| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a band pass filter eliminating an unnecessary frequency component in a mixer output of superheterodyne structure, having a large attenuation characteristic in a broad range of a signal pass band. <P>SOLUTION: The band pass filter is configured by a multiple stages of cascade connection of full differential operational amplifiers OP1i-OP3i, OP1q-OP3q and a plurality of low pass filters, composed of resistors R1-R3 and capacitors C1-C3, Cz connected in parallel between the inputs and the outputs of the operational amplifiers. Among the low pass filters in cascade connection, a capacitor is added to one filter, so that a zero point is provided only in a frequency on the minus side. By the change to a notch filter by adding the capacitor, the zero point is added to a low signal pass band frequency, and thus, the large attenuation characteristic can be obtained in the broad range of the signal pass band. <P>COPYRIGHT: (C)2012,JPO&INPIT |
