| 摘要 |
An R.F. circuit with at least one R.F. transmission line including a strip conductor (15) and a ground plane (13) on an insulating substrate (3) and having two diodes (24, 25) respectively D.C.-connected to two portions (38,39) of the ground plane (13). The two portions are mutually D.C.-isolated by a slot (37) to enable the diodes (24, 25) to be biased. The substrate (3) is mounted in a housing (1, 2) of conductive material, and the two portions (38, 39) of the ground plane (13) are mutually R.F.-coupled via the conductive material. One of the portions (39) is electrically-connected to an adjacent housing member (2) and the other portion (38) is separated therefrom by a thin insulating layer. The slot (37) inhibits coupling of R.F. energy out of the circuit into the slot (37), suitably being very narrow, e.g. 20 mu m, so as to form a further transmission line with a very low characteristic impedance and also to have a high attenuation along its length for operation at mm-wavelengths.
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