Ultra-Wideband Millimeter-Wave Tight and Loose Microstrip Aperture Couplers

Compact multiaperture couplers for ultra-wideband millimeter-wave (mmWave) operation are presented, employing an artificial magnetic conductor (AMC) for radiation-free performance. Elliptical coupling apertures are used to enable efficient operation across a 50% bandwidth, while fixed elliptical matching patches are employed for any coupling level to achieve matching levels exceeding −19 dB. Minimal phase and amplitude variation are achieved over 15 dB directivity within coupling ranges from 3 to 20 dB. Validation through fabrication and testing of two packaged lines with different aperture configurations confirms practicality and efficiency.