| 摘要 |
Circuit arrangement for shifting the phase of an input signal, which circuit arrangement consists of two branches whose two output signals are 90° phase-shifted, and use of this phase shifter in a circuit arrangement for suppressing the mirror frequency. The filter systems in the two branches of the phase shifter are implemented in such a way that the phase difference between these two branches is 90°, independent of the frequency of the input signal. In the mirror frequency circuit, a frequency band is amplified or blanked during transmission. The base frequency BF constitutes the center of the frequency band. The amplitude difference is small in the solutions according to the invention. The amplitude difference is improved when the two 90° phase-shifted signals are matched or substantially equalized as regards their amplitude. The matching is performed in that the two signals are rectified and subsequently subtracted from each other. The result is supplied to an integrator whose output signal, together with a reference signal, constitutes the control value. This results in a substantially ideal suppression of the mirror frequency. The circuit arrangement can be used in a radio or television receiver.
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