Abstract: An optical isolator includes an optical isolator unit including a main polarization discriminator in concatenation with a Faraday rotator, and an auxiliary polarization discriminator disposed in series with the optical isolator unit. One of the polarization discriminators initially divides an applied optical signal propagating in a forward direction along a reference axis into two polarized signals subsequently experiencing polarization dispersion and differential transverse deflection, while the other polarization discriminator eventually eliminates the polarization dispersion. Tile auxiliary discriminator includes a plate of a uniform thickness inclined at a tilt angle with respect to the reference axis selected so that the transverse deflection difference incurred during the passage through the one polarization discriminator is eliminated in the other polarization discriminator. This facilitates achieving very low polarization dependent loss in the isolator.

Abstract: An apparatus for stabilizing microwave oscillator circuits is disclosed. The apparatus comprises a dielectric resonator positioned in the vicinity of a microwave semiconductive device for completing a feedback path between two electrode circuits of the device. A dielectric spacer is positioned between the resonator and the electrodes for supporting the resonator and controlling the magnitude of coupling between the two electrode circuits. A folded mechanical structure is described wherein the oscillating device and the resonator are located at the fold for improving the frequency stability of the oscillator. The microwave semiconductive device may be a bipolar transistor or a field effect transistor.

Abstract: An improved low-noise microwave amplifier comprises a circuit arrangement coupled in parallel with a GaAs FET amplifying stage for reducing transmission loss in case of dc power failure or amplifying stage failures. The circuit arrangement comprises two microwave circulators and a microwave isolator connected therebetween.