Band-pass filter

A band-pass filter comprising:

• an input end for inputting electromagnetic signals;
• an output end corresponding to the input end, for outputting electromagnetic signals;
• a first coupling line, electronically connected to the input end;
• a second coupling line, parallel to the first coupling line and electronically connected to the output end;
• a resonator, disposed between the first coupling line and the second coupling, and defining a groove therein.

A band-pass filter comprising:

• an input line for inputting electromagnetic signals;
• an output line for outputting said electromagnetic signals;
• a first coupling line electrically connectable with said input line to receive said input electromagnetic signals from said input line;
• a second coupling line spaced from said first coupling line and electrically connectable with said output line to transmit said electromagnetic signals to said output line for outputting;
• and
• a resonator disposed between said first coupling line and said second coupling line, and spaced from both of said first and second coupling lines, said resonator formed as a closed-loop shape and electrically coupling with said first and second coupling lines respectively in order to transmit and filter said electromagnetic signals passing through said resonator.