A Compact Tri-Band Bandpass Filter With Independently Controllable Harmonic Bandwidth by Using Two Grounded Vias

Abstract

Abstract-A new class of tri-band bandpass filter(BPF) is presented, and harmonic passband bandwidth can be independently controlled. In the implementation, three coupling paths are used to control the bandwidth of each passband. The first coupling path is two grounded vias which are utilized to realize coupling between two short-stub loaded resonators. And the first coupling path delivers signals at the first passband. Meanwhile, the second coupling path delivers signals at both the first and second passbands. And the third coupling path only delivers signals at the third passband. Using this method, both the frequency and bandwidth of each passband can be designed and tuned easily. In this filter design, the first harmonic passband can be adjusted separately and is independent of the fundamental passband. Two grounded vias improve flexibility and form a fundamental passband and harmonic passband independently controllable passband filter. For demonstration, a tri-band BPF with three passbands at 1.5 GHz, 2.5 GHz, and 3.5 GHz with insertion losses of 0.34, 0.76 and 1.08 dB is designed, fabricated and measured. So this proposed filter will be attractive in wireless communication systems.

Design of a Compact Microstrip Triple Independently Controlled Pass Bands Filter for GSM, GPS and WiFi Applications

“…various applications. So, in this regard, many studies have been published in recent years to design a miniaturized dual and triple-band (BPFs) based on different techniques such as stub loaded resonators (SLRs), embedded stub loaded resonators, ring resonators, multimode resonators and step impedance resonators (SIRs) etc [7]- [33].…”

“…However, the design suffers from large circuit dimensions and poor fractional bandwidth. The authors of [33] modelled a triband response using shorted SLR and quarter-wave uniform SIR. The first and second band were created using shorted SLR and controllable harmonic while the third frequency band was excited using uniform quarter wavelength SIR.…”