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

In this paper, the harmonic rejection low-pass filter using coupled lines is proposed. The design formula is derived using the equivalent circuit of coupled transmission line. Proposed low-pass filter structure provides compact size, low insertion loss and wide stop band range up to five times of the cutoff frequency. The higher order low-pass filters can be realized by wing the proposed structure as a unit element. Experimental results show excellent agreement with theoretical results.