Design of Quad-Band Bandpass Filter Using Dual-Mode SLRs and Coupled-Line for DCS/WLAN/WiMAX and 5G Applications

Area of Science:

• Electrical Engineering
• Electromagnetics
• Microwave Engineering

Background:

• Microstrip bandpass filters (BPFs) are crucial components in modern wireless communication systems.
• Achieving multi-band operation with independently controllable bandwidths presents a significant design challenge.

Purpose of the Study:

• To design and demonstrate a compact microstrip quad-band BPF with flexibly controlled bandwidths.
• To enable independent tuning of each passband with minimal impact on others.

Main Methods:

• Utilized dual-mode short-circuited stub-loaded resonators (SLRs) for the first two passbands.
• Implemented a second-order half-wavelength coupled-line resonator for the third passband.
• Employed a dual-mode open-circuited SLR for the fourth passband.

Main Results:

• Achieved quad-band operation centered at 1.80/2.45/3.50/4.90 GHz for DCS/WLAN/WiMAX and 5G applications.
• Demonstrated independent and flexible control of each passband's bandwidth by adjusting resonator lengths and coupling parameters.
• Fabricated filter achieved compact dimensions (0.12 × 0.20 λg) with measured results matching simulations.
• Reported measured return loss (S11) ≥ 12 dB and low insertion loss (S21) ranging from 0.65 to 1.42 dB across the passbands.

Conclusions:

• The proposed design offers a novel and effective solution for multi-band filtering with tunable bandwidths.
• The filter's compactness and performance make it suitable for various wireless communication systems.
• The independent control mechanism provides significant design flexibility for future applications.