Bandwidth-Controllable Third-Order Band Pass Filter Using Substrate-Integrated Full- and Semi-Circular Cavities.

Area of Science:

• Electrical Engineering
• Electromagnetics
• Microwave Engineering

Background:

• Substrate-Integrated Waveguide (SIW) technology offers advantages for microwave circuit integration.
• Bandpass filters (BPFs) are crucial components in modern communication and sensing systems.
• Controlling filter bandwidth and achieving sharp rejection are persistent challenges in BPF design.

Purpose of the Study:

• To propose and validate a novel circular SIW bandpass filter with controllable bandwidth.
• To investigate the use of capacitive slots and inductive vias for filter performance enhancement.
• To demonstrate a third-order BPF design with a generated transmission zero.

Main Methods:

• The BPF was designed using cascaded semi-circular SIW cavities and microstrip feed lines.
• Capacitive slots and inductive vias were incorporated to tune filter characteristics.
• A coupling matrix was generated to analyze the design concept.
• A third-order BPF prototype was fabricated and experimentally verified.

Main Results:

• The fabricated BPF prototype exhibited a wide passband of 8.7%.
• Low insertion loss of 1.1 dB was achieved.
• A stopband of 1.5 f0 with over 20 dB rejection was demonstrated, attributed to a generated transmission zero.

Conclusions:

• The proposed circular SIW BPF design successfully achieves controllable bandwidth and high performance.
• The integration of inductive vias effectively generates a transmission zero, enhancing filter selectivity.
• The validated BPF prototype shows significant potential for applications in microwave sensing and communication industries.