Homodyne communication system
First Claim
1. A homodyne communication system of the type including an interrogating unit and at least one remote unit, and wherein said interrogating unit includes means for transmitting an interrogation signal to said remote unit, means for receiving an information-bearing reply signal from said remote unit, phase detector means, receptive of first and second input signals respectively indicative of said interrogation signal and said reply signal, for generating an output signal indicative of the relative phase of said first and second input signals, and means to extract said information from said phase detector output signal;
- wherein the improvement comprises;
means, receptive of at least one of said first phase detector input signal, said interrogation signal, and said reply signal, for selectively shifting said relative phase of said first and second phase detector input signals by a predetermined angle whereby errors and loss of information caused by amplitude nulls in said phase detector output signal at certain relative phase relationships between said first and second phase detector input signals are substantially eliminated.
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Abstract
A homodyne communication system comprising an interrogating unit and a plurality of responsive remote units wherein a continuous wave RF signal is transmitted from the interrogating unit to illuminate a remote unit. The remote unit causes a return (reply) signal to be transmitted or reflected back to the interrogating unit. A sample of the transmitted (interrogation) signal is mixed with the return signal. Amplitude nulls in the mixer output signal at given relative phase relationships between interrogation and reply signals, are substantially eliminated by selectively shifting the relative phase of the signals. Also disclosed are a homodyne communication system utilizing phase modulation to impress FSK signaling on the reply signal and an automatic vehicle location system utilizing the present invention.
87 Citations
17 Claims
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1. A homodyne communication system of the type including an interrogating unit and at least one remote unit, and wherein said interrogating unit includes means for transmitting an interrogation signal to said remote unit, means for receiving an information-bearing reply signal from said remote unit, phase detector means, receptive of first and second input signals respectively indicative of said interrogation signal and said reply signal, for generating an output signal indicative of the relative phase of said first and second input signals, and means to extract said information from said phase detector output signal;
- wherein the improvement comprises;
means, receptive of at least one of said first phase detector input signal, said interrogation signal, and said reply signal, for selectively shifting said relative phase of said first and second phase detector input signals by a predetermined angle whereby errors and loss of information caused by amplitude nulls in said phase detector output signal at certain relative phase relationships between said first and second phase detector input signals are substantially eliminated.
- wherein the improvement comprises;
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2. A homodyne system comprising an interrogating unit and at least one remote unit for communicating information to said interrogating unit from said remote unit;
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said interrogating unit including; a transmitter for transmitting a signal of a predetermined frequency to said remote unit, a receiver for receiving an information-bearing return signal from said remote unit, said return signal bearing the information at a given bit rate, mixer means, receptive of a sample of said transmitted signal and said return signal, for generating an output signal representative of phase differences therebetween, and signal processor means, receptive of said mixer output signal, for extracting said information from said return signal; said remote unit including; an antenna network, responsive to said transmitted signal, for producing an antenna output signal representative of said transmitted signal, and for radiating said return signal, means, coupled to said antenna network and receptive of a signal representative of said information, for modulating said antenna output signal in accordance with said information, and means, coupled to said antenna network, for shifting at a given rate the phase of said antenna output signal alternately by a first and a second predetermined angle, said phase-varied modulated antenna output signal being applied to said antenna network and radiated by said antenna network as said return signal, whereby said return signal is modulated in accordance with said information and is phase shifted at said given rate, thereby substantially eliminating errors and loss of said information due to amplitude nulls in said mixer output signal at given relative phase relationships between said sample of said transmitted signals. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A homodyne system comprising an interrogating unit and at least one remote unit for communicating information to said interrogating unit from said remote unit;
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said interrogating unit including; a transmitter for transmitting an interrogation signal of a predetermined frequency to said remote unit, a receiver for receiving an information-bearing return signal from said remote unit, said return signal bearing the information at a predetermined bit rate, phase detector means, receptive of a sample of said interrogation signal and said return signal, for generating an output signal representative of phase differences therebetween, and signal processor means, receptive of said phase detector output signal, for extracting the information from said return signal; said remote unit including; an antenna network, responsive to said interrogation signal, for producing an antenna output signal representative of said interrogation signal, and for radiating said return signal, an encoder for generating a binary output signal representative of said information, said binary signal having said predetermined bit rate, gating means, responsive to said encoder output signal and receptive of a signal having a first predetermined frequency and a signal having a second predetermined frequency, for producing an output signal comprising bits of said first and second predetermined frequencies in accordance with respective corresponding bits of said encoder output signal, and voltage-controlled phase shifting means, coupled to said antenna network and responsive to said gating means output signal, for modulating the phase of said antenna output signal in accordance with said gating means output signal, said phase modulated antenna output signal being applied to said antenna network and radiated by said antenna network as said return signal; whereby said phase detector means output signal in said interrogating unit is representative of said gating means output signal and said processor extracts said information by detecting the respective presence of said first and second predetermined frequencies in said phase detector means output signal. - View Dependent Claims (14)
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15. In a homodyne system of the type including an interrogating unit and at least one remote unit for communicating information to said interrogating unit from said remote unit;
- wherein said interrogating unit includes a transmitter for transmitting a signal of a predetermined frequency to said remote unit, a receiver for receiving an information-bearing return signal from said remote unit, said return signal bearing the information at a given bit rate, mixer means, receptive of a sample of said transmitted signal and said return signal, for generating an output signal representative of phase differences therebetween, and signal processor means, receptive of said mixer output signal, for extracting the information from said return signal;
an improved remote unit comprising; an antenna network, responsive to said transmitted signal, for producing an antenna output signal representative of said transmitted signal, and for radiating said return signal, means, coupled to said antenna network and receptive of a signal representative of said information, for modulating said antenna output signal in accordance with said information, and means, coupled to said antenna network for shifting at a given rate the phase of said antenna output signal alternately by a first and a second predetermined angle, said phase-varied modulated antenna output signal being applied to said antenna network and radiated by said antenna network as said return signal, whereby said return signal is modulated in accordance with said information and is phase shifted at said given rate, whereby errors and loss of information due to amplitude nulls in said mixer output signal at given relative phase relationships between said sample of said transmitted signal and said return signal are substantially eliminated.
- wherein said interrogating unit includes a transmitter for transmitting a signal of a predetermined frequency to said remote unit, a receiver for receiving an information-bearing return signal from said remote unit, said return signal bearing the information at a given bit rate, mixer means, receptive of a sample of said transmitted signal and said return signal, for generating an output signal representative of phase differences therebetween, and signal processor means, receptive of said mixer output signal, for extracting the information from said return signal;
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16. In a homodyne system of the type including an interrogating unit and at least one remote unit for communicating information to said interrogating unit from said remote unit;
- wherein
said interrogating unit includes;
a transmitter for transmitting a signal of a predetermined frequency to said remote unit, a receiver for receiving an information-bearing return signal from said remote unit, said return bearing the information at a predetermined bit rate, phase detector means, receptive of a sample of said transmitted signal and said return signal, for generating an output signal representative of phase differences therebetween, and signal processor means, receptive of said phase detector output signal, for extracting the information from said return signal;an improved remote unit comprising; an antenna network, responsive to said transmitted signal, for producing an antenna output signal representative of said transmitted signal, and for radiating said return signal, an encoder for generating a binary output signal representative of said information, said binary signal having said predetermined bit rate, gating means, responsive to said encoder output signal and receptive of a signal having a first predetermined frequency and a signal having a second predetermined frequency, for producing an output signal comprising bits of said first and second predetermined frequencies in accordance with respective corresponding bits said encoder output signal, and voltage-controlled phase shifting means, coupled to said antenna network and responsive to said gating means output signal, for modulating the phase of said antenna output signal in accordance with said gating means output signal, said phase modulated antenna output signal being applied to said antenna network and radiated by said antenna network as said return signal; whereby said phase detector means output signal in said interrogating unit is representative of said gating means output signal and said processor extracts said information by detecting the respective presence of said first and second predetermined frequencies in said phase detector means output signal. - View Dependent Claims (17)
- wherein
Specification