| 摘要 |
PURPOSE: To improve the signal exclusion performance of a prescribed frequency by providing an additional inductor in the branch leg of theπ-type part of an inductance M-type constant K high pass filter having an intermediateπ-type filter part and resonating to the bridging capacitance of thisπ-type part to form an additional trap in the prescribed frequency. CONSTITUTION: An intermediate filter part 28 isπ-type and is provided with an inductor 30 which branches a signal line, a capacitor 32 connected in series to the signal line, and a branch inductor 34, and values of the capacitor 32 and inductors 30 and 34 are selected in accordance with calculation of an inductive M-type constant K filter circuit network so that the corner frequency is about 52MHz. The signal obtained from the intermediate filter part 28 and subjected to high pass filtering processing is coupled to an output filter part 36 including an inductor (L) 38, which forms a parallel connection resonance circuit 43 connected in series to the signal line, and a parallel capacitor 40. Thus, an inductor 42 is additionally provided in the earth-side leg of each of inductors 30 and 34, and an additional CB trap is added without inserting an additional circuit element to a printed circuit board neither reducing the function of a filter 14.
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