Multi-mode filter

Abstract

The present invention relates to a multi-mode filter comprising a carrier on which is mounted a dielectric resonator having a covering of an electrically conductive material in which there is provided an aperture and a coupling structure for coupling input signals to the dielectric resonator or for extracting filtered output signals from the dielectric resonator. The carrier is provided with an enclosing formation of electrically conductive material, which enclosing formation is electrically coupled to the electrically conductive covering of the dielectric resonator, such that the covering and the enclosing formation together form an electrically conductive enclosure for the dielectric resonator. The enclosure formed from the covering of the dielectric resonator and the enclosing formation increases the isolation of the filter and reduces leakage. The filter of the present invention is particularly suitable for use in cascaded resonator filter arrangements, and in duplex / diplex filters.

Description

BACKGROUND[0001]The present invention relates to a multi-mode filter.DESCRIPTION OF PRIOR ART[0002]The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that the prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.[0003]Single mode dielectric filters are in widespread use in many communications systems, and are used in both in low power and high power applications within the cellular communications industry. In particular, duplex filters, which are used in many cellular telephone handsets, typically employ single mode dielectric filter technology.[0004]Single mode dielectric filters typically include a resonator made of a dielectric material such as a ceramic. In many filtering applications a steep rol...

AI Technical Summary

Benefits of technology

The invention is a new design for a filter that reduces leakage from the resonator, resulting in improved filter performance. This design allows the filter to be used in a cascaded filter arrangement without compromising its characteristics, such as stop band isolation.

Problems solved by technology

Cascading resonators in this way typically results in a significant increase in the loss in the (wanted) pass-band, due to both the insertion loss of the dielectric material itself (i.e. the dielectric losses within that material) and the coupling losses in transferring energy into and out of the dielectric.

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