Low Passive-Intermodulation Contactless Waveguide Adapter Based on Gap Waveguide Technology

To solve the passive intermodulation (PIM) of waveguide connection caused by metallic contact, a contactless waveguide adapter (CWA) is proposed, basing on gap waveguide. Two artificial magnetic conductor (AMC) surfaces, in the form of bed of nails, are designed to be a back-to-back structure, composing a contactless transition of waveguide connection. The contact nonlinearity of traditional waveguide flange is dramatically eliminated by contactless design, and PIM is therefore suppressed. The size of the AMC structure is carefully designed to form a proper forbidden band, which prevents electromagnetic (EM) leakage from the contactless air gap. A Ku-band prototype of the CWA is designed and manufactured for standard WR75 waveguide connection. Over the frequency range from 10 to 15GHz, the measured insertion loss and return loss is better than 0.1dB and 20dB respectively. And the PIM performance is improved better than 20dB compared to common waveguide flange connection.