PURPOSE: An UWB(Ultra Wide Band) low pass filter having a specific frequency band obstruction function is provided to reduce the whole size by forming a micro-strip line connected with an output port of a ring resonator into a meander line. CONSTITUTION: A ring resonator(210) comprises an input port(211) and an output port(212). The input port and the output port are formed into an inter-digital type line in order to improve rejection band characteristics. An open type stub(220) is perpendicularly arranged on a micro-strip line. The open type stub is formed into a linear shape. The micro-strip line is connected with the output port of the ring resonator in order to block a specific frequency band. The micro-strip line is formed between the output port of the ring resonator and the open type stub.
