Abstract: A patch array microwave antenna comprising spaced sub-arrays each consisting of a patch and at least a pair of parasitic patches fed from the non-radiating edges of the fed patch. In a second embodiment a second pair of parasitic patches fed from the radiating edges are also provided so as to form a five-member cross. Spacings between patches in a group are kept to below .lambda./15, and groups spaced apart by at least double this. Intergroup distances P are kept below 2.lambda., but may be greater than .lambda. if alternate lines of patches are staggered by P/2 so no on-axis diffraction lobes appear in the radiation pattern.

Abstract: This invention relates to photonic amplifiers, e.g., fibre amplifiers, which are specially suitable for use in long distance telecommunications optical linkages. The amplifier includes an optical transmitter, which is adapted to provide to the output of the amplifier a default signal which is digitally modulated and the digital modulation includes the identity of the amplifier. The default condition is constituted when the traffic signals fall below a preset level, e.g., in the case of a cable break when the signal falls to zero. In a preferred embodiment, the traffic signals are modulated with a control tone which is used to control the AGC's of the telecommunications link. In this system, the default condition is constituted when the level of control tone falls below a predetermined level, and the default signals also contain control tone, so that subsequent amplifiers are held out of default state.