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 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 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.