| 摘要 |
A highly directional transmitter suitable to mobile telephony includes a square array of N<2> active reflectors is built up from individual elements which each consist of a number of active and passive components. These include a receive antenna (10), a pass band filter (12), an amplifier (14), a mixer (16), an electronic phase shifter (18) and a harmonic rejection filter, with a transmit antenna (20). The active components are made from Josephson junctions (mixers) (16) and/or flux flow transistors (amplifiers) (14, 22). The phase shifter (18) is realised using coplanar transmission line on a paraelectric substrate such that an applied d.c. electric field induces a change in the permittivity and thus a voltage dependent phase change along a fixed length of transmission line. A local oscillator feed (24) is provided to each reflector which will be transmitted by a system of paralleled non-dispersive superconductive transmission lines. The device may be realised in high temperature superconductive material or conventional metallic superconductors with the addition of paraelectric substrates such as SrTiO3.
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