| Summary: | 碩士 === 國立高雄第一科技大學 === 電子工程系碩士班 === 106 === A novel design of a wide-band bandpass filter with half-wavelength( λ/2) step impedance resonators (SIR) is proposed in this article. Due to the λ/2 SIR, two transmission zeros (T_Z) are not only located at each edge of the passband but also symmetrical to the center frequency (f_c). In addition, the position of T_ZS can be conveniently controlled by means of adjusting the characteristic impedance ratio of the SIR. Two controllable transmission zeros are introduced to sharpen the passband skirts.
The bandpass filter is composed of two λ/2 SIR, three shorted-curcuit stubs (SC) and two λ/2 transmission lines and it is theoretically analyzed using J-inverter and resonators method. Therefore, a series of simple formulas can be derived. Two prototypes with 3-dB fractional bandwidths of 65.67% (0.68-1.355GHz) and 61.75% (1.78–3.396 GHz) are designed and fabricated for demonstration. Good agreement can be observed between simulated and measured performances.
The designed filters have the properties of flexible T_ZS, easy fabrication, low cost, and low loss.
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