Strip line filter having dual mode loop resonators

A strip dual mode loop resonator in which a microwave is resonated, comprising:

• a loop-shaped strip line having a pair of parallel lines arranged in parallel to each other, a line length of the loop-shaped strip line being equal to a wavelength of the microwave to resonate the microwave which is circulated in the loop-shaped strip line in two difference directions according to a characteristic impedance of the loop-shaped strip line, and the parallel lines being coupled to each other in electromagnetic coupling to change the characteristic impedance of the loop-shaped strip line;
• an input strip line in which the microwave is transmitted;
• an input impedance element for coupling the input strip line to the loop-shaped strip line in electromagnetic coupling to transmit the microwave from One input strip line to an input point of tile loop-shaped strip line;
• an output strip line in which the microwave resonated in the loop-shaped strip line is transmitted;
• an output impedance element for coupling the output strip line to the loop-shaped strip line in electromagnetic coupling to transfer the microwave from an output point of the loop-shaped strip line to the output strip line, the output point of the loop-shaped strip line being spaced a half of the wavelength of the microwave apart from the input point of the loop-shaped strip line;
• and
• a line-to-line impedance element arranged between the parallel lines of the loop-shaped strip line for changing the characteristic impedance of the loop-shaped strip line, one end of the line-to-line impedance element connected to one of the parallel lines being spaced a quarter of the wavelength of the microwave apart from the input point of the Loop-shaped strip line, and another end of the line-to-line impedance element connected to the other parallel line being positioned to the output point of the loop-shaped strip line.