TABLE OF CONTENTS Multipath is a free space signal transmission path that is different from the desired, or direct, free space signal transmission path, in radar and communications applications. The amplitude, phase and angle of arrival of the multipath signal interferes with the amplitude, phase and angle of arrival of the desired, or direct path signal. This interference can create errors in angle of arrival information and in received signal amplitude in some radar applications. Angle of arrival errors are called "glint" errors. Amplitude fluctuations are called "scintillation" or "fading" errors. Therefore, the angle of arrival, the amplitude and the phase of the multipath signal are all critical parameters to consider when analyzing the effects of multipath signals in radar receivers.
Frequency diversity and spread spectrum systems contain a degree of immunity from multipath effects because these effects vary with frequency. For example, one frequency component for a given range and angle may have multipath which severely distorts the desired signal whereas another frequency may have little effect. This is mainly due to the difference in wavelength of the different frequencies.
Multipath reflections can be separated into two types of reflections, specular and diffuse, and are generally a combination of both specular and diffuse. Specular multipath is a coherent reflection, which means that the phase of the reflected path is relatively constant with relation to the phase of the direct path signal. This type of reflection usually causes the greatest distortion of the direct path signal because most...
