TABLE OF CONTENTS Of course, frequency coverage of the antenna system and receiver front-end must include all of the frequencies used by the transmitters of interest. In many cases, the frequencies in use are not known, and thus wide frequency coverage is the rule for intercept systems. Since the total range of frequencies potentially used by radar and radar-related systems is so broad (ranging from below 30 MHz to above 100 GHz), the coverage must be divided into bands compatible with practical components (e.g., antennas, amplifiers, mixers, filters, and detectors). The typical system makes use of octave bands (i.e., the ratio of the upper band edge frequency to the lower band edge frequency is 2:1). This is useful in that any harmonics which may be generated by nonlinearities will be outside the band. Broader bands are possible and practical, particularly in receivers which do not use frequency conversion (heterodyne conversion), such as crystal video or instantaneous frequency measurement (IFM) types (also termed direct detection receivers). In the microwave region, coverage of several octaves in one antenna and receiver can be achieved (e.g., 1 to 10 GHz), if desired.
Both radar designers and intercept receiver designers are subject to the constraints of the state of the art in components. However, the designer of a particular radar, who must design a high power transmitter as well as a receiver, is generally subject to more constraints than the intercept receiver designer when it comes to the band covered by the radar s...
