Producing and Exploiting Simultaneously the Forward and Backward Coupling in EBG-Assisted Microstrip Coupled Lines

• Published in: IEEE antennas and wireless propagation letters 2016, Vol.15, p.873-876
• Main Authors: Percaz, Jon Mikel, Chudzik, Magdalena, Arnedo, Israel, Arregui, Ivan, Teberio, Fernando, Laso, Miguel A. G., Lopetegi, Txema
• Format: Article
• Language: English
• Subjects: Coupled lines; coupled mode theory; Couplings; electromagnetic band-gap (EBG); Frequency control; Metamaterials; Microstrip; microstrip circuits; Microwave theory and techniques; Periodic structures; Propagation constant; triplexer
• ISSN: 1536-1225; 1548-5757
• DOI: 10.1109/LAWP.2015.2478595

In this letter, a methodology is proposed for the design of electromagnetic band-gap (EBG)-assisted coupled-line structures in microstrip technology, controlling independently the forward and backward coupling. It is based on the use of a single-frequency-tuned EBG structure to produce a single backward-coupled frequency band, in combination with the forward-coupled frequency bands produced by the difference between the even- and odd-mode propagation constants present in microstrip technology. Thus, the central frequency of the backward-coupled band is controlled by the period of the EBG structure, while the frequencies of the forward-coupled bands are fixed by the length of the device. The rest of the frequencies go to the direct port giving rise to a device with the input port matched at all the frequencies and where the coupled bands are easily controllable by adjusting the corresponding design parameter. The novel methodology proposed has been successfully demonstrated by designing a triplexer intended for the GSM (900 MHz) and WLAN (2.4 and 5.5 GHz) telecommunication bands.