Abstract: A local oscillator noise rejection circuit is described which has a resistance between the output of an MES FET/HEMT and ground. This resistance has the effect of introducing a self-biasing arrangement to the oscillator circuit which means that when there is any increase in current through the MES PET/HEMT device, the voltage drop across the resistance also increases. Since the gate is tied to ground via a low resistance (51 .OMEGA.) this leads to an increased negative gate to source voltage which causes the device to "pinch-off" slightly which, in turn, gives a reduction in the current level through the device. This arrangement therefore has the effect of reducing any current surges within the device and produces an improvement in phase noise. In a preferred arrangement a 30 Ohm resistor is located between the source of the FET/HEMT and ground, the resistor being located in series within the printed circuit inductor and the output line.

Abstract: A waveguide includes a waveguide body, a twist plate, and a first and second probes. The waveguide body defines a waveguide cavity therein wherein the waveguide cavity has an aperture at a first end thereof, and wherein the waveguide cavity has a waveguide axis therethrough extending from the first end to a second end. The twist plate is in the waveguide cavity at the second end of the waveguide cavity wherein the twist plate is parallel to the waveguide axis, wherein the twist plate includes a leading edge facing the aperture, and wherein the leading edge includes first and second portions with the second portion being more distant from the aperture than the first portion. The first probe is in the waveguide cavity between the aperture and the leading edge of the twist plate for receiving a first signal having a first polarization entering the aperture.

Abstract: An RF waveguide signal transition apparatus for minimizing leakage at RF frequency is described which consists of providing a plurality of plated through-holes (16) of blind holes in a circuit board (10). The plated holes (16) are disposed on the circumference of a circle around the RF waveguide to microstrip transition of probe (14) and each of the plated holes (16) is connected to a ground plane (24). The size of distribution of the plated holes provides a barrier to signal leakage at RF frequencies in the range 10.95-11.7 GHz and they also provide a transition impedance similar to the 50 ohm characteristic impedance providing satisfactory matching and minimizing leakage into the board. The apparatus can also be used to minimise leakage from microstrip to microstrip transitions passing through the circuit board.