Minimum shift keying modulating apparatus

Claim 2

Data modulating apparatus comprising, in combination: voltage controlled frequency signal generating means including control input means and signal output means; first means for supplying a carrier frequency signal; second means, including output means, connected to said signal output means of said signal generating means and to said first means for receiving signals therefrom, said second means supplying signals at said output means thereof indicative of the difference frequency of the signals supplied thereto; third means for supplying modulating binary data; fourth means for supplying clock signals; and phase detecting fifth means connected to said second, third, and fourth means for receiving signals therefrom and connected to said control input means of said signal generating means for supplying thereto a control signal indicative of said difference frequency after phase detection with respect to said clock signals and selective amplitude filtration in accordance with said binary data.

Claim 3

Apparatus as claimed in claim 1 wherein said second means includes means for doubling the frequency received from said signal generating means and further includes means for mixing said doubled frequency signal with the signal received from said first means.

Claim 4

Apparatus as claimed in claim 2 wherein said second means includes a low-pass filter for providing said difference frequency, said signal generating means supplying a frequency modulated output which varies from said carrier frequency by one-fourth the data rate as supplied by said third means.

Claim 5

Apparatus as claimed in claim 1 wherein: the clock signals and the binary data supplied by said fourth and third means, respectively, is supplied at the same rate; and said phase detecting means includes first and second phase detectors for detecting said difference frequency at the positive and negative peaks thereof for providing first and second phase detected signals which are used in the selective amplitude filtration.

Claim 6

Apparatus as claimed in claim 1 wherein said phase detection means includes: first and second combinations of phase detectors and filters from which said selective amplitude filtration is selected; and logic circuitry such that supplied binary data logic 1 signals supply a first amplitude filtered signal to said signal generating means as a control signal and supply the second amplitude filtered signal as the control signal when said binary data is representative of a logic 0.

Claim 7

Apparatus as claimed in claim 5 wherein said logic circuitry includes: sixth and seventh means for supplying the difference amplitude filtered signals; differential limiting means connected to said sixth and seventh means for providing a limited output indicative of the relative polarity between the input signals received from said sixth and seventh means; exclusive OR gate means connected for receiving the output of said differential limiting means and for receiving said binary data from said third means and providing output gating signals; and first and second AND gate means for receiving said signals from said sixth and seventh means, respectively, and for gating said signals therefrom through said gate means in accordance with gating signals received from said exclusive OR gate means whereby a logic 1 binary data signal from said third means passes as the control signal to said generating means the more positive of the signals from said sixth and seventh means and a logic 0 binary signal from said third means passes the less positive of the signals from said sixth and seventh means.

Claim 10

Apparatus for providing a frequency shift keyed signal which is binary data modulated with respect to a reference frequency f0 by + or - R/4 where R is the data rate comprising, in combination: oscillator means for supplying an output signal which is controlled in frequency in accordance with an input control voltage; means for supplying a carrier frequency reference signal; frequency doubling and combining means connected to said last named means and to said oscillator means for providing an output signal indicative of the difference frequency obtainable by combining frequency doubled versions of said reference carrier frequency signal and the output of said oscillator means; binary data supplying means having first and second logic levels; phase detector means connected to the last two named means for supplying one of first and second phase detected control signals to said oscillator means in accordance with the logic level of the binary data, the phase detection occurring with respect to two opposite phase signals.

Claim 11

Apparatus for providing a frequency shift keyed signal which is binary data modulated with respect to a reference frequency f0 by + or - R/4 where R is the data rate comprising, in combination: oscillator means for supplying an output signal which is controlled in frequency in accordance with an input control voltage; means for supplying a carrier frequency reference signal; frequency doubling and combining means connected to said last named means and to said oscillator means for providing an output signal indicative of the difference frequency obtainable by combining frequency doubled versions of said reference carrier frequency signal and the output of said oscillator means; binary data supplying means having first and second logic levels; phase detector means connected to the last two named means for supplying one of first and second phase detected control signals to said oscillator means in accordance with the logic level of the binary data, the phase detection occurring with respect to two opposite phase signals.