Radar warning receiver

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.

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.