Multipath phase errors in CW-FM tracking systems

High-precision, cw, missile-tracking systems are subject to multipath errors due to ground reflections and reflections from neighboring objects. To reduce the effects of ground reflection, advantage may be taken of the characteristic of frequency modulation to discriminate against a weaker interfering signal. This paper discusses the magnitude of the phase error reduction to be obtained by use of frequency modulation. It is demonstrated that the phase error can be reduced to any desired value if sufficient band width is utilized in the frequency modulation signal and significant improvement over an amplitude modulation system can be obtained with a wide-band FM system.