FI104298B - The resonator structure - Google Patents

Description

* 104298

Resonator structure - Resonatorstruktur

Object of the invention

The invention relates to a resonator structure according to the preamble of claim 1. Most preferably, the invention is applicable to filter structures consisting of coaxial resonators.

Description of the technical background

In prior art coaxial high-frequency filters, adjusting the resonators is typically accomplished by screw adjustment, which requires a separate frequency-10 adjusting screw and a nut to lock it. Especially in thin-walled, especially aluminum cases, a separate fastener is needed for the screw. US-5,023,579 discloses the use of a screw for adjusting the frequency of a resonator. Screw control is also disclosed, for example, in U.S. Patent Nos. 4,224,587 and 4,268,809. The disadvantage of screw control is that it increases the number of components of the filter and thus increases the manufacturing cost and the price of the end product.

In addition, screw-adjustable coaxial filter structures have a problem with high power, namely, sensitivity to breakthroughs. When screw adjustment is used, the screw tip must be placed close to the open end of the resonator in order for the screw to sufficiently influence the resonator and the frequency control to work. The proximity of the screw and the ends of the resonator poses a risk of breakthrough because very high voltages can occur at the open end of the resonator when using high power.

In known filter structures, an inductive or capacitive coupling between resonators is effected, for example, by providing a coupling opening in the metal wall between the resonators through which the required electromagnetic coupling is provided; can be implemented. The connection between the circuits through the opening can be adjusted, for example, with a screw. Such a structure is disclosed, for example, in WO-96/29754. Such a structure requires a separate screw and a part needed for locking it as components of the switch control, which again increases the number of components required. U.S. Pat. No. 4,216,448 discloses an adjustment of the coupling between resonators which is accomplished by attaching to the top of the resonators circular metal wires by means of which the coupling between the resonators can be adjusted. U.S. Patent No. 4,268,809, on the other hand, discloses a structure in which an open end of a coaxial resonator 104298 2 is provided with a plate of dielectric material with metal coupling adjusting members attached thereto for adjusting the strength of the couplings. Even such a solution is complicated and expensive.

US-4,292,610 discloses shortening a resonator by capacitively loading a resonator at an open end. With such a solution, the physical dimension of the resonator can be reduced by several tens of percent without reducing the quality ratio too much. U.S. Pat. No. 4,224,587 discloses an interdigital filter structure in which the length of the resonator is shortened by capacitive loading of the resonator. In the structure of the invention, the resonator is also shortened by loading the open end of the resonator, more particularly by a mechanical coupling member connected to the open end. Hereby, the length of the straight portion of the resonator may have been shortened from about 70 mm to 23 mm, with the Q value of the resonator decreasing by only less than 30% compared to a full-length resonator.

In serial production, filters are typically tuned after manufacture. During manufacture, the filters are preset so that their properties are close to the desired value. For example, the adjusting screw used to adjust the frequency can be turned to a certain depth at which the resonant frequency of the filter will be close to the desired value. After manufacture, each filter is typically attached to a measuring device for measuring the frequency response of the filter, after which the screw or other control means is adjusted so that the desired property of the filter is set to the desired value. With prior art filter structures, this final adjustment is laborious and time consuming.

Brief Description of the Invention

It is an object of the invention to provide a coaxial resonator structure whose structure of frequency adjusting members is as simple as possible. It is also an object of the invention to provide a coaxial resonator structure having as simple a structure as possible for the regulating elements of the coupling between the resonators. It is a further object of the invention to provide a coaxial resonator structure having as few parts as possible. It is a further object of the invention to provide a low resonator structure according to the preceding objects.

The objects are achieved by implementing the frequency and switching control means as protrusions of the resonator, whereby the frequency and switching can be adjusted by bending the respective regulating means, i.e. the projections. At the same time, the projections act as capacitive loads, whereby the physical length of the resonator can be shortened. Preferably, the adjusting members can be implemented as protrusions of a single plate-like capacitive load component, requiring only one component to be attached to the resonator.

The filter structure according to the invention is characterized by it. as described in the main part of the claim. Other preferred embodiments of the invention are set forth in the dependent claims.

The invention relates to a coaxial resonator structure which enables the implementation of a low frequency filter implemented with coaxial resonators. The frequency adjusting element of the resonator and the adjusting element of the coupling are implemented by means of projections. The frequency adjusting means controls the connection of the open end of the resonator to the exterior or septum of the filter structure and the connection adjusting means adjusts the connection of the open end of the resonator to another resonator of the filter structure or the input or output of the filter structure. The adjusting members are preferably plate-like projections, the engagement of which is effected, for example, by bending their ends towards or away from the outer or partition wall or adjacent to the adjusting member of the resonator. The coupling force can also be influenced by the area of the adjusting member. The control means may be one or more, whereby the control elements of different sizes can, for example, provide coarse and fine-tuning of the frequency or the switching. The coupling of the actuators can also be adjusted, for example, by changing the surface area of the actuators. The adjusting members also act as capacitive loads so that the physical length of the resonator relative to the unloaded resonator can be reduced.

Most preferably, the frequency and switching control means are implemented as protrusions of a single plate component, wherein the resonator according to the invention consists of two parts: a resonator and a capacitive load member connected thereto, which simultaneously functions as a switching control element and a frequency control element. In such a resonator structure, the frequency control of the resonator and the control of the coupling between the resonant circuits are combined by using one mechanical part such that the adjustments are almost electrically and mechanically independent of each other, whereby the adjustment of the coupling and frequency

BRIEF DESCRIPTION OF THE DRAWINGS In the following, the invention will be described in more detail with reference to exemplary preferred embodiments and accompanying drawings, in which Figure 1 illustrates a structure of a preferred embodiment of the invention; Fig. 4 illustrates a structure of a coupling adjusting member according to a preferred embodiment of the invention, Fig. 5 illustrates another embodiment of a coupling adjusting member 5 according to the invention, Fig. 6a shows a third structure of a coupling adjusting member Fig. 7 shows a structure of a frequency adjusting member according to a preferred embodiment of the invention.

In the pictures, the same reference numerals and notations are used for like parts.

Detailed Description of Preferred Embodiments of the Invention

Figure 1 is a perspective view of a resonator structure according to a preferred embodiment of the invention. For the sake of clarity, parts 1 of the resonator body shell, such as wall 5, are omitted from Figure 1. The first end 1a of the resonator 1 is secured by galvanic connection to the filter base plate 2 or housing ground plane 2. An element 4 for adjusting the frequency and an element 7 for adjusting the coupling are formed in the upper part 3 of the resonator. At the same time, the resonator top part 3 acts as a capacitive loading member to shorten the physical length of the resonator 1. The frequency adjusting members 4 are preferably bent towards the ground plane 2 as shown in Fig. 1. The resonator frequency of the resonator can be lowered by bending the frequency adjusting members 25 towards the metal wall 5 surrounding the resonator, which is most preferably earthed. The frequency of the resonator is adjusted upwardly by bending the frequency adjusting members 4 towards the resonator 1. The frequency adjusting members may have different sizes in their area, whereby the intensity of the frequency adjusting is different when changing the position of the different adjusting members 4. For example, in an embodiment such as Figure 1 with two frequency control means 4. the first frequency control means may be used for coarse frequency control, for example in the frequency band of several tens of megahertz, and the second for fine tuning in the frequency band of some megahertz. There may also be more than two frequency control elements 104298 5 depending on the particular filter application, or for example only one. One frequency adjusting member may be sufficient, for example, in such an embodiment. wherein the structure of the invention is used in a very narrow band filter. The surface area of the frequency adjusting member or members 4 is preferably dimensioned, for example, according to the desired range of adjustment.

Advantageously, the resonator frequency of the resonator can be controlled by frequency adjusting means 4 by bending the frequency adjusting means with a special adjusting key made of insulating material, whereby the effect of the adjusting key on the resonator frequency of the resonator is almost negligible. By selecting the upper part of the resonator structure from a sufficiently strong plate 10 and attaching the upper part 3 to the open end of the resonator in a sufficiently rigid manner, the structure is mechanically rigid so that for example mechanical resonance frequency and other properties are not affected. In this case, the adjustment of the resonator is also simple, because the torque generated by the bending of the adjusting members does not bend the entire structure of the resonator.

During the manufacture of the resonator, the resonator frequency of the resonator can be preset close to the desired value and, after manufacture, the frequency adjusting means 4 can be adjusted to the desired value. The presetting can be implemented, for example, by a suitable design of the resonator top part 3.

Figure 1 further illustrates the coupling adjusting means 7 for adjusting the coupling between the two resonators of the filter unit. The coupling between the resonators is thus mainly determined by the dimensions and the position of the opening 8 and the size of the coupling adjusting members 7 and the distance between them.

Part of the coupling between the resonant circuits of the filter can thus be accomplished by appropriate dimensioning of the switch field aperture 8. In a preferred embodiment of the invention, the major part of the coupling between the resonators is formed through an opening 8 in the wall and fine-tuned by the coupling adjusting members 7. This results in an insensitive filter structure that is easy to tune. For example, a 20 MHz switching between circuits may be accomplished by providing an opening for 15 MHz switching and 30 for the remaining 5 MHz switching controls. Larger aperture allows greater inductive coupling and smaller vice versa.

In cases where the basic coupling between the resonant circuits through the coupling opening is too strong, a second coupling opening may be formed in the partition 5 separating the resonant circuits near the grounded end 1a of the resonator. The effect of such a second aperture of 104298 6 is opposite to a coupling formed by a coupling aperture in the vicinity of the open end of the resonator. In this case, the coupling opening formed near the grounded end of the resonator can be used to adjust the coupling to an approximately appropriate level, whereby fine tuning of the coupling can be accomplished by adjusting the position of the coupling adjusting members 7.

The coupling openings 8 may be formed in the partition walls, for example, by piercing or by other means known in the art. With the structure of the invention, all coupling openings can be made of the same size, so that they can be serially formed with a single tool, which reduces manufacturing costs. 10 In such an embodiment, the necessary differences in coupling intensities between resonators can be realized by means of coupling adjusting means 7.

Figure 2 illustrates a structure according to another preferred embodiment of the invention. Figure 3 illustrates the structure of Figure 2, viewed from different directions. In this embodiment 15 there is no separate resonator top part 3, but the frequency adjusting members 4 and the coupling adjusting members 7 are separate parts which are galvanically mounted to the 'resonator 1. In the embodiment of Figures 2 and 3 the frequency adjusting member 4 and the switching member 7' in addition, act as capacitively-loading members of the resonator to shorten the physical length of the resonator. For clarity, the arms 4 '. 7 'is shown in Figures 2 and 3 for only one resonator.

The switching control elements 7 and the frequency adjusting elements 4 illustrated in the exemplary embodiment of Figures 2 and 3 can of course also be implemented in the form of substantially equivalent single-piece projections for each resonant ton, to provide the corresponding embodiments described in Figures 2 and 25 3 .

Figures 2 and 3 also illustrate a structure according to the invention in which the same projection is used as two coupling adjusting members 7. In Figures 2 and 3, one projection is used for coupling the other two resonators.

• ·

In the embodiment of Figures 2 and 3, the open ends of the coupling adjusting members 7 are implemented differently than in the embodiment of Figure 1. In the embodiment of Figures 2 and 3, the ends of the coupling adjusting members 7 are bent such that the bent ends of the coupling adjusting members of the adjacent resonators are at least a certain portion of substantially the same direction. By bending the ends of the coupling adjusting members closer to one another, the coupling between the resonators can be strengthened, and by bending the coupling adjusting members further away from each other, the coupling between the resonators can be weakened. With the solution of the coupling regulating members according to the embodiment of Figures 2 and 3, a very strong coupling between resonators can be realized, i.e. so-called. overcurrent, if a strong zero point is desired in the frequency response of the filter, whereby the filter attenuation is very high at the frequency corresponding to the zero point. Further, Figures 2 and 3 illustrate that more than one switching control member 7 can be attached to a single resonator, for example to switch the entire resonator output and input signal to the resonators.

In an embodiment of the filter structure according to the invention, a separate capacitive loading member, preferably for example a plate-like body, may be added to the structure according to the embodiment shown in Figures 2 and 3 in order to create capacitive loading and shorten the physical length of the resonator.

Figure 2 also illustrates, by way of example, a preferred embodiment of the invention in which the adjusting means are attached to the resonator at a position other than the open end of the re-15. In the exemplary embodiment of Figure 2, the actuating members are fixed closer to the open end of the resonator than to the grounded end, but not directly to the open end, as in the embodiment of Figure 1. In such a structure, the control members are not fixed at the point of the resonator where the highest voltages occur, i.e. at the open end, but at the lower-20 voltage point. This in turn contributes to increasing the air gap between the open end and the grounded parts of the filter structure, thereby reducing the risk of breakthrough compared to prior art solutions. Also, in preferred embodiments of the invention in which the adjusting members 4, 7 are implemented as protrusions of one piece such as, for example, in Fig. 1, this one piece may be secured to the desired position 25 between the open end and the grounded end of the coaxial resonator. Further, the distance of the open end from said grounded parts such as the shell structure can be further increased in the present invention by shortening the resonator by capacitive loading in any of the ways described herein, such as by capacitive load 30 The size of the capacitive load may be influenced, for example, by the size of the area of the member to be loaded or by the choice of anchorage of the member. If the frequency adjusting members and the switching adjusting members are separate components, they can also be mounted independently of each other at different spacings with respect to the open end of the resonator. Of course, they can also be fixed at 104298 δ at substantially the same distance from the open end as shown in Figure 2.

In addition, the resonant frequencies of the resonator structure can be influenced by the attachment point of the control elements. This is particularly advantageous for serial production of filters. 5, since similar resonators and filter housing shells can then be manufactured for a variety of filter solutions, and the resonance frequencies of the filter structure can be determined, at least in part, by the attachment point of the control members. In some prototype designs, the resonant frequency could be shifted up to 300 MHz with a base frequency of about 1800 MHz by selecting the attachment site of the actuators. Such adjustability allows the use of filter structures based on similar resonators and envelopes in a variety of mobile communication system devices.

The dimensions of the switching actuators can be selected according to the needs of the particular application. If a strong inter-circuit coupling is required, the coupling adjusting members may be wide in the portion at which their open ends are in close proximity to one another. If the connection between the circuits does not need to be strong, the open ends of the connection control members may be spaced apart or have a small surface area.

The adjustment of the coupling adjusting means may be similar to the adjustment of the frequency adjusting means, such as a tool made of insulating material. The coupling adjusting members may also be preset during assembly or manufacture of the member as required to provide the desired coupling.

• ·

The shape, size and number of the switching control member (s) and frequency adjusting member (s) may be selected according to the conditions of the particular application, and the invention is not limited to the examples provided herein.

Fig. 4 illustrates a preferred embodiment of the invention in which the coupling adjusting members 7 extend partially through an opening 8 in the partition 5 so that the coupling adjusting members 7 of the adjacent resonators are partially overlapping. In such an embodiment, the strength of the coupling can be increased by bending the members 7 towards each other and decreasing by bending the members 7 away from one another.

Figure 5 illustrates a preferred embodiment of the invention wherein the coupling adjusting member 7 has two arms 7a, 7b. Two different size branches allow for coarse and fine adjustment of the coupling intensity.

104298 9

Figures 6a and 6b illustrate a preferred embodiment of the invention in which the material between the open ends of the coupling adjusting members 7 is also a substance other than air. In Figure 6a, the partially overlapping ends of the coupling adjusting members 7 are secured to an insulating piece 21, which in turn can advantageously be secured to a partition 5 5. Such a solution is mechanically more robust than an air insulated solution, which provides better resistance to vibration and shock. Fig. 6b illustrates an embodiment in which the ends of the coupling adjusting means 7 are adjacent to each other, secured to the insulating body 21, which in this embodiment can also preferably be secured to the partition wall 5. In the embodiments shown by bending the ends of the coupling adjusting members 7 as described above.

However, the invention is not limited to adjusting the intensity of the coupling and adjusting the frequency of the corresponding elements 4, 7, but the adjustment can also be accomplished by modifying the respective elements 4, 7 in other ways, such as cutting or otherwise affecting the surface of the element 4, 7.

Figure 7 illustrates an embodiment in which the frequency adjusting member 4 is secured to the partition wall 5 by means of an insulating piece 21 for mechanical strength. In this embodiment, the frequency can be adjusted by bending the end of the frequency adjusting member 4 as described above

Figures 6a, 6b and 7 show only some examples of the use of insulating material between different members. However, the invention is not limited to the use of a particular dielectric piece 21, but the frequency adjusting member 4 and the coupling adjusting member 7 may be coated with plastics or other dielectric material, for example the coupling adjusting members of parallel resonators may be glued to one or more the adjusting member 4 may be glued to the partition at one or more locations.

The solutions of Figures 4, 5, 6 and 7 can be used in all preferred embodiments of the invention described in this application, such as those in which the frequency adjusting member 4 and the coupling adjusting member 7 are protruding single integral components in those embodiments of the frequency adjusting member separately mounted components.

104298 ΙΟ

The configuration of the filter solution according to the invention is simpler than that of the prior art solutions because the number of components required is smaller. Furthermore, the electrical performance of the solution according to the invention is better compared to the previous screw-controlled solution. The filter solution according to the invention 5 is thus cheaper, easier and faster to produce in series than the prior art solutions. In addition, one advantage of easy and wide adjustability of the solution according to the invention is that product development and design time of different versions of different filter frequencies and bandwidths are facilitated, which saves product development and manufacturing costs. As the number of components required decreases, the control of the product ranges required is improved.

The resonator top 3, frequency adjusting members 4, and coupling adjusting members 7 may be formed, for example, of a thin copper sheet or other suitable sheet material, such as any other metal sheet or metal-coated insulating sheet or insulating sheet which is co-metallized. The upper part 3 of the resonator, the frequency adjusting elements 4 and the switching control elements 7 can also advantageously be coated with silver, gold or some other material of high electrical conductivity.

The galvanic connections described above can most preferably be made by soldering, but also by other known means, such as spot welding or conductive adhesive bonding.

The examples described above in which the frequency control element 4 and the switch control element 7 are substantially separate components, both of which also act as capacitive loads. However, this does not limit the invention, but in the solution according to the invention it is sufficient that at least one of them, or the component to which the members are attached 'or the projections thereof, act as a capacitive load.

Although the solution of the invention is particularly well suited for use in filter structures having more than one coaxial resonator, the solution of the invention can also be used in filter structures having only one coaxial resonator. In this case, the coupling adjusting means 7 can be used to adjust the intensity of the coupling of the resonator to the input and output of the filter structure or to the filter stages implemented by other techniques of the filter structure, for example.

The resonator structure according to the invention can be particularly advantageously used in mobile communication devices and various devices of cellular network systems, such as 900 104298 11 MHz GSM base station filters and 1800 MHz DCS and 1900 MHz PCS base station filters. However, the invention is not limited to these examples, but the filter solution of the invention can be used in any other application.

The invention has been described above with reference to some preferred embodiments thereof, but it is to be understood that the invention may be modified in many different ways according to the inventive idea defined in the appended claims.

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Claims (6)

1. Filter structure. having at least one coaxial resonator (1), characterized in that the filter structure comprises at least one frequency adjusting member (4) for adjusting the resonance frequency of the coaxial resonator. at least one coupling adjusting member (7) for adjusting the coupling strength of the coaxial resonator to the other members of the filter structure and the capacitive loading member (3, 4 ', 7') of at least one coaxial resonator, wherein at least one of said adjusting members (4, 7) (3, 4 ', 7). Filter structure according to Claim 1, characterized in that said adjusting members (4, 7) are implemented as projections of one integral component (3), which component is a capacitive loading member of a coaxial resonator. Filter structure according to Claim 1, characterized in that said adjusting means (4, 7) are made of plate-like material. Filter structure according to Claim 3, characterized in that the plate material used for the manufacture of said adjusting elements (4. 7) is a silver-plated copper plate. Filter structure according to claim 1, characterized in that said adjusting means (4, 7) are implemented separately in said at least one coaxial resistor. pieces attached to the viewer. Filter structure according to claim 1, characterized in that at least one of said adjusting means (4, 7) is attached to said at least one coaxial resonator between the open end and the grounded end 25 of the coaxial resonator. Filter structure according to Claim 1, characterized in that said adjusting means (4, 7) are attached to the open end of said at least one coaxial resonator. 104298 13