Gte Automatic Electric Laboratories Incorporated

Ronald J Violet

Robert J Tracey

Thomas E Clark

The input waveform is applied via an input resistor to the inverting input of an operational amplifier. The non-inverting input is grounded. In the preferred embodiment, two feedback networks, each comprising a diode and resistor network, are connected between the output and the inverting input of the amplifier. The diodes are oppositely poled. A capacitor is connected to ground at one end and to a charging resistor at the other. The other end of the charging resistor is connected to a junction formed by the resistor and diode in one of the feedback loops. The charging resistor is selected so that the value of the voltage for the reference which is supplied by the voltage across the capacitor C, e.sub.c, is of the value to obtain the percentage clipping desired. A discharge resistor is selected so that the capacitor and discharge resistor has a long time constant with respect to the input frequency of the waveform. The ratio of the resistor in the resistor diode feedback path which supplies the charging current to capacitor C to the resistance of the input resistor provides the constant percentage ratio of the clipper.

Constant percentage clipping circuit

A digital phase detector which periodically detects the phase angle .theta..sub.k of a carrier signal in which data are encoded as discrete phase changes. A coherent or differential phase-modulated carrier signal is split into its in-phase and quadrature phase components R.sub.o Sin.theta.(t) and R.sub.o Cos.theta. (t). Each signal component is sampled at a predetermined modulation interval and converted into a digital word having the form R.sub.o Cos.theta..sub.k and R.sub.o Sin.theta..sub.k. In one configuration, the two signal components are applied to a digital divider network which forms the quotient .PSI. of the two digital words such that .vertline..PSI..vertline..ltoreq. 1. The quotient .PSI.is applied to a data look-up ROM, programmed for Tan.sup.-.sup.1 operation, which forms a digital reference phase angle .PHI.limited to an angle .ltoreq. 45.degree. is corrected by selection logic to form the desired phase angle .theta..sub.k. Once .theta..sub.k is known for each modulation interval, the encoded data may be readily extracted, since .theta..sub.k is proportional to the encoded data.

Growing community of inventors

Belmont, CA, United States of America

Ronald J Violet