Theory and Experiments of Mode Coupling and Power Leakage on Coplanar Wavewguides of Finite Width

Arthur A. OLINER

IEICE TRANSACTIONS on Electronics   Vol.E74-C    No.5    pp.1264-1269
Publication Date: 1991/05/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on the 3rd Asia-Pacific Microwave Conference)
Category: Transmission Lines and Waveguides

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We report here a new mode-coupling effect that occurs on coplanar waveguides of finite width. The coupling occurs between the standard CPW dominant mode and a new dominant mode identified by us for the first time, and called here the CPW dominant surface-wave-like mode. This coupling is different from that which is known to occur when a printed-circuit waveguide is placed in a box or package; here there is no box, and the finite width by itself is sufficient to produce the coupling effect. This effect results in a complicated dispersion behavior, and we investigate it experimentally and theoretically. In addition to this new coupling effect, a new leakage effect on this class of waveguides has been investigated by us for many variant forms. The details will be discussed elsewhere, but a brief discussion of this leakage effect is also included here in order to place the new coupling effect in proper perspective. We also investigate the sets of structural dimensions needed for the coplanar waveguide to operate without leakage. Finally, we perform a set of measurements in X-band on a standard coplanar waveguide of finite width, and it is found that the experimental results agree very well with the theoretical calculations.