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Altitude Measurement Based on Beam Split and Frequency Diversity in VHF Radar

A new beam split altitude interferometry based on altitude diversity and frequency diversity for very high frequency (VHF) radar is proposed in this paper. As opposed to microwave radar, VHF radar has a wide beam which is usually split when ground reflection occurs. The reflected wave which is coherent with the direct wave will always be contained in the target echo. In this paper, several antennas of different heights are utilized. Owing to the certain relationship among the phases of the split beams, the elevation region where the targets are located can be determined using the phases of echoes. Using "amplitude-comparison" of echoes from various antennas to get the normalized error signals, the elevation of the target can be obtained by looking it up in the error signal table. The effect of roughness on the altitude measurement accuracy is also analyzed. The real data processing on flat and slope terrains testifies to the validity of the proposed method. The altitude measurement precision, especially in low-elevation regions, is greatly improved by using frequency diversity.