Radar warning receiver
First Claim
1. An apparatus for distinguishing pulsed or continuous signals emitted from a fixed frequency source from other signals generated by a variable frequency source, said apparatus comprising:
- a receiver having a local oscillator and includingfirst means for sweeping the frequency of the local oscillator over a predetermined range of frequency;
second means for mixing said local oscillator signal with said received pulsed or continuous signals and for providing output pulses during each sweep of the local oscillator in response to detection of signals within the receiver bandpass, wherein the time of occurrence of the output pulses during said sweep relative to a zero time reference defined by the beginning of the sweep are representative of the frequencies of the corresponding received signals,correlation means for providing an alarm output in response to repeated occurrences of an output pulse at the same time relative to said zero time reference during a first predetermined number of sweeps of the local oscillator substantially independent of amplitude variations of said repeated output pulses.
19 Assignments
0 Petitions
Accused Products
Abstract
A radar warning receiver includes means for distinguishing pulsed or continuous fixed frequency radar signals emanating from a radar transmitter from variable frequency signals such as those radiated from a nearby superhomodyne receiver. This invention includes a superheterodyne receiver having a local oscillator that is repeatedly varied in frequency over a range of frequencies sufficiently large and at a rate fast enough to cause any signals within an input range of frequencies to be detected by a sensitive, limited bandwidth detector. If an input signal is fixed in frequency, that signal will be detected at the same time during successive sweeps of the local oscillator, and a correlated output will be generated; otherwise, an uncorrelated output will be generated. If the number of correlated outputs equal or exceed the uncorrelated outputs detected, then an alarm is provided. Even when the receiver of this invention is receiving signals from a superhomodyne receiver, if a fixed frequency signal is detected for a predetermined number of consecutive sweeps of the local oscillator, then an alarm, indicating the presence of that fixed frequency signal, is again provided.
59 Citations
20 Claims
-
1. An apparatus for distinguishing pulsed or continuous signals emitted from a fixed frequency source from other signals generated by a variable frequency source, said apparatus comprising:
-
a receiver having a local oscillator and including first means for sweeping the frequency of the local oscillator over a predetermined range of frequency; second means for mixing said local oscillator signal with said received pulsed or continuous signals and for providing output pulses during each sweep of the local oscillator in response to detection of signals within the receiver bandpass, wherein the time of occurrence of the output pulses during said sweep relative to a zero time reference defined by the beginning of the sweep are representative of the frequencies of the corresponding received signals, correlation means for providing an alarm output in response to repeated occurrences of an output pulse at the same time relative to said zero time reference during a first predetermined number of sweeps of the local oscillator substantially independent of amplitude variations of said repeated output pulses. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18)
-
-
2. In an apparatus for detecting the presence of continuous or pulsed radio frequency signals within an input range of frequencies, said apparatus including:
-
a local oscillator, a limited bandwidth detector circuit, means for sweeping the frequency of the local oscillator over a range sufficiently large, and at a rate fast enough that any radio frequency signal occurring within said input range of frequencies will fall within the limited response bandwidth of said detector circuit, said detector circuit providing a detect output pulse in response to sensing a radio frequency signal within its limited bandwidth, the improvement comprising; means for discriminating against variable radio frequency signals occurring within said range of frequencies, said means including; means for comparing the frequencies of the detected radio frequency signals during each sweep of the local oscillator, and means for providing an alarm output in response to the occurrence of a detected radio frequency signal at the same frequency during multiple sweeps of the local oscillator. - View Dependent Claims (19, 20)
-
-
3. In an apparatus for detecting the presence of fixed frequency continuous or pulsed radio frequency signals within an input range of frequencies, said apparatus including:
-
a local oscillator, a limited bandwidth detector circuit, means for sweeping the frequency of the local oscillator over a range sufficiently large, and at a rate fast enough that any radio frequency signal occurring within said input range of frequencies will fall within the limited response bandwidth of said detector circuit, wherein said means for sweeping the frequency of the local oscillator includes a sweep generator providing a variable output signal for controlling the frequency of said local oscillator, clocking signals and a start signal representing the beginning of each sweep, said detector circuit providing a detect output pulse in response to sensing a radio frequency signal within its limited bandwidth, the improvement comprising; clock means responsive to said clocking signals for providing a first predetermined number of clock pulses during each sweep of the local oscillator, delay line means responsive to said clock pulses and to said detect output pulses for storing the detect pulses from one sweep of the local oscillator, means for comparing the detect output pulses from said detector circuit, and the detect pulses from a previous sweep stored in said delay line means for providing a correlated output pulse in response to the coincidence of said detect pulses and an uncorrelated output pulse whenever said detect pulses are not coincident, counter means for comparing the number of correlated output pulses to the number of uncorrelated output pulses during each said sweep, and means responsive to the status of said counter means at the beginning of each said sweep for providing an alarm output whenever the number of correlated output pulses bears a predetermined relationship to the number of uncorrelated output pulses. - View Dependent Claims (4, 5, 6, 7, 8, 9)
-
Specification