Abstract: A photodetector comprises a semiconductor substrate having an input surface for receiving illumination, control electrodes for control of photogenerated charge within the substrate and a filter on the radiation input surface of the substrate, the filter comprising a dielectric-metal band pass filter having a metal layer and one or more dielectric layers with one dielectric layer between the substrate surface and the metal layer. A connector is provided for applying a bias voltage to the metal layer with respect to the substrate. In effect, the metal layer of the band pass filter provides two functions. The first function is as part of the ITF filter selecting the wavelength desired for the device. The second function is as a conductive layer allowing a bias to be provided between the substrate and the metal layer thereby producing a field within the surface of the substrate to which the filter is applied.

Abstract: An electrical arrangement, which may, for example be a magnetron, has a sealed chamber and electrically insulating fluid contained within the chamber. A temperature expansion compensation bladder comprising a helical tube is located within the chamber, the helical tube having an end open to ambient atmosphere outside the chamber, and having a closed end within the chamber.

Abstract: An electrical arrangement, which may, for example be a magnetron, has a sealed chamber 12 and electrically insulating fluid contained within the chamber. A temperature expansion compensation bladder comprising a helical tube 13 is located within the chamber 12, the helical tube 13 having an end 15 open to ambient atmosphere outside the chamber 12 and having a closed end 14 within the chamber.

Abstract: A pulse modulator comprises a solid state power switch having a source, a drain, a gate and a separate gate drive connected to ground. One pulse modulator comprises a plurality of stages connected as an induction adder. Each stage includes a plurality of cells and at least some of the cells each include a solid state power switch having a source, a drain, a gate and a separate gate drive connected to ground to control the discharge of a capacitor. In one embodiment the solid state power switch is a power MOSFET.

Abstract: A pulse modulator comprises a solid state power switch having a source, a drain, a gate and a separate gate drive connected to ground. One pulse modulator comprises a plurality of stages connected as an induction adder. Each stage includes a plurality of cells and at least some of the cells each include a solid state power switch having a source, a drain, a gate and a separate gate drive connected to ground to control the discharge of a capacitor. In one embodiment the solid state power switch is a power MOSFET.

Abstract: The present invention relates to an isolation transformer suitable for use in a modulator for generating high voltage pulses for supply across a high voltage load having a thermionic cathode such as a magnetron, the isolation transformer comprising a primary winding formed from a triaxial cable where the triaxial cable comprises a core conductor surrounded by a dielectric insulator, in turn surrounded by a screening conductor, with an outer insulating jacket.

Abstract: A high power electron tube, such as a magnetron, has the disadvantage that, to reduce the chances of the ceramic RF window failing in use, the manufacturing step entails a prolonged ageing period of powering the magnetron at low power on test, in order to drive any absorbed gases out of the RF window. According to the invention, the RF window 6 is internally glazed (8), which makes it possible to avoid the ageing period.

Abstract: A microwave generation system comprising a microwave generator, a pulse generator and an impedance network. The pulse generator is arranged to provide pulses of electrical power to the microwave generator and is operable to vary the power of the pulses of electrical power which are provided to the microwave generator. The impedance network is connected between the pulse generator and the microwave generator. The impedance network is switchable so as to substantially match an impedance across the pulse generator according to variations in the impedance of the microwave generator.

Abstract: The present invention relates to a modulator system adapted to generate high voltage pulses suitable for supply across a high voltage load having a thermionic cathode, such as a magnetron. The modulator system comprises a high voltage DC PSU connected to a switching mechanism adapted to generate high voltage pulses from the high voltage DC PSU for application to a thermionic cathode of a high voltage load. The modulator system further comprises an isolation transformer; a heater PSU adapted to be connected to a cathode heater through the isolation transformer and to provide an AC current thereto.

Abstract: A high frequency energy generator system includes a plurality of high frequency energy generator heads. Each head includes a respective magnetron; a common drive unit for producing power for the plurality of magnetrons; and a connector arrangement connecting each of the plurality of heads to the common drive unit to supply power to the magnetrons. At least one of the heads is located remote from the common drive unit.