JPH0878903A - Dual mode dielectric waveguide type filter and characteristic adjusting method for the same - Google Patents

Abstract

PURPOSE: To provide the miniaturized low-cost dual mode dielectric waveguide type filter by providing a notch at a resonator equipped with a mode to be oscillated in two directions. CONSTITUTION: Concerning a block 2 consisting of a dielectric resonator, its cross-sectional shape in a horizontal plane is almost square-shaped and that block is formed in the shape of a vertically extended pillar. On the four side faces and the bottom face of the block 2, most of the areas or all the areas are coated with a conductive film 4. A hole 12 with a shape and a dimension almost corresponding to the cross-sectional shape of the block 2 is formed at the center of a substrate 10 for a microstrip line. The upper end part of the block 2 is suited into this hole, and the apex surface of the block 2 and the upper surface of the substrate 10 are positioned at the same height. Concerning the block 2, the upper half part of a ridge line on one of side surfaces is cut and a notch 6 is formed. With this notch 6, degeneration is canceled, two modes of an even mode and an odd mode are provided, and a band pass filter to utilize frequency width almost corresponding to the difference of the resonance frequencies of these two modes is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dual mode dielectric waveguide type filter and a characteristic adjusting method thereof. The filter of the present invention can be suitably used, for example, as a filter of a small communication device used for mobile communication using microwaves.

[0002]

2. Description of the Related Art Conventionally, the problems to be solved by the invention
A waveguide type resonator using a cavity is used to generate a dual mode resonance and use it for a filter. However, this is large in size, and it is difficult to meet the demand for miniaturization. Further, since it is necessary to make the inner surface of the cavity a mirror surface, it is difficult to manufacture, and the cost is high. Although it has been attempted to fill the inside of the cavity with a dielectric in order to reduce the size, it is still difficult to connect the resonator and the signal line (excitable connection) because of the half-wavelength type.

On the other hand, the planar microwave filter may be formed on the dielectric substrate by using the microstrip technique. However, this is small in size but low in practical use due to high insertion loss, and it has been proposed to use a superconductor for solving the problem, but it is not practical at present.

Therefore, it is an object of the present invention to provide a dual mode dielectric waveguide type filter which can be easily miniaturized.

A further object of the present invention is to provide a dual mode dielectric waveguide filter which is easy to manufacture and can be manufactured at low cost.

Another object of the present invention is to provide a dual mode dielectric waveguide type filter which can be easily coupled with a signal input / output line.

Another object of the present invention is to provide a dual mode dielectric waveguide type filter whose frequency characteristics can be easily adjusted, and a method for adjusting the characteristics of the filter.

[0008]

According to the present invention, in order to achieve the above object, a dielectric block having a columnar shape and a cross section orthogonal to the longitudinal direction thereof is substantially square or circular. A conductive film is formed on a side surface and a first end surface of the magnetic field to enable two electromagnetic signal modes vibrating in first and second directions orthogonal to each other in the cross section.
Symmetry in which a coupling forming means for coupling an electromagnetic signal between two modes extends in the longitudinal direction of the dielectric block including a direction forming an angle of 45 degrees with respect to the first and second directions of the dielectric block. A dielectric resonator formed on the surface, and an input / output unit for respectively coupling with the electromagnetic signals of the two modes of the dielectric resonator, A dual mode dielectric waveguide filter is provided.

In one mode of the present invention, the coupling forming means of the resonator couples the two modes by disturbing the symmetry of each of the two modes.

In one aspect of the present invention, the coupling forming means of the resonator includes a notch formed in a side surface of the dielectric block.

In one aspect of the present invention, the resonator coupling forming means includes a conductive film provided on the second end surface of the dielectric block.

In one aspect of the present invention, the coupling forming means of the resonator includes a dielectric stub provided on a side surface of the dielectric block.

In one aspect of the present invention, the resonator is provided with a resonance frequency adjusting means.

In one aspect of the present invention, the resonance frequency adjusting means is on a plane of symmetry that includes the first direction and / or the second direction of the dielectric block and extends in the length direction of the block. Is formed in.

In one aspect of the present invention, the resonance frequency adjusting means is formed by partially removing the conductive film on the side surface of the dielectric block.

In one aspect of the present invention, the resonance frequency adjusting means includes a conductive film provided on the second end surface of the dielectric block.

In one aspect of the present invention, the input / output unit is provided to one end of the second end face of the dielectric block in the first direction and one end of the second direction in the second direction. Input / output electrodes.

In one aspect of the present invention, the input / output electrodes are connected to a microstrip line.

In one aspect of the present invention, the grounding conductive film of the microstrip line is connected to the conductive film provided on the side surface of the dielectric block.

Further, according to the present invention, in order to achieve the above object, a plurality of the resonators are provided, and one of the two modes of electromagnetic signals of the resonators adjacent to each other is connected. And an input / output unit for respectively coupling with one of the electromagnetic signals of the two modes of the resonator at both ends. A multi-stage dual mode dielectric waveguide filter is provided.

In one aspect of the present invention, the interstage coupling means is formed by connecting electrodes provided to the second end faces of the adjacent resonators to each other.

In one aspect of the present invention, two of the resonators are used, the resonators are arranged such that the first end faces face each other, and the interstage coupling means are adjacent to each other. This is achieved by removing corresponding portions of the conductive film applied to the first end surface of the resonator.

In one aspect of the present invention, the input / output unit includes an input / output electrode provided on the second end surface of the dielectric block.

In one aspect of the present invention, the input / output electrodes are connected to a microstrip line.

In one aspect of the present invention, the grounding conductive film of the microstrip line is connected to the conductive film provided on the side surface of the dielectric block.

Further, according to the present invention, in order to achieve the above object, there is provided a method of adjusting the characteristics of the filter, wherein the size of the coupling forming means is changed. A method for adjusting the characteristics of a dielectric waveguide filter is provided.

Further, according to the present invention, in order to achieve the above object, there is provided a method for adjusting the characteristics of the filter, wherein the dimensions of the resonance frequency adjusting means are changed. A method of adjusting characteristics of a mode dielectric waveguide type filter is provided.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a partially cutaway schematic perspective view showing a first embodiment of a dual mode dielectric waveguide type filter according to the present invention, and FIG. 2 is a schematic vertical sectional view thereof.

In these figures, reference numeral 2 is a dielectric block constituting a dielectric resonator, and the block has a substantially square cross-section in a horizontal plane and a column shape extending in the vertical direction. The block 2 preferably has a dielectric constant of 20 or more from the viewpoint of reducing radiation loss in the case of a quarter-wave resonator, and is made of, for example, a barium titanate-based ceramic dielectric having a dielectric constant of 90. The conductive film 4 is provided on most or all of the four side surfaces and the bottom surface of the block 2. The conductive film 4 is made of silver or copper, for example. The conductive film is not formed in most areas on the top surface of the block 2 (the top surface, ie, the end surface on which this conductive film is not formed is referred to as an “open end surface”).

Reference numeral 10 denotes a microstrip line substrate, and a hole 12 having a shape and size substantially corresponding to the sectional shape of the dielectric block 2 is formed in the center of the substrate. The upper end of the dielectric block 2 is fitted in the hole, and the top surface of the block 2 and the top surface of the substrate 10 are at the same height.

The substrate 10 is made of a dielectric material, a ground conductive film 14 is formed on the entire lower surface thereof, and input / output stripline conductive films 16a and 16b are formed on the upper surface thereof.
Are formed.

As shown in FIG. 1, the dielectric block 2 has a notch 6 formed by cutting the upper half of one ridgeline on the side surface. The notch 6 vibrates in the X direction and the Y direction which are orthogonal to each other in the horizontal section (XY section) 2
It is intended to couple electromagnetic signals between two electromagnetic signal modes by disturbing each symmetry,
The coupling forming means of the dual mode dielectric resonator is formed on a symmetry plane of the block 2 in a direction forming an angle of 45 degrees with the X direction and the Y direction.

The block 2 is provided in the portion corresponding to the input / output stripline conductive films 16a and 16b.
The conductive film at the upper end portion of the side surface of is partially removed. Further, on the top surface of the block 2, input / output electrodes 8a and 8b are formed so as to extend from the tips of the input / output strip conductive films. By the input / output electrodes 8a and 8b and the input / output stripline conductive films 16a and 16b,
An input / output unit is configured to couple with the electromagnetic signals of the two modes of the resonator.

The ground conductive film 14 of the substrate 10 is used.
Are electrically connected to the conductive film 4 on the side surface of the block 2.

The resonator of this embodiment has a mode of vibrating in two directions of XY, and when the notch 6 is not provided, the two modes vibrate independently of each other, so that the resonance frequencies are the same (degenerate). However, if the notch 6 is made as described above, the degeneration is released, and two modes of an even (EVEN) mode and an odd (ODD) mode are set up, and as described later, a difference in resonance frequency between these two modes occurs. It is possible to obtain a bandpass filter that uses a frequency band that is substantially equivalent as a passband.

In the filter of this embodiment, unlike the conventional waveguide type resonator using a cavity, since the resonator is basically composed of the dielectric block 2, the 1/4 wavelength type resonance is obtained. And the block has a high dielectric constant, so that downsizing of the filter can be easily achieved.

Further, in the filter of this embodiment, a resonator can be easily obtained by applying a conductive film to a desired portion on the outer surface of the dielectric block, so that the filter can be easily manufactured and the cost can be reduced. Realization is possible.

Further, in the filter of this embodiment, the signal input / output line is directly connected to the top surface of the dielectric block, so that input / output coupling can be easily achieved.

Further, in the filter of this embodiment, the frequency characteristic can be easily adjusted. Hereinafter, this point will be described.

FIG. 3 is a diagram showing changes in the resonance frequency when the size of the notch 6 of the dielectric block 2 is changed in the above embodiment. As shown in FIG. 3, the dimensions of the dielectric block 2 are 5 (mm) × 5 (mm) × 10.
(Mm), and the dimension of the notch 6 is 0.
A change in the resonance frequency f of the ODD mode and the EVEN mode of the resonator when the length ΔC is changed assuming that the width is 7 (mm) × 0.7 (mm) and the length ΔC is shown.
The pass band width f _PASS of the filter substantially corresponds to the frequency width between the ODD mode resonance frequency f _ODD and the EVEN mode resonance frequency f _EVEN . For example, ΔC is 4 (m
m), the pass bandwidth f _PASS is approximately 300 (M
Hz).

Therefore, the characteristics of the filter can be changed by changing the length ΔC of the notch 6.
Specifically, a notch 6 slightly smaller than the size expected to obtain a desired bandwidth is formed in advance, the frequency characteristic is inspected, and until the desired characteristic is obtained,
Repeat the notch and check little by little. As a result, it is possible to obtain a filter having a desired frequency characteristic after compensating for a deviation from the design value of the frequency characteristic due to another accuracy error in manufacturing the dielectric block or an error in the coupling degree of the input / output means. it can.

More generally speaking, as shown in FIG. 4, one of the side surfaces of the dielectric block 2 having a length L and one side of the square cross section orthogonal to the length direction is W. On the ridge,
When the notch 6 having one side of W ₁ and the length ΔC is formed, the frequency characteristic of the filter can be changed by changing the dimensions of W ₁ and ΔC. ΔC is 0
It can be changed within the range of <ΔC ≦ L, and ΔC is L
The closer to, the larger the bond size can be,
In addition, the bond size can be increased as W ₁ is increased. A conductive film may be formed on the surface of the notch 6 to suppress radiation loss and improve the Q value, but without the conductive film, stronger coupling can be obtained. The adjustment is easier. In some cases, a conductive film may be formed in a desired region on the surface of the notch 6 in advance, and the conductive film may be trimmed to finely adjust the frequency characteristic.

The shape of the notch does not necessarily have to be as shown in FIGS. 1, 3 and 4, but may be as shown in FIGS. 5 and 6. The embodiment of FIG. 5 shows a case where the notch 6 is formed from the end face opposite to that of FIG. 3, and the embodiment of FIG. 6 forms two notches 6A and 6B and one notch 6B.
The size is fixed and the length of the other notch 6A is changed. In FIG. 5 and FIG. 6, FIG.
Changes in the resonant frequency f of the ODD mode and the EVEN mode of the resonator similar to those in FIG.

The above-described notch-forming means joins two orthogonal modes by disturbing their symmetry, but the present invention is not limited to this, and the orthogonal means are not limited to this. Other means may be used as long as they are coupled by disturbing the symmetry of the two modes. As such a means, a conductive film 7 provided on the top surface (open end surface) of the dielectric block 2 as shown in FIG. 7 may be used. The conductive film 7 is formed in a portion corresponding to the ridgeline of the block 2 similar to the cutout 6 of the embodiment of FIG. 1, and changes the dimension ΔF of two sides sandwiching the right angle of the right-angled isosceles triangle. The change in the resonance frequency f of the ODD mode and the EVEN mode of the resonator in the case of

According to this embodiment, the mechanical work for forming the notch in the dielectric block 2 is unnecessary, and the frequency characteristic can be adjusted more easily. In order to change the dimension ΔF, conductive films may be sequentially added, or conversely, the conductive film may be formed in a large size in advance,
You may remove sequentially. The partial formation of the conductive film 7 is easier than the notch formation in the block 2, and further,
Even if the dimensions are too small, the conductive film can be added, which has the advantage of not lowering the product yield.

FIG. 8 also shows an embodiment of the bond forming means by applying a conductive film to the open end surface of the dielectric block 2 similar to that in FIG. However, in this embodiment,
In addition to the conductive film 7 of the embodiment shown in FIG. 7, a conductive film 7'is provided also at two corners adjacent to the block top surface corner where the conductive film 7 is located. Then, the resonance frequency change when the dimension ΔF of the conductive film 7 is changed is shown.

In the case of this embodiment, the ODD mode resonance frequency f _ODD and the EVEN mode resonance frequency f _EVEN intersect each other on the way. In this case, the frequency characteristic may be interesting. That is, as shown in FIG. 9, depending on whether the magnitude of ΔF is below or is above the intersection of the f _{OD D} and f _EVEN on the frequency characteristics, is formed in the vicinity of the pass band That is, the position of the attenuation pole changes between the high band side and the low band side. By utilizing such characteristics, desired frequency characteristics can be realized.

FIG. 10 is a schematic plan view showing another example of the bond forming means. Here, in the portion of the block 2 where the notch 6 and the conductive film 7 are located, a bulge (stub) 9 is formed by the dielectric material of the block. By appropriately changing the length of the stub 9 in the block length direction (Z direction) (that is, cutting off an appropriate portion), it is possible to change the coupling size and adjust the frequency characteristic.

FIG. 11 is a schematic plan view for explaining the function of the bond forming means as described above.

When the vibration directions of the two orthogonal modes are X and Y, the block structure is changed substantially on the diagonal line of the block end face square shape in the directions (x, y) forming an angle of 45 degrees with these X and Y directions. By adding or removing or adding a conductive film, the symmetry of the waveguide can be broken and a perturbation can be generated to couple two orthogonal modes. Also, the strength of the bond can be changed by changing these dimensions. At that time, generally, when the bond forming means is formed at the first corner of the block 2, the bond is strengthened by forming the bond forming means also at the second corner diagonal to the first corner. Bonding is weakened by forming bond forming means also in the third corner and / or the fourth corner adjacent to them.

It should be noted that at the position on the block within the plane indicated by broken lines X ₁ and Y ₁ in FIG. 11 (that is, within the plane extending through the center of the sectional shape of the block 2 in the X or Y direction) When the conductive film is partially provided on the end face or the conductive film on the side face is partially removed, the resonance frequency of the mode in the X ₁ and Y ₁ planes of the resonator can be changed.

A specific example will be described with reference to FIG. In FIG. 12, X ′ and Y ′ are broken lines X ₁ and Y _{1 of} FIG.
The position of the block surface that intersects with the surface indicated by is shown. Block 2
In the open end face of the above, conductive films 22a and 22b can be formed on X'and Y'as resonance frequency adjusting means separately from the input / output electrodes so as to face them, for example. Further, on the side surface of the block 2, the removed portions 24a and 24b of the conductive film 4 can be formed on the X'and Y'as resonance frequency adjusting means. With such a resonance frequency adjusting means, the resonance frequencies of the two orthogonal modes can be adjusted independently, and the deviation of the resonance frequencies of the two orthogonal modes due to a dimensional error in manufacturing the block or the like can be adjusted.

FIG. 13 is a diagram for explaining the operation of the resonance frequency adjusting means. As shown in the figure, input / output electrodes 8a and 8b having a width of 1 (mm) and a length of 0.5 (mm) are formed on the open end surface of the dielectric resonator block 2, and further A conductive film 22b for adjusting the resonance frequency is formed at a position facing the output electrode 8b. Conductive film 22b
Is 2 (mm), and changes in the resonance frequency of the X-direction mode and the resonance frequency of the Y-direction mode when the length M is changed are shown. Here, the bond forming means is not formed. The X-direction mode does not change substantially with changes in M. The difference between the resonance frequency in the X-direction mode and the resonance frequency in the Y-direction mode when M = 0 (mm) is due to a dimensional error in the X-direction and the Y-direction having a square block cross section. Therefore, by adopting a value of M that allows the resonance frequency of the X-direction mode and the resonance frequency of the Y-direction mode to coincide with each other, the resonance frequencies of the two orthogonal modes caused by dimensional errors in manufacturing the block are adjusted. You can

Although the resonance frequency adjusting means for the X-direction mode is not formed in FIG. 13, the resonance frequency adjusting means for the X-direction mode can be formed in the same manner as the Y-direction mode and can function similarly. . Although the bond forming means is not formed in FIG. 13, the filter of the present invention can be formed by forming a desired bond forming means. In order to adjust the center frequency of this filter, the dimensions of the orthogonal two-mode resonance frequency adjusting means can be changed so that the same resonance frequency change can be obtained.

In the above embodiments, the case where the cross-sectional shape in the plane orthogonal to the length direction of the dielectric block is a square has been described, but the dielectric block should be a columnar one having a circular cross section. Also, in this case, the same effect as the above embodiment can be obtained. FIG. 14 shows an example thereof. In FIG. 14, the dielectric block 2 has a radius of 3 in cross section.
It has a circular shape of (mm) and a length of 10 (mm), a conductive film 4 is provided on the side surface and one end surface, and a conductive film 7 as a bond forming means is provided on the open end surface. 8
Reference numerals a and 8b are input / output electrodes. In FIG. 14, the conductive film 7
The change in the resonance frequency is shown when the dimension ΔF is changed.

Further, in the above-mentioned embodiments, the case where the input / output means is directly connected to the open surface is shown, but in the present invention, the input / output means is not limited to this, but the open end surface of the block is the end. Or it is arranged at an appropriate interval to the side surface,
It may be one that realizes input / output coupling by forming a desired capacitance.

Next, FIGS. 15 and 16 show an embodiment of a multi-stage dual mode dielectric waveguide type filter. In these drawings, members having the same functions as those in FIGS. 1 to 14 are designated by the same reference numerals.

In the embodiment of FIG. 15, two dielectric resonators used in the embodiment shown in FIG. 1 are arranged in series, and the first-stage resonator and the second-stage resonator are arranged. Is a stripline conductive film 32 for interstage coupling as interstage coupling means.
And the stripline conductive film 34a for input / output is connected to the first-stage resonator,
The stripline conductive film 34 for input and output is used for the resonator of the stage.
b is connected. The stripline substrate is not shown in FIG. Similarly, a filter having three or more stages can be configured.

In the embodiment shown in FIG. 16, two dielectric resonators used in the embodiment shown in FIG. 1 are used, and the open end faces of these resonators are opposite to each other. It is arranged so as to abut. The inter-stage coupling means is realized by removing the corresponding portions of the conductive film 4 provided on the opposite end faces of the two blocks 2 to form the opening 36 (opening of the second-stage resonator). 36
Although only the first resonator is shown,
An opening is formed in the part facing the step). The stripline conductive film 34a for input and output is used for the first-stage resonator.
And the strip line conductive film 34b for input / output is connected to the second-stage resonator. FIG.
In FIG. 6, the stripline substrate is not shown.

[0061]

As is apparent from the above description, according to the dual mode dielectric waveguide type filter of the present invention, it is possible to obtain an effect that the miniaturization is easily realized, and the fabrication is easy and the cost is low. The effect that it can be realized is obtained,
The effect of facilitating coupling with the signal input / output line is obtained, and the effect of facilitating adjustment of frequency characteristics is obtained.

Further, according to the characteristic adjusting method of the dual mode dielectric waveguide type filter of the present invention, the filter characteristic can be easily adjusted.

[Brief description of drawings]

FIG. 1 is a partially cutaway schematic perspective view showing a first embodiment of a dual mode dielectric waveguide filter according to the present invention.

2 is a schematic vertical cross-sectional view of the filter of FIG.

FIG. 3 is a diagram showing a change in resonance frequency when the size of the cutout of the dielectric block is changed in the filter of FIG.

FIG. 4 is a diagram showing a dielectric block in a filter according to the present invention.

FIG. 5 is a diagram showing a change in resonance frequency when the size of the cutout of the dielectric block is changed in the filter according to the present invention.

FIG. 6 is a diagram showing changes in the resonance frequency when the dimensions of the cutouts of the dielectric block are changed in the filter according to the present invention.

FIG. 7 is a diagram showing changes in the resonance frequency when the dimensions of the conductive film provided on the open end surface of the dielectric block are changed in the filter according to the present invention.

FIG. 8 is a diagram showing a change in resonance frequency when the size of the conductive film provided on the open end surface of the dielectric block is changed in the filter according to the present invention.

9 is a diagram showing frequency characteristics of the filter of FIG.

FIG. 10 is a schematic plan view showing an example of a filter bond forming means according to the present invention.

FIG. 11 is a schematic plan view for explaining the function of the filter bond forming means according to the present invention.

FIG. 12 is a schematic perspective view for explaining a specific example of the filter bond forming means according to the present invention.

FIG. 13 is a view for explaining the action of the resonance frequency adjusting means of the filter according to the present invention.

FIG. 14 is a diagram showing a change in resonance frequency when the size of the conductive film provided on the open end surface of the dielectric block is changed in the filter according to the present invention.

FIG. 15 is a partially omitted schematic perspective view showing an embodiment of a multi-stage dual mode dielectric waveguide type filter according to the present invention.

FIG. 16 is a partially omitted schematic perspective view showing an embodiment of a multi-stage dual mode dielectric waveguide type filter according to the present invention.

[Explanation of symbols]

 2 Dielectric Block 4 Conductive Film 6 Notch 7 Conductive Film 8a, 8b Input / Output Electrode 9 Stub 10 Microstripline Substrate 12 Hole 14 Ground Conductive Film 16a, 16b Input / Output Stripline Conductive Film 22a, 22b Conductive Film 24a, 24b conductive film removed portion 32 interstage coupling stripline conductive film 34a, 34b input / output stripline conductive film 36 opening

Claims (6)

[Claims] 1. A conductive film is formed on a side surface and a first end surface of a dielectric block that is columnar and has a cross section that is substantially square or substantially circular and that is orthogonal to the cross section. Two electromagnetic signal modes oscillating in the first and second directions, and a coupling forming means for coupling an electromagnetic signal between the two modes is provided in the first and second dielectric block. A dielectric resonator formed on a plane of symmetry extending in the length direction of the block including a direction forming an angle of 45 degrees with respect to the direction of 2; and the two modes of the dielectric resonator. A dual-mode dielectric waveguide filter, characterized in that it is provided with input / output means for respectively coupling with the electromagnetic signals of. 2. The dual mode dielectric waveguide filter according to claim 1, wherein the resonator is provided with a resonance frequency adjusting means. 3. The input / output unit includes input / output electrodes provided on one end of the second end surface of the dielectric block in the first direction and one end of the second end in the second direction. A dual mode dielectric waveguide filter according to claim 1 or 2 comprising. 4. An interstage coupling comprising a plurality of the resonators according to claim 1 or 2 for coupling one of the electromagnetic signals of the two modes of each of the adjacent resonators. Means and an input / output means for respectively coupling with one of the electromagnetic signals of the two modes of the resonator at both ends, and a multi-stage dual-mode dielectric waveguide. Tube type filter. 5. A method for adjusting the characteristics of the filter according to any one of claims 1 to 4, wherein the dimensions of the coupling forming means are changed. Method of adjusting characteristics of type filter. 6. A method for adjusting the characteristics of the filter according to claim 2, wherein the dimensions of the resonance frequency adjusting means are changed. How to adjust the characteristics of a tubular filter.