Wave transmission lines and networks – Resonators – Cavity resonator
Reexamination Certificate
2001-10-19
2004-07-06
Lee, Benny (Department: 2817)
Wave transmission lines and networks
Resonators
Cavity resonator
C333S02400C
Reexamination Certificate
active
06759929
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates in general to a device for receiving or transmitting electromagnetic waves in a cavity, where the device comprises a loop and a dielectric part that houses at least a first end part of the loop. The invention also relates to a method for manufacturing the device, a method for manufacturing the loop, a cavity filter and a casing for electrical and/or electronic components.
DESCRIPTION OF RELATED TECHNOLOGY
In, for example, radio base stations for mobile telephony, cavity filters are normally used for a combiner between radio frequency transmitters and an antenna. Such a system is shown in U.S. Pat. No. 6,005,452 which is hereby incorporated as a reference.
U.S. Pat. No. 6,005,452 shows an insulator with integral input signal loop, This loop is inserted and attached in a cavity filter that is earthed arid the loop is insulated from the cavity filter by means of the insulator. The distance between an end, that is not in contact with the insulator, and a hollow screw, can be adjusted, which means that the capacitance between the loop and the cavity filter can be adjusted. This adjustment means that, for example, the bandwidth of the radio frequencies that pass through the filter can be increased or decreased, The end is connected to an electrically conductive spindle which in turn is surrounded by a dielectric casing. This dielectric casing is connected to the wall of the cavity filter, which helps to fix the position of the loop in relation to the cavity filter.
Even though the cavity filter and the input device in the document mentioned above have been found to work well, it could be desirable to reduce the number of parts required for fixing the loop and for adjusting the capacitance between the loop and the casing, in order to ensure in a simple way that the position of the loop is better fixed and that the assembly and disassembly of the loop in a cavity filter can be carried out more quickly.
SUMMARY OF THE INVENTION
A general aim of the present invention is to achieve a device that allows a more simple design and fixing of a loop in a cavity filter for electromagnetic waves, while at the same time making possible simple changing of the capacitance between the loop and a grounded casing. Additional aims, effects and advantages will be apparent from the following description. The general aim of the present invention is achieved by a device for transmitting or receiving electromagnetic waves for a cavity, where the device comprises a loop and a dielectric part that houses at least a first end part of the loop, where the dielectric part defines a first recess designed to receive a means for setting the capacitance between the loop and a casing connected to earth, cavity housing and/or cover. A device is hereby achieved that only consists of one dielectric item with an embedded loop, for the transmission of signals to or from a cavity, while at the same time a means can easily be used to set the capacitance between the loop and the casing.
The loop suitably comprises an essentially flat section that is designed for a predetermined frequency. This flat section is located in the first recess and has a flat first area that is designed to be turned towards the means for setting the capacitance. The flat section has also an essentially flat second area that is parallel to the first area and the first recess is continuous in order to be able to receive the means for setting the capacitance from two directions. A symmetric hole is hereby achieved that, together with the two areas, provides a greater degree of choice for the location of the device in, for example, a casing.
The first end part has an essentially straight longitudinal axis and the first recess is turned essentially at right angles to this longitudinal axis. The first recess is preferably turned essentially at right angles to the main plane of the loop. By this means, simple adjustments of the capacitance can be carried out when the device is inserted in the casing or assembled in such a way that a distance between the end part and a means for changing the capacitance, adjustable in the axial direction of the end part, is not able to be adjusted from outside, but where a radial distance between the end part and the means can be adjusted from outside.
In addition, the device comprises at least one rib that is inserted in the first recess to make contact with the means for setting the capacitance. This rib helps to fix the means in relation to the loop in such a way that it is adjustable. If the means is a screw that is screwed into a threaded hole in, for example, a casing for electrical and/or electronic components and inserted in the recess, the rib provides a continuation of the threads in the threaded hole, which guarantees a reliable fastening of the screw at the required distance from the loop.
The device can also comprise at least one stop pin projecting into the first recess in front of the flat first area or second area in the direction of insertion of the means towards the flat area, in order to prevent the means for setting the capacitance from coming into galvanic contact with the loop and to prevent electrical flash-over between the loop and the means for setting the capacitance.
The dielectric part preferably houses a second end part of the loop. In addition to a simplification of both the device itself and its assembly, this also achieves a more secure fixing of the loop in relation to the dielectric part and in relation to the cavity in which it is inserted, in comparison to the previous technology.
In addition, the second end part is essentially parallel to the first end part and at least one of them is milled in order to provide good fixing of the loop when it is embedded in the dielectric part, The dielectric part is designed to provide a particular impedance to the grounded casing or cavity housing, together with the loop. In this way, a method can be used for adjusting, for example, the bandwidth of frequencies that pass through a cavity filter, where, for example, the bandwidth is only changed by changing the capacitance between earth and the loop.
In order to reduce still further the assembly time and to make the actual assembly work easier, the dielectric part comprises a locking device. This locking device can be inserted into a corresponding recess or through-hole in, for example, a casing for electrical and/or electronic components and makes possible rapid locking between the device and the casing. In order to fix the device to the casing more securely, the dielectric part comprises a fixing hole designed to receive a fixing element for fixing the device to the casing.
The dielectric part suitably comprises at least a second recess that ensures that more dielectric in the form of air surrounds the loop. In this way, an optimization is achieved between mechanical stability requirements and position accuracy requirements for the loop and the creation of a higher impedance around the means for setting the capacitance.
Instead of stop pins, the dielectric part can comprise a bottom surface of the first recess, which bottom surface covers the flat section from a first direction, in order to prevent the means for setting the capacitance coming into galvanic contact with the loop and to prevent electrical flash-over between the loop and the means for setting the capacitance. In an alternative embodiment, the dielectric part can also comprise a recess essentially reversed in relation to the first recess, with a bottom surface that covers the flat section from an opposite direction to the first direction.
The present invention also relates to a method for manufacturing the device, comprising the steps of:
determining the length of the loop that is to be inserted at least partially into the cavity;
forming, for example by stamping, the essentially flat area that is designed for a particular frequency; and
at least partially embedding the first end part of the loop in the dielectric part, which is, for example, of plastic and is so formed that t
Ahlberg Christer
Henningsson Uno
Lee Benny
Telefonaktiebolaget LM Ericsson (publ)
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