Abstract: A switching modulator for a microwave radar transmitter is presented. In embodiment, a string of series connected transistors is controlled from an external source for pulse modulating the cathodes of transmitter microwave tubes. The individual components of the series string can be individually switched ON or OFF in order to maintain regulation of the modulation pulse. In a second embodiment, a pulse transformer has a plurality of individual primary windings and a single secondary winding wherein the primary windings are specially wound to provide isolation between the primary windings with the flux in the secondary winding and the voltage generated in the secondary winding being proportional to the sum of the excitation of the primary windings. Each of the primary windings are individually switchable for regulating the generated output voltage at the secondary winding.
May 8, 1984
Date of Patent:
August 6, 1991
The United States of America as represented by the Secretary of the Navy
Jeffrey C. Firman, Richard E. Rouse, William H. Zinger
Abstract: A differential delta-sigma modulator of switched-capacitance type is operated with a three-phase cycle, rather than the two-phase cycle of the prior art. In the first phase of operation the switched capacitors are charged in accordance with the previous single-bit output of the modulator. Structural modifications permit the switching capacitors to be connected in series to receive the modulator input voltage during the second phase of operation so that voltage need not be balanced with regard to any specified common-mode potential. In the third phase of operation the switched capacitors discharge from first plates thereof to the differential-input integrator while the second plates thereof are driven in accordance with the previous single-bit output of the modulator.
Abstract: ASCII characters are coded in the form of 8, 16 or longer digital words. Signal pulses with durations proportional to such digital words are generated and filtered so that the filtered signal has substantially the same duration as the unfiltered signal. The filtered signal fits within the voiceband so that it can be transmitted through a voiceband medium such as a telephone network. At the receiver, zero-crossings of the received signal are detected and from the duration between consecutive zero-crossings, the particular ASCII represented by the duration of such signal may be recovered.