Telecommunications – Transmitter and receiver at separate stations – Frequency or phase modulation
Patent
1983-02-10
1984-10-02
Griffin, Robert L.
Telecommunications
Transmitter and receiver at separate stations
Frequency or phase modulation
332 16R, 358144, 381 3, 381 16, 375 49, H03C 300
Patent
active
044752440
ABSTRACT:
A system for time-period modulating (TPM) a subcarrier in accordance with the amplitude of an input signal includes generating a ramp signal of constant slope, comparing the ramp signal with the input signal, and resetting the ramp signal when the ramp signal reaches the input signal. Each time the ramp signal is reset, a clock pulse is counted. These clock pulses are counted in cyclic groups of N. After each clock pulse is counted, the then attained count is converted to a value of a sinusoid about some reference. The values for each of N counts define one sinusoidal cycle of the modulated subcarrier. Converting these values to voltage levels produces a sinusoidal stepwave which has a period linearly proportional to the amplitude of the input signal at the time. At a receiver, demodulation of the signal is achieved by squaring each cycle of the TPM signal, and during a predetermined half cycle of each squarewave cycle, generating a ramp signal of constant slope which reaches a voltage level in one half cycle linearly proportional to the period of the TPM cycle. The voltage level attained in each demodulating half cycle is sampled and held until the next demodulating half cycle. In that manner, a step waveform is generated which follows the input signal to the modulator at the transmitter. This system may be used for the L-R signal of a monaural compatible stereophonic transmission system which combines an L+R signal with the TPM L-R signal. The composite is then modulated on a carrier.
REFERENCES:
patent: 2697745 (1954-12-01), Halstead
patent: 2851532 (1958-09-01), Crosby
patent: 3046329 (1962-07-01), Reesor
patent: 3069505 (1962-12-01), Collins et al.
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patent: 3824498 (1974-07-01), McBride
patent: 4079204 (1978-03-01), Takahashi et al.
patent: 4328554 (1982-05-01), Mantione
"Stereophonic Sound for Television", Ronald K. Jurgen, Senior Editor, IEEE Spectrum, Sep. 1982, pp. 30-33.
Griffin Robert L.
Neal John A.
Taylor Thomas M.
Watkins Albert W.
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