Doppler radio direction finder - evaluates transient HF signals using circular array of cyclically scanned dipole antenna

摘要

A Doppler radio direction finder has several receiver antenna arranged on a circle and with a cyclic scanner. It can receive and evaluate horizontally polarised and abruptly occurring spatial waves of any polarisation in the short wave region, unlike devices with exclusively vertical monopoles or dipoles. This is aachieved without loss of directional sensitivity. Suitable frame or dipole antenna are used for reception of circularly polarised waves. They may be vertical crossed frame antenna or horizontally crossed dipole antenna. Individual frame or dipole antenna are scanned individually by the cyclic scanner. The individually acquired rotating receiver signals are assembled, using 90 degree phase shifts, into a left or right rotating circularly polarised signal by a further circuit. The left or right rotating output may be selected for evaluation by a switch.