Demultiplexer, antenna device, and fading elimination method

摘要

Used is a demultiplexer/multiplexer including: an input terminal, which receives input signals from respective phases of a quadrifilar helix antenna; a first phase shifter/separator/mixer, which is configured to alternately phase shift right-handed circularly polarized waves and left-handed circularly polarized waves of an input signal of phase 1 and phase 2, respectively, by 90°/-90° to produce phase-shifted waves and then combine the phase-shifted waves in an inphase combination; a second phase shifter/separator/mixer, which is configured to alternately phase shift right-handed circularly polarized waves and left-handed circularly polarized waves of an input signal of phase 3 and phase 4, respectively, by 90°/-90° to produce phase-shifted waves, and then combine the phase-shifted waves in an inphase combination; a first phase shifter/mixer, which receives the left-handed circularly polarized waves from the first phase shifter/separator/mixer and the second phase shifter/separator/mixer, and is configured to phase shift one of the left-handed circularly polarized waves by 180°/-180° to produce a phase-shifted wave, and then combine the phase-shifted wave and the other of the left-handed circularly polarized waves in an antiphase combination; a second phase shifter/mixer, which receives the right-handed circularly polarized waves from the first phase shifter/separator/mixer and the second phase shifter/separator/mixer, and is configured to phase shift one of the right-handed circularly polarized waves by 180°/-180° to produce a phase-shifted wave, and then combine the phase-shifted wave and the other of the right-handed circularly polarized waves in an antiphase combination; a variable phase shifter, which is configured to adjust an output signal from one of the first phase shifter/mixer and the second phase shifter/mixer by an amount of phase shift that is received in advance; and an output terminal, which outputs an output signal from the variable phase shifter and the other output signal that is not input to the variable phase shifter. As a result, a multipath effect on the quadrifilar helix antenna is reduced.