JPH09232812A - Dielectric filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the insertion loss in a pass-band by not employing a coil employing a dielectric resonator as a coupling element. SOLUTION: Two sets of 1st dielectric resonators R1 are provided and a 2nd dielectric resonators R2 is used as a coupling element to couple the 1st dielectric resonators R1 with each other. The 1st dielectric resonators R1 and the 2nd dielectric resonators R2 are coaxial dielectric resonators. Moreover, the 1st dielectric resonators R1 and the 2nd dielectric resonators R2 from respectively resonators of 1/4 wavelength. The resonance frequency of the 2nd dielectric resonators R2 matching the frequencies being twice and there of the pass- band frequencies of a filter at a transmitter side and the impedance is set equal to the impedance of a conventional coil in order to couple the 1st dielectric resonators R1 with each other and to form an attenuation pole at twice and three times high frequencies of the pass-band frequencies of the transmitter side filter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric filter used in mobile communication equipment and the like, and more particularly to a dielectric filter used in a microwave band or the like (for example, a high frequency band of several 100 MHz to several GHz).

[0002]

2. Description of the Related Art Generally, a dielectric filter includes a plurality of dielectric resonators and a plurality of electric elements such as coils connecting the dielectric resonators.

Here, a conventional dielectric filter will be briefly described with reference to FIG. The dielectric filter shown is 2
A band elimination filter using two coaxial dielectric resonators, two dielectric resonators R1 and coils L
1 and L1a, and two capacitors C1 and C2 are provided, and these dielectric resonator R1 and coil L
1 and L1a and capacitors C1 and C2 are mounted on the printed circuit board S.

The dielectric resonator R1 is provided with a dielectric block 1a and an inner conductor 1. The entire surface of the dielectric block 1a except one end surface is covered with an outer conductor 2. Is short-circuited. The outer conductor 2 of each dielectric resonator R1 is the grounding conductor pattern P of the printed circuit board S.
It is electrically connected to 1 and grounded. The inner conductor 1 of each dielectric resonator R1 is electrically connected to the connecting conductor pattern P2 by the terminal pin P, and the connecting conductor pattern P2 is connected to the transmission line connecting conductor pattern P3 via the capacitor C1. Has been done. Input / output terminals P4 are provided at both ends of the transmission line connecting conductor pattern P3.

Referring also to FIG. 15 showing an equivalent circuit of the illustrated dielectric filter, each dielectric resonator R1 is connected in series with a capacitor C1 via a connecting conductor pattern P2, and each capacitor C1 is It is connected to the coil L1 by the connecting conductor pattern P3. Further, the capacitor C2 is connected to the grounding conductor pattern P1 and is also connected to the coil L1a and the capacitor C1 via the connecting conductor pattern P3.

[0006]

By the way, in the band elimination filter, the coupling between the dielectric resonators is an inductance coupling, and a coil (inductor) is generally used as a coupling element.

However, the Q of the coil is lower than that of the other electric elements constituting the filter, which causes a large insertion loss. Dielectric filters are required to have low power consumption as well as size and weight reduction. Therefore, it is preferable that the insertion loss is low. In order to improve the Q characteristic of the coil, the coil must be upsized, and upsizing of the coil causes the filter itself to be upsized. That is, in order to reduce the size and weight of the filter, the size of the coil must be reduced, which causes a problem that the filter characteristics deteriorate.

Further, in order to realize the inductance of several nH or less, it is necessary to make the wire diameter of the coil thin. On the other hand,
In order to realize an inductance of several tens of nH or more, the winding diameter must be increased, which makes production difficult when considering the structure of the dielectric filter.

Further, in order to realize the desired inductance, it is necessary to adjust the number of turns of the coil. Therefore, it is difficult to implement unless the number of turns of the coil is an integral multiple. If the coil shape is standardized, it is necessary to manually adjust the shape such as widening the winding interval in order to obtain a desired inductance value, which raises the problem of increasing the manufacturing cost of the dielectric filter. .

In addition, when the coil is mounted by using the automatic mounting machine, the coil is easily deformed. That is, in the case of a coil, handling is difficult. As described above, it is difficult to automatically mount the coil, and the productivity is reduced.
Further, during soldering, the coil is likely to be blitted, which causes a defect.

In the conventional dielectric filter, it is difficult to obtain sufficient attenuation in the stop band which is twice or three times as large as the pass band of the transmission side filter. Therefore, a low pass filter using a coil and a capacitor in a discrete manner is used. Need to be introduced. When such a filter circuit is provided, not only the dielectric filter itself becomes large, but also the number of parts increases.

A first object of the present invention is to provide a small dielectric filter having a low insertion loss.

A second object of the present invention is to provide a dielectric filter which is easy to be automatically mounted and has excellent productivity, and which has no adjustment of characteristics after mounting or automation of adjustment work. To provide.

A third object of the present invention is to double the pass band of the transmitting side filter without adding a filter such as a low pass filter, that is, without increasing the number of parts.
An object of the present invention is to provide a dielectric filter that can obtain a sufficient amount of attenuation at a frequency of 3 times.

[0015]

In the present invention, in order to realize low insertion loss, a dielectric resonator (second dielectric resonator) is used as a coupling element instead of a coil. This improves Q and results in lower insertion loss in the passband. At this time, the element value of the second dielectric resonator is determined so as to be equivalent to the impedance of the coil.

As the second dielectric resonator, a coaxial dielectric resonator, a triplate dielectric resonator, or a double plate dielectric resonance is used.

According to the present invention, there is provided a dielectric filter comprising at least two first dielectric resonators, wherein a second coupling element is arranged between the first dielectric resonators.
There is obtained a dielectric filter characterized by using the dielectric resonator of.

Further, according to the present invention, an input / output terminal,
A first dielectric resonator disposed between the input / output terminals, and the second dielectric resonator is used as a coupling element for coupling the first dielectric resonator and the input / output terminal. A dielectric filter characterized by the above is obtained.

According to the present invention, the transmission line defined between the input and output terminals, the first dielectric resonator connected to the transmission line, and the second dielectric resonator connected in parallel to the transmission line. A dielectric filter having the above-mentioned dielectric resonator is obtained.

In addition, according to the present invention, the transmission line defined between the input and output terminals, the first dielectric resonator, and the first dielectric resonator are provided.
And a second dielectric resonator that is connected in series to the second dielectric resonator and that connects the first dielectric resonator to the transmission line.

[0021]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below with reference to the drawings.

Referring to FIG. 1, the illustrated dielectric filter is provided with two first dielectric resonators R1. The first dielectric resonator R1 serves as a coupling element for coupling the first dielectric resonator R1. Two dielectric resonators R2 are used.

First and second dielectric resonators R1 and R2
Are both coaxial dielectric resonators. Each of the first and second dielectric resonators R1 and R2 includes a dielectric block 1a, and the dielectric block 1a has a rectangular column shape with one surface (bottom surface) of 3 mm × 3 mm. Each dielectric block 1
A hole is formed in the center of a, and the internal conductor 1 is formed in this hole. In addition, each dielectric block 1a
Is covered with the outer conductor 2 except one end surface thereof, and the outer conductor 2 and the inner conductor 1 are short-circuited.

The first and second dielectric resonators R1 and R2 each form a quarter wavelength resonator.
Further, in this example, one of the first dielectric resonators R1 has a resonance frequency of 1543 MHz and the other of the first dielectric resonators R1 has 1522 MHz in order to form a pass band.
Was used. Since the first dielectric resonator R1 is coupled to form an attenuation pole at a frequency twice or three times the pass band of the transmission side filter, the second dielectric resonator R2 changes its resonance frequency. The frequencies were adjusted to twice and three times the passband of the transmitting filter, and the impedance at this time was made equal to the impedance of the conventional coil.

Here, referring also to FIG. 2, the dielectric filter includes a printed board S, a first dielectric resonator R1, a second dielectric resonator R2, and capacitors C1 and C2.

In the illustrated example, the printed wiring board S has printed wiring formed on the insulating substrate, and the external dimensions (length L, width W, and thickness T) of the insulating substrate are (L × W × T). Is 1
The size is 2 mm × 10 mm × 0.5 mm, and the material is, for example, glass epoxy. As the capacitors C1 and C2, for example, plate capacitors or chip capacitors are used, and the capacitors C1 and C2 are 0.
It is 5 to 1.0 pF.

The outer conductor 2 of the first dielectric resonator R1 is
It is electrically connected to the grounding conductor pattern P1 on the printed board S and grounded. On the other hand, the first dielectric resonator R
The inner conductor 1 of 1 is electrically connected to the connecting conductor pattern P2 by the terminal pin P inserted in the center hole thereof. The connecting conductor pattern P2 is the capacitor C1.
Is connected to the transmission line connecting conductor pattern P3. Input / output terminals P4 are provided at both ends of the transmission line connecting conductor pattern P3.

As shown, the first dielectric resonator R1
Are connected in series with the capacitor C1, and the capacitor C1 is connected to the transmission line connecting conductor pattern P3. The capacitor C2 is electrically connected to the transmission line connecting conductor pattern P3 and is also electrically connected to the grounding conductor pattern P1.

The second dielectric resonator R2 is connected to the transmission line (transmission line connecting conductor pattern P3). The second dielectric resonator R2 is connected to the grounding conductor pattern P1.
Is not connected to That is, it is not grounded. Specifically, as shown in FIG. 3A, the second dielectric resonator R
The outer conductor 2 is electrically connected to the transmission line connecting conductor pattern P3, and the inner conductor 1 is electrically connected to the transmission line connecting conductor pattern P3 by the terminal pin P.

In the second dielectric resonator R2,
There is no directivity in the polarity when connecting the inner conductor 1 and the outer conductor 2.

When mounting the second dielectric resonator R2 on the substrate S, for example, the mounting method shown in FIG. 3B may be adopted.

In the mounting method shown in FIG. 3B, the terminal pin P of the first dielectric resonator R1 is used to connect the terminal pin P of the first dielectric resonator R1 to the second dielectric resonator R1. The terminal pin P inserted into the inner conductor 1 of the container R2 and the outer conductor 2 are electrically connected to each other by soldering or the like by the aerial wiring. FIG.
In the method shown in (b), the first dielectric resonator R1 and the second dielectric resonator R1 are used without using the conductor pattern of the printed board S.
Is connected to the dielectric resonator R2.

FIG. 12 shows the frequency characteristic of the above dielectric filter.

In FIG. 12, the solid line shows the frequency characteristic in the vicinity of the pass band of the dielectric filter (band elimination filter) shown in FIG. On the other hand, for comparison,
The broken line shows the frequency characteristic in the vicinity of the pass band of the conventional dielectric filter shown in FIG. As shown, in the dielectric filter shown in FIG. 1, frequencies 1429 to 1453M are used.
It can be seen that the insertion loss is about 0.4 dB in the range of Hz.

On the other hand, in the dielectric filter shown in FIG.
It can be seen that the insertion loss is about 0.7 dB. In the dielectric filter shown in FIG. 14, the coil wire diameter is 0.2 m.
A coil having a diameter of m and an outer diameter of 0.6 mm was used.

As described above, the dielectric filter shown in FIG. 1 has attenuation (insertion loss) as compared with the conventional dielectric filter.
Is improved by about 0.3 dB. That is, a lower insertion loss can be obtained within the pass band.

Further, FIG. 13 shows frequency characteristics at frequencies twice or three times the pass band of the transmitting filter.
In FIG. 13, the solid line shows the frequency characteristic of the dielectric filter shown in FIG. 1, and the broken line shows the frequency characteristic of the conventional dielectric filter.

In the dielectric filter shown in FIG. 1, the frequency is twice or triple the pass band of the transmitting filter, that is, 28 times.
The attenuations at 58 MHz and 4359 MHz are about 73 dB and 87 dB, respectively. 2858MHz and 4359MH compared to conventional dielectric filter
The attenuation amount at z increases by about 50 dB.

Even when there is a deviation between the frequency twice or three times the pass band of the transmitting filter and the frequency at which the attenuation pole is formed,
Since the dielectric filter shown in FIG. 1 has a sufficiently large attenuation amount, a desired attenuation amount can be obtained. When frequency adjustment is necessary, the frequency can be adjusted by adjusting the length of the second dielectric resonator.

In the above example, a dielectric resonator having a 1/4 wavelength is used at the time of resonance, but the same characteristic can be obtained by using a dielectric resonator having a 1/2 wavelength.

Next, with reference to FIG. 4, a description will be given of a dielectric filter when a triplate dielectric resonator is used as the second dielectric resonator.

This tri-plate type dielectric resonator is provided with a quadrangular prism-shaped dielectric, and a first conductor film is formed on one side surface of this dielectric. Further, a second conductor film is formed on the side surface facing the first conductor film. In the dielectric body, sandwiched between the first conductor film and the second conductor film,
A plane-shaped third conductor film extending parallel to the first and second conductive films is provided. Then, in order to short-circuit the first conductor film, the second conductor film, and the third conductor film, a short-circuit conductor film is formed on one end surface of the dielectric.

The third conductor film is used as the inner conductor 1, and the first and second conductor films are used as the outer conductor 2. The bottom surface (one surface) of this triplate-type dielectric resonator is a quadrangular prism having a size of 3 mm × 3 mm.

Then, as described with reference to FIG.
Making the impedance of the second dielectric resonator R2 equal to the impedance required for coupling between the first dielectric resonators R1 and forming an attenuation pole at a frequency twice or three times the pass band of the transmitting filter. For this reason, the resonance frequencies of the two second dielectric resonators R2 are adjusted to the frequencies twice and three times the pass band of the transmitting filter, respectively.

When mounting such a second dielectric resonator R2, the inner conductor 1 and the outer conductor 2 are electrically connected to the transmission line connecting conductor pattern P3 without being grounded. Inner conductor 1 and conductor pattern P3 for connecting transmission line
For connection, the third conductor film is extended to the open end side to form a terminal, and is electrically connected to the transmission line connecting conductor pattern P3. Also, there is no polarity direction when connecting.

In the dielectric filter shown in FIG. 4, frequency characteristics similar to those of the dielectric filter shown in FIG. 1 were obtained. In particular, when a triplate-type dielectric resonator is used as the second dielectric resonator, the attenuation of the insertion loss in the pass band is about 0.35 dB compared with the conventional dielectric filter.
Improved.

When mounting the second dielectric resonator R2 on the substrate S, for example, the mounting method shown in FIGS. 5A to 5C may be adopted. In any implementation method, the second
The dielectric filter R2 is not grounded, and the inner conductor 1 and the outer conductor 2 are electrically connected to the transmission line connecting conductor pattern P3.

In the method shown in FIG. 5A, the second dielectric resonator R2 is mounted upright in the same manner as in the example shown in FIG. 4, and the inner conductor 1 and the transmission line connecting conductor pattern P3 are connected to terminals. It is connected by a pin P.

In the method shown in FIG. 5B, the second dielectric resonator R2 is laterally mounted, and the internal conductor 1 and the transmission line connecting conductor pattern P3 are connected by the terminal pin P.

In the method shown in FIG. 5C, the terminal pin P, the first and second conductor films (outer conductor 2) and the third conductor film (inner conductor 1) are directly connected to the transmission line connecting conductor pattern P.
It is electrically connected to 3 with solder or the like.

In this example as well, the dielectric resonator having a quarter wavelength at the time of resonance is used, but the same characteristics can be obtained by using the dielectric resonator having a half wavelength.

With reference to FIG. 6, description will be given of a dielectric filter when a double plate type dielectric resonator is used as the second dielectric resonator.

This double plate type dielectric resonator is provided with a quadrangular prism-shaped dielectric, and the conductor film 3 is formed on one side surface of the dielectric. Then, the conductor film 4 is formed on one side surface facing the conductor film 3. In order to short-circuit the conductor film 3 and the conductor film 4, the short-circuit conductor film 5 is formed on one end face of the dielectric.
Is formed. In this example, the second dielectric resonator is a rectangular column having a bottom surface (one surface) of 0.75 mm × 0.75 mm.

As described with reference to FIG. 1, the impedance of such a second dielectric resonator R2 is made equal to the impedance required for coupling between the first dielectric resonator R1 and the transmission is performed. In order to obtain a sufficient amount of attenuation at a frequency twice or three times the pass band of the side filter, the resonance frequency of each of the two second dielectric resonators R2 is set to twice the pass band of the transmission side filter. And tripled frequency.

When mounting such a second dielectric resonator R2, as shown in detail in FIG. 7A, for example,
The conductor film 4 and the transmission line connecting conductor pattern P3 are electrically connected, and the end face 5 and the transmission line connecting conductor pattern P3 are electrically connected. Also, there is no polarity direction when connecting.

In the dielectric filter shown in FIG. 6, the frequency characteristics similar to those of the dielectric filter shown in FIG. 1 were obtained. In particular, when a double plate type dielectric resonator is used as the second dielectric resonator R2, the attenuation of the insertion loss in the pass band is about 0.4d compared to the conventional dielectric filter.
B Improved.

When mounting the second dielectric resonator R2 on the substrate S, for example, the mounting method shown in FIGS. 7B and 7C may be adopted.

In the method shown in FIG. 7B, the conductor film 4 is formed so as to wrap around the lower side of the dielectric block, and the conductor film 4 is electrically connected to the transmission line connecting conductor pattern P3.

In the method shown in FIG. 7C, a double plate type dielectric resonator (second dielectric resonator) is mounted sideways, and the conductor film 3 and the transmission line connecting conductor pattern P3 are electrically connected. The conductive film 4 near the open end is electrically connected to the transmission line connecting conductor pattern P3.

In this example as well, the dielectric resonator having a quarter wavelength at the time of resonance is used, but the same characteristic can be obtained by using the dielectric resonator having a half wavelength.

Next, an example in which the dielectric filter is configured as a bandpass filter will be described with reference to FIGS. 8 and 9.

FIG. 9A shows an equivalent circuit of the conventional bandpass filter. As shown in FIG.
In the conventional bandpass filter, the coil L2 is connected in parallel to the transmission line coupled by the capacitor C3. In the bandpass filter shown in FIG. 8, the coil L2
Is replaced by a second dielectric resonator R3. That is,
The equivalent circuit is the circuit shown in FIG.

The same components as those of the dielectric filter shown in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

As described above, by replacing the coil with the dielectric resonator, frequency adjustment becomes unnecessary or easy. In the case of a coil, the winding interval was manually adjusted to adjust the inductance, but as described above, if the dielectric resonator is used, the adjustment can be automated using trimming or the like. it can. That is, when the coil connected in parallel to the transmission line is replaced with the dielectric resonator, the inductance adjustment becomes easy. Furthermore, handling by an automatic mounting machine becomes easy.

Another example in which the dielectric filter is configured as a bandpass filter will be described with reference to FIGS.

FIG. 11A shows an equivalent circuit of a conventional bandpass filter. As shown in FIG. 11A, in the conventional bandpass filter, the coil L3 is connected in series to the first dielectric resonator R1. In the bandpass filter shown in FIG. 10, the coil L3 is replaced with the second dielectric resonator R3. That is, the equivalent circuit becomes the circuit shown in FIG.

The same components as those of the dielectric filter shown in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

As described above, the coil L3 is connected to the dielectric resonator R.
By replacing with 3, the inductance adjustment of the coil becomes unnecessary or easy. That is, for the reason described above, when the coil connected in series to the first dielectric resonator is replaced with the dielectric resonator, the inductance adjustment becomes easy. Furthermore, handling by an automatic mounting machine becomes easy.

[0069]

As described above, according to the present invention, the coil is not used as the coupling element and the dielectric resonator is used as the coupling element, so that the insertion loss can be reduced in the pass band. effective.

Further, since the coil is not used as the coupling element, not only the automatic mounting is easy and the productivity is excellent, but also the characteristics after mounting can be adjusted or the adjustment work can be automated. As a result, the manufacturing time can be shortened, the production cost can be reduced, and an inexpensive dielectric filter can be provided.

Further, it is possible to obtain a sufficient amount of attenuation at a frequency twice or three times the pass band of the transmitting side filter without using a low pass filter or the like, that is, without increasing the number of parts.

[Brief description of drawings]

FIG. 1 is a perspective view showing a first example of a dielectric filter according to the present invention.

FIG. 2 is a diagram showing an equivalent circuit of the dielectric filter shown in FIG.

3A and 3B are diagrams for explaining a mounting method of a dielectric resonator in the dielectric filter shown in FIG.

FIG. 4 is a perspective view showing a second example of the dielectric filter according to the present invention.

5A to 5C are views for explaining a mounting method of a dielectric resonator in the dielectric filter shown in FIG.

FIG. 6 is a perspective view showing a third example of the dielectric filter according to the present invention.

7A to 7C are diagrams for explaining a mounting method of a dielectric resonator in the dielectric filter shown in FIG.

FIG. 8 is a perspective view showing a fourth example of a dielectric filter according to the present invention.

9 is a diagram showing an equivalent circuit for explaining the configuration of the dielectric filter shown in FIG. 8, (a) is a diagram showing an equivalent circuit of a corresponding conventional dielectric filter, and (b) is a diagram. It is a figure which shows the equivalent circuit of the dielectric filter shown in FIG.

FIG. 10 is a perspective view showing a fifth example of the dielectric filter according to the present invention.

11 is a diagram showing an equivalent circuit for explaining the configuration of the dielectric filter shown in FIG. 10, FIG. 11 (a) is a diagram showing an equivalent circuit of a corresponding conventional dielectric filter, and FIG.
FIG. 11 is a diagram showing an equivalent circuit of the dielectric filter shown in FIG. 10.

FIG. 12 is a diagram showing frequency characteristics in the vicinity of a pass band.

FIG. 13 is a diagram showing characteristics at frequencies twice or three times the pass band.

FIG. 14 is a perspective view showing an example of a conventional dielectric filter.

15 is a diagram showing an equivalent circuit of the dielectric filter shown in FIG.

[Explanation of symbols]

 R1 to R3 dielectric resonator C1 to C3 capacitor L1 to L3 coil L1a coil S substrate P1 grounding conductor pattern P2 connection conductor pattern P3 transmission line connection conductor pattern P4 input / output terminal 1 inner conductor 1a dielectric block 2 outer conductor 3,4 Conductor film 5,6 End face (short-circuit conductor film) P Terminal pin

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor ▲ Yoshi ▼ Sakae Ta ▲ yoshi ▼ 6-7 Koriyama, Taichiro-ku, Sendai City, Miyagi Prefecture Tokin Co., Ltd.

Claims (7)

[Claims] 1. A dielectric filter comprising at least two first dielectric resonators, wherein the second dielectric resonator is used as a coupling element arranged between the first dielectric resonators. A dielectric filter characterized by the fact that it was used. 2. A coupling element having an input / output terminal and a first dielectric resonator arranged between the input / output terminals, and coupling the first dielectric resonator with the input / output terminal. A dielectric filter using a second dielectric resonator as the. 3. A transmission line defined between the input and output terminals,
A dielectric filter, comprising: a first dielectric resonator connected to the transmission line; and a second dielectric resonator connected in parallel to the transmission line. 4. A transmission line defined between the input and output terminals,
A first dielectric resonator; and a second dielectric resonator connected in series with the first dielectric resonator and connecting the first dielectric resonator to the transmission line. And a dielectric filter. 5. The dielectric filter according to claim 1, wherein the second dielectric resonator is a coaxial dielectric resonator. 6. The dielectric filter according to claim 1, wherein the second dielectric resonator is
A dielectric filter, which is a double plate type dielectric resonator having a dielectric having at least a pair of opposing surfaces and a conductor electrode formed on the opposing surfaces. 7. The dielectric filter according to claim 1, wherein the second dielectric resonator is
Triplate-type dielectric resonance having a dielectric having at least a pair of opposing surfaces and internally including a first conductor electrode extending parallel to the opposing surfaces, and a second conductor electrode formed on the opposing surfaces. A dielectric filter characterized by being a container.