Title: Automatically centered pulsed radar receiver

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1. In a pulsed non-coherent radar system of the class in which each transmitted pulse is sampled and compared with a reference frequency to generate an error signal which controls a local oscillator frequency to cause the return signal intermediate frequency to equal the reference frequency, the improvement comprising frequency adjusting means coupled to the reference frequency source, sampling means for sampling the receiver intermediate frequency signal between return pulses, and frequency comparator means for comparing the sampled intermediate frequency to the reference frequency to generate a second error signal for driving the frequency adjusting means whereby the reference frequency is maintained equal to the actual center frequency of the receiver filter pass band.

2. A pulsed non-coherent radar system comprising:

transmitter means for transmitting RF pulses towards a target,

receiver means for receiving RF pulses reflected from a target and for generating an IF signal in response thereto,

an electronically tunable frequency reference,

a frequency discriminator coupled to the transmitter, the receiver, and the frequency reference for tuning the frequency reference to the frequency of the receiver thermal noise output and for maintaining the receiver IF at said noise frequency.

3. A pulsed non-coherent radar system comprising:

a. a detecting means for detecting the true center frequency of an input filter, said detecting means including an electronically tunable frequency reference, and a frequency discriminator coupled to the frequency reference and to the input filter for comparing the frequency of thermal noise passing through said filter to said frequency reference to produce a first error signal proportional to the frequency difference and for tuning the frequency reference to reduce said first error to zero; and

b. adjusting means for adjusting a receiver intermediate frequency to said true center frequency of the input filter, said adjusting means including an electronically tunable local oscillator, and the frequency discriminator coupled to the frequency reference, the local oscillator, and a radio frequency transmitter for mixing the transmitter output signal with the local oscillator output to produce an intermediate frequency, comparing the intermediate frequency to the frequency reference to produce a second error signal proportional to the frequency difference, and beating the output of the local oscillator with the frequency of the second error signal to adjust the output frequency of the local oscillator and reduce said second error to zero.

4. A pulsed non-coherent radar system comprising:

a. an electronically tuned local oscillator;

b. a transmitter means for transmitting radio frequency pulses towards a target, said transmitter means including a mixer coupled to the transmitter means and electronically tuned oscillator;

c. a receiver means for receiving radio frequency pulses reflected from a target, a mixer coupled to the receiver means and electronically tuned local oscillator;

d. a frequency discriminator including a frequency reference means; and

e. a gating means for selectively coupling said frequency discriminator to the transmitter means and electronically tuned oscillator for producing an intermediate frequency, comparing the intermediate frequency with the frequency of the frequency reference means to produce a first error signal proportional to the frequency difference and applying the first error signal to the local oscillator to reduce the error to substantially zero, and coupling said frequency discriminator to said receiver means and said frequency reference for comparing the frequency of thermal noise passing through the receiver means to the frequency of frequency reference means and producing an error signal proportional to the frequency difference and applying said error signal to the frequency reference means to reduce the error signal to substantially zero.

5. A pulsed non-coherent radar system comprising:

a. a detecting means for detecting the true center frequency of an input filter, said detecting means including an electronically tunable frequency reference, and a frequency discriminator selectively coupled to the frequency reference and to the input filter for comparing the frequency of thermal noise passing through said filter to said frequency reference to produce a first error signal proportional to the frequency difference and for tuning the frequency reference to reduce said first error signal to zero; and

b. an adjusting means for adjusting a receiver intermediate frequency to said true center frequency of the input filter, said adjusting means including an electronically tunable local oscillator, a radio frequency transmitter, and a mixer said mixer beating the local oscillator signal with the radio frequency transmitter output to produce an intermediate frequency signal, said mixer selectively coupled to the frequency discriminator for comparing the intermediate frequency signal with the frequency reference signal, said frequency discriminator producing a second error signal and applying said second error signal to the local oscillator for changing the local oscillator frequency to reduce said second error to zero.

6. A pulsed radar system comprising:

a. a RF transmitter means for selectively transmitting pulses of RF energy, said transmitter means including a modulator trigger, and a mixer for receiving a portion of the pulses of RF energy being transmitted;

b. an RF receiver means for detecting the pulses of RF energy reflected from a target, said receiver means including a mixer and a filter means coupled to said mixer for selectively passing transmitted pulse widths;

c. a local oscillator means for producing a carrier frequency for the transmitter means mixer for beating the oscillator carrier frequency with a sample of the RF pulses being transmitted, and for the receiver mixer for beating the local oscillator signal with reflected RF pulses;

d. a frequency discriminator including a tunable frequency reference means coupled to a phase detector;

e. gating means coupled to the radar modulator signal, transmitter mixer and receiver filter means for selectively coupling the output signal of the transmitter mixer to the frequency discriminator for producing an error signal proportional to the frequency difference for changing the carrier frequency of the local oscillator, and the output of the receiver filter means to the frequency discriminator for producing an error signal proportional to the frequency difference; and

f. an error feedback integrator coupled to the output of the frequency discriminator for feeding back the filter means frequency difference error signal to the tunable frequency reference means to automatically tune the frequency reference of the frequency discriminator whereby the carrier frequency of the local oscillator and the frequency of the tunable frequency reference is adjusted to produce zero error signals.

Other info:

Inventors: Couvillon, James B. (Dallas, TX, US)

Application Number: 495163
Filing Date: 1974-08-06
Publication_date: 1976-04-27
Assignee: Texas Instruments Incorporated (Dallas, TX)
Primary Class(es): 342/100
Other Classes:
US Patent Ref:

3707718

Dec, 1972

Ames

343/7.

Other Refs:
Primary Examiner: Tubbesing, T. H.
Assistant Examiner:
Attorney: Levine; Harold, Grossman; Rene' E., Bandy; Alva H.