Internal calibration system

Appartus for automatically calibrating a pulse-type radar receiver, which comprises:

• pulse generation means coupled to a radar trigger for producing pulses of RF radiation at a selectable time delay after receiving said radar trigger for injection into the radar receiver to simulate signals reflected from a target;
• attenuation control means coupled to said pulse-generation means for selectively varying the attenuation of said time-delayed RF pulses, said attenuation control means comprising a first down-counter, a second down-counter, a tens attenuation selector for setting the initial count in said first down-counter, a ones attenuation selector for setting the initial count in said second down-counter, a first storage register coupled to said first down-counter to receive the counts from said first down-counter, a second storage register coupled to said second down-counter to receive the count from said second down-counter, a modulus - n - divider coupled to said first and said second storage registers for transferring the count in said first down-counter to said first storage register and the count in said second down-counter to said second storage register each nth count, means coupled to said first and said second storage registers for attenuating said RF pulses corresponding to the counts in said first and said second storage registers, and means for resetting said first and said second down-counters with the initial counts when the counts in said first and said second down-counters are zero;
• range control means control coupled to said pulse-generation means for selecting the time delay of said RF pulses, said range control means comprising a third down-counter coupled to said pulse-generation means to select the time delay of said RF pulses, said third down-counter being further coupled to said attenuation control means so that the third down-counter is clocked when the counts in said first down-counter and said second down-counters are zero, and a range selector coupled to said third down-counter for setting the initial count in said third down-counter;
• manual/automatic control means coupled to said range control means to control the counting of said third down-counter and to reset said third down-counter to the initial count when the count is zero, said manual/automatic control means further coupled to said attenuation control means to control the counting of said first and said second down-counters;
• and
• display and evaluation means coupled to said attenuation control means and to a radar lock signal for determining the amplitude of said RF pulses which produces a radar lock, said display and evaluation means further comparing the amplitude of said RF pulses which produces a radar lock with a predetermined standard to provide an indication of the radar receiver's operational status.