DE10304524A1 - Band-pass filter topology e.g. for satellite communication transponders, has coupling to first resonator and decoupling from resonator lying opposite this in rectangular structure - Google Patents

Abstract

The filter is implemented in dielectric technology, has resonators (1-11) in a highly circular filter structure, whose transmission zeroes lie pair-wise on the imaginary frequency axis close to the pass band. Selective couplings are provided between the resonators (1-11). A 'box' section of four resonators (1-4) is present and a coupling to the first resonator and a decoupling from another resonator (3), which lies opposite to the first in a rectangular structure is carried out such that each of the two remaining resonators (2;4) of the rectangular structure has a wing of further resonators (6-8;9-11), in which the number of resonators per wing is at least greater than two.

Description

State of technology

The invention is based on a Band-pass filter incorporated in satellite multiplexer ingress multiplexers is used. The bandpass filter has a high outband damping and simultaneously a flat course of the insertion loss and the group delay within the passband. Because filters during the group runtime to an inclined position tend, are measures to compensate for this tilt necessary.

From the US 5,608,363 a microwave filter is known which has a housing which is divided by walls and these cavities are equipped with dielectrics and serve as resonators. Two rows of dielectric resonators are coupled together. Different coupling configurations are possible. The described asymmetric design is associated with considerable additional effort, since additional couplings must be inserted, in this example from the first to the penultimate, from the second to the third last resonator, etc.

In the US 5,739,733 a filter is described, which consists of resonator cavities, which are equipped with dielectrics. Some of the cavities are coupled in such a way that the filter has a flat course of the group delay. The skew is corrected for this filter by adding an external equalizer whose center frequency differs from that of the filter. The external equalizer is disadvantageous due to its mass and volume.

In the US 6,337,610 B1 describes a filter topology that allows asymmetric filter curves to be achieved. It comprises two rows of resonators, each coupled in series, one coupled into one of the top row resonators, one output from one of the bottom row resonators, and at least one coupling between a top and bottom row resonator. The disadvantage of this invention, however, is that it only relates to asymmetric filter curves. In all the examples shown, the number of zeros is odd, which is why the filter curve must necessarily be asymmetric.

The invention and their benefits

The topology for bandpass filters according to the invention with the characterizing features of the main claim in the application for dielectric filters for use in input multiplexers in satellite communication or waveguide technology with high Bandwidth as well as with filters in planar technology, in contrast, the Advantages that advantageous by the new arrangement an inherent skew in the Compensate group delay. For filters in dielectric technology or in waveguide technology is the skew mostly caused by dispersion, in planar technique by long-range interactions; inclinations can also caused by lossy couplings.

According to an advantageous embodiment of the invention, the invention comprises topologies with a core ("box section") with the resonators 1 - 4 , with a coupling to the resonator 1 and a coupling out of resonator 3 , as well as with two wings hanging on resonator 2 respectively. 4 , Within the wings, any number of resonators can be coupled together in any manner.

After a further advantageous Embodiment of the invention leaves yourself a filter with a big one Generate number of zeros in the transmission, as for input multiplexer necessary is. The maximum number of zeros that with a certain topology is generated, equal to the number of resonators of the Total filters minus the number of resonators that make up the signal on the shortest Path from entry to exit touched.

According to a further advantageous embodiment of the invention, this last number is here 3 , The path leads through resonators 1 - 2 - 3 or alternatively via 1 - 4 - 3 , With the topology according to the invention, it is possible to realize filters with a straight as well as an odd number of resonators. In addition, other filter components such as individual resonators, multiple resonators, CQ or CT sections between the two gates and the core piece can be coupled.

After a further advantageous Embodiment of the invention can with the topology according to the invention both symmetric filter curves and asymmetric filter curves be generated. Asymmetric solutions include both those with odd number zeros in the transmission and even number, with the zeros in the latter then distributed asymmetrically to the center frequency of the filter.

After a further advantageous Embodiment of the invention is in the filter structure, the maximum number used the zeros, because when preserving fewer zeros certain Interference effects must be noted, which makes the filter sensitive do.

After a further advantageous Embodiment of the invention needed one for one the above even number of zeroes an odd total on resonators.

After a further advantageous Embodiment of the invention is characterized by a slight modification in the individual couplings and center frequencies a symmetric solution changed to an asymmetric. The asymmetry, e.g. an oblique position the runtime, is only generated when existing couplings and center frequencies amended but not by adding more sizes. The modifications can be achieved by anyway necessary adjustment devices.

After a further advantageous Embodiment of the invention is the process of readjustment, which is always necessary in complex filter structures, easier, because new degrees of freedom are given by the new filter topology. For example, the topology according to the invention for the left wing infinite solutions. It no longer needs to be readjusted to any size become. Is a coupling after the construction of the filter is no more for one Readjustment accessible, because a very small and compact body was chosen so can in the inventive solution a Deviation in this coupling can also be corrected by just the other sizes of this wing be readjusted.

After a further advantageous Embodiment of the invention, the topology of the invention also in the dual - mode technology be used. Here are two degenerate in a resonator Used modes with perpendicular field lines, which Halve the mass and volume of the filter approximately. In practice the two modes are not decoupled, since even the smallest deviations from the symmetrical structure, such as a balance screw to readjust the center frequency of a mode cancel the symmetry and couple the two fashions together. Naturally suitable the dual-mode technology is good for Filter topologies in which the two modes of a resonator one as low as possible Have frequency difference. The topology of the invention ensures more degrees of fuzziness by combining modes in a dual-mode resonator allowed with particularly low frequency difference.

Further advantages and advantageous Embodiments of the invention are the following description of the Embodiment, the drawings and the claims refer to.

drawings

An embodiment of the invention is shown in the drawings and described in more detail below. Show it:

1 an exemplary filter topology according to the invention

2 Filter curves for the filters according to Table 1.
Above: Amounts of reflected and transmitted signal
Bottom: Runtime of the transmitted signal

Description of the embodiment

In 1 an exemplary filter topology according to the invention is shown. It has more couplings than those known from the prior art, in 1 this extra coupling is between the resonators 5 and 8th ,

In 2 the filter curves for the filters according to Table 1 are shown. The solid curves are the symmetric solutions according to "X_sym", the broken curves are the asymmetric solutions according to "X_asym" (X = A, B, C).

Some concrete filter examples are in Table 1 (Values for Coupling constants and resonant frequencies). The values Ai, j give the strength the coupling between the resonators i and j (where i = 0 for the input and J = 12 for stand the exit). The values Bi, i give the shift of the resonance frequency of the resonator i in the normalized frequency range (passband (-1,1)) on. The solution "A_asym" corresponds to the stand technology, the solutions "B_xxx" or "C_xxx" are according to the invention.

The solution "A_sym" in Table 1 is a symmetric filter that satisfies a typical filter specification, as in the curves in FIG 2 shown. It shows that an asymmetric solution "A_asym" can be achieved by slight modification in the individual couplings and center frequencies.

While every single value for coupling constant and center frequency is fixed in the known solution "A_asym", the new topology in the example for the left wing has infinitely many possibilities with regard to the adjustment of the individual couplings and resonance frequencies.The solution shown "B_asym" yields after arbitrary choice of coupling between the resonators 5 and 8th to 0.3 and after optimization of the remaining sizes. It must be readjusted so no new size when filtering adjustment.

In the alternative "C_xxx" in Table 1, the resonators 6 and 7 not coupled. This allows the structure in 1 to change into the equivalent structure, at the resonator 7 no more left of 8th and above 6 lies, but new above 8th , Likewise, resonator 6 no longer left, but below 5 to be ordered. This results in a new structure with a minimized geometric expansion in the horizontal direction, which is superior to all other alternatives due to this property in accordance with given installation dimensions.

At realization of the left wing 1 With two dual - mode resonators and the well - known topology "A_asym" one is forced to create a dual - mode resonator for the modes 5 and 6 to use and the second for the fashions 7 and 8th , because the fashions 5 and 8th must not be used in the same dual - mode resonator, because then the complete decoupling between these two could not be guaranteed. With the new solution according to "B_asym" one has more degrees of freedom, as here also the modes 5 and 8th such as 6 and 7 can each be combined in a dual-mode resonator. Then the maximum difference of two resonance frequencies in a dual - mode resonator is 0.2324 (resonator with modes 5 and 8th ), while in "A_asym" the maximum difference is 0.3962 (resonator with modes 7 and 8th ).

All in the description, the following claims and the features illustrated in the drawings can be used individually as well be inventive in any combination with each other.

Claims (5)

Topology for bandpass filters in dielectric engineering, with resonators ( 1 to 11 ) in a highly circular filter structure whose transmission zeros lie in pairs on the imaginary frequency axis near the passband; with optional couplings between the resonators ( 1 to 11 ), characterized in that a "box section" of four resonators ( 1 ; 2 ; 3 ; 4 ), that a coupling to a first resonator ( 1 ) and a coupling out of another resonator ( 3 ), which is diagonally opposite the first in a quadrangular structure, is designed such that each of the two remaining resonators ( 2 ; 4 ) of the quadrangular structure, each having a vane of further resonators ( 6 to 8th and 9 to 11 ), wherein the number of resonators per wing is at least greater than two. Bandpass filter topology according to claim 1, characterized in that within each wing any number of resonators greater than two are coupled together in any desired manner. Topology for Bandpass filter according to claim 1, characterized in that the Total number of resonators is odd. Topology for Bandpass filter according to claim 1, characterized in that the Arrangement of the resonators in the wings to a minimum horizontal Extension of the structure is turned off. Bandpass filter topology according to claim 1, characterized in that the resonators ( 6 ; 7 ; 8th or 10 ; 11 ) at least one wing above and below the resonator ( 5 or 9 ), which connects the wing to the box section ( 1 to 4 ) manufactures are arranged.