Metal deforming – By extruding through orifice – Utilizing internal forming means
Utility Patent
1999-06-30
2001-01-02
Tolan, Ed (Department: 3725)
Metal deforming
By extruding through orifice
Utilizing internal forming means
C072S352000
Utility Patent
active
06167739
ABSTRACT:
The invention relates to a filter comprising a shell construction with a wall construction and a bottom portion forming at least one section in the shell construction, said filter further comprising at least one resonator within a section of the shell construction.
The invention also relates to a method for manufacturing a filter comprising producing a shell construction with a wall construction, a bottom portion and at least one section, and at least one resonator in said shell construction.
Radio frequency filters are used for implementing high-frequency circuits for instance in base stations of mobile telephone networks. Filters can be used, for example, as interface and filtering circuits in the amplifiers of transmitter and receiver units in base stations.
There are several different types of resonator filters comprising a shell construction, or body, e.g. coaxial resonator filters. In coaxial resonator filters, the shell envelops a conductor which is positioned in a section of the shell and which is called a resonator or resonator pin. High-frequency filters, for example, particularly more complicated filters, are provided with a multi-section shell construction and so-called subdivision. In this case, the resonator filter has a multi-section, or multi-cavity, shell construction; in other words, it comprises a plurality of resonator cavities, or sections in the shell construction, each of which forms a separate resonant circuit with the corresponding resonator.
In some known coaxial resonator filters, the shell construction and the resonators are made of separate pieces, wherefore the resonators must be, for instance, soldered onto the bottom of the shell construction. Such a construction increases the probability of detrimental intermodulation and is slow to manufacture. There are also known solutions in which material is milled away from a sufficiently large metal block so that the remaining part of the block constitutes the shell construction and resonator pins of the filter. Such a solution consumes a great deal of raw material and requires time-consuming manufacturing steps.
U.S. Pat. No. 4,706,051 discloses a solution according to which halves of a waveguide shell construction are manufactured by forging into a die: a slug of material is hit by a punch such that the slug material is displaced in the closed space between the die and the punch. This publication does not disclose any solution for manufacturing resonators. The solution according to this publication has drawbacks, since it involves the manufacture of complementary halves of a shell, and since the slug material displaced as a result of punching to form a half of the shell construction does not flow freely, since the flow of the material is restricted by the closed die.
U.S. Pat. No. 5,329,687 discloses a solution according to which both a shell construction and a resonator are moulded or extruded from plastic as an integral unit to be coated with metal. However, the thermal conductivity of such a construction is not good. In addition, U.S. Pat. No. 4,278,957 discloses a solution according to which resonators are cast in the shell construction. The construction of the last-mentioned publication is manufactured by die casting, which requires a multielement die arrangement which must open in at least three directions. On account of the material residues left in the joints of the die, a resonator made by die casting will not be entirely circular, which impairs the electrical properties of the resonator.
The object of the present invention is to provide a new type of filter which avoids the problems associated with the known solutions.
This is achieved with the filter of the invention, which is characterized in that at least the bottom portion of the shell construction and one or more resonators, or at least the part thereof close to the bottom portion of the shell construction, are an integral unit extruded from the same basic block in one piece.
This is also achieved with a method of the invention for manufacturing a filter, said method being characterized in that at least the bottom portion of the shell construction and the resonator, or at least the part thereof close to the bottom portion of the shell construction, are manufactured by impact extrusion from the same basic block in one piece.
The solution of the invention has several advantages. The method of the invention solves the problem pertaining to the joint between the lower ends of the resonators and the shell. When manufactured by the method of the invention, the shell and the resonator, or at least the lower end of the resonator, are integral, wherefore no soldered joint or any other joint is needed between the lower end of the resonator and the bottom portion of the shell construction. The method of the invention allows the number of separate parts to be reduced in the products, and the intermodulation problems with the product are clearly less serious than in the case of products assembled from separate parts. In addition, the solution of the invention saves raw materials as compared with the milling method. The solution of the invention also improves the quality factor of the filter, as no joint is needed between the lower end of the resonator and the bottom of the shell construction. The new solution reduces the weight of the filter and the number of manufacturing steps. The invention provides better thermal conductivity as compared with known solutions extruded from plastic and coated with an electroconductive material such as metal. In the solution of the invention, the shell construction and resonators can be formed by a single motion, and the die has to open in only one direction. The solution of the invention allows the cross-section of the resonators to be made completely circular. The preferred embodiments and other more detailed embodiments of the invention emphasize the advantages of the invention.
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ADC Solitra Oy
Ladas and Parry
Tolan Ed
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