Investigation of external quality factor and coupling coefficient for a novel SIR based microstrip tri-band bandpass filter.

Abdul Basit,Muhammad Irfan Khattak,Gulzar Ahmad,Jamel Nebhen,Atif Jan,Mohammad Maktoomi

doi:10.1371/journal.pone.0258386

Abdul Basit, Muhammad Irfan Khattak + Show 4 more

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https://doi.org/10.1371/journal.pone.0258386

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Abstract

In this article, a new method is developed to design a three-band miniaturized bandpass filter (BPF) that uses two asymmetrically coupled resonators with one step discontinuity and open-circuited uniform impedance resonator (UIR) to achieve Global Interoperability with Microwave Access (WiMAX) and Radio Frequency Identification (RFID) applications. First, a pair of asymmetrical step impedance resonators (ASIR) is used to implement a dual band filter, then a half wavelength uniform impedance resonator is added below to the transmission line to achieve a triple band response. The proposed filter resonates at frequencies of 3.7 GHz, 6.6 GHz, and 9 GHz with the fractional bandwidth of 7.52%, 5.1%, and 4.44%, respectively. By adjusting the physical length ratio (α) and the impedance ratio (R) of the asymmetric SIR, the proposed fundamental frequencies of the triple BPF are obtained. Moreover, the coupling coefficient (Ke) and external quality factor (Qe) are investigated between the resonators and the input/output ports of the transmission line and are calculated using full-wave EM simulator HFSS. In addition, five transmission zeros are introduced near the passbands to increase the filter selectivity. Finally, the proposed filter is designed and fabricated with a size of 13.69 × 25 mm (0.02 λg × 0.03 λg), where λg represents the guiding wavelength in the first passband. The simulated and measured results have a good correspondence, thus confirming the design concept.

Highlights

The field of microwave and RF communication continuously demands a compact wireless transceiver for commercial products, especially in the combination of IEEE 802.11b/g (GSM), IEEE 802.11a (WLAN), GPS, Radio Frequency Identification (RFID), 3G, 4G, Bluetooth, and automotive radar system
Targeting the IEEE 802.16 (WiMAX) and RFID wireless applications, this paper proposes an ultra-compact tri-band bandpass filter (BPF) using two asymmetrically coupled resonators with one-step discontinuity and a uniform impedance resonator, centered at 3.7 GHz, 6.6 GHz, and 9 GHz with the fractional bandwidth of 7.52%, 5.1% and 4.44%, respectively
The first and second passband centered at 3.7 GHz and 6.6 GHz are obtained by the two coupled asymmetric step impedance resonator (SIR) consist of high impedance section (Z1) and low impedance section (Z2) for WiMAX and RFID applications, while the third passband centered at 9 GHz is achieved through uniform impedance resonator (UIR) which is attached to the input/output port transmission line

Summary

Introduction

The field of microwave and RF communication continuously demands a compact wireless transceiver for commercial products, especially in the combination of IEEE 802.11b/g (GSM), IEEE 802.11a (WLAN), GPS, RFID, 3G, 4G, Bluetooth, and automotive radar system. A tri-band BPF loaded with pi-section SIR is presented in [16], for GPS (Link-2), WIMAX, and WLAN applications with their merit of greater bandwidth but filter selectivity, insertion losses, and larger size still need to be improved.

Results

Conclusion