JPH0752802B2 - Multi-cavity microwave filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multi-cavity microwave film that exhibits minimal size, electrical losses, weight and production costs, yet has structural simplicity, reproducibility, and high mechanical strength.

As is well known, transmission bridges are created in Tx transmissions by removing all improper frequencies and generating a signal useful in allowing the rest to pass only one useful signal. Also, in Rx reception, a microwave film suitable for canceling all undesired signals and receiving only useful signals is required.

The two filters TX and RX are the same, and have the fundamental importance that they have very little attenuation in the constant passband and have a damping action that decreases gradually away from the ends of this band. Have sex.

To date, microwave filters have been manufactured with multiple cavities in 1) a flanged waveguide, 2) welded and machined cut ends, and 3) solid mass.

Such conventional filters have a number of deficiencies such as large size and high cost, complicated manufacturing process, low reproducibility, difficult automatic machining in numerically controlled machine tools and the like.

An object of the present invention is to provide a multi-cavity microwave film that does not have the above defects.

Another object of the present invention is to provide a microwave filter which, in addition to having small dimensions, has high reproducibility and a structure which can be manufactured by a very simple and effective method.

The above and other objects include a microwave filter provided with a substantially parallelepiped metal body provided with a plurality of cavities, each of which is provided with a rod resonator and a tuning and connecting screw at the center of each cavity. This is achieved by using a microwave filter characterized in that the centers of the cavities of are placed at each apex of the polyline and the intercepts of the polyline make an angle between them of more than 90 °.

The connection between one cavity and the other is made by a slit located on the axis of the corresponding segment of the polyline. Preferably, the bottom of each cavity has a threaded hole that communicates with the outer surface of the filter body bottom.

According to an advantageous feature of the invention, at least one of the two longitudinal faces has two holes (preferably counterbored on the outside) which respectively communicate with the first and last cavities. A plurality of blind screw holes are formed on the surface opposite to the bottom surface and parallel to this.

According to an advantageous feature of the invention, the filter body with the corresponding cavities, resonators and screws is cut into cuboids and then milled, drilled, counterbored, tapped, deburred and heat treated. It is realized using stabilized extruded rods.

According to a preferred feature of the invention, the filter body comprising the cavities, the resonators and the holes is made by pressure die casting of an aluminum alloy, preferably followed by a mild flattening of the surface of the parallelepiped, a vertical Spotting and tumbling of holes in the longitudinal and lateral surfaces is performed.

In the pressure die casting process, the resonant cavity is made with a slight draft taper (eg about 2%), and the filter body has an empty recess in the solid part and a wall thickness of 2-4 mm. Weight is reduced by adjusting within. Blind holes are advantageously changed to through holes.

Another object of the invention is that the ratio between the cavity diameter D _c and the corresponding resonator diameter d _r is different for each cavity,
It is preferably adapted to be reduced in the passageway leading to the central cavity, which is more important in that the electrical losses of the central cavity are greater than those of the peripheral cavity.

It is advantageous to use a pressure die casting alloy with a high fluidity in the die, the expansion coefficient of which is made of a material different from that of the pressure die casting alloy and which has a frequency fluctuation pair within very limited limits. To get the temperature range,
It is compensated for by using tuning rods and screws with different coefficients.

Various features of the present invention will be more clearly understood from the description of the embodiments shown in the accompanying drawings.

FIG. 1 shows an upper surface A and a lower surface B, two longitudinal surfaces F and E,
And schematically a filter defined by two lateral planes C and D.

According to a first feature of the invention, this filter consists of n cavities C ₁ , C ₂ -C ₁ -C _n , whose centers 0 ₁ , 0 ₂ -0 _i ...
0 _n is aligned along a polygonal line LS composed of n-1 pieces LS ₁ and LS _{2 to} LS _{i to} LS _n-1 . Each intercept LS _i has a length L _i
(Ie the distance between two adjacent centers 0 _i-1 and 0 _i )
, And the angle formed between the adjacent segment LS _{i + 1} .

Each cavity C _i communicates with an adjacent cavity C _{i + 1} by a slit. Although this slit cannot be clearly shown in FIG. 1, it is shown by P-P ₁ , N-N ₁ and M-M ₁ in FIG.

Each slit is located along the orthogonal axis of each segment of the polyline and has a depth approximately equal to the depth of the cavity (H in Figures 4A and 4D).

The faces C and D on both sides of FIG. 1 have first and second holes 21, 22 respectively, which are respectively the initial cavities C ₁
And one of the holes penetrating into the last cavity C _n , on each side, is countersunk with an outward facing step.

The surface E has two holes E ₁ and E ₂ (which are countersunk toward the outside) communicating with the first and second cavities C ₁ and C ₂ .

FIG. 2 shows the back side of the rod type resonator shown in FIG. This surface B has n screw holes AS _{1 to} AS _n ,
The open surface of each threaded hole is flush with the cavity so that they can be closed by a suitable cover (not shown).

According to a preferred feature, this filter has cavities distributed along a polygonal line whose sections have a symmetrically equal length with respect to the central cavity. For example, LS ₁ = L
S _n , LS ₂ = LS _n-1 , LS ₃ = LS _n-2 and so on.

The filters shown in FIGS. 1 and 2 have equal dimensions,
That is, it can be easily made starting from a solid rod of a parallelepiped having paired surfaces with a = b, c = d, e = f. Where a, b, c, d, e, f are the corresponding faces A, B, C,
It is an edge of D, E, F, and in this case, A = B, C = D, E = F.

If the filter is a solid rod, for example, "corrosion resistant (ANTICORROD
AL) ”when made from a solid extrusion bar, this bar is cut into AxCxE pieces, then each piece is processed into a rectangular parallelepiped, and the subsequent machining is chip removal, milling (cavity formation). ), Using a machine tool for tapping and trimming, the rod machined in this way preferably being subjected to material stabilization in a furnace.

According to another object of the invention, it has been found that the body A × C × E is surprisingly advantageously produced by pressure die casting. This solution has been found to be ideal because it optimizes the following items: -Dimension-Electrical loss-Weight-Structural function-Mechanical strength-Production cost-As mentioned above, the optimization of dimension is the arrangement of cavities forming the filter along the polygonal line, and the critical line is critical. Obtained by the distribution of cavities with an interior angle greater than 90 °. In fact, the distribution along the polygonal line with a 90 ° interior angle (thunderbolt) was not used. Because this solution optimizes the total length of the filter, but requires a large width.

Finally, for cavities arranged along a right-angled polyline, a reduction of about 15% was possible, while maintaining a width equal to 1.5 times the size of the same cavity.

-Electrical loss: the significant loss is caused by the central cavity with the ratio Dc / dr (Dc = cavity diameter, dr = resonator diameter) = 3.33, which is the ratio of the loss to the theoretical value, not the surrounding one. . In fact, the central cavity preferably has a line flow.
ar flow), the first and last cavities have a ratio Dc / dr =
It is important to obtain a ratio such that it is 2.67.

Preferably, the rod diameter dr is kept constant and the cavity diameter Dc is modified in order to be related to the above ratio.

If the solution of providing a cavity with Dc / dr = constant = 3.33 is chosen, there is only a small advantage in terms of the above losses, it is necessary to increase the filter length to about 10-15%. Will be

In contrast, the ratio Dc / dr will always remain constant, but if the cavity is kept within the expected length, the ratio Dc / dr will be disadvantageous with respect to the above losses.

-Weight: if the material used is an aluminum alloy (Silumin) containing at least traces of Si and other elements, weight = 335 g with single filter, connector, resonant rod, adjusting screw for connection and A complete filter with cover can limit weight = 740g. (On the contrary, the same filter machined from a solid rod weighed 935g and a conventional filter weighed 1.9kg).

Ease of construction: If an aluminum alloy is chosen which allows it to be produced by pressure die casting, its design is simplified despite the complexity of the filter structure.

-In addition, some weight reduction of the solid part is introduced, the thickness of the filter wall is designed within the range of 2 to 4 mm, and the outer shape of the filter is a regular shape which makes positioning on the processing machine easier. If we take care that we have a reasonably strong structure.

The solution according to the invention makes it possible for the screw holes to be in the form of through holes, including those used for closing the filter by means of a cover. However, it is practically impossible to form a through-hole type using the conventional structure unless a large amount of machining cost is invested.

The presence of blind holes is a major problem for components that must be plated (in this case silver plated) as they retain the acid in the finishing bath and thus corrode in the final process. It is important to be careful.

With regard to the material selected (aluminum alloy, in particular "Silumin"), aluminum alloy has been found to be one of the most advantageous in terms of cost and weight. In addition, the extremely high flowability index
x), it is an excellent material used in pressure die casting. The use of this material has been largely considered due to its high dilatation co-efficient.

Surprisingly, this difficulty is especially due to the use of materials with different coefficients of expansion, alloys of iron and copper, in order to keep the frequency displacement vs. temperature below 10 p.pm/°C, rods, tuning and connections. Overcame by making a screw. Figure 2 shows a bottom B of the pressure die casting filter, on this surface B, has a hole VA ₁ to VA _n for weight reduction unit AL ₁ ~AL _n, a screw hole AS ₁ ~AS _n adjustment screw, Holes 21 and 22 are the holes used for the connector. The most typical embodiment of the present invention has been shown. Preferably, as shown in FIG.
Cavities C ₁ -C ₁ ′, C ₂ -C ₂ ′, C ₃ -C ₃ ′ having a central cavity C ₀ and symmetrical with respect to the XX axis are provided.

The diameters of the symmetric cavities C ₁ -C ₁ ′ are equal to each other, but different from the diameters of the symmetric cavity pair C ₂ -C ₂ ′, and the cavities C ₂ −
The diameters of C ₂ ′ are equal to each other, but also different from the diameter of the symmetrical cavity C ₃ −C ₃ ′. Although the diameter of the cavity C ₃ -C ₃ 'equal to each other, it is different from the diameter of the central cavity C _0, the diameter of the cavity C _0, preferably different from the diameter of the symmetrical cavity of the above .

The diameter of the cavity C ₀ is larger than the diameter of the next pair C ₃ −C ₃ ′,
Sequentially C ₃ -C ₃ 'diameter of pairs C ₂ -C _2' greater than the diameter of,
It is preferred order larger than the diameter of the 'diameter of the to-C ₁ -C _1' pair C ₂ -C _2.

These diameters preferably decrease in a first-order law from the center to the periphery.

The same applies to the slits between the cavities if the length of the segment LS _i connecting the centers of adjacent cavities also decreases according to the first-order law.

FIG. 3 (top view of die cast filter with unthreaded holes), FIG. 4 (top view of the same filter but with screw holes on the end face), and FIG. 5 (fourth view).
As shown in the bottom view of the filter), which finished as shown in FIG. Preferred features of the present invention, the screw holes AS ₇ -AS ₆ constituting the tuning rod _{pairs, AS 5 -AS 4, AS 3} -AS 2 All have the same diameter, and a pair of connecting screws VA ₆ −VA ₅ , VA ₄
−VA ₃ and VA ₂ −VA _{1 have} the same diameter.

Another advantage of the pressure die casting filter is that the upper surface (Figs. 3 and 4) has a recess for reducing the weight, AL ₁ , AL ₂ , AL ₃ , A.
L _{4 to} AL ₆ and recess A for weight reduction on the bottom (Fig. 5)
It is possible to reduce the weight to the minimum value by L ₁ ′ to AL _n ′.

FIG. 4A is a cross-sectional view taken along the line AA of FIG. 4, in which the weight-reducing portion at the bottom extends at a height approximately equal to the total height H of the cavity, while the weighing portion at the top extends at an extremely short height h. Indicates that FIG. 4A also shows the thickness of the outer wall PA.E, the cavity wall PA.C and the bottom wall PA.F, which all consist of a small thickness, for example within 2 mm to 4 mm, so that This filter has excellent strength with minimal weight.

Fig. 4B (F-F cross section in Fig. 5), Fig. 4C (G- in Fig. 5)
(G section), the holes related to the cover are through holes FPC ₀ and FP
It shows an advantageous example of being C ₀ ′ (not a blind hole).

As shown in the cross section of FIG. 4D (C-C cross section of FIG. 4), the structure of the central cavity C ₀ has the lightening portions (AL′4) and (AL′4).
Of particular note is that it has 4) on the top and bottom respectively.

The total height H of the cavity is kept substantially constant, but its diameter varies, for example, from about 30 mm of the cavity C ₀ to about 25 mm of the cavity C ₁ -C ₁ ′. The diameters of adjacent symmetrical cavity pairs decrease according to a first-order law between two limits.

As previously mentioned, the difference between the top views of FIGS. 3 and 4 is that the filter of FIG. 3 is an unfinished pressure die cast filter, with holes AS ₇ through AS ₁ for the resonator and While none of the holes VA ₆ to VA ₁ for connecting screws are tapped, the filter shown in FIG. 4 is tapped and additionally has holes A ₁₄ -A ₁ for the cover. And in.

FIG. 4E shows side C of the finished filter of FIG. 4 with stepped counterbore 21 for the connector.

FIG. 5 is a bottom view of the filter shown in FIG. 4, showing recesses AL ′ ₁ , AL ′ ₂ , AL ′ ₃ , AL ′ ₄ , on the lower surface B for weight reduction.
~ AL ' ₇ having different shapes and depths with respect to the shape and depth of the lightened parts AL ₁ to AL ₇ of the top surface A in order to obtain the minimum weight and maximum strength. It has a shape and a depth.

Another advantageous feature of the invention is that the holes 21 and 22 for the connectors in the transverse planes C and D, respectively, are not coaxial and they lie on two different axes. Therefore, it is possible to keep the position of one hole, for example, the input hole 21 constant, and rotate the filter connected to the other hole 22 around the axis passing through the center of this hole 21. Therefore, it enables extremely light branching.

This advantage is particularly advantageous when a plurality of filters are arranged substantially parallel to each other, each filter having one hole in a fixed or restrained position, but with a longitudinal direction passing through the center of the hole in the restrained position. Of the various positions obtained by rotating the filter about its axis, the other hole can be provided in a relatively convenient position.

Although the present invention has been described for purposes of illustration with reference to the preferred embodiments illustrated in the accompanying drawings, all variations, modifications and substitutions of the present invention which can occur to those skilled in the art are also included in the scope and spirit of the present invention. It is self-evident.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of a microwave filter according to an embodiment of the present invention seen from a first side surface. FIG. 2 shows the first part of the microwave filter shown in FIG.
The side surface of is a schematic perspective view seen from the opposite second side surface. FIG. 3 is a plan view of an unfinished filter formed by pressure die casting. FIG. 4 is a plan view of the filter obtained by finishing the filter of FIG. FIG. 5 is a bottom view of the finished filter shown in FIG. FIG. 4A is a sectional view taken along the line AA of FIG. FIG. 4B is a sectional view taken along the line FF of FIG. FIG. 4C is a sectional view taken along the line GG in FIG. FIG. 4D is a sectional view taken along the line CC of FIG. FIG. 4E is a side view of the filter shown in FIG. C ₁ , C ₂ 〜C _i 〜C _n …… Cavity, 0 ₁ , 0 ₂ 〜 0 _i 〜0 _n …… Center, LS
₁ , LS _{2 to} LS _{i to} LS _n ... intercept, P-P ₁ , N-N ₁ , M-M ₁ ... slit, 21, 22 ... hole, E ₁ , E ₂ ... hole, AS ₁ 〜AS _n …… Screw hole, AL ₁ 〜 AL _n・ ・ ・ Light weight part, AL ′ ₁ 〜 AL ′ ₇ …… Recess

Claims (2)

[Claims] 1. A plurality of resonant cavities are created, with a rod-type resonator, a tuner and a connecting screw at the center of the cavity.
A microwave filter made of a substantially parallelepiped metal body, wherein the centers of n cavities are located at the vertices of a polygonal line, and each segment of the polygonal line forms an angle greater than 90 ° with each other, and is adjacent to each other. Between the two cavities to be connected by a slit provided in the transverse central axis of the corresponding segment of the polyline and having a depth approximately equal to the depth of the cavity, the diameter of the cavity and the corresponding resonance Microwave filter characterized in that the ratio between the diameter of the vessel and the diameter of the central cavity decreases from the central cavity to the peripheral cavity. 2. A filter according to claim 1, characterized in that the diameter of the cavity and the segment of the polygonal line are equal for a pair of cavities symmetrically arranged with respect to the central cavity. .