Split-Type Multiband Filter Design Using Ultra-Miniaturized Substrate-Integrated Coaxial Cavities

Area of Science:

• Electrical Engineering
• Electromagnetics
• Microwave Engineering

Background:

• Multiband filters are crucial for modern wireless communication systems.
• Existing designs often face challenges with miniaturization and circuit-area efficiency.
• Substrate-Integrated Waveguide (SIW) technology offers a planar solution for filter fabrication.

Purpose of the Study:

• To design and experimentally validate split-type dual- and tri-band bandpass filters (BPFs).
• To achieve exceptional circuit-area efficiency using highly miniaturized substrate-integrated coaxial cavities (SICCs).
• To explore the fabrication of size-reduced SICCs using substrates of different thicknesses.

Main Methods:

• Employing the coupling matrix method for synthesizing filter responses.
• Designing and fabricating miniaturized SICCs using dual-thickness substrates.
• Utilizing substrate-integrated waveguide (SIW) related split-type filter topology.

Main Results:

• A dual-band filter achieved a circuit size of 0.17 λd × 0.17 λd with insertion losses of 0.78/0.89 dB and >15 dB isolation.
• A tri-band filter occupied 0.27 λd × 0.34 λd with insertion losses of 0.96, 2.6, and 1.21 dB.
• Experimental validation confirmed strong agreement between measured and simulated filter performance.

Conclusions:

• The proposed split-type multiband filter design demonstrates superior circuit-area efficiency.
• Miniaturized SICCs fabricated with dual-thickness substrates are effective for multiband filtering.
• The validated designs show practical applicability in high-frequency systems.