A novel branch-line coupler design for millimeter-wave applications

A three-branch-line coupler with three-quarter wavelength series lengths has been designed to work from 26.5 to 40 GHz. It takes advantage of the odd mode nature of the series lines to increase the line lengths. The loss in bandwidth because of the 3/4 wavelength series lines is acceptable because of what is gained by having higher aspect ratios and by using a three-branch-line coupler design. These same design rules scale well to designs all the way up to W-band.<
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