| 摘要 |
A quadraphase modulato comprising a first and a second quadrature hybrid, a first and a second phase reversal switch, a selector switch and a switch control means. The quadrature hybrids are connected in tandem by means of two lines connected between the two output ports of the first hybrid and the two input ports of the second hybrid with a phase reversal switch being connected in series with each of these lines. The input port of the quadraphase modulator is one of the input ports of the first hybrid while the output port of the quadraphase modulator is one or the other of the two output ports of the second hybrid. The positions of the phase reversal switches determine the port at which the output signal will appear and its relative phase, which maybe 0, 90, 180 or 270 degrees. The switch control means sets the positions of the phase reversal switches and thus the phase of the output signal and the output port of the second hybrid at which the output signal will appear. The switches control means automatically sets the selector switch to the proper output port to receive the output signal, thereby providing at the selector switch, a single output port for the quadrature modulator. Due to the use of tandem quadrature hybrids which inherently produce signals at low loss that are very nearly in precise quadrature, the present invention provides improved phase accuracy, insensitivity to amplitude imbalance and typically 3 dB less loss than conventional quadraphase modulators.
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