Abstract: A digital automatic frequency control for a pulse-type radar receiver having a voltage controlled local oscillator. A first digital number is generated and converted to a first analog voltage for coarse control of the local oscillator frequency. The first digital number is varied during the time output from the radar transmitter is present at the receiver mixer. The first digital number is varied causing sweep of the local oscillator frequency. When the difference frequency output from the mixer is at a value to cause output from the receiver intermediate frequency amplifier of a predetermined level, variation of the first digital number is halted, providing a coarsely tuned local oscillator frequency. A second digital number is then generated, converted to a second analog voltage which is combined with the first analog voltage. The second digital number is varied to cause the local oscillator frequency to be sidestepped above and below the coarsely tuned frequency.

Abstract: A multi-mode radar includes a local oscillator referenced to the radar magnetron and includes logic provided to side step the local oscillator during the latter portion of the radar interpulse period so as to permit adjustment of the receiver gain during this period without interference from distant targets. In addition, IF amplifiers are selectable in accordance with the operational radar mode selected.