A High Directivity Microstrip Coupler Technique - IEEE Xplore

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and be less 10SSY.2 Above 7DB coupling, however, there is no need for the cross-over; a single coupler can be etched with the necessary tolerances for reproducibility. In order to exploit the broadband possibilities of a wiggly coupler, a 54 to 290 MHz 3 section 18DB coupler was built. The 3 Sections were individually built and tested before being patched together. Figure IV shows the coupling and directivity performance of this coupler, built on glass epoxy circuit board. The side effects of wiggling seem to be to increase the coupling for a given line spacing, and to slightly increase the loss. When the wiggle spacing becomes an appreciable fraction of a wavelength, the coupler will no longer appear continuous, but this does not appear to be a serious limi– tation until well above X band. What has been described here is a technique for the broadband equalization of the even and odd mode velocities of a microstrip coupler. This technique makes possible simple, multi-octave microstrip couplers of more than 20DB directivity. 1 H.E. Brenner “Perturbations of the critical parameters of quarter-wave directional couplers” IEEE MTT and J.E. Morris, IEEE TMTT, July 1968. Overlay Coupler 2 Julius Lange, IEEE TMTT, December 1969 34
g z— z 0 !- 5 15 FIGUF@ 1 - TYPICAL WIGGLY LINE COUPLER COUPLING 1 25 \ / 35 150LA TION 45 .5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 FREQ GHz FIGURE 2 - COUPLING AND DIRXCTIVITY FIGURI 3 - 3 DB COUPLER 35
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A High Directivity Microstrip Coupler Technique - IEEE Xplore

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