Design of a Switchable Filter for Reflectionless-Bandpass-to-Reflectionless-Bandstop Responses

Area of Science:

• Electromagnetic theory and microwave engineering.
• Development of advanced electronic components and circuits.

Background:

• Traditional filters often suffer from reflections, impacting signal integrity.
• The need for multifunctional and reconfigurable filters in modern electronic systems is increasing.

Purpose of the Study:

• To design, theoretically validate, and fabricate a novel switchable filter with reflectionless bandpass-to-bandstop responses.
• To demonstrate a single-port multifunctional filtering device using microstrip line technology.

Main Methods:

• Design of a single-port reflectionless bandpass filter (R-BPF) and a single-port reflectionless bandstop filter (R-BSF).
• Integration of PIN diodes for reconfiguring between R-BPF and R-BSF modes.
• Theoretical analysis of terminal impedance to explain the reflectionless mechanism.

Main Results:

• Fabrication and measurement of a prototype demonstrating switchable R-BPF and R-BSF responses.
• R-BPF mode achieved a 3-dB fractional bandwidth (FBW) of 36.75% (1.67-2.42 GHz) and a 10-dB reflectionless bandwidth (RBW) of 61.9% (1.36-2.58 GHz).
• R-BSF mode achieved a 10-dB bandwidth of 13% (1.85-2.11 GHz) and a 10.7-dB RBW of 100% (1-3 GHz).

Conclusions:

• The fabricated switchable filter successfully demonstrated both reflectionless bandpass and bandstop functionalities.
• The theoretical analysis and experimental results show acceptable agreement, validating the proposed design.
• The developed multifunctional filter holds promise for applications requiring adaptable filtering characteristics.