A Wide Stopband Balun Bandpass Filter with Its Application to Balanced Quasi-Yagi Antenna

Gang Zhang,Yushou Chen,Zhenyao Qian,Yang Zhao

doi:10.1155/2018/4725072

Gang Zhang, Yushou Chen + Show 2 more

Open Access

https://doi.org/10.1155/2018/4725072

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Abstract

A new microstrip balun bandpass filter (BPF) with wide stopband is presented. It is realized by utilizing the out-of-phase feature of standing-wave distribution on a half-wavelength (λ/2) open-ended microstrip line and the resonant characteristics of the triple-mode resonators. For demonstration, a prototype balun BPF operating at central frequency (f0) of 2.34 GHz with fractional bandwidth (FBW) of about 16.7% is designed. The presented balun BPF not only exhibits nice balanced response with 0.47 dB magnitude imbalance and 4.3° phase difference but also achieves 30-dB harmonic suppression up to 6.40 GHz (2.7f0). Afterward, this presented design is embedded into a balanced quasi-Yagi antenna to obtain high-selective radiation and wide stopband rejection. Experimental results of the implemented antenna indicate less than −10 dB reflection coefficient, 4.49–5.38 dBi gain, and 12.71–19.62 dB front-to-back ratio within the operating bandwidth.

Highlights

A balun bandpass filter (BPF) is an important multifunctional integrated component, which provides both balanced conversion of a balun and bandpass frequency selectivity of a BPF simultaneously, since it can reduce the cost and size of the functional block for modern compact wireless communication systems
Good performance can be achieved, the balun filter still requires via holes connected to the ground and a large size, which cannot accommodate the growth of modern wireless communication system
Our research demonstrates that the proposed balun BPF possesses nice balanced responses across the operation passband with about

Summary

Introduction

A balun bandpass filter (BPF) is an important multifunctional integrated component, which provides both balanced conversion of a balun and bandpass frequency selectivity of a BPF simultaneously, since it can reduce the cost and size of the functional block for modern compact wireless communication systems. Open-type resonator, which is widely used in microwave circuit design, is utilized to realize balun BPFs with good balanced performance and high frequency selectivity [2, 7]. Its limited bandwidth [7] and stopband suppression [2] of the balun BPFs are not satisfactory and need further improvement, while considering its practical application for feeding antenna Apart from these above listed designs, a balun BPF [8] based on substrate integrated waveguide cavity concept has been reported. The proposed design is embedded into quasi-Yagi antenna as a feeder, for sake of getting high-selective radiation and wide stopband rejection. Both simulated and measured results are displayed to verify these properties predicted in theory

Proposed Broadband Balun Bandpass Filter

Balun BPF Feeding Broadband Quasi-Yagi Antenna

Findings

Conclusion