RF Filter Circuit, RF Filter with Improved Attenuation and Duplexer with Improved Isolation

摘要

A filter circuit providing improved attenuation, a filter having improved attenuation and a duplexer with improved isolation are provided. The filter circuit has a first and a second coupling conductor segment which couple an input port to a ground port or the filter's output port. The filter circuit can be realized in the filter. The duplexer can comprise the filter, especially as its transmission filter.

主权项

1. An RF filter circuit, comprising:
an input port with an input terminal; an output port with an output terminal; a signal path between the input port and the output port, the signal path having a first series resonator; a ground terminal; a first coupling conductor segment that is a part of the signal path, the first coupling conductor segment and being directly connected to the input terminal; and a second coupling conductor segment directly connected to the output terminal or to the ground terminal, wherein the first coupling conductor segment and the second coupling conductor segment are arranged next to each other and are electromagnetically coupled such that the coupling enhances attenuation of the RF filter circuit in a rejection frequency band.