Patent ID: 8324989

Claim:
A method of manufacturing a re-entrant resonant cavity comprising an electrically conductive surface defining a volume and a re-entrant stub extending into the volume and having a first central longitudinal axis and an end face, there being a capacitive gap between the end face and a facing portion of the electrically conductive surface and the end of the stub and the facing portion being configured so that the end of the re-entrant stub and the facing portion are non-planar such that a spatially dependent gap distance is defined, the method including the steps of: providing a first cavity part as a metallized plastic component that integrally comprises the re-entrant stub and a first end wall of the cavity; providing a second cavity part which comprises the facing portion, the facing portion having a second central longitudinal axis; configuring the re-entrant stub and the facing portion so that, with no relative movement in the longitudinal axial direction, and with the first central longitudinal axis and the second central longitudinal axis longitudinally aligned, relative rotation between the re-entrant stub and the facing portion about said first and second central longitudinal axes alters the profile of the capacitive gap at least in part by changing the gap distance in at least a portion of the capacitive gap to provide a gap capacitance for at least one relatively rotated position which is different compared to that of another relatively rotated position; and positioning the first and second cavity parts relative to one another to obtain a gap profile that gives a required gap capacitance.