Keying Circuits Patents (Class 375/309)
  • Patent number: 5475684
    Abstract: A time-division multiplex communication transmission apparatus includes a logic processing circuit, a digital filter, a modulation circuit, and a high-frequency amplification unit. The logic processing circuit performs logic processing of input burst data and outputs a burst timing signal for each time slot for time-division transmission. The digital filter converts output data from the logic processing circuit into baseband data for modulation. The digital filter is reset at a time slot boundary when no burst data signal is present in an adjacent time slot. The modulation circuit modulates an output signal from the digital filter. The high-frequency amplification unit performs burst waveform processing of an output signal from the modulation circuit on the basis of a burst timing signal from the logic processing circuit.
    Type: Grant
    Filed: January 25, 1994
    Date of Patent: December 12, 1995
    Assignee: NEC Corporation
    Inventor: Hiroyuki Shimizu
  • Patent number: 5469479
    Abstract: A monolithic digital chirp synthesizer (DCS) chip using GaAs/AlGaAs HI.sup.2 L technology. The 6500 HBT gate DCS chip is capable of producing linear frequency modulated (chirp) waveforms or single frequency waveforms. The major components of the DCS are two pipelined accumulators, a sine ROM, a cosine ROM and two digital to analog converters.
    Type: Grant
    Filed: February 27, 1992
    Date of Patent: November 21, 1995
    Assignee: Texas Instruments Incorporated
    Inventors: Christopher T.-M. Chang, William A. White