Transmitter for frequency shift keyed modulation
AssigneeRCA Corporation
InventorHoward Robert Mathwich
Life of this patent
Estimating the term…
Abstract
A transmitter for communicating binary data by minimum shift keying (MSK) wherein control of the radiated spectrum of the transmitted signal is achieved by controlling the rate of switching between mark and space frequency signals such that the MSK switch acts as an equivalent of a low pass filter.
Claims8
A transmitter for communicating binary data by frequency shift keying (FSK), wherein the FSK signal comprises bits of mark frequency signals and space frequency signals in accordance with said binary data, said mark frequency and said space frequency being respectively indicative of predetermined values in said data, comprising:
- means for generating said mark and space frequency signals;
- analog switching means, receptive of said mark and space frequency signals and said binary data, for generating said FSK signal;
- said analog switching means effecting, in accordance with said binary data, transitions between said mark frequency signals and said space frequency signals and controlling the respective amplitudes of said mark and space frequency signals during said transitions to lengthen said transitions as compared to an abrupt transition between said mark and space frequency signals, thereby controlling derivatives with respect to time of the phase of said FSK signal at said transitions.
A transmitter for communicating binary data by frequency shift keying (FSK), wherein the FSK signal comprises bits of mark frequency signals and space frequency signals in accordance with said binary data, said mark frequency and said space frequency being respectively indicative of predetermined values in said data, comprising:
- means for generating said mark and space frequency signals;
- function generator means, receptive of said binary data, for producing a first and a second analog signal;
- said first analog signal having a waveform having predetermined maximum and minimum amplitude levels and a predetermined transition waveform, said first analog waveform changing in response to said binary data, between said maximum and minimum levels, in accordance with said predetermined transition waveform;
- said second analog signal having a waveform inversely related to said first waveform;
- and
- first and second variable gain amplifier means, respectively receptive of said mark frequency and said space frequency signals, and, respectively, having applied as control signals, said first and second analog signals, for respectively modulating the amplitude of said mark and space frequency signals with said first and second analog waveforms.
A method for generating a frequency shift keying (FSK) signal comprising:
- a. generating a first continuous wave signal at a preselected mark frequency and a second continuous wave signal at a preselected space frequency;
- b. generating an FSK signal by switching between said mark and said space frequency signals in accordance with binary data, said mark frequency and said space frequency signals being respectively indicative of a first and a second binary value in said data;
- c. controlling the respective amplitudes of said mark and space frequency signals during said switching to lengthen the switching transition interval between said mark and space frequency signals as compared to an abrupt switching therebetween, thereby controlling the magnitude of the derivitives of the phase of the FSK signal during said switching.
A method for generating a frequency shift keying (FSK) signal comprising:
- a. generating a first continuous wave signal at a pre-selected mark frequency and a second continuous wave signal at a pre-selected space frequency;
- b. generating a first analog signal having a waveform corresponding to said binary data, said first analog waveform having a predetermined maximum amplitude and a predetermined transition waveform,
- c. generating a second analog waveform having both a predetermined maximum amplitude and a predetermined transition waveform inversely related to said first analog waveform,
- d. respectively applying said first and second analog waveforms as control signals to a first and a second variable gain amplifier means, respectively receptive of said mark and space frequency signals,
- e. respectively modulating the amplitudes of said mark and space frequency signals in accordance with said first and second analog waveforms;
- and
- f. summing said amplitude modulated mark and space frequency signals to generate said FSK signal.
Dependencies are inferred from the claim text.