Abstract: A differential time delay shifter may comprise a 1-to-N switch, where N is an integer greater than 1. The switch may have a pole contact, N throw contacts, and a pole arm to selectively couple the pole contact to one of the throw contacts. One throw contacts may be a first throw contact at a first switch position, and one throw contacts may be a last throw contact at a last switch position. The shifter may further comprise one or more transmission lines, each of which is electrically connected between two of the N throw contacts. The shifter may further comprise a source configured to generate an electromagnetic signal. The source may be electrically coupled to the pole contact, to convey the signal to the pole contact. The shifter may further comprise one or more loads, a first of which is electrically coupled to the first throw contact.

Abstract: A microwave resonator comprising a hollow tube comprising an electrically conductive tube wall which defines a tube bore, the tube extending along a length axis from a first end to a second end; a first electrically conductive closing plate closing the first end of the tube, the first electrically conductive closing plate comprising at least one coupling slot extending therethrough; a second electrically conducting closing plate closing the second end of the tube, the second electrically conductive closing plate comprising at least one coupling slot extending therethrough; a plurality of dielectric resonant pucks, each puck comprising first and second end faces and a side wall extending therebetween, each puck being dimensioned such that when in the tube its dominant mode is a doubly degenerate mode; the pucks being arranged within the tube bore spaced apart from each other and the closing plates, each puck being arranged centered on the length axis and its side wall abutting the tube wall such that there is

Abstract: A microwave resonator comprising a hollow tube comprising fan electrically conductive tube wall which defines a tube bore, the tube extending along a length axis from a first end to a second end; a first electrically conductive closing plate closing the first end of the tube; a second electrically conductive closing plate closing the second end of the tube; a plurality of dielectric resonant pucks, each puck comprising first and second end faces and a side wall extending therebetween, each puck being dimensioned such that its dominant mode is a doubly degenerate mode; the pucks being arranged within the tube bore spaced apart from each other and the closing plates, each puck being arranged with its end faces normal to the length axis and centered on the length axis and its side wall abutting the tube wall such that there is no air gap between the puck and tube wall which extends from one end face to the other of the puck, the puck adjacent to the first closing plate being termed the input puck; each puck bein

Abstract: A differential time delay shifter may comprise a 1-to-N switch, where N is an integer greater than 1. The switch may have a pole contact, N throw contacts, and a pole arm to selectively couple the pole contact to one of the throw contacts. One throw contacts may be a first throw contact at a first switch position, and one throw contacts may be a last throw contact at a last switch position. The shifter may further comprise one or more transmission lines, each of which is electrically connected between two of the N throw contacts. The shifter may further comprise a source configured to generate an electromagnetic signal. The source may be electrically coupled to the pole contact, to convey the signal to the pole contact. The shifter may further comprise one or more loads, a first of which is electrically coupled to the first throw contact.

Abstract: A microwave resonator comprising a hollow tube comprising a plurality of electrically conductive wall faces which together define a tube wall defining a tube bore, the tube extending along a length axis from a first end to a second end; the tube wall having an N fold rotational symmetry about the length axis where 2<N<10; a first electrically conductive covering plate covering the first end of the tube; a second electrically conductive covering plate covering the second end of the tube; a dielectric puck comprising first and second end faces and a side wall extending therebetween, the puck being dimensioned such that when in the tube bore its dominant resonant mode is a doubly degenerate mode; the puck being arranged in the tube bore spaced apart from the covering plates with its end faces normal to the length axis and centered on the length axis; the puck being spaced apart from the tube wall by a plurality N of electrically conductive spacer blocks, the spacer blocks being spaced equally around the le

Abstract: A microwave resonator comprising a hollow tube comprising an electrically conductive tube wall which defines a tube bore, the tube extending along a length axis from a first end to a second end; a first electrically conductive closing plate closing the first end of the tube, the first electrically conductive closing plate comprising at least one coupling slot extending therethrough; a second electrically conducting closing plate closing the second end of the tube, the second electrically conductive closing plate comprising at least one coupling slot extending therethrough; a plurality of dielectric resonant pucks, each puck comprising first and second end faces and a side wall extending therebetween, each puck being dimensioned such that when in the tube its dominant mode is a doubly degenerate mode; the pucks being arranged within the tube bore spaced apart from each other and the closing plates, each puck being arranged centered on the length axis and its side wall abutting the tube wall such that there is

Abstract: A microwave resonator comprising a hollow tube comprising a plurality of electrically conductive wall faces which together define a tube wall defining a tube bore, the tube extending along a length axis from a first end to a second end; the tube wall having an N fold rotational symmetry about the length axis where 2<N<10; a first electrically conductive covering plate covering the first end of the tube; a second electrically conductive covering plate covering the second end of the tube; a dielectric puck comprising first and second end faces and a side wall extending therebetween, the puck being dimensioned such that when in the tube bore its dominant resonant mode is a doubly degenerate mode; the puck being arranged in the tube bore spaced apart from the covering plates with its end faces normal to the length axis and centered on the length axis; the puck being spaced apart from the tube wall by a plurality N of electrically conductive spacer blocks, the spacer blocks being spaced equally around the le

Abstract: A microwave resonator comprising a hollow tube comprising fan electrically conductive tube wall which defines a tube bore, the tube extending along a length axis from a first end to a second end; a first electrically conductive closing plate closing the first end of the tube; a second electrically conductive closing plate closing the second end of the tube; a plurality of dielectric resonant pucks, each puck comprising first and second end faces and a side wall extending therebetween, each puck being dimensioned such that its dominant mode is a doubly degenerate mode; the pucks being arranged within the tube bore spaced apart from each other and the closing plates, each puck being arranged with its end faces normal to the length axis and centered on the length axis and its side wall abutting the tube wall such that there is no air gap between the puck and tube wall which extends from one end face to the other of the puck, the puck adjacent to the first closing plate being termed the input puck; each puck bein

Abstract: A linear actuator includes a drive arm and an extension arm each extending along a common drive axis. One of the arms has a plurality of resiliently deformable fingers extending beyond the end of the arm towards the other arm. At least one of the fingers has a thread on its inner face while the other arm has a threaded portion. At least part of the threaded portion is received between the fingers. The fingers are adapted to urge the threads of the two arms into interengagement such that rotation of the drive arm about the drive axis displaces the extension arm along the drive axis. The two threads are arranged such that when the ridge of one thread is received in the groove of the other thread the two sides of the ridge abut the two edges of the mouth of the groove.

Abstract: A microwave TM mode resonator includes a resonator cavity defined by an electrically conducting cavity wall having first and second spaced apart end faces and a side wall extending therebetween. The resonator further includes a resonator body within the cavity extending along its length between the first and second end faces, wherein a portion of the length of the resonator body is a dielectric and a further portion of the length is a metal.

Abstract: A linear actuator includes a drive arm and an extension arm each extending along a common drive axis. One of the arms has a plurality of resiliently deformable fingers extending beyond the end of the arm towards the other arm. At least one of the fingers has a thread on its inner face while the other arm has a threaded portion. At least part of the threaded portion is received between the fingers. The fingers are adapted to urge the threads of the two arms into interengagement such that rotation of the drive arm about the drive axis displaces the extension arm along the drive axis. The two threads are arranged such that when the ridge of one thread is received in the groove of the other thread the two sides of the ridge abut the two edges of the mouth of the groove.

Abstract: A tuneable bandpass filter includes a plurality of coupled resonators. A common structure of the filter includes at least one common coupling or one common resonator. An upper loop includes first and second end resonators coupled together by a signal path and further includes at least one further signal path extending between end resonators. The further signal path includes at least one further resonator with the end resonators being coupled to the common structure. A lower loop includes first and second end resonators coupled together by a signal path and further includes at least one further signal path extending between end resonators. The further signal path includes at least one further resonator with the end resonators being coupled to the common structure.

Abstract: A tuneable filter comprising a filter body defining a tuning cavity; a tuning member within the tuning cavity; and, a linear actuator adapted to displace the tuning member within the cavity to tune the filter; the linear actuator comprising a motor; a drive arm connected to the motor and extending along a drive axis, the drive arm being adapted to be rotated about the drive axis by the motor; an extension arm extending along the drive axis being connected at one end to the tuning member and being in engagement with the drive arm at the other end; the engagement between the drive arm and extension arm being arranged such that rotation of the drive arm about the drive axis displaces the extension arm along the drive axis; each of the drive arm and extension arm comprising an end stop, the end stops being arranged such that as the extension arm reaches the end of its range of travel towards the drive arm the drive arm end stop rotates into abutment with the extension arm end stop, preventing further rotation of

Abstract: A TEM mode resonator (12) comprising a tuneable cavity (13) defined by an electrically conducting cavity wall (14), the cavity wall comprising a grounding face (15), a capacitor face (16) and a surrounding wall (17) extending therebetween; an electrically conducting resonator member (18) within the cavity extending from the grounding face (15) part way to the capacitor face; a tuning member (19) within the cavity between the resonator member and capacitor face adapted to be displaced towards and away from the capacitor face along a displacement axis to tune the resonator; the capacitor face (16) further comprising an electrically conducting temperature compensation plate (25), the temperature compensation plate being connected to the capacitor face at two spaced apart points (23, 24) and forming a bowed surface therebetween; the temperature compensation plate having a smaller coefficient of thermal expansivity than the capacitor face.

Abstract: A tuneable bandpass filter comprising a plurality of coupled resonators, the filter comprising a common structure comprising at least one common coupling or one common resonator; an upper loop comprising first and second end resonators coupled together by a signal path, the loop further comprising at least one further signal path extending between end resonators, the further signal path comprising at least one further resonator, the end resonators being coupled to the common structure; a lower loop comprising first and second end resonators coupled together by a signal path, the loop further comprising at least one further signal path extending between end resonators, the further signal path comprising at least one further resonator, the end resonators being coupled to the common structure; the resonators being coupled together such that the bandpass filter can be divided into a low pass sub filter and a high pass sub filter, one of the sub filters being arranged to receive the output of the other.

Abstract: A Doherty amplifier is described which comprises: a power splitter (120) having a first output and a second output, wherein the first output is connected to a main power splitter (392) having first and second outputs which differ in phase by 90°; and the second output is connected to an auxiliary power splitter (342) having first and second outputs which differ in phase by 90°; a main final stage amplifier (234) comprising first (324) and second (325) main paired amplifiers, the inputs of which are connected to the first and second outputs of the main power splitter (352); an auxiliary final stage amplifier (244) comprising first (344) and second auxiliary (345) paired amplifiers, the inputs of which are connected to the first and second outputs of the auxiliary power splitter (342); wherein the output from the first main paired amplifier (334) is connected to the output from the first auxiliary paired amplifier (344) by an impedance inverter (250); and the output from the second main paired amplifier (345) i