Elements for E-Plane Split-Block Waveguide Circuits,” ALMA Memo 381 at http://www.alma.nrao.edu/memos

E-plane split-block waveguide construction is well suited to many millimeter-wave components, including power dividers, frequency multipliers, and single-ended, balanced and sideband-separating mixers [1]. Recent ALMA memos have described quadrature hybrids [2] and a matched power divider [3] suitable for split-block construction. This memo describes four additional waveguide elements which can be used as building blocks in more complex circuits: a compact H-plane bend, a short E-plane bend, a matched E-plane Y-junction, and a broadband transducer from full-height waveguide to quartz suspended stripline. The components are suitable for fabrication on a CNC milling machine using an end-mill of diameter equal to the waveguide height, and do not require the insertion of separate waveguide short-circuit pieces at the ends of waveguides. Prototype designs are given for WR-10 waveguide (75-110 GHz), which can be scaled for any other waveguide size with the same 2:1 aspect ratio. 1. H-Plane Waveguide Bend A split-block H-plane waveguide bend allows coupling from a waveguide in the plane of the split to a waveguide perpendicular to the plane of the split. Such a bend allows waveguide circuits on different planes to be interconnected, thereby making complex circuits more compact. Two H-plane bends are described here, one with both waveguides of rectangular cross section, and the other with an oval waveguide perpendicular to the plane of the joint. These are shown in Figs. 1 and 2, with their characteristics as simulated by QuickWave [4], and with measurements for comparison in Fig. 1. Figures 3 and 4 show the dimensions of the two designs. In the first design, the rectangular waveguide perpendicular to the plane of the split can be fabricated as a cylindrical insert and pressed or soldered into the upper half of the block prior to machining the rest of the waveguide in that half. In the second design, the oval waveguide can be machined directly into the block with an end-mill, but the length of the oval waveguide is limited by the length of the milling cutter. Fig. 1. WR-10 H-plane bend with rectangular waveguides. QuickWave simulation and measured |S11 | and |S21 | (dB)