A WIDE-BAND VARIABLE WAVE-GUIDE COUPLER FOR MILLIMETER APPLICATIONS

We present a variable waveguide coupler for the short millimeter-wavel ength range. The coupler has low ohmic and insertion losses in all pat hs, flat coupling characteristic, and high directivity over a large ba ndwidth, The construction of the coupler allows a variable independent adjustment of power transferred into several paths when several coupl ers are used in series, The coupler is therefore useful for multichann el receivers and especially for superconductor-insulator-superconducto r (SIS) mixer arrays where individual local oscillator (LO) power adju stment might be necessary, We present measurements for a coupler worki ng at 230 GHz and compare them with a simple analytical model.