WIRELESS STEREO SOUND SPEAKER SYSTEM AND MODULATOR-OSCILLATOR CIRCUIT
First Claim
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1. A wireless stereo sound speaker system comprising:
- a first FM transmitter including first input terminals for supplying recorded electric stereo signals from a first sound track, a first coupling transformer receiving the first track stereo signal and having a primary and secondary winding with a common terminal, first modulator-oscillator circuit coupled to said first coupling transformer for frequency modulating a radio frequency carrier signal produced in a tank with said first track stereo signal and radiating the resulting modulated carrier signal as wave energy along a first channel; and
a second FM transmitter including second input terminals for supplying the recorded electric stereo signal from a second sound track, a second coupling transformer receiving the second track stereo signal and having a primary and a secondary winding with a common terminal, and a second modulator-oscillator circuit coupled to said second coupling transformer for frequency modulating a second radio frequency carrier signal at a different frequency from said first carrier signal with said second track stereo signal and radiating the resulting second modulated carrier signal as wave energy along a second channel simultaneously with said first transmitter, each said modulator-oscillator circuit including a parallel connected inductor-capacitor tank and a feedback capacitor having a pair of plates connected in series with the tank, said tank being connected to one side of said secondary winding and a transistor oscillator connected in a common-base configuration, said transistor having emitter, base and collector electrodes, one of said plates being connected to said collector and the other of said plates to said emitter, said base being coupled to said common terminal to apply the modulating signals to said base; and
first and second receiver at a location remote from said first and second transmitters, said first receiver being tuned to said first carrier signal frequency for reproducing stereophonic sounds from the electric stereo signals transmitted from said first transmitter and said second receiver at a selected spaced distance from the first receiver being tuned to the carrier frequency of said second transmitter for reproducing audible stereophonic sounds from the electric stereo signals transmitted from said second transmitter, each said first and second receivers having an intensity control to provide a phase balance in the sound being reproduced by said receivers at a listener'"'"''"'"'s ears.
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Abstract
Portable wireless stereo sound transmitter and system including one transmitter adapted for connection to one sound source for transmitting sound by wave energy at one high frequency channel to first remote receiving station and another transmitter adapted for connection to another sound source for simultaneously transmitting sound from another sound source by wave energy at another high frequency to second remote receiving station. The novel FM modulator-oscillator includes the series connection of a transformer, an L-C tank circuit, and a capacitor with the collector and emitter electrodes of a transistor connected thereto.
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Citations
8 Claims
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1. A wireless stereo sound speaker system comprising:
- a first FM transmitter including first input terminals for supplying recorded electric stereo signals from a first sound track, a first coupling transformer receiving the first track stereo signal and having a primary and secondary winding with a common terminal, first modulator-oscillator circuit coupled to said first coupling transformer for frequency modulating a radio frequency carrier signal produced in a tank with said first track stereo signal and radiating the resulting modulated carrier signal as wave energy along a first channel; and
a second FM transmitter including second input terminals for supplying the recorded electric stereo signal from a second sound track, a second coupling transformer receiving the second track stereo signal and having a primary and a secondary winding with a common terminal, and a second modulator-oscillator circuit coupled to said second coupling transformer for frequency modulating a second radio frequency carrier signal at a different frequency from said first carrier signal with said second track stereo signal and radiating the resulting second modulated carrier signal as wave energy along a second channel simultaneously with said first transmitter, each said modulator-oscillator circuit including a parallel connected inductor-capacitor tank and a feedback capacitor having a pair of plates connected in series with the tank, said tank being connected to one side of said secondary winding and a transistor oscillator connected in a common-base configuration, said transistor having emitter, base and collector electrodes, one of said plates being connected to said collector and the other of said plates to said emitter, said base being coupled to said common terminal to apply the modulating signals to said base; and
first and second receiver at a location remote from said first and second transmitters, said first receiver being tuned to said first carrier signal frequency for reproducing stereophonic sounds from the electric stereo signals transmitted from said first transmitter and said second receiver at a selected spaced distance from the first receiver being tuned to the carrier frequency of said second transmitter for reproducing audible stereophonic sounds from the electric stereo signals transmitted from said second transmitter, each said first and second receivers having an intensity control to provide a phase balance in the sound being reproduced by said receivers at a listener'"'"''"'"'s ears.
- a first FM transmitter including first input terminals for supplying recorded electric stereo signals from a first sound track, a first coupling transformer receiving the first track stereo signal and having a primary and secondary winding with a common terminal, first modulator-oscillator circuit coupled to said first coupling transformer for frequency modulating a radio frequency carrier signal produced in a tank with said first track stereo signal and radiating the resulting modulated carrier signal as wave energy along a first channel; and
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2. A wireless stereo sound speaker system as set forth in claim 1 including a DC power supply for each said modulator-oscillator circuit having a solid-state diode bridge rectifier, a pi section filter coupled to the output of the bridge rectifier and at least one power transistor coupled to the output of the pi section filter.
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3. A modulator-oscillator circuit for frequency modulating a carrier signal comprising a coupling transformer having a primary and a secondary winding for supplying modulating signals from a signal source, said secondary winding having a first terminal in common with a primary terminal and having a second terminal, a parallel connected inductor-capacitor tank circuit, a feedback capacitor having a pair of plates, said feedback capacitor being connected in series with the tank, an oscillator transistor including an emitter, collector, and base, said transistor being connected in a common-base configuration, one of said plates being connected to said collector and the other of said plates being connected to said emitter, said collector being coupled to said second terminal through said tank circuit to bias said collector with the modulating signals, said emitter being coupled to said second terminal to bias said emitter with the modulating signals and said base being coupled to the common terminal to apply the modulating signals to said base whereby the potential at said emitter and collector vary in phase with the modulating signals applied to said terminals, said transistor operates as an amplifier to counteract losses and said feedback capacitor serves to change the effective capacitance of said tank circuit in a direct relation so that the oscillations in said tank circuit vary at a rate prOportional to the amplitude of the modulating signals and produce a frequency modulated carrier signal as wave energy from said tank circuit.
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4. A modulator-oscillator circuit as set forth in claim 3 wherein said emitter is coupled to said second terminal through a resistor and a capacitor.
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5. A modulator-oscillator circuit as set forth in claim 3 wherein said base is biased by a voltage divider to establish a reference for the modulating signals being applied to the emitter and collector.
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6. A modulator-oscillator circuit as set forth in claim 3 wherein the capacitor and inductor in said tank circuit are variable to change the frequency of the oscillations of the tank circuit.
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7. A modulator-oscillator circuit as set forth in claim 3 wherein the inductor forms the antenna for transmitting the modulated carrier signal as wave energy.
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8. A modulator-oscillator circuit as set forth in claim 3 including means for amplifying the modulating signals before applying them to said coupling transformer.
Specification