Millimeter-Wave Broadband Mode Transition between Grounded Coplanar Waveguide and Post-Wall Waveguide

Ryohei HOSONO  Yusuke UEMICHI  Xu HAN  Ning GUAN  Yusuke NAKATANI  

IEICE TRANSACTIONS on Communications   Vol.E99-B   No.1   pp.33-39
Publication Date: 2016/01/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.2015ISP0020
Type of Manuscript: Special Section PAPER (Special Section on Recent Progress in Antennas, Propagation and Wireless Systems Related to Topics in ISAP2014)
Category: Antennas and Propagation
broadband mode transition,  grounded coplanar waveguide,  post-wall waveguide,  liquid crystal polymer substrate,  antenna-in-package,  

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A broadband mode transition between grounded coplanar waveguide (GCPW) and post-wall waveguide (PWW) is proposed. The transition is composed of GCPW, microstrip line (MSL) and PWW, where the GCPW and PWW are connected via the MSL. The transition is fabricated on liquid crystal polymer (LCP) substrate because of its low dielectric loss and cost effectiveness based on a roll-to-roll fabrication process. Center strip of the GCPW is sandwiched by two ground pads in each of which two through-holes and a rectangular slit are structured. Broadband impedance matching is achieved by this structure thanks to an addition of lumped inductance and capacitance to the transition. A part of the MSL is tapered for the broadband operation. A 25% impedance bandwidth for |S11| less than -15dB is achieved in measurement of a fabricated transition. Loss of the GCPW ground-signal-ground (GSG) pad of 0.12dB and that of the MSL-PWW transition of 0.29dB at 60GHz are evaluated from the measurement. Fabrication error and the caused tolerance on performance are also evaluated and small variation in production is confirmed. The mode transition can be used for low loss antenna-in-package in millimeter-wave applications.