Doppler direction finder with noise suppression - obtains sum and difference values from separate reception channels

摘要

The Doppler direction finder uses a frequency modulated HF signal and an antenna (1) with a rotating antenna characteristic. This antenna (1) is coupled to one reception channel (3) while a reception antenna is coupled to a second reception channel (5), the output voltages (Up,Ur) of both channels being held at the same amplitude and used to obtain sum and difference values fed to an evaluation circuit. The latter includes a multiplier (13), a filter (14) and a rectifier (15) and indicates whether or not a phase offset of 90 degrees exists between the min. and difference voltages. Pref. this filter (14) comprises a low-pass filter, several frequency adjacent band-pass filters or a Fourier processor.