A millimeter wave reflection phase shifter employs a fin-line structure within a waveguide network which has a central leg and four arms which together form two symmetric Y-junctions. The fin-line forms a septum within the waveguide and includes a conductive layer having a central gap or slot therein...http://www.google.com.au/patents/US4568893?utm_source=gb-gplus-sharePatent US4568893 - Millimeter wave fin-line reflection phase shifter
