Digital single-sideband modulator

• US 3,868,601 A
• Filed: 06/18/1973
• Issued: 02/25/1975
• Est. Priority Date: 06/18/1973
• Status: Expired due to Term

• Current Assignee: John W. Macafee
• Original Assignee: John W. Macafee
• Inventors: MacAfee, John W.
• Primary Examiner(s): Brody, Alfred L.
• Application Number:
  US05/371,316
• Time in Patent Office: 617 Days
• Field of Search: 332/44,45R 325/137,138,136,49,50,60,38R 178/68
• US Class Current: 332/170
• CPC Class Codes: H04L 27/04 Modulator circuits; Transmitter circuits

Abstract

Apparatus for digitally generating information tones and for translating the frequency of transient information tones to a spectrum location amenable to communications. In response to a digital data input, discrete tones of definite assigned frequency and duration are generated and economically combined to form a spurious-free, single-sideband, suppressed carrier signal. The frequency location of the signal is conveniently determined by an ordinary mixing process.

Claims

1. Modulator apparAtus comprising:

input means for receiving digital data;

generator means connected to said input means and being responsive to said digital data to produce trigger pulses at a selectively predetermined rate;

in-phase read-only memory means connected to the output of said generator means and being responsive to said trigger pulses to store the binary representation thereof on a selectively predetermined waveform and wherein each binary word stored represents a distinct amplitude of said waveform;

first digital-to-analog converter means connected to the output of said in-phase read-only memory means;

quadrature read-only memory means connected to the output of said generator means and being responsive to said trigger pulses in the same manner as said in-phase read-only memory means, second digital-to-analog converter means connected to the output of said quadrature read-only memory means;

first and second mixer means connected to the outputs of said first and second digital-to-analog converter means, respectively;

oscillator means connected at the output to said first mixer means to provide at the output thereof an in-phase carrier signal, and being further connected through a 90* phase shifter to said second mixer to provide a quadrature carrier signal; and

, summation network means connected at the input to the outputs of said first and second mixer means and being responsive to said in-phase and quadrature carrier signals to provide a singlesideband, suppressed carrier signal.

2. The apparatus of claim 1 wherein said means for generating said trigger pulses comprises a rate generator and a rate selector switch connected in series with respect to each other and in parallel with respect to said input terminal means.

3. The apparatus of FIG. 1 further including first and second filter means connected between said first and second converter means and said mixer means, respectively, for smoothing the outputs of said converters.

4. Digital, single-sideband modulator apparatus comprising:

generator means responsive to digital data input for providing a frequency tone corresponding to a selectively predetermined digital input;

memory means connected to the output of said generator means for storing said frequency tone synchronously in-phase and in quadrature;

converter means connected to the output of said memory means for providing analog equivalent waveforms of said in-phase and quadrature representations;

oscillator means for providing a first drive signal and a second drive signal which is 90* out of phase with respect to said first drive signal;

first and second mixer means connected to the output of said converter means and to said oscillator means for mixing said in-phase analog waveform with said first drive signal to provide an in-phase carrier input and said quadrature analog waveform with said second drive signal to provide a quadrature carrier input, respectively; and

, summation network means connected to the output of said first and second mixer means and being responsive to said in-phase and quadrature carrier inputs to provide a single-sideband suppressed carrier signal.