Differential Narrow Bandpass Microstrip Filter Design for Material and Liquid Purity Interrogation

• Published in: IEEE sensors journal Vol. 19; no. 22; pp. 10545 - 10553
• Main Authors: Amirian, Mohsen, Karimi, Gholamreza, Wiltshire, Benjamin D., Zarifi, Mohammad Hossein
• Format: Journal Article
• Language: English
• Published: New York IEEE 15.11.2019; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Band-pass filters; Bandpass filters; constant dielectric; differential structure; Differential thermal analysis; Electronic filters; Equivalent circuits; Filter design (mathematics); Interrogation; Liquids; Microstrip; Microstrip devices; Microstrip filters; Microwave filters; Narrow band microstrip; Noise reduction; Noise sensitivity; Permittivity; Product design; Purity; Resonance; Resonant frequency; sensitivity; Sensors; Sharpness; Substrates; transmission line
• ISSN: 1530-437X; 1558-1748
• DOI: 10.1109/JSEN.2019.2932693

In this paper, a new narrow bandpass microstrip filter is proposed with a differential structure based on an analytical approach. A new model of the differential structure, employing an LC equivalent circuit is discussed. Differential/common mode using an odd/even mode analysis is used to calculate the operating frequency of the circuit theoretically. The narrow bandwidth structure is a suitable choice in sensory applications to detect the purity of various liquid materials. The permittivity of materials was measured by using various liquid materials as upper substrates; this changed the resonance frequency depending on the material used and the results could be interpreted as a measured material permittivity. The resonance frequency of the proposed filter fabricated with Rogers RO4003 substrate was 1.75 GHz. Compact size (0.3018λ × 0.141λ), higher sensitivity, roll-off sharpness, noise reduction, and a new theoretical method are advantages of this proposed design.