Self-oscillating mixer circuits, and FMCW radar
First Claim
1. A circuit for producing an IF signal, said circuit comprising:
- a. a self-oscillating mixer for producing an RF signal, modulating the RF signal in response to a modulating signal, and mixing the modulated RF signal with a reflected return of said modulated signal, said mixer including;
(1) an input for receiving the modulating signal;
(2) an RF line for carrying the modulated RF signal and the reflected return;
(3) an output for providing an IF signal resulting from said mixing; and
b. cancellation means for combining the IF signal with the modulating signal to cancel from the IF signal a modulation corresponding to that of the modulated RF signal, said cancellation means including a first input coupled to the output of the mixer, a second input for receiving the modulating signal, and an output for producing a demodulated IF signal.
1 Assignment
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Accused Products
Abstract
A simple self-oscillating mixer circuit is provided, suitable for forming with an antenna (21) the complete front end of an inexpensive short-range FMCW radar. A modulating signal (40), e.g. from a sweep generator (44), is applied to a control terminal (14) to sweep the RF output (R) of the self-oscillating mixer SOM (10). A cancellation circuit (6 to 9) is connected between the control terminal (14) and an IF output line (13) to remove a corresponding modulation (41) which occurs on the IF line (13) and so to generate a substantially demodulated IF output signal (I). Advantageously a grounded-source MESFET in a feed-back network forms the SOM (10) and has the IF output line (13) taken from its gate. In this case the IF modulation (41) is inverted with respect to the modulating signal (40), and so the cancellation is achieved by adding the modulating signal (40) to the modulated IF output signal (41), e.g. via a resistor network 6 to 8.
27 Citations
8 Claims
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1. A circuit for producing an IF signal, said circuit comprising:
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a. a self-oscillating mixer for producing an RF signal, modulating the RF signal in response to a modulating signal, and mixing the modulated RF signal with a reflected return of said modulated signal, said mixer including; (1) an input for receiving the modulating signal; (2) an RF line for carrying the modulated RF signal and the reflected return; (3) an output for providing an IF signal resulting from said mixing; and b. cancellation means for combining the IF signal with the modulating signal to cancel from the IF signal a modulation corresponding to that of the modulated RF signal, said cancellation means including a first input coupled to the output of the mixer, a second input for receiving the modulating signal, and an output for producing a demodulated IF signal. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A frequency-modulated continuous-wave radar comprising an antenna, a sweep waveform generator for producing a modulating signal, and a circuit for producing an IF signal, said circuit comprising:
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a. a self-oscillating mixer for producing an RF signal, modulating the RF signal in response to the modulating signal, and mixing the modulated RF signal with a reflected return of said modulated signal, said mixer including; (1) an input electrically connected to the sweep waveform generator for receiving the modulating signal; (2) an RF line electrically connected to the antenna for carrying the modulated RF signal and the reflected return; (3) an output for providing an IF signal resulting from said mixing; and b. cancellation means for combining the IF signal with the modulating signal to cancel from the IF signal a modulation corresponding to that of the modulated RF signal, said cancellation means including a first input coupled to the output of the mixer, a second input electrically connected to the sweep waveform generator for receiving the modulating signal, and an output for producing a demodulated IF signal.
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Specification