Abstract
In this paper, we present a simple method to design a miniaturized wideband bandpass filter with suppression of the third harmonic, using only two quarter-wavelength stepped-impedance resonators (SIRs). The resonant modes of the quarter-wavelength SIR, depending on the impedance ratio (K) and electrical length ratio (α), are discussed first. As to setting the resonant frequency of the SIR for the lower band edge of the required band, the size parameters of two quarter-wavelength SIRs can be determined by selecting the desired impedance ratio (K) and length ratio (α). By using the opposite directional arrangement of two SIRs with direct taped input/output ports, the wideband response can be formed. A filter example is shown in this study to address this simple design procedure. The measured results of the fabricated filter have a wide passband response from 3.3 to 5.8 GHz, with an insertion loss of 1.5 dB, a return loss of 20 dB, an extended bandwidth ration of 55%, a low-average group delay of less than 0.75 ns, and a stopband from 6 to 12 GHz, with an attenuation level of 20 dB. Due to the similar 0° feeding, a transmission zero at 8.3 GHz appears near the band edge; thus, improving the band selectivity. The proposed filter can have a very simple structure and a miniature size. Simulated results and measured results are in good agreement.
Highlights
In the last 20 years, communications systems have developed rapidly
Two coaxial cables of the network analyzer, which were connected to the input and output (I/O) ports of the fabricated filter sample, were carefully calibrated by using short-open-load-through calibration
Steps were carefully processed to make sure that the S21wideband was close toatzero the two coaxial cables were connected to the load-through device
Summary
In the last 20 years, communications systems have developed rapidly. Used in the radio-frequency (RF) front end is an important device for selecting the desired signals for the use of the communications system [1]. The wideband system has been rapidly expanding ever since in 2002 the U.S Federal Communications Commission (FCC) approved the unlicensed applications of ultra-wideband (UWB) with frequency ranging from. As one of the important component blocks, some wideband BPFs were developed to obtain the desired fractional bandwidth (FBW) [3,4,5,6,7,8,9,10,11,12,13,14,15]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
