Frequency selecting/switching circuit

A frequency selecting/switching circuit comprising:

• an input terminal to input a signal;
• an output terminal to output a signal;
• a two-way splitter circuit that has an input end connected to the input terminal, splits the signal inputted to the input terminal into a first frequency component and a second frequency component, and outputs the first frequency component to a first output end and the second frequency component to a second output end;
• a first phase-adjusting circuit having a first end connected to the first output end of the two-way splitter circuit;
• a second phase-adjusting circuit having a first end connected to the second output end of the two-way splitter circuit;
• a first switch having an input end connected to a second end of the first phase-adjusting circuit and an output end directly or indirectly connected to the output terminal, the first switch being configured to switch an output of a signal inputted to the input end, to the output end between a conductive state and a non-conductive state;
• and
• a second switch having an input end connected to a second end of the second phase-adjusting circuit and an output end directly or indirectly connected to the output terminal, the second switch being configured to switch an output of a signal inputted to the input end, to the output end between the conductive state and the non-conductive state, wherein
• when a signal having a frequency of the second frequency component passes through the first switch in the conductive state and the first phase-adjusting circuit, is reflected at the first output end of the two-way splitter circuit, and passes again through the first phase-adjusting circuit and the first switch in the conductive state, the first phase-adjusting circuit adjusts a phase of the signal outputted last from the first switch and a phase of the signal inputted first to the first switch to a same phase,
• when a signal having a frequency of the first frequency component passes through the second switch in the conductive state and the second phase-adjusting circuit, is reflected at the second output end of the two-way splitter circuit, and passes again through the second phase-adjusting circuit and the second switch in the conductive state, the second phase-adjusting circuit adjusts a phase of the signal outputted last from the second switch and a phase of the signal inputted first to the second switch to a same phase,
• the first phase-adjusting circuit is a transmission line whose electrical length θ1 is equal to θ1(f2) obtained from Equation (1), as follows:
• 2(θS(f2)+θ1(f2))−φd1(f2)=±2nπ (1)
• here, θ1(f2) is a pass phase of the first phase-adjusting circuit at a frequency component f2, θs(f2) is a pass phase of the first switch in an ON state at the frequency component f2, φd1(f2) is a reflection phase of an f1 output terminal of the two-way splitter circuit at the frequency component f2, and n is a natural number including zero;
• and
• the second phase-adjusting circuit is a transmission line whose electrical length θ2 is equal to θ2(f1) obtained from Equation (2), as follows:
• 2(θS(f1)=θ2(f1))−φd2(f1)=±2mπ (2)
• here, θ2(f1) is a pass phase of the second phase-adjusting circuit at a frequency component f1, θs(f1) is a pass phase of the second switch in an ON state at the frequency component f1, φd2(f1) is a reflection phase of an f2 output terminal of the two-way splitter circuit at the frequency component f1, and m is a natural number including zero.