JP3309379B2 - Dual mode dielectric waveguide filter and method for adjusting characteristics thereof - Google Patents

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 filter and a method for adjusting the characteristics thereof. INDUSTRIAL APPLICABILITY 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
A dual-mode resonance is generated by a waveguide-type resonator using a cavity, and this is used for a filter. However, this has a drawback that it is large in size, it is difficult to meet the demand for miniaturization, and it is necessary to make the inner surface of the cavity a mirror surface. In order to reduce the size, the inside of the cavity is filled with a dielectric material. However, it is still difficult to connect the resonator and the signal line (excitable connection) because of the half-wavelength type.

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

Accordingly, an object of the present invention is to provide a dual-mode dielectric waveguide type filter that can be easily reduced in size.

Another object of the present invention is to provide a dual mode dielectric waveguide type filter which can be easily manufactured 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 to 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 of adjusting the characteristics of the filter.

[0008]

According to the present invention, a dielectric block having a columnar shape and a cross section orthogonal to the length direction of the column is substantially square or substantially circular. Conductive film is formed on the side surface and the first end surface
And the second end face of the dielectric block is an open end face,
The dielectric block enables two electromagnetic signal modes oscillating in first and second directions orthogonal to each other in the cross section, and includes a coupling forming means for coupling an electromagnetic signal between the two modes. A quarter-wavelength dielectric resonator formed on a symmetric plane extending in the length direction of the block including a direction at an angle of 45 degrees with respect to the first and second directions. A dual mode dielectric waveguide type filter comprising input / output means for respectively coupling the electromagnetic signals of the two modes of the dielectric resonator.

In one embodiment of the present invention, the coupling forming means of the resonator couples the two modes by disturbing their respective symmetries.

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

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

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

In one embodiment of the present invention, the resonance frequency adjusting means is provided on a symmetric plane extending in the length direction of the dielectric block including the first direction and / or the second direction of the dielectric block. Is formed.

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

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

In one embodiment of the present invention, the input / output means is provided at one end of the second end surface of the dielectric block in the first direction and one end of the dielectric block in the second direction. Input / output electrodes.

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

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

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 the electromagnetic signal of each of the adjacent resonators is provided. , And input / output means for respectively coupling one of the two modes of the electromagnetic signals of the resonators at both ends, A multi-stage dual mode dielectric waveguide filter is provided.

In one embodiment of the present invention, the inter-stage coupling means is formed by connecting electrodes provided on the second end faces of the adjacent resonators.

In one embodiment of the present invention, two resonators are used, and these resonators are arranged with the first end faces facing each other. This is realized by removing corresponding portions of the conductive film provided on the first end face of the resonator.

In one embodiment of the present invention, the input / output means includes an input / output electrode provided on a second end face of the dielectric block.

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

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

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

Further, according to the present invention, there is provided a method for adjusting the characteristics of the filter, wherein the size of the resonance frequency adjusting means is changed. A method for adjusting the characteristics of a mode dielectric waveguide filter is provided.

[0028]

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 longitudinal sectional view thereof.

In these figures, reference numeral 2 denotes a dielectric block constituting a dielectric resonator, and the block has a substantially square cross section in a horizontal plane and has a column shape extending vertically. The block 2 preferably has a dielectric constant of 20 or more, and is made of, for example, a barium titanate-based ceramic dielectric having a dielectric constant of 90 from the viewpoint of reducing radiation loss when a quarter wavelength resonator is used. 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, for example, silver or copper. The conductive film is not formed on the top surface of the block 2 in most regions (the top surface, ie, the end surface where the conductive film is not formed, is referred to as “open end surface”).

Reference numeral 10 denotes a substrate of a microstrip line, and a hole 12 having a shape and a 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 upper surface of the substrate 10 are at the same height.

The substrate 10 is made of a dielectric material, and a ground conductive film 14 is formed on the entire lower surface thereof, and input / output strip line 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 cutout 6 formed by cutting off the upper half of one ridge on the side surface. The notch 6 vibrates in the X direction and the Y direction orthogonal to each other in a horizontal section (XY section).
For coupling electromagnetic signals between two electromagnetic signal modes by disturbing their respective symmetries,
The coupling forming means of the dual mode dielectric resonator is formed on a plane of symmetry in a direction forming an angle of 45 degrees with respect to the X and Y directions of the block 2.

In a portion corresponding to the input / output strip line conductive films 16a and 16b, the block 2
The conductive film on 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, which can extend following the tip of the input / output strip conductive film. By the input / output electrodes 8a, 8b and the input / output strip line conductive films 16a, 16b,
Input / output means for respectively coupling the electromagnetic signals of the two modes of the resonator with each other are provided.

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 modes in which vibrations occur in the two directions of XY, and when there is no notch 6, the two modes vibrate independently of each other, so that the resonance frequency is the same (degenerate). However, when the notch 6 is formed as described above, the degeneracy is released and two modes of an even (EVEN) mode and an odd (ODD) mode are established. As described later, the difference between the resonance frequencies of the two modes is determined. A band-pass filter that uses a substantially equivalent frequency width as a pass band is obtained.

In the filter of the present embodiment, unlike the conventional waveguide type resonator using a cavity, the resonator is basically constituted by the dielectric block 2, so that the 1/4 wavelength type resonator is used. A filter can be formed, and in combination with the high dielectric constant of the block, miniaturization 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 lines are directly connected to the top surface of the dielectric block, so that input / output coupling can be easily achieved.

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

FIG. 3 is a diagram showing a change 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 size of the notch 6 is set to 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 is 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, if ΔC is 4 (m
m), the pass band width f _{PASS becomes} approximately 300 (M
Hz).

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

More generally, as shown in FIG. 4, one of the side surfaces of the dielectric block 2 having a length L and a side W of a square cross section orthogonal to the length direction is W. On the ridgeline,
In the case where one side to form a notch 6 of length [Delta] C in W _1, by changing the size of the W ₁ and [Delta] C, it is possible to change the frequency characteristic of the filter. ΔC is 0
<ΔC ≦ L, ΔC can be changed to L
The closer to, the larger the bond can be,
Further, it is possible to increase the size of the binding Higher W _1. A conductive film can also be formed on the surface of the notch 6, thereby suppressing radiation loss and improving the Q value. However, a stronger bond can be obtained without the conductive film. 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 characteristics.

The form 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 of the notches 6B.
Are fixed, and the length of the other cutout 6A is changed. 5 and 6 show FIG.
7 shows changes in the resonance frequency f of the ODD mode and the EVEN mode of the resonator similar to those in FIG.

The above-mentioned notch forming means connects two orthogonal modes by disturbing their respective symmetries. However, the present invention is not limited to this. Other means may be used as long as the two modes are combined by disturbing their respective symmetries. 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. This conductive film 7 is formed at a portion corresponding to the ridge line of the block 2 similar to the notch 6 of the embodiment of FIG. 1, and changes the dimension ΔF of two sides sandwiching the right angle of the right angle isosceles triangle. 4 shows changes in the resonance frequency f of the resonator in the ODD mode and the EVEN mode when the resonance frequency f is changed.

According to this embodiment, no mechanical work such as forming a notch in the dielectric block 2 is required, and the frequency characteristics can be adjusted more easily. In order to change the dimension ΔF, a conductive film may be sequentially added, or conversely, a conductive film may be formed in a large dimension in advance, and
They may be sequentially removed. Partial formation of the conductive film 7 is easier than formation of a notch in the block 2.
Even if the dimensions are made too small, a conductive film can be added, so that there is an advantage that the yield of the product is not reduced.

FIG. 8 also shows an embodiment of the means for forming a bond by applying a conductive film to the open end face of the dielectric block 2 as 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 also provided on two corners adjacent to the top corner of the block where the conductive film 7 is located. The change in resonance frequency when the dimension ΔF of the conductive film 7 is changed is shown.

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

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

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

Assuming that the vibration directions of the two orthogonal modes are X and Y, the block structure changes on the substantially diagonal line of the square end face of the block (x, y) at an angle of 45 degrees with these X and Y directions. By applying or removing the conductive film, the symmetry of the waveguide is broken, and a perturbation is generated, so that coupling of two orthogonal modes can be obtained. By changing these dimensions, the strength of the connection can be changed. At that time, generally, when the coupling forming means is formed at the first corner of the block 2, the coupling is strengthened by forming the coupling forming means also at the second corner which is diagonal thereto, If the connection forming means is formed at the third corner and / or the fourth corner adjacent thereto, the connection is weakened.

In the plane shown by broken lines X ₁ and Y ₁ in FIG. 11 (that is, in a plane extending in the X direction or the Y direction passing through the center of the sectional shape of the block 2), When a 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 in} FIG.
The position of the block surface that intersects the plane indicated by. Block 2
On the open end surfaces of the above, conductive films 22a and 22b can be formed on X 'and Y' as resonance frequency adjusting means separately from, for example, the input / output electrodes so as to face them. Further, on the side surface of the block 2, portions 24a and 24b from which the conductive film 4 has been removed can be formed on 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 a shift between the resonance frequencies of the two orthogonal modes due to a dimensional error or the like in block fabrication 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 each having a width of 1 (mm) and a length of 0.5 (mm) are formed on the open end face of the dielectric resonator block 2, and the input / output electrodes 8a and 8b are further formed. 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 in the X-direction mode and the resonance frequency in the Y-direction mode when the length M is changed are shown. Here, no bond forming means is formed. The X-direction mode is not substantially changed by the change of M. Note that 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 Y direction of a square block cross section. Therefore, by adopting the value of M at which the resonance frequency in the X-direction mode matches the resonance frequency in the Y-direction mode, adjustment of the resonance frequencies of the two orthogonal modes caused by a dimensional error or the like in block fabrication. Can be.

In FIG. 13, the resonance frequency adjusting means in the X-direction mode is not formed, but the resonance frequency adjusting means in the X-direction mode can be formed in the same manner as in the Y-direction mode, and can function similarly. . Further, in FIG. 13, the coupling forming means is not formed, but the filter of the present invention can be formed by forming desired coupling 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 equivalent resonance frequency changes can be obtained.

In the above embodiment, the case where the cross-sectional shape in a plane orthogonal to the length direction of the dielectric block is a square has been described, but a cylindrical block having a circular cross-section is used as the dielectric block. In this case, the same operation and effect as those of the above embodiment can be obtained. FIG. 14 shows the embodiment. In FIG. 14, the cross section of the dielectric block 2 has a radius of 3
The conductive film 4 is provided on the side surface and one end surface, and the conductive film 7 is provided on the open end surface as a bond forming means. 8
Reference numerals a and 8b denote input / output electrodes. FIG. 14 shows the conductive film 7.
Of the resonance frequency when the dimension ΔF is changed.

Further, in the above embodiment, the case where the input / output means is directly connected to the open surface is shown. However, in the present invention, the input / output means may be connected to the open end face of the block. Or it is arranged at an appropriate interval to the side,
The input / output coupling may be realized by forming a desired capacitance.

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

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

Further, 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. They are arranged in contact with each other. The inter-stage coupling means is realized by removing the corresponding portions of the conductive film 4 provided on the opposite end surfaces of the two blocks 2 to form the opening 36 (the opening of the second-stage resonator). 36
Although only the first stage is illustrated, the second stage
An opening is formed in a portion facing the step). The first-stage resonator has an input / output strip line conductive film 34a.
Are connected, and an input / output strip line conductive film 34b is connected to the second-stage resonator. FIG.
In FIG. 6, the strip line 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, the effect that the miniaturization can be easily achieved is obtained, and the fabrication is easy and the cost is low. The effect of realizing the realization is obtained,
The effect that the coupling with the signal input / output line is facilitated is obtained, and the effect that the adjustment of the frequency characteristic is facilitated is obtained.

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 the 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.

FIG. 2 is a schematic longitudinal sectional view of the filter of FIG.

FIG. 3 is a diagram showing a change in resonance frequency when the size of a notch in a dielectric block is changed in the filter of FIG. 1;

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 a notch of a dielectric block is changed in the filter according to the present invention.

FIG. 6 is a diagram showing a change in the resonance frequency when the size of the notch of the dielectric block is changed in the filter according to the present invention.

FIG. 7 is a diagram showing a change in resonance frequency when the size of a conductive film provided on an open end face of a dielectric block is changed in the filter according to the present invention.

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

FIG. 9 is a diagram illustrating a frequency characteristic of the filter of FIG. 8;

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

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

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

FIG. 13 is a diagram for explaining the operation 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 a conductive film provided on an open end face of a 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 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 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 Microstrip line substrate 12 Hole 14 Grounding conductive film 16a, 16b Input / output strip line conductive film 22a, 22b Conductive film 24a, 24b Conductive film-removed portion 32 Strip line conductive film for inter-stage coupling 34a, 34b Strip line conductive film for input / output 36 Opening

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-251904 (JP, A) JP-A-61-253901 (JP, A) JP-A-60-174501 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H01P 1/208 H01P 7 / 06,7 / 10 H01P 1/20

Claims (6)

(57) [Claims] 1. A conductive film is formed on a side surface and a first end surface of a dielectric block having a columnar shape and having a substantially square or substantially circular cross section orthogonal to a length direction thereof,
The second end face of the lock is an open end face to enable two electromagnetic signal modes oscillating in first and second directions orthogonal to each other in the cross section, and to couple electromagnetic signals between the two modes. to form a bond formation means for the dielectric block of the first and second directions with respect to an angle of 45 degrees of the block includes a direction forming a longitudinal symmetry plane to extend formed by 1 / A dual mode dielectric comprising: a four-wavelength type dielectric resonator; and input / output means for respectively coupling the electromagnetic signals of the two modes of the dielectric resonator. Waveguide filter. 2. The dual mode dielectric waveguide filter according to claim 1, wherein said resonator is provided with a resonance frequency adjusting means. 3. The input / output unit includes: an input / output electrode provided at one end of the second end surface of the dielectric block in the first direction and one end of the dielectric block in the second direction. The dual-mode dielectric waveguide filter according to claim 1 or 2, comprising: 4. An inter-stage coupling comprising a plurality of resonators according to claim 1 or 2 for coupling one of the electromagnetic signals of the two modes of each of adjacent resonators. Means for coupling to one of the electromagnetic signals in the two modes of the resonator at both ends, respectively. Tube filter. 5. A dual mode dielectric waveguide according to claim 1, wherein the size of said coupling forming means is changed. How to adjust the characteristics of a type filter. 6. A method for adjusting the characteristics of a filter according to claim 2, wherein a size of said resonance frequency adjusting means is changed. How to adjust the characteristics of a tubular filter.