Ladder-type filter and communication device using the same

摘要

A ladder-type filter contains a broad-band filter and narrow-band filter, and the output terminal of the broad-band filter is switched to an output terminal or the narrow-band filter by a switch. In the signal processing circuit of a communication device, the output signal of a mixer circuit is input into the broad-band filter of the ladder-type filter. By changing the switch, the output signal of the broad-band filter is made to be output from the output terminal directly or through the narrow-band filter. The broad-band filter and narrow-band filter are desirable to be formed on one substrate. <IMAGE>