modification (by the oscillator signal) of the received signal to further reduce the phase jitter. Preferably the results of the comparison are also used to reduce the frequency difference between the oscillator signal and the phase jitter.