Allen Telecom Group, Inc.

Orion Industries, Ltd.

Allen Telecom, Inc.

Douglas R Jachowski

Chia-Sam Wey

David P Halley

An electromagnetic bandstop filter comprises a microwave circuit, at least one microwave resonator, coupling means that couples electromagnetic energy to and from the microwave resonator, and an impedance transformer coupled to, and in series with, the coupling means, wherein the transformer is coupled to the resonator only through the coupling means, and wherein the impedance transformer is shunt coupled to the microwave circuit. The impedance transformer comprises at least two series-connected transmission line sections of different impedances.

Dual-mode dielectric resonator bandstop filter

A preferred realization of a frequency spectrum filter incorporating multiple signal paths is selected using a new design tool, a plot of resonator coupling coefficient values representing filter designs having equivalent signal transfer characteristics. The design plot is formed by first subjecting an initial matrix of resonator coupling coefficients, representing a particular filter design, to pre-multiplications by selected plane rotation matrices--which each have their respective rotation angles--and to post-multiplications by their transposes. Equations for the individual elements that form the resulting modified coupling coefficient matrix are then plotted over a range of one of the rotation angles. Examination of the result plot leads to a selection of a set of coupling values in observance of predetermined criteria. An optimum realization of the filter is then constructed by adjusting the physical resonator couplings so that they conform to the coupling values selected from the plot. Some preferred realizations of dual-mode bandpass filters, which have been designed using this technique, are described.

Optimum, multiple signal path, multiple-mode filters and method for

A dual-mode dielectric-resonator-loaded cavity filter comprises a generally cylindrical cavity, at least two longitudinally-spaced dielectric resonator elements coaxially aligned within the cavity, and at least one coupling obstacle disposed between the resonators and extending a distance from the cavity wall. The coupling obstacles are preferably conductive and are electrically connected to the cavity wall. However, the obstacles may be constructed of a dielectric material in some applications. Each obstacle may be aligned with one of the reference planes corresponding to a resonant mode of the resonators to effectively control or reduce the coupling between the parallel resonant modes of adjacent resonators. The reduction in coupling between resonant modes of adjacent resonators allows large coupling differentials to be produced, allowing a filter designer to implement a wide variety of high-performance filters without expensive irises. The coupling obstacle achieves the reduction in coupling without requiring large spacing between adjacent resonators. The coupling obstacles may be conveniently and inexpensively produced in bar, wire, hemi-disk, and other configurations. Several adjustments allow the resonators to be tuned, and the couplings to be adjusted, after the filter is assembled, reducing the complexity and expense of manufacture. In particular, the coupling obstacles arc mounted for limited translation along the longitudinal axis of the cavity, and for rotation about their own longitudinal axes, thereby adjusting the amount of coupling reduction they provide.

Apparatus for providing desired coupling in dual-mode dielectric

An improved multiplexer comprises a housing, a transmission line transformer section within the housing extending in a first direction, and at least two interdigital transmission line filters adjacently disposed within the housing along the first direction. The transformer section has a first end electrically coupled to an antenna circuit connector, and a second end electrically coupled to the housing (i.e. grounded). Each filter includes several resonating elements. At least one resonating element of each filter is located in proximity with a portion of the transformer such that electrical coupling between the filter and the transformer is established. The length of each coupling portion of the transformer is approximately one-quarter electrical wavelength at the center frequency of the associated filter. The dimensions of the filter cavities are preferably selected to be as small as possible without unacceptably degrading the filter insertion loss. Further, the filters, and the associated coupling portions of the transformer, are disposed in close proximity. The filter cavity size and spacing are such that the transformer coupling portions of adjacent filters are no more than about one-eighth wavelength apart (measured along the first direction). This provides a significant reduction in the physical volume required for prior art multiplexers employing interdigital filters. An adjustable-frequency resonating element formed as a longitudinally extending body portion having an deformable leaf adjustment member at one end. Deformation of the adjustment member modifies the effective electrical length, and thereby, the resonant frequency, of the resonator.

Compact, low-intermodulation multiplexer employing interdigital filters

An RF filter having a housing defining a cavity with plural elongated resonators and plural resonator decouplers adjacent each of plural pairs of the resonators in the housing. The decouplers are grounded adjacent each of their ends only to the housing to provide an enhanced resonator decoupling effect. The filter may instead comprise a dielectric block with resonator holes and resonator decoupler holes each appropriately metalized with the decoupler holes being grounded at each end at external metalized block surfaces.

RF filters and multiplexers with resonator decouplers

A poly-band filter includes a folded metal housing which defines an interior region partitioned by a divider. First and second pluralities of resonators are provided in the housing. Alternately increasing and decreasing degrees of coupling are provided between adjacent resonators in the housing. Slot coupling is provided between first and second non-adjacent resonators displaced from input/output connectors for the filter.

Folded multiple bandpass filter with various couplings

A multi-resonator notch filter incorporates a variable impedance transmission line with impedance values going from a relatively low value and increasing upward to a relatively high value then back down to a relatively low value again. A plurality of resonant cavities is coupled to the relatively high central impedance line section of the filter at odd multiples of quarter wavelength intervals. Other resonators can be coupled to lower impedance sections of the transmission line. The locations of selected resonators on the quarter wavelength intervals can be altered thereby increasing and decreasing the nominal quarter wavelength intervals of selected internal pairs by a predetermined amount thereby providing acceptable levels of performance with fewer resonators.

Bandstop filter having symmetrically altered or compensated quarter

A multi-resonant notch filter incorporates a stepped impedance transmission line with impedance values going from a relatively low value and increasing upward to a relatively high value then back down to a relatively low value again. A plurality of resonant cavitites is coupled to the relatively high central impedance line section of the filter. Other resonators can be coupled to lower impedance sections of the transmission line.

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Redwood City, CA, United States of America

Douglas R Jachowski