Radio receiving and retransmitting apparatus with frequency lock circuit
First Claim
1. A method of detecting an incoming RF signal and transmitting a corresponding regenerated signal at a predetermined frequency, comprising:
- sweeping a first local oscillator signal through a range of frequencies and mixing the first local oscillator signal with an incoming RF signal;
detecting the presence, in the mixed signals, of a first IF signal within a predetermined frequency range and thereupon stopping the sweep;
enabling closed-loop frequency locking means which adjusts the frequency of the first local oscillator until the frequency of the first IF signal is equal to a first reference frequency;
thereafter sweeping a second local oscillator signal through a range of frequencies and mixing the second local oscillator signal with the output of the first local oscillator;
detecting the presence, in the mixed local oscillator signals, of a second IF signal within a predetermined frequency range and thereupon stopping the sweep;
enabling closed-loop frequency locking means to cause it to adjust the frequency of the second local oscillator until the frequency of the second IF signal is equal to a second reference frequency; and
thereupon transmitting the signal at the frequency of the output of the second local oscillator.
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Accused Products
Abstract
In radar apparatus for actively enhancing and retransmitting a received radar signal, the incoming signal is mixed with the output of a first local oscillator, the resulting signal being supplied to a frequency lock loop which varies the frequency of the first local oscillator until the frequency of the resulting IF signal is equal to a first reference IF frequency. The first local oscillator output is mixed with the output of a second local oscillator, the frequency of which is varied until the frequency of the resulting second IF signal is equal to a second reference IF frequency. The output from the second local oscillator is retransmitted. The first and second reference IF frequencies are identical if the frequency to be retransmitted is the same as the incoming RF carrier frequency.
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Citations
7 Claims
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1. A method of detecting an incoming RF signal and transmitting a corresponding regenerated signal at a predetermined frequency, comprising:
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sweeping a first local oscillator signal through a range of frequencies and mixing the first local oscillator signal with an incoming RF signal; detecting the presence, in the mixed signals, of a first IF signal within a predetermined frequency range and thereupon stopping the sweep; enabling closed-loop frequency locking means which adjusts the frequency of the first local oscillator until the frequency of the first IF signal is equal to a first reference frequency; thereafter sweeping a second local oscillator signal through a range of frequencies and mixing the second local oscillator signal with the output of the first local oscillator; detecting the presence, in the mixed local oscillator signals, of a second IF signal within a predetermined frequency range and thereupon stopping the sweep; enabling closed-loop frequency locking means to cause it to adjust the frequency of the second local oscillator until the frequency of the second IF signal is equal to a second reference frequency; and
thereupon transmitting the signal at the frequency of the output of the second local oscillator. - View Dependent Claims (2, 3)
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4. Apparatus for detecting an incoming RF signal and transmitting a corresponding regenerated signal at a predetermined frequency, comprising:
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first and second local oscillators producing first and second signals; means for sweeping the first local oscillator signal through a range of frequencies; a first mixer for mixing the first local oscillator signal with an incoming RF signal to provide a mixed signal output; a first detector for sensing the presence, in the output of the first mixer, of a first IF signal within a predetermined frequency range said first detector having an output; closed-loop frequency locking means; means responsive to the output of the first detector to stop the frequency sweep of the first local oscillator when the IF signal within the predetermined frequency range is sensed and to enable the frequency locking means to adjust the frequency of the first local oscillator until the frequency of the first IF signal is equal to a first reference frequency; means for sweeping the second local oscillator signal through a range of frequencies; a second mixer for mixing the second local oscillator signal with the output of the first local oscillator to provide a mixed signal output; a second detector for sensing the presence, in the output of the second mixer, of a second IF signal within a predetermined frequency range said second detector having an output; means responsive to the second detector output to stop the sweep of the second local oscillator when the second IF signal is detected within the predetermined frequency range and to enable the closed-loop frequency locking means to cause it to adjust the frequency of the second local oscillator until the frequency of the second IF signal is equal to a second reference frequency; and means using the output of the second local oscillator to transmit a signal at the frequency to which the second local oscillator has been adjusted. - View Dependent Claims (5, 6, 7)
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Specification