Frequency control for frequency agile pulse radar

A frequency agile pulse radar comprising:

• a transmitter for transmitting a frequency modulated signal;
• a local oscillator for generating a mixing signal;
• an average frequency control responsive to the frequency modulated signal of said transmitter and to the mixing signal of said local oscillator, said average frequency control providing a discriminator signal of a pulse train whose envelope varies at the frequency modulation rate of said transmitter signal, said average frequency control also providing an average frequency signal for controlling the average frequency of the local oscillator signal with respect to the average frequency of the transmitter signal;
• a frequency transducer for monitoring the frequency of the transmitter signal;
• a sample and hold network responsive to said frequency transducer, said sample and hold network amplifying the output of said frequency transducer to provide a modulating signal prior to the transmission of the transmitter signal;
• and
• a modulation gain control responsive to said frequency transducer and to the discriminator signal of said average frequency control, said modulation gain control providing an output signal to the local oscillator, said output signal being an attenuation of the modulating signal with respect to the discriminator signal to compensate for variations in the modulating signal due to variations in the electrical and mechanical transfer functions of the transducer and the sample and hold circuit.

An improved frequency agile pulse radar that transmits a frequency agile output signal, and that is responsive to echos of the transmitted signal, said radar having a transmitter for transmitting frequency modulated signal pulses;

• a local oscillator for generating a mixing signal;
• a mixer for mixing the oscillator signal with echos of the transmitter signal to provide an intermediate frequency signal;
• and a filter responsive to said intermediate frequency signal to provide an output signal, said filter having a bandwidth substantially matched to the pulse width of the signal pulses of said transmitter signal;
• wherein the improvement comprises:
• an average frequency control responsive to the frequency modulated signal of said transmitter and to the mixing signal of said local oscillator, said average frequency control providing a discriminator signal of a pulse train whose envelope varies in accordance with the frequency modulation rate of said transmitter signal, said average frequency control also providing an average frequency signal for controlling the average frequency of the local oscillator signal with respect to the average frequency of the transmitter signal;
• a frequency transducer for monitoring the frequency of the transmitter signal;
• a sample and hold circuit responsive to said frequency transducer, said sample and hold network amplifying the output of said frequency transducer to provide a modulating signal;
• and
• a modulation gain control responsive to said frequency transducer and to the discriminator signal of said average frequency control, said modulation gain control attenuating the modulating signal of the sample and hold circuit to provide an output signal to the local oscillator, said modulation gain control attenuating the modulating signal to compensate for variations in the gain of the frequency transducer and the local oscillator.

A method for frequency modulating an oscillator of a radar set in response to the frequency modulation of the radar transmitter, said method comprising:

• transmitting a frequency modulated signal from the transmitter;
• mixing the transmitter signal and the oscillator signal to provide an intermediate frequency signal;
• controlling the average frequency of the oscillator signal in response to the average frequency of said intermediate frequency signal;
• and
• determining the average value of the commutation of the intermediate frequency signal with respect to the frequency modulation of said transmitter;
• modulating the average frequency of said oscillator in response to the frequency modulation of said transmitter and in response to the average value of the commutated intermediate frequency signal.