Height Finding Technique of Metric Wave Radar

Abstract

The main difficulties in low-elevation height finding of VHF radar are as follows: (1) VHF radar is characterized by long wavelength, wide beam, low angle resolution and high accuracy of measurement. (2) Pitch beam is easy to illuminate the ground, so the received beams include not only the direct wave signals reflected from the targets, but multipath signals reflected from the ground (the sea surface) because it tracks targets in low elevation, which results in lobe splitting. It causes the detection and measurement errors increase. (3) When detecting low elevation targets, multipath reflections and strongly correlated direct waves enter the receiving beam mainlobe simultaneously. (4) The included angle between the direct wave and multipath echoes is very small and is usually within one beamwidth, so the conventional angle measurement method by amplitude comparison becomes invalid. (5) Reflections of undulating surfaces and irregular reflectors (such as vegetation and buildings) will result in complicated multipath reflections, such as diffuse reflections and scattering, which are difficult to model and will have a strong impact on the height-finding performance of metric wave radar. (6) Height-finding technique of metric wave radar is not only suitable for complanate site, but also for a variety of other environments, such as rough terrain, mountain environment and some complex sites.