| 摘要 |
PROBLEM TO BE SOLVED: To reduce the leakage of local oscillation signal into a modulated output signal in digital radio communication equipment mainly utilizing the phase modulation system ofπ/4.shift QPSK. SOLUTION: This equipment is provided with a 1st quadrature modulation part 2 for outputting a modulated signal through quadrature phase modulation by inputting I-signal and Q-signal S1 and S2, to which the DC offset of a required voltage is applied respectively, and the local oscillation signal from a local oscillator 3 and a quadrature modulation part 4 equal with the 1st quadrature modulation part 2. Besides, this device is provided with local oscillation signal leak detecting means (4 to 8) for inputting this local oscillation signal, detecting the leak component of the local oscillation signal contained in the output signal of the quadrature modulation part, generating a reference voltage Vr corresponding to this detection and inputting the reference voltage to the 1st quadrature modulation part 2, and the leak component of the local oscillation signal in the output signal of the 1st quadrature modulation part is reduced by the reference voltage Vr.
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