| 摘要 |
PCT No. PCT/FI93/00566 Sec. 371 Date Nov. 13, 1995 Sec. 102(e) Date Nov. 13, 1995 PCT Filed Dec. 29, 1993 PCT Pub. No. WO94/16496 PCT Pub. Date Jul. 21, 1994A device and a method for adjusting a bandpass filter, especially a combiner filter. The method includes deriving an RF sample signal proportional to the power of a modulated RF signal which is one of: passing forward to the bandpass filter, reflected from the input of the bandpass filter and passed through the bandpass filter; down-converting the sample signal by another RF signal; detecting the signal strength of the mixing result; adjusting the center frequency of the passband of the bandpass filter on the basis of the detected signal strength. There is an essential frequency or modulation difference between the signals to be mixed, and so the mixing result is an AC signal of a lower frequency. No accurate adjustment of the phase relation of the signals to be mixed is required. Preferably, the frequency or phase difference between the signals to be mixed is accomplished by utilizing the phase modulation contained in the transmission when one of the signals is unmodulated. The DC component is filtered off the AC signal, which eliminates the measuring problems that otherwise would be caused by the DC offset properties of the mixer./!
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