Forward‐wave directional coupler based on slow‐wave coupled microstrip lines. Issue 14 (9th September 2019)

• Record Type: Journal Article
• Authors: Luong, Duc‐Long; Acri, Giuseppe; Podevin, Florence; Vincent, Didier; Pistono, Emmanuel; Serrano, Ariana; Ferrari, Philippe
• Is Part Of: IET microwaves, antennas & propagation. Volume 13:Issue 14(2019)
• Page Start: 2486
• Page End: 2489
• Publication Date: 2019-09-09
• Subjects: printed circuits -- microstrip lines -- microstrip directional couplers -- slow wave structures; slow‐wave coupled microstrip lines -- forward‐wave directional coupler -- multilayered printed circuit board technology -- odd‐mode phase velocities -- odd‐mode characteristic impedances -- reduced‐length forward couplers -- even‐mode phase velocities -- length miniaturisation -- frequency 4.5 GHz -- loss 10 dB; Microwaves -- Periodicals; Microwave antennas -- Periodicals; Antennas (Electronics) -- Periodicals; Radio wave propagation -- Periodicals; Microwave communication systems -- Periodicals; 621.381305
• DOI: 10.1049/iet-map.2019.0296
• Languages: English
• ISSNs: 1751-8725

Abstract

Abstract : This study presents the design of a forward‐wave directional coupler based on slow‐wave coupled microstrip lines realised in a multilayered printed circuit board technology. Thanks to the concept of slow‐wave, a high difference between the even‐ and odd‐mode phase velocities can be inherently achieved. Hence, by choosing adequate even‐ and odd‐mode characteristic impedances close to 50 Ω, reduced‐length forward couplers can be designed. As a proof of concept, a 0 dB forward coupler operating at 4.5 GHz is proposed. It exhibits a very high coupling of 0.56 dB at the centre frequency and a very large bandwidth of 43%, corresponding to 10 dB of isolation. A length miniaturisation of 84% is obtained as compared to the standard microstrip, leading to a total surface area of 0.132 λ g 2, the smallest one reported so far.