Dual Band-Pass Filter Based on Split Ring Resonators with Controlled Asymmetric Bandwidth Response

Area of Science:

• Electrical Engineering
• Electromagnetics
• Microwave Engineering

Background:

• Dual-band bandpass filters are crucial for modern wireless communication systems, enabling devices to operate across multiple frequency bands simultaneously.
• Compact filter designs are highly desirable for miniaturization in portable electronic devices.
• Split-ring resonators (SRRs) offer unique electromagnetic properties suitable for filter design, but achieving dual-band operation with controlled bandwidths presents challenges.

Purpose of the Study:

• To present a novel synthesis method for compact dual-band bandpass filters based on split-ring resonators (SRRs).
• To demonstrate precise control over the center frequencies and bandwidth ratio (BWR) of the two passbands.
• To experimentally validate the proposed methodology using microstrip prototypes.

Main Methods:

• The synthesis method combines coupling-matrix synthesis with an energy-based SRR model.
• A control technique is employed to manage the center frequencies and bandwidth ratio (BWR) of the dual passbands.
• Two third-order microstrip filter prototypes were fabricated on Rogers RO3010 substrate for experimental validation.

Main Results:

• Two prototypes operating at 1.9 and 2.4 GHz were successfully fabricated and tested.
• Measured results demonstrated asymmetric bandwidths with BWR values of approximately 0.5 and 1.9.
• Achieved compact footprints of 32 × 12.37 mm² and 27.87 × 12.42 mm², with insertion losses as low as 0.6 dB.

Conclusions:

• The proposed synthesis method effectively enables the design of compact dual-band bandpass filters with controllable asymmetric bandwidths.
• Experimental validation confirmed the accuracy of the synthesis technique and the performance of the fabricated prototypes.
• The methodology provides a viable approach for realizing compact planar dual-band filters without requiring reconfigurable elements.