Electronically tunable coaxial right / left handed transmission line for carbon fibre reinforced polymer waveguides

The Slotted Waveguide Antenna Stiffened Structure (SWASS) utilizes conventional carbon fiber reinforced polymer (CFRP) blade stiffeners in aircraft sandwich structures as microwave waveguides. Slotted waveguide antenna arrays may therefore be integrated into the CFRP structure by machining slots through the outer skin. This work presents a simple addition to the SWASS concept that permits electronic control over the propagating mode in a slotted CFRP waveguide for the purpose of beam steering. This is achieved using a varactor loaded coaxial composite right/left handed transmission line (CRLH-TL) with integrated bias circuit. The proposed CRLH-TL does not require a perfect electrical connection to the outer coaxial conductor and is therefore ideally suited to CFRP waveguides.