Patent ID: 6927648

Claim:
A multiplexer comprising: a first demultiplexing filter circuit for separating a frequency band including a first RF signal f 1 , a second RF signal f 2 , a third RF signal f 3 and a fourth RF signal f 4 different from one another (where f 1 <f 2 <f 3 <f 4 ) into a frequency band which includes the f 1 and the f 2 but neither of the f 3 and the f 4 practically, and a frequency band which includes the f 3 and the f 4 but neither of the f 1 and the f 2 practically; a second demultiplexing filter circuit for separating the frequency band including the f 1 and the f 2 which is obtained by the separation of the first demultiplexing filter circuit into a frequency band which includes the f 1 but none of the f 2 to the f 4 practically, and a frequency band which includes the f 2 but none of the f 1 , the f 3 and the f 4 practically; and a third demultiplexing filter circuit for separating the frequency band including the f 3 and the f 4 which is obtained by the separation of the first demultiplexing filter circuit into a frequency band which includes the f 3 but none of the f 1 , the f 2 and the f 4 practically, and a frequency band which includes the f 4 but none of the f 1 to the f 3 practically, wherein the second demultiplexing filter circuit comprises a filter of combination of low-pass and band elimination filters or a band pass filter as a filter where the frequency band including the f 2 but none of the f 1 , the f 3 and the f 4 practically is set to be a pass band, and the third demultiplexing filter circuit comprises a filter of combination of high-pass and band elimination filters or a band pass filter as a filter where the frequency band including the f 3 but none of the f 1 , the f 2 and the f 4 practically is set to be a pass band, wherein the second demultiplexing filter circuit comprises a low-pass filter as a filter where the frequency band including the f 1 but none of the f 2 to the f 4 practically is set to be a pass band, and the third demultiplexing filter circuit comprises a high-pass filter as a filter where the frequency band including the f 4 but none of the f 1 to the f 3 practically is set to be a pass band.