Miniaturized Dual-Band Bandpass Filter with Multiple Transmission Zeros Using Modified Stepped-Impedance Resonators.

In this article, a modified stepped-impedance resonator is proposed in which an open stub is loaded between the low-impedance line and high-impedance line of a conventional λ/4 stepped-impedance resonator. Based on the proposed modified stepped-impedance resonators, a compact dual-band bandpass filter with an enhanced stopband is presented. Multiple transmission zeros are employed for high selectivity and a wider upper-stopband by the mixed electric/magnetic coupling and open stub loaded in the input/output port. To verify the proposed method, a new dual-band bandpass filter that operated at 2.4/5.2 GHz for wireless local area networks application is fabricated and measured. The measured result shows six finite transmission zeros in the stopband, located at 1.82, 3.14, 5.83, 7.01, 10.50, and 13.14 GHz, respectively; the circuit only occupies 0.07 λg × 0.11 λg. [ABSTRACT FROM AUTHOR]