| 摘要 |
An unbalanced quarternary phase-shift keying modulator provides relatively higher signal power for one of two signal information channels. The carrier to be modulated is split into two equal-amplitude, equal-phase portions, each of which is applied to a biphase modulator. Each of the information signals is also applied to one of the biphase modulators, for producing two equal-amplitude, phase modulated carriers, each biphase modulated by one of the information signals. The modulated carriers are applied to the ports of a quadrature hybrid coupler which is other than a 3 dB (equal-amplitude) coupler. In one embodiment, the coupler is a 7 dB coupler. The modulated carrier applied to the through port of the coupler appears with reference amplitude and phase at the output of the hybrid. The modulated carrier applied to the other or coupled port appears at the output with relatively reduced amplitude and a relative phase shift. In one embodiment, the phase shift is 90 DEG . The resulting sum signal is quarternary keyed by the information signals. Waveguide and microstrip unbalanced couplers are described.
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