Filter, communication module, and communication apparatus

Abstract

A filter includes a substrate; a signal line formed on the substrate and including an input terminal and an output terminal at either end of the signal line; and a first pair of resonant lines connected between the signal line and a ground portion, wherein the first pair of resonant lines are connected to the signal line at the same point.

What is claimed is: 
     
         1 . A filter comprising:
 a substrate;   a signal line formed on the substrate and including an input terminal and an output terminal at either end of the signal line;   a first pair of resonant lines connected between the signal line and a ground portion, wherein   the first pair of resonant lines are connected to the signal line at a same point;   a second pair of resonant lines connected between the signal line and the ground portion;   a coupling section provided between the first pair of resonant lines and the second pair of resonant lines, wherein   the coupling section includes:
 a first circuit block connected to the signal line and including a first terminal and a second terminal; 
 a second circuit block connected between the first terminal of the first circuit block and the ground portion; and 
 a third circuit block connected between the second terminal of the first circuit block and the ground portion. 
   
     
     
         2 . The filter according to  claim 1 , wherein
 the coupling section includes:   a first circuit block and a second circuit block connected in series to the signal line; and   a third circuit block connected between a point between the first circuit block and the second circuit block, and the ground portion.   
     
     
         3 . The filter according to  claim 1 , wherein
 the plurality of resonant lines are connected to the same ground portion.   
     
     
         4 . The filter according to  claim 1 , wherein
 the resonant lines are formed into an arc shape.   
     
     
         5 . The filter according to  claim 1 , further comprising:
 a variable capacitor including a variable capacitor electrode provided above the resonant line via an air gap and a drive electrode for changing distance between the variable capacitor electrode and the resonant line.   
     
     
         6 . The filter according to  claim 1 , wherein
 the substrate is a ceramic substrate including a plurality of laminated internal wirings.