| 摘要 |
PROBLEM TO BE SOLVED: To increase a relative out-band attenuation of the filter. SOLUTION: In a multi-stage connection of a lateral mode coupling surface acoustic wave(SAW) filter, inputs 10, 12 are balanced signal inputs, an inter- stage connection between a 1st stage filter and a 2nd stage filter is realized as an unbalance connection, the 1st stage output 11, the 2nd stage input 20 and the 1st stage output 13, the 2nd stage input 22 are connected to ground. Then outputs 21, 23 of the 2nd stage act again like balanced signal outputs. Though the configuration above, propagation of an electric direct wave from the inputs 10, 12 of the device to the outputs 21, 23 can be prevented. As a result, the attenuation of the device at other bands than the pass band of the filters, that is, the block band in the filter characteristic can be improved.
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