Abstract: A substrate integrated waveguide to air filled waveguide transition includes an electrically conductive top layer, an electrically conductive base layer spaced apart from the top layer, wherein the top and base layers each extend along a length axis from a first end to a second end of the transition, the top layer defining a width axis normal to the length axis in the plane of the top layer, and wherein a separation between the top layer and base layer increases towards the second end in a transition region, wherein the transition further includes a dielectric layer sandwiched between the top and base layers, the dielectric layer including a taper portion having a width which tapers to a point at an end point between first and second ends, the width of the taper decreasing towards the second end.

Abstract: A multiband filtering apparatus (40) for use in a communications system, said apparatus including a housing (21); a plurality of cavities (22.1, 22.2) disposed within said housing wherein each cavity includes a resonant structure, the resonant structure having at least one ceramic element (23.1, 23.2); at least one input port (27) coupled to a first resonator of said plurality of resonators; at least one output port (28) coupled to a second resonator of said plurality of resonators; and a closure member (25) adapted to engage said housing (21) and cap said cavities.

Abstract: A III-V field effect transistor comprising a semiconductor channel layer having an electrically conducting channel; an ohmic contact layer on the semiconductor channel layer, the ohmic contact layer having a recess structure disposed therethrough to the semiconductor channel layer; the bottom of the ohmic contact layer comprising an etch stop layer comprising Aluminium and Phosphorous and defining the shape of the recess at its junction with the semiconductor channel layer.

Abstract: Iterative pre-conditioning of an electrical signal for supply to an amplifier, comprising: a first pre-conditioning iteration comprising limiting the amplitude of the electrical signal to produce a limited signal; generating a difference signal for subtracting the electrical signal from the limited signal; and generating an output signal by subtracting the difference signal from the limited signal; at least one further iteration comprising the steps of: Limiting the amplitude of the output signal of the previous iteration to produce a subsequent limited signal; generating a subsequent difference signal by subtracting the electrical signal from the subsequent limited signal; and generating an output signal by subtracting the subsequent difference signal from the subsequent limited signal.

Abstract: A III-V field effect transistor comprising a semiconductor channel layer having an electrically conducting channel; an ohmic contact layer on the semiconductor channel layer, the ohmic contact layer having a recess structure disposed therethrough to the semiconductor channel layer; the bottom of the ohmic contact layer comprising an etch stop layer comprising Aluminium and Phosphorous and defining the shape of the recess at its junction with the semiconductor channel layer.

Abstract: A coplanar waveguide line comprising a substrate; a central electrode strip on the substrate; first and second electrode strips disposed on opposite sides of the central electrode strip and extending parallel thereto; first and second optical waveguides on the substrate, the optical waveguides being positioned between the first and central electrode strips and extending parallel thereto; the central electrode comprising at least one T-rail extending proximate to the first optical waveguide; the first electrode comprising at least one T-rail extending proximate to the second optical waveguide; the substrate comprising an n+ electrically conducting layer extending between the optical waveguides; wherein the coplanar waveguide line further comprises an electrical connection between first and second electrode strips.

Abstract: A III-V field effect transistor includes a semiconductor channel layer having an electrically conducting channel and an ohmic contact layer on the semiconductor channel layer. The ohmic contact layer has a recess structure disposed therethrough to the semiconductor channel layer. The bottom of the ohmic contact layer includes an etch stop layer including Aluminum and Phosphorous and defining the shape of the recess at its junction with the semiconductor channel layer.

Abstract: A III-V field effect transistor comprising a semiconductor channel layer having an electrically conducting channel; an ohmic contact layer on the semiconductor channel layer, the ohmic contact layer having a recess structure disposed therethrough to the semiconductor channel layer; the bottom of the ohmic contact layer comprising an etch stop layer comprising Aluminium and Phosphorous and defining the shape of the recess at its junction with the semiconductor channel layer.

Abstract: A four arm linearized Mach Zehnder modulator comprising first and second primary electro-optic waveguides; first and second secondary electro-optic waveguides, each secondary electro-optic waveguide being arranged adjacent to a primary electro-optic waveguide; an RF electrode having a stub extending therefrom, the stub having a first foot portion extending partially along the first primary electro-optic waveguide and a second foot portion extending at least partially along the first secondary electro-optic waveguide; an RF ground electrode having a stub extending therefrom, the stub having a first foot portion extending partially along the second primary electro-optic waveguide and a second foot portion extending at least partially along the second secondary electro-optic waveguide; an optical source for providing an optical signal to the waveguides; the RF electrodes being arranged such that when a voltage is applied between the RF electrode and RF ground electrode the magnitudes of the phase shifts experie

Abstract: A method and circuitry for pre-conditioning an electrical signal. The method comprises limiting the strength of the signal to not exceed a limit signal strength corresponding to the onset of substantial non-linear response of an amplifier to which the limited signal is to be supplied for amplification.

Abstract: An amplifier comprising a field effect transistor, a terminating network comprising inductors connected in series separated by capacitors connected in parallel, a filter and a load, wherein the values of the capacitors and inductors are arranged to present open circuits to a predetermined number of odd harmonics of a signal frequency being amplified, and to present short circuits to a predetermined number of even harmonics of the signal frequency, wherein the normalised values of the inductors and capacitors of the terminating network are selected using the following procedure: Let gr=Cr r odd=Lr r even then g1=1, g1g2=(a); grgr+1=(b), r=2?2m?1 and g2mg2m+1=(c) where (m?1) represents the predetermined number of odd harmonics which are presented with an open circuit 1 m ? ( 2 ? m - 1 ) ( a ) 4 ( 2 ? m - 1 + r ) ? ( 2 ? m - r ) ( b ) 1 m .

Abstract: A method of producing filters using lower unloaded Q factor components than filters with the same performance characteristics but requiring higher unloaded Q factor components is disclosed. The method includes the steps of defining a desired filter characteristic and applying an algorithm which provides a filter having infinite Q factor elements and having a theoretical characteristic corresponding to the desired characteristic transformed to a compensate for the difference between finite Q factor and infinite Q factor elements.

Abstract: A microwave frequency composite resonator comprising a metal housing having an internal surface and defining a resonator cavity, a dielectric member having a top face and a bottom face and a conducting plate. The dielectric member is located within the resonator cavity and the bottom face of the dielectric member directly abuts the internal surface of the metal housing and the conducting plate directly abuts the top face of the dielectric member.

Abstract: A microwave resonator, particularly for use in cellular telecommunications, comprising a hollow electrical conductor defining a resonant cavity and a substantially cubic member located within the cavity. The substantially cubic member has a high dielectric constant compared with the remainder of the cavity.