A compact and wide stop-band low-pass filter using a wire wound chip-inductor

In this paper, an elliptic-function low-pass filter using a wire wound chip inductor is proposed. To reduce the filter size and to realize the sharp roll-off skirt characteristic, the wire wound chip inductor, which has the large inductance with small size, is employed. The proposed low-pass filter has wide stop-band with three attenuation poles. The two of them are generated by the gap capacitance of the symmetrical open ended stubs, and the other is created by self resonant frequency of the wire wound chip inductor. The three attenuation poles are designed to suppress 2^nd, 3^rd, and 4^th harmonics. The fabricated LPF exhibits 3-dB cutoff frequency of 930 MHz, insertion loss below 0.07 dB and stop-band from 1.48 to 9.10 GHz below the rejection level of 20 dB.