CN1320288A - High performance dielectric ceramic filter - Google Patents

Abstract

A reduced size ceramic block filter has trap holes whose center is askew from the line running through the center of the transmission poles such that the height-wise distance between its center and the center line of the transmission poles is greater than (dt+dl)/2, but not greater than 3/8 of the height of the filter. The trap hole is also width-wise spaced from the next nearest transmission hole by an amount which approximates the distance between transmission holes. Due to this layout the diameter of the trap holes are reduced in order to maintain performance which is equivalent to a conventional filter whose trap holes are timely aligned with its transmission poles. The combination of reduced trap hole diameter and reduced width-wise spacing between traps and transmission holes, results in a reduced size ceramic filter.

Description

High performance dielectric ceramic filter is to the mutual reference of related application

The application be the unsettled U.S. Patent application that is entitled as high performance dielectric ceramic filter submitted on March 17th, 2000 _ _ _ _ number part continue; the rights and interests that No. 60/147,676, the U.S. Provisional Application of submitting in this application on August 6th, 1 and and the application be common transfer.

Invention field

The present invention relates to have the ceramic sheet filter of high-performance and compact package.

Background of invention

Ceramic body with the coaxial aperture that passes through its length direction forms a resonator, its specific frequency generation resonance to be determined by the effective dielectric constant of the length in hole and ceramic material.These holes generally are circular or oval-shaped.Can form a dielectric ceramic filter to a plurality of resonator group altogether.These holes in the filter must be passed whole, promptly from the top surface to the basal surface.Just in time the axial length with filter is identical to this means the degree of depth in hole.The axial length of filter is to select according to the available dielectric constant of required frequency and pottery.

Potsherd plays a part filter, because these resonators are inductance coupling high and/or capacity coupled between per two adjacent resonators.These parts form by designing the electrode pattern on the potsherd top surface and using such as silver or this class electric conducting material plating of copper.

Ceramic filter is being known in the art, and at for example United States Patent (USP) 4,431,977; 5,250,916; With 5,488, explanation is generally arranged in 335, all these is herein incorporated with for referencial use just as proposing at this fully.

About its performance, knowing that in the art the bandpass characteristics of dielectric ceramic filter is to increase and become sharp-pointed along with the hole count of passing potsherd.Required hole count depends on the desirable attenuation properties to filter.In general, the one-way communication filter needs at least two holes and the hole of two-way communication needs more than three.This is shown among Fig. 1, and wherein curve 10 shows the filter response that has less hole count compared with curve 12 and 14.Clearly, curve 14 is the responses with filter of maximum hole counts, and is the most sharp-pointed in its three response shown in being.With reference to figure 2, as can be seen, the bandpass characteristics of a certain specific dielectric ceramic filter is owing to used the trapped wave hole that passes potsherd also to become more sharp-pointed.Curve 21 expressions of solid line do not have the response of the filter of high-end trap.Dashed curve 23 expressions have the response of the same filter of high-end trap.

Trapped wave hole perhaps just abbreviates them as trap usually, is meant resonance at the resonator that is different under the frequency of senior filter hole, and these senior filter holes just abbreviate the hole usually as.They are designed to resonance on undesirable frequency.Like this, no matter transmitting the signal trap of the desired frequency of wanting, these holes then remove at low side or the high-end signal of not wishing to want frequency.The characteristic of filter just defines by this way, and promptly high pass, low pass or band are logical.Trap is bigger than the distance between the hole from the distance in hole, avoids mutual interference mutually between hole and the trap with this.As shown in Figure 3, hole 31 distance separating each other is D, and the distance between the transmission hole of trap 33 and the most close trap 33 then is arranged to 2D.Trap and the accurate distance of transmission between the utmost point be one of selection of design so that reach the performance of regulation, but it preferably 1 to 10mm.In general, trap is that 1.5D is to 2D to the distance in hole.

According to routine, hole 41 and trap 43 in the ceramic filter are arranged in line, as shown in Figure 4.This design and the top space requirement of mentioning have limited the scope of filter aspect minification.Specifically, the performance index of a given filter are its quantity in width, length, hole and the function of the diameter in hole.Common axial length L is 2 to 20mm.Width W is by the decision of the quantity in hole.The used width of sheet filter is 2 to 70mm.The quantity in minimizing hole, the diameter or the pitch of holes defection in hole influence its performance.Therefore, hope can be designed such dielectric ceramic filter, and it can reduce the size of given filter effectively and keep its given performance index simultaneously.

Summary of the invention

For the new design of the size that reduces a given filter is achieved in that the diameter that reduces trap and they are removed from the center of transmission hole, shorten the distance between trap and the most close next transmission hole simultaneously.Like this, the width of arbitrary given filter can reduce and not influence the performance of filter.In one particular embodiment of the present invention, each trap from its horizontal range of the position of the hithermost transmission utmost point of the next one be 0.8D to 1.5D, D is the spacing of respectively transmitting between the utmost point here.Each trap also separate a segment distance in the vertical direction and the transmission utmost point, its scope from greater than the diameter of trap and transmit the utmost point the major diameter sum half but be not more than 3/8H, wherein H is the height of filter.

The accompanying drawing summary

Fig. 1 shows that the band-pass response of dielectric ceramic filter increases the situation of its sharpness with the increase of hole count in the filter.

Fig. 2 illustrates the validity of trap in removing high-end frequency.

Fig. 3 is between conventional ceramic sheet filter mesopore and the expression at the interval between hole and trap.

Fig. 4 is the plane graph of the top surface of conventional dielectric ceramic filter, and hole on it and trap are located along straight line.

Fig. 5 shows one embodiment of the present of invention, and trap off-center wherein also has the diameter that dwindles.

Fig. 6 represents that according to trap of the present invention to the departing from of hole, the transmission utmost point wherein is a circular cross-section on the filter top surface.

Fig. 7 represents that according to trap of the present invention to the departing from of hole, the transmission utmost point wherein has elliptic cross-section on the filter top surface.

Detailed description of the invention

Consult Fig. 5, show one embodiment of the present of invention here, trap 53 wherein moves on to and deviates from the centerline that intersects with each hole 51.In addition, the diameter of trap 53 is made littler than the diameter in hole 51.The combination of these two adjustment makes trap more to be close to the hole on level and does not influence its performance.Therefore, any linear pattern sheet filter with given specification can reduce its width.

Say that more specifically as shown in Figure 6, the horizontal interval x between the trap 63 and the nearest transmission utmost point 61 approximates D, D is the distance of respectively transmitting between the utmost point 61 here.Horizontal range x preferably should not be greater than 1.5D less than 0.8D yet.Compared with an end sheet filter of a trap is arranged, this is equivalent to have a very big saving on width W, compared with all have at two ends trap and with the transmission utmost point be that the filter of linear array comes, its saving is bigger.Because trap is off-centered, it has a vertical side-play amount y to the center line in hole.The height of supposing ceramics is H, and as shown in Figure 6, hole 61 is they are centered close to from the 0.5H of two limits 60 and 62 of making at the center of getting with the height of filter, and then the minimum point of trap 63 should be positioned on the peak in hole 61 at least.In other words, trap and hole in vertical direction can not be overlapping.In a preferred embodiment of the invention, the diameter of given trap is dt and the diameter in hole 61 is dl, and then 61 vertical displacement preferably should be not more than (dt+dl)/2 to trap 63 from the hole, but is not more than 3H/8.

Consult Fig. 7, the cross section in hole 61 is oval-shaped here, and the vertical displacement of trap 63 center line of 61 from the hole preferably still should be greater than (dt+dl)/2, and are not more than 3H/8, and wherein dl is the major axis of elliptic cross-section.

In addition, as mentioned above, the diameter of trapped wave hole should be reduced to preferred this scope of diameter less than the hole, but is not less than 0.3mm.

The same with other delectric filter, the selection dielectric is in the design.In a preferred embodiment of the present invention, dielectric is a pottery, and its dielectric constant is between 20 to 150.

Being manufactured on of sheet filter is known in the art, and this comprises electric conducting material is applied process on dielectric.As mentioned above, copper or silver are usually selected electric conducting materials.Electric conducting material generally will cover basic all bottom surfaces and the sidewall of potsherd.This is with finishing someway in some known methods.These methods comprise immersion plating, spraying plating or with copper or silver paste is printed on the dielectric and baking applies dielectric.Other method comprises electroplates or electroless plating, and they also are processes known in the art.

The filter of making according to the present invention can be (for example combination of transmitter filter and two filters of filter for receiver) that one-way communication (the single filter) used or two-way communication are used.

Principle of the present invention only has been described above.Persons skilled in the art can design various modifications, though these modifications do not offer some clarification on or illustrate, have embodied principle of the present invention here, thereby are within its spirit and scope.

Claims (8)

1. filter comprises:

One dielectric material sheets, two relative sidewalls that it has a top surface, a basal surface, said top surface and said basal surface are coupled together along the Width of this sheet are with two relative sidewalls that said top surface and said basal surface are coupled together along the short transverse of this sheet;

Spaced apart from each other and extend through at least three holes of this sheet from said top surface to said basal surface along said Width, wherein at least one hole in these at least three holes is a trapped wave hole, its sidewall in the said sidewall that said top surface and said basal surface is coupled together along the said Width of this sheet is comparatively close, and the hole of at least two vicinities in said at least three holes is transmission holes, said transmission hole is D along the spacing distance of the Width of sheet each other, and wherein the center of said trapped wave hole is to depart from the line that intersects with the center of said transmission hole; And

Electric conducting material is gone up the said inner surface that covers said basal surface and sidewall surfaces and said at least three holes substantially.

2. filter as claimed in claim 1 along the said interval of said said Width, between said trapped wave hole and the hithermost transmission hole of the said next one, is between the 1.5D at 0.8D wherein.

3. filter as claimed in claim 2 along the said interval of said said Width, between said trapped wave hole and the hithermost transmission hole of the said next one, is between the 1.2D at 0.8D wherein.

4. filter as claimed in claim 2, wherein said trapped wave hole is about D along said said Width and next hithermost transmission hole distance separately.

5. filter as claimed in claim 1, wherein the center in said each hole except said trapped wave hole is located substantially on the straight line.

6. filter as claimed in claim 4, wherein the center of each said transmission hole is left the spacing distance that connects the sidewall of said top surface and said basal surface along the said Width of said sheet filter and is about 0.5H.

7. filter as claimed in claim 6, the distance that wherein said trapped wave hole is separated by along the said height and the said transmission hole of this sheet is for being not less than (dt+dl)/2 but be not more than 3/8H, wherein dt is the diameter of said trapped wave hole, dl is the diameter of said transmission hole, and H is a said height.

8. filter as claimed in claim 7, wherein said transmission hole is an oval cross section, and said dl is the major axis of said oval cross section.

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