JPH09167902A - Dielectric filter - Google Patents

Abstract

(57) Abstract: In a dielectric filter using a quarter-wave coaxial dielectric resonator, while maintaining good attenuation in the vicinity of the pass frequency band, a frequency twice that of the pass frequency band is provided. The spurious characteristics are improved by reducing the peak of harmonics in the band. A first inner conductor (4A to 4D) and an outer conductor (3) on the inner surface of a first through hole are formed in a dielectric block (5), and the first inner conductor (4A to 4D) is formed.
Form a short-circuit conductor between the inner conductor and the outer conductor 3 on the short-circuit end face, and
Input / output terminal 7 that forms an array of quarter-wave coaxial dielectric resonators 1A to 1D and is coupled to the resonators at both ends of the array.
A and 7D are formed, a second inner conductor 4R is formed on the inner surface of the second through hole that is formed adjacent to the resonator 1D and that is formed in parallel with the first through hole, and the second inner conductor 4R and the outer conductor 3 are formed. Are short-circuited on the short-circuited end face side and are connected on the open end face side by the pattern-shaped connecting conductor 8 to form a 1/2 wavelength coaxial dielectric resonator 1R, and the conductive shield case 10 is arranged so as to face the open end face. I placed it.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric filter technology, and in particular, a dielectric filter intended to improve the spurious characteristics of a dielectric filter formed by combining a plurality of quarter-wave coaxial dielectric resonators. Regarding body filters. The dielectric filter of the present invention can be effectively used as a band pass filter in a VHF band and UHF band wireless device.

[0002]

2. Description of the Related Art In a dielectric filter for microwaves, for example, a plurality of through holes are formed in parallel in one dielectric block, and an inner conductor is formed on the inner surface of the through holes. , An outer conductor is formed on the surface parallel to the through hole of the dielectric block to open the through hole of the dielectric block. 2
A short-circuit conductor that short-circuits the inner conductor and the outer conductor is formed on one end surface (short-circuit end surface) of the two surfaces to form an array of quarter-wave coaxial dielectric resonators having the number of stages of the through holes. Then
It is fabricated by forming input / output terminals coupled to the dielectric resonators at both ends of the array.

In such a dielectric filter, in order to prevent a decrease in attenuation due to radiation of electromagnetic waves from an end face (open end face) which is not short-circuited on the opposite side of the short end face of the dielectric block, the dielectric block is prevented. A conductive shield case is arranged facing the open end surface. That is, as shown in FIG. 9, when the conductive shield case is not added (Y), the attenuation in the vicinity of the pass frequency band W ₁ is not good, and when the conductive shield case is added (X).
Has good attenuation near the pass frequency band W ₁ .

However, in this dielectric filter, as shown in FIG. 9, since the conductive shield case is added, the peak of resonance occurs in the frequency band W ₂ which is approximately twice the pass frequency band W _1. Appears strongly. This is because the addition of the shield case facilitates the existence of 1/2 wavelength resonance.

[0005] From the viewpoint of spurious characteristic, the peak of the higher order modes is required to be kept low, in particular, the pass frequency band W ₁ 2 times the frequency band W (corresponding to the fundamental mode frequency of the dielectric resonator) ₂ (2 of the fundamental mode of the dielectric resonator
The peak at twice the frequency) is the closest to the fundamental mode and causes various problems in actual use.

Therefore, conventionally, (1) the size of the resonator, that is, the ratio of the axial length to the diameter of the resonator is changed, or (2)
By lowering the Q of the higher-order mode, the peak at a frequency twice the fundamental mode frequency is lowered to improve the spurious characteristics.

However, in the above (1), although the peak can be shifted, the shift amount is not large enough and the peak cannot be further lowered. Further, in the above (2), it is impossible to decrease the Q in only the higher mode, and at the same time, the Q in the basic mode also decreases.

In view of the above, the present invention provides a dielectric filter using a quarter-wave coaxial dielectric resonator, which maintains a good attenuation in the vicinity of the pass frequency band and which has a frequency twice that of the pass frequency band. It is to improve the spurious characteristics by reducing the peak of harmonics in the band.

[0009]

According to the present invention, in order to achieve the above object, a plurality of first through holes are formed in parallel in a dielectric block, and a first inner hole is formed on an inner surface of the first through hole. A conductor is formed, an outer conductor is formed on a surface of the dielectric block parallel to the first through hole, and one of two end faces of the dielectric block, which is open to the first through hole, is a first one.
A short-circuit conductor that short-circuits the first inner conductor and the outer conductor is formed on the end face to form an array of quarter-wave coaxial dielectric resonators having the number of the first through holes, and both ends of the array are formed. A dielectric filter comprising an input / output terminal coupled to a quarter-wave coaxial dielectric resonator, wherein the dielectric filter is provided adjacent to at least one of the quarter-wave coaxial dielectric resonators at both ends. A second through hole is formed in the body block in parallel with the first through hole, a second inner conductor is formed on the inner surface of the second through hole, and the first end surface side of the dielectric block and the first through hole. Forming a half-wavelength coaxial dielectric resonator in which the second inner conductor and the outer conductor are connected or disconnected on both sides of the second end surface, which is the other of the two end surfaces which can be opened. A dielectric filter is provided.

In one aspect of the present invention, a patterned connection conductor for connecting the second inner conductor and the outer conductor is formed on the second end surface of the dielectric block.

In one aspect of the present invention, a conductive shield case is arranged so as to face the second end surface.

In one aspect of the present invention, at least one of the quarter-wave coaxial dielectric resonators at both ends of the second end face and a half-wave coaxial dielectric resonator disposed adjacent to the at least one quarter-wave coaxial dielectric resonator. The corresponding input / output terminal extends to and from the container.

In the present invention, the half-wave coaxial dielectric resonator is formed by forming an attenuation pole at a frequency approximately twice the fundamental resonance frequency of the quarter-wave coaxial dielectric resonator. Block a specific frequency band in the vicinity.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an exploded perspective view showing an embodiment of a dielectric filter according to the present invention, and FIGS. 2 and 3 are a sectional view and a front view in the assembled state, respectively.

In these figures, 5 is a dielectric block having a high dielectric constant such as barium titanate. The dielectric block has a prismatic outer shape in the XYZ directions,
Five cylindrical through holes 2A, 2 in the column direction (Z direction in the figure)
It has B, 2C, 2D and 2R. These through holes are parallel to each other and are arranged in one row in the X direction. An outer conductor 3 is formed on the side surfaces of the dielectric block 5 in the XZ plane and the YZ plane, and the through holes 2A, 2B, 2 are formed.
The inner surfaces of C and 2D have cylindrical inner conductors 4A, 4B, 4C,
4D is formed, and XY of the dielectric block 5 is formed.
A short-circuit conductor 3 ′ is attached to one of the two end faces in the plane, and the inner conductors 4A to 4D and the outer conductor 3 are short-circuited by the short-circuit conductor 3 ′ [this end face is referred to as a short-circuit end face]. . The other end face of the two end faces in the XY plane of the dielectric block 5, that is, the end face where the inner conductors 4A to 4D are not short-circuited with the outer conductor 3 [this end face is referred to as an open end face] is the inner conductor 4A. Patterned coupling conductors 6A, 6B, 6C and 6D respectively connected to 4D are attached. These patterned coupling conductors 6A to 6D are separated from the outer conductor 3. The inner conductor, outer conductor, short-circuit conductor, and coupling conductor are all films made of silver or the like.

1A, 1B, 1C and 1D are quarter wavelength coaxial dielectric resonators. Each of the quarter-wave coaxial dielectric resonators is formed by interposing a dielectric between the inner conductors 4A, 4B, 4C, 4D and the outer conductor 3, and the common block 5 is used as the dielectric. The outer conductor 3 is commonly used for each resonator. The above pattern-shaped coupling conductor 6A
6D is for capacitive coupling between the quarter-wave coaxial dielectric resonators, and the degree of coupling can be adjusted according to the pattern.

On the open end surface of the dielectric block 5, an input terminal 7A is attached adjacent to the coupling conductor 6A, and an output terminal 7D is attached adjacent to the coupling conductor 6D. These input / output terminals 7A and 7D are films made of silver or the like like the outer conductor, and extend to the side surface.
Is separated from.

1R is a 1/2 wavelength coaxial type dielectric resonator for blocking a specific band. The resonator 1R is formed by forming a cylindrical inner conductor 4R on the inner surface of the through hole 2R and interposing a dielectric between the inner conductor and the common outer conductor 3. At the short-circuited end face of the dielectric block 5, the inner conductor 4R and the outer conductor 3 are short-circuited. Dielectric block 5
A pattern-shaped connecting conductor 8 for connecting the inner conductor 4R and the outer conductor 3 is attached to the open end surface of the.

Reference numeral 10 is a conductive case for electrical shielding. The conductive shield case 10 is a resonator 1A.
The main body portion 10a is arranged in contact with the common outer conductors 1 to 1D and 1R, and the flap portion 10b attached to the main body portion and located at an appropriate distance from the open end surface of the dielectric block 5.

FIG. 4 is an explanatory diagram of characteristics of the dielectric filter of this embodiment.

In FIG. 4, A shows the characteristics of the filter of this embodiment. The attenuation near the pass frequency band W ₁ is good, and the resonance peak P does not exist and the attenuation pole T exists in the frequency band W ₂ that is approximately double.

For comparison, FIG. 4 shows a characteristic B of a dielectric filter manufactured in the same manner as the above-described embodiment of the present invention except that the half-wavelength coaxial dielectric resonator 1R is not formed. Are also shown. This characteristic B is equivalent to the characteristic X in FIG. In this characteristic B, there is a resonance peak P in the frequency band W ₂ which is approximately double.

That is, in the present embodiment, since the 1/2 wavelength coaxial type dielectric resonator 1R is additionally provided, the peak of the double harmonic shifts to a band outside the frequency band W ₂ and the frequency is increased. An attenuation pole T is formed in the band W ₂ . This is because the fundamental mode of the half-wave coaxial dielectric resonator 1R is half-wave resonance, and therefore a resonance point exists near the frequency band W ₂ , and therefore the half-wave coaxial dielectric resonance. By coupling the resonator 1R with the quarter-wave coaxial dielectric resonators 1A to 1D capacitively or inductively, an attenuation pole (trap) is generated in the vicinity of the frequency band W ₂ in the filter characteristic, and a double harmonic wave is generated. The peak shifts to the low frequency side of the frequency band W ₂ .

In the example of FIG. 4, the spurious characteristic in the frequency band W ₂ is improved by 20 dB or more.

By changing the distance between the quarter-wave coaxial dielectric resonator 1D and the half-wave coaxial dielectric resonator 1R or changing the cross-sectional shape of the through hole 2R, The depth of the attenuation pole T can be adjusted. Further, the position of the attenuation pole can be adjusted by changing the width and shape of the patterned connection conductor 8. For example, if the width of the connecting conductor 8 is reduced, the number of electromagnetic waves radiated from the open end face increases, the wavelength effectively increases, and the trap moves to the low frequency side. On the contrary, if the width of the connecting conductor 8 is increased, the trap moves to the high frequency side. By appropriately adjusting such a shape and dimensions, it is possible to improve spurious characteristics at a desired frequency and its vicinity.

FIG. 5 is a diagram showing 1 / th of the above embodiment of the present invention.
It is a schematic diagram showing a modification of two-wavelength coaxial type dielectric resonator 1R. In (a) to (d), the connection position of the pattern-shaped connecting conductor 8 and the outer conductor 3 and the shape and size of the pattern are changed. In (e), two through holes 2R and 2R 'are provided, and connection conductors 8 and 8'are formed for each through hole. In (f), the cross-sectional shape of the through-hole 2R is not circular but oval.

FIG. 6 is a partial schematic view showing another embodiment of the dielectric filter according to the present invention. In this figure, parts having the same functions as those in FIGS. 1 to 5 are given the same reference numerals. In this embodiment, the output terminal 7
The pattern of D is extended and interposed between the coupling conductor 6D of the quarter-wave coaxial dielectric resonator 1D and the half-wave coaxial dielectric resonator 1R. As a result, the half-wave coaxial dielectric resonator 1R is coupled to the output terminal 7D.

FIG. 7 is a partial schematic view showing still another embodiment of the dielectric filter according to the present invention. In this figure, parts having the same functions as those in FIGS. 1 to 6 are given the same reference numerals. In the present embodiment, the first quarter wavelength coaxial dielectric resonator 1D on the output side is adjacent to the first resonator.
Second half-wavelength coaxial dielectric resonator 1R adjacent to the input side quarter-wavelength coaxial dielectric resonator 1A while forming the half-wavelength coaxial dielectric resonator 1R of FIG. 1R "
Is formed. In the second half-wavelength coaxial dielectric resonator 1R ″, 2R ″, 4R ″ and 8 ″ represent through holes, inner conductors and connecting conductors similar to 2R, 4R and 8, respectively.

FIG. 8 is a partial schematic view showing another embodiment of the dielectric filter according to the present invention. (A) And (b) shows a partial top view and a partial bottom view, respectively.
In this figure, parts having the same functions as those in FIGS. 1 to 7 are given the same reference numerals. In the present embodiment, on the short-circuited end face side of the dielectric block 5, 1/2
The inner conductor 4R of the wavelength coaxial dielectric resonator 1R is not connected to the outer conductor 3 and the short-circuit conductor 3 ', and also on the open end face side of the dielectric block 5, the half-wave coaxial dielectric is used. The inner conductor 4R of the body resonator 1R is not connected to the outer conductor 3. That is, this embodiment is different from the embodiment shown in FIGS. 1 to 7 in that the half-wavelength coaxial dielectric resonator of which both ends are short-circuited is used. Type dielectric resonator is used.

[0031]

As described above in detail, according to the dielectric filter of the present invention, the 1 /
Adjacent to at least one of the 1/4 wavelength coaxial dielectric resonators at both ends of the array of 4 wavelength coaxial dielectric resonators, a 1/2 wavelength coaxial dielectric resonator is formed by using a common dielectric block. Due to the formation, the attenuation pole is formed in the frequency band twice the pass frequency band, and the peak of the double harmonic can be shifted to a position outside the frequency band double the pass frequency band. It is possible to improve spurious characteristics while maintaining good attenuation near the pass frequency band.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing an embodiment of a dielectric filter according to the present invention.

FIG. 2 is a sectional view of the dielectric filter of FIG. 1 in an assembled state.

FIG. 3 is a front view of the dielectric filter of FIG. 1 in an assembled state.

FIG. 4 is an explanatory diagram of characteristics of the dielectric filter of FIG.

5 is a schematic diagram showing a modification of the 1/2 wavelength coaxial type dielectric resonator in the dielectric filter of FIG. 1. FIG.

FIG. 6 is a partial schematic view showing another embodiment of the dielectric filter according to the present invention.

FIG. 7 is a partial schematic view showing still another embodiment of the dielectric filter according to the present invention.

FIG. 8 is a partial schematic view showing another embodiment of the dielectric filter according to the present invention.

FIG. 9 is an explanatory diagram of characteristics of a conventional dielectric filter.

[Explanation of symbols]

1A, 1B, 1C, 1D 1/4 wavelength coaxial type dielectric resonator 1R, 1R "1/2 wavelength coaxial type dielectric resonator 2A, 2B, 2C, 2D, 2R, 2R ', 2R" through hole 3 outside Conductor 3'Short-circuit conductor 4A, 4B, 4C, 4D, 4R, 4R ', 4R "Inner conductor 5 Dielectric block 6A, 6B, 6C, 6D Coupling conductor 7A Input terminal 7D Output terminal 8, 8', 8" Connection conductor 10 Conductive shield case

Claims (5)

[Claims] 1. A plurality of first through holes are formed in parallel in a dielectric block, a first inner conductor is formed on an inner surface of the first through hole, and the first inner conductor is parallel to the first through hole of the dielectric block. An outer conductor is formed on the surface, and a short-circuit conductor that short-circuits the first inner conductor and the outer conductor is formed on a first end surface that is one of the two end surfaces of the dielectric block where the first through hole is open. And forming an array of quarter-wave coaxial dielectric resonators and forming input / output terminals coupled to the quarter-wave coaxial dielectric resonators at both ends of the array. A second through hole is formed in the dielectric block in parallel with at least one of the ¼ wavelength coaxial dielectric resonators at both ends, in parallel with the first through hole, and on the inner surface of the second through hole. A second inner conductor is formed, and the first end face side of the dielectric block and the first through hole are formed. A half-wavelength coaxial dielectric resonator is formed by connecting or disconnecting the second inner conductor and the outer conductor on both sides of the second end surface, which is the other of the two open end surfaces. A dielectric filter characterized by: 2. The pattern-shaped connecting conductor for connecting the second inner conductor and the outer conductor is formed on the second end surface of the dielectric block. Dielectric filter. 3. The dielectric filter according to claim 1, wherein a conductive shield case is arranged so as to face the second end surface. 4. A quarter of the both ends of the second end face.
The corresponding input / output terminal extends between at least one of the wavelength coaxial dielectric resonators and a half wavelength coaxial dielectric resonator arranged adjacent to the at least one wavelength coaxial dielectric resonator. The dielectric filter according to claim 1. 5. The half-wave coaxial dielectric resonator has an attenuation pole formed at a frequency approximately twice as high as a fundamental resonance frequency of the quarter-wave coaxial dielectric resonator, thereby identifying the vicinity thereof. The dielectric filter according to claim 1, wherein the dielectric filter blocks a frequency band.