AM/FM Noise in the Target Illumination Signal for Semi-Active Missiles

n semi-active missile guidance, a high-power transmitter not collocated with the missile generates continuous wave or interrupted continuous wave illumination that is reflected from the target to the homing missile. Noise introduced into this illumination, which is reflected from rain, chaff, land, or sea clutter or is carried on spillover, can compete with the target return. The Navy has tasked APL to specify allowable illuminator AM/FM noise and to work with its contractors to design stable oscillators and noise test equipment to meet these noise requirements. This article focuses on the effects of noise on system performance, the specification of noise requirements, low-noise X-band sources, and test equipment used to measure noise.