| 摘要 |
<p>PROBLEM TO BE SOLVED: To shorten the time required for measurement of all bands and make the measurement precise by switching the gain of GPF circuit and/or the gain of a peak hold circuit according to at least one switching of the central frequency of the pass band. SOLUTION: The frequency is set to f2=f1/2, f3=f1/4, fn=f1/2<n-1> , and the gain is set to A1=1, A2=2, An=2<n-1> . A capacitor is selected according to the central frequency of the pass band to switch the gain. One of capacitors Ci1-Cin is selected by one pair of analog switches Xi1-Xin. ON/OFF is performed according to control signals M1-Mn. When only the control signal Mn is active, a pair of switches X1n, X2n are simultaneously ON, the central frequency is set to the pass band of fn, and the gain is set to An. The measuring time of the pass bands of the central frequencies f1-fn can be set to the shortest measuring times, so that the whole measuring time can be thus shortened, and the precision can be also ensured with the shortest time necessary and sufficient for measurement.</p> |
