A filter-based duplexer having low-loss and high-isolation performance was developed for a wireless broad-band asymmetric digital subscriber line by using NRD guide technology at 60 GHz. Emphasis was placed on rigidity of the circuit configuration. The duplexer consists of a junction circuit and low-loss ceramic resonators. The junction circuit, made by a mode transformer between an NRD guide and a vertical strip line, provided good rigidity and well balanced output levels as well as small insertion loss. The NRD guide band-pass filter using circular ceramic resonators embedded in a thin Teflon sheet has good advantages such as low insertion loss in a pass band and sharp skirt cutoff nature in rejection bands. The NRD guide duplexer was fabricated by assembling them. The isolation between a transmitter port and a receiver port was measured to be more than 45 dB. and besides, the insertion loss was measured to be less than 3 dB in the 60 GHz band.
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