A design of the novel coupled line low-pass filter with attenuation poles

In this paper, a novel low-pass filter structure using coupled lines is proposed. The design formula is derived using the equivalent circuit of coupled transmission line. The proposed low-pass filter structure provides compact size, low insertion loss and two attenuation poles in the stop band. The higher order low-pass filters can be realized by using the proposed structure as a unit element. Experimental results show the validity of the proposed low-pass filter structure and the design method.