Abstract: A modulator is disclosed for use with digitized multiplexed voice channels in which service bits are transmitted using QPSK modulation while the audio information is transmitted using amplitude and phase modulation. The audio information in each channel is digitized and compressed using a mapping technique in which zero crossings of the audio signal are represented by binary O. The digitized channels are then multiplexed and coupled to the address inputs of a read-only memory. In the memory are stored digital numbers which represent in quadrature the amplitude and phase of the pulse to be transmitted corresponding to the digital data sample or service word then being presented at the address inputs of the memory. The digital numbers for the control words represent a constant amplitude while those corresponding to the data words represent an amplitude dependent upon the level of the original audio signal. No output carrier is produced for zero-value audio signals.

Abstract: A microwave guide switch having a rotor and stator each having ports spaced at 60.degree. intervals and a connecting waveguide transmission means connected to two ports spaced 120.degree. apart which forms a 3-position, 4-port switch.

Abstract: A multibeam communications satellite uses a dish-shaped reflector whose surface is a surface of revolution generated by rotating a plane parabola about an axis of revolution located in the plane of the parabola but angularly displaced from the axis of symmetry thereof. The line of revolution of the focal point of the parabola defines a focal circle, and a feed located on the focal circle will illuminate an area lying on a circle near the edge of the earth's apparent disc. Since every plane in which the axis of revolution lies is a plane of symmetry, the antenna exhibits good cross polarization cancellation, making the satellite particularly useful in frequency reuse communications systems.

Abstract: Phase and amplitude modulation of single or multiple pulses and/or dual polarizations are used in a digital communications system which transmits multidimensional codes. Four dimensional code transmission is specifically disclosed, although the scheme may be extended to eight-dimensional and even 16-dimensional code transmission. The four-dimensional codes are constructed by mapping a digital word into two two-dimensional plane as two sets of x and y coordinates. Signals proportional to these x and y coordinates are used to modulate a transmitted pulse or pulses. When a single pulse is used to transmit the four-dimensional code, polarization modulation is used. A signal proportional to the square root of the sum of the squares of the coordinates assigned to both the horizontal and vertical polarizations is used to control the total RF amplitude of the pulse.