Frequency agile imaging radar with error frequency correction

摘要

A system is disclosed for utilizing frequency agile magnetron radars to perform one, two and three dimensional target imaging using coherent frequency agile radar waveforms. The pulses from a frequency agile magnetron are controlled so that their frequencies are approximately those of a highly coherent stepped frequency source. Means are provided for monitoring the magnetron's tuning piston position read-out voltage and for triggering the pulse forming network associated with the magnetron at the occurrence of each one of a set of predetermined read-out voltage levels. A feedback loop is utilized to determine the difference between the frequencies of the actual output pulses of the magnetron and a set of precise, stepped reference frequencies. Correction values are generated and are utilized to generate a new set of magnetron read-out voltage levels at which the pulse forming network is to be triggered. The phase of the echo pulse is measured for each frequency step of each burst from the magnetron. The transmit and echo phase are obtained from the in-phase and quadrature samples produced by two sample gates. Subtraction of the transmit phase from the receive phase is carried out digitally by a digital mixer.