| 摘要 |
397,571. Impedance networks. GENERAL ELECTRIC CO., Ltd., Magnet House, Kingsway, London, and LEY, D. A., c/o General Electric Co., Coventry. March 14, 1932, No. 7527. [Class 40 (iii).] A low-loss transformer terminating-impedance for a filter is matched over a substantial part of the pass range but mismatched in the attenuation range. Thus the network shown is matched in the pass range to a filter connected at 1, 2, while a valve input circuit of infinite impedance is connected at 3, 4. The Specification gives examples in which for a T-section filter the match is effected for the geometrical mean of the cut-off frequencies of the filter ; the termination shown is made resonant at this frequency and its (purely resistive) impedance at that frequency is made equal to the image impedance of the filter. A further relation is obtained by equating the real part of the terminating impedance to that of the filter image impedance at a frequency midway between one of the cut-offs and the geometric mean of the cut-offs. The Specification also gives an example of a lattice-section filter in which matching is effected at the mid-frequency of the pass range and at frequencies near the cut-offs.
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