Design of Microstrip Quasi-Elliptic Bandpass Filter with Upper Wide Stopband Using Quarter-Wavelength Stepped-Impedance Resonators

作者：Hayati Mohsen^*; Asadbeigi Hamid; Sheikhi Akram

来源：Electromagnetics, 2013, 33(7): 507-516.

DOI：10.1080/02726343.2013.824310

• bandpass filter
• microstrip
• stepped-impedance resonator
• wide stopband

In this article, a miniaturized quasi-elliptic bandpass filter using four quarter-wavelength (/4) stepped-impedance resonators is presented. With a simple design method, the presence of spurious harmonics can be avoided without using an extra filter or stub elements. The /4 stepped-impedance resonators in the structure of the filter resulted in a wide stopband and reduced circuit size. The combination of resonators with the same fundamental frequency but different spurious frequencies improved the stopband bandwidth. The proposed filter has the center frequency at 2.02 GHz and a 3-dB fractional bandwidth of 17.5%. On the other hand, the proposed filter shows wide upper stopband with attenuation level better than -22.2 dB up to 13.86f(o), where f(o) is the passband center frequency. The circuit has a simple structure and a compact size. The designed bandpass filter has been simulated, fabricated, and measured, and there is good agreement between the measured and simulated results.

• 出版日期2013-10-3