JPH11195905A - Dielectric filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized dielectric filter that is used in a high frequency band of 5 GHz or over. SOLUTION: The filter is structured such that rectangular prism shaped dielectric bodies 11, 12 adhere to each other. Input/output electrodes 13, 14, respectively surrounded by earth electrodes 15, 16, are formed on one side of the respective dielectric bodies 11, 12. Earth conductors are formed also on faces other than the adhered faces of the dielectric bodies 11, 12. Resonators are coupled on the adhered faces to form the filter where dielectric materials 11, 12 are exposed. A conductor film for adjusting coupling is formed to each adhered face. The input output electrodes 13, 14 connect with input/output signal lines respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a small-sized dielectric filter suitable for use in a high frequency band of 5 GHz or more.

[0002]

2. Description of the Related Art With the spread of mobile communication equipment, utilization of a frequency higher than a frequency band currently used is being studied. In the conventional mobile communication, a frequency up to about 2 GHz band is used, and as a filter used in a mobile station, a combination of a dielectric coaxial resonator and a filter has been mainly used.

However, this dielectric coaxial resonator has a frequency of 5 GHz.
When used at the above frequencies, the dimensions defined by the frequency become thin, making it difficult to obtain input / output coupling, and it is necessary to increase the outer diameter to ensure a high Q. For example, in order to secure the required Q at a frequency of 5 GHz, an outer diameter of more than 10 mm is required. This goes against the demand for smaller electronic components and is not practical.
Alternatively, a TE mode resonator is used, but the structure is increased in size and the input / output coupling structure is complicated.

[0004]

SUMMARY OF THE INVENTION The present invention provides a dielectric filter which has sufficient filter characteristics in a high frequency band of 5 GHz to 30 GHz, has a high Q, and meets the requirements of miniaturization and thinning. is there.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems by employing a structure completely different from the conventional structure.

That is, a dielectric filter in which two rectangular parallelepiped dielectrics are joined to each other has an input / output electrode made of an island-shaped conductor film on one surface of each dielectric, and is separated and insulated from the input / output electrode. An earth electrode made of a conductor film surrounding the input / output electrodes is provided on the entire surface, and the other surface except the joining surface is also provided with an earth electrode made of the conductor film on the entire surface, and at least one part of the joining surface is connected to the earth electrode. It is characterized by having a conductive film.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Although the analysis of the resonance mode of the dielectric filter according to the present invention has not been completely performed, it is considered that the dielectric filter has a function close to that of a waveguide. It is considered that an island-shaped electrode on one surface of the dielectric is used as the input / output structure, and a resonator is coupled at the joint surface where the dielectric is exposed, thereby obtaining filter characteristics.

In the present invention, by forming a conductor film connected to the ground potential on the joint surface, the coupling of the resonator is adjusted to adjust the bandwidth. By increasing the width of the conductor film, the coupling can be weakened.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing an embodiment of the present invention, in which (a) shows a state before assembly and (b) shows a state after assembly. 3.5 × 5.0 × 1.7 mm rectangular parallelepiped dielectric (dielectric constant 90) 11, 12 1.0 × 1.0 in the center of 3.5 × 5.0 mm surface
mm electrodes 13 and 14 are formed, and electrodes 15 and 16 of a conductor film surrounding the electrodes 13 and 14 are formed.

Conductive films are formed on the other surfaces except for the joint surfaces, and these conductive films are set to the same potential (earth potential) as the electrodes 15 and 16. The dielectric is exposed at the bonding surface, and an electrode 18 for adjusting the coupling is formed on a part of the dielectric if necessary. These dielectrics are joined at the exposed surface of the dielectric.

The electrodes 13 and 14 are connected to input / output signal lines, the electrodes 13 are connected to input strip lines and signal lines of coaxial lines, and a conductor film surrounding them is connected to an earth line to form a filter. You.

FIG. 2 is an explanatory diagram of the characteristics of the dielectric filter of FIG. 1. In the case of the above configuration, the center frequency is 5.64 GHz.
85MHz 3dB bandwidth, 4.2dB peak insertion loss
Had become. In this case, 4.2dB seems to be a large loss, but considering the extremely narrow bandwidth of 85MHz, it is considered to be low loss.

Hereinafter, another embodiment of the present invention will be described. The dielectric constant of each of the dielectrics used was 37. FIG.
Is formed in the same manner using a 6.0 × 6.0 × 1.7 mm dielectric, the input and output electrodes are formed to 1.2 × 1.2 mm, and a 2.0 mm wide coupling adjustment electrode is formed at the center of the joint surface. It is. FIG. 4 shows the characteristics in this case.
GHz, 3dB bandwidth 135MHz, peak insertion loss 1.
A result of 51dB was obtained.

FIG. 5 shows the same structure formed using a 5.0 × 8.0 × 1.7 mm dielectric. The input / output electrodes are formed to have a size of 1.2 × 1.2 mm. An electrode is formed. FIG. 6 shows the characteristics in this case.
The center frequency was 5.88 GHz, the 3 dB bandwidth was 153 MHz, and the insertion loss at the peak was 1.32 dB.

FIG. 7 shows a case in which a dielectric material of 8.0 × 5.0 × 1.7 mm is formed in the same manner. The input / output electrodes are formed in a size of 1.2 × 1.2 mm, and a 3.5 mm wide coupling adjusting member is formed at the center of the joint surface. An electrode is formed. FIG. 8 shows the characteristics in this case.
The center frequency was 5.89 GHz, the 3 dB bandwidth was 177 MHz, and the insertion loss at the peak was 1.62 dB.

The input / output portion of the dielectric filter according to the present invention is capacitively coupled, and its capacitance changes depending on the size of the input / output electrodes. Therefore, the input / output coupling capacitance can be adjusted by adjusting the size.

Further, the coupling state between the resonators changes depending on the conductive film formed on the bonding surface. When the width of the conductor film is small, the coupling coefficient increases, and the pass band width as a filter increases. Conversely, when the width of the conductor film is increased, the coupling coefficient is reduced, and the pass band width as a filter is reduced.
Both inductive coupling and capacitive coupling can be adjusted depending on the direction across the conductor film.

[0019]

According to the present invention, a dielectric filter which can be used in a frequency band of 5 GHz or more and has good characteristics can be obtained. Since the coupling state of the resonator can be adjusted by the conductive film on the bonding surface, a filter having an arbitrary bandwidth can be configured.

Further, not only the size and thickness can be reduced, but also the dielectric filter can be obtained only by forming a conductive film on the surface of a rectangular parallelepiped dielectric, so that a dielectric filter which is easy to manufacture and inexpensive can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of characteristics of the dielectric filter of FIG.

FIG. 3 is a perspective view of another embodiment of the present invention.

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

FIG. 5 is a perspective view of another embodiment of the present invention.

FIG. 6 is an explanatory diagram of characteristics of the dielectric filter of FIG.

FIG. 7 is a perspective view of another embodiment of the present invention.

FIG. 8 is an explanatory diagram of characteristics of the dielectric filter of FIG. 7;

[Explanation of symbols]

 11, 12: Dielectric 13, 14: I / O electrode 15, 16: Earth electrode 18: Conductive film

Claims (5)

[Claims] 1. A dielectric filter in which two rectangular parallelepiped dielectrics are joined to each other, and each of the dielectrics is provided with an input / output electrode made of an island-shaped conductor film on one surface thereof and separated and insulated from the input / output electrode. A ground electrode made of a conductive film is formed on almost the entire remaining surface of those surfaces, and a ground electrode made of a conductive film is provided on the entire surface except for the bonding surface, and a ground electrode is formed on at least one part of the bonding surface. 1. A dielectric filter comprising a conductive film connected to a dielectric film. 2. A dielectric filter in which two rectangular parallelepiped dielectrics are joined to each other, comprising an input / output electrode formed of an island-shaped conductor film at the center of one surface of each dielectric, and separated from the input / output electrode. A ground electrode made of a conductive film surrounding the input / output electrodes insulated is provided on the entire surface, and a ground electrode made of a conductive film is provided on the entire surface except for the bonding surface, and a ground electrode is provided on at least one part of the bonding surface. 1. A dielectric filter comprising a conductive film connected to a dielectric film. 3. The dielectric filter according to claim 1, wherein both ends of the conductive film formed on the bonding surface are connected to the ground electrode across the surface. 4. A dielectric filter in which two rectangular parallelepiped dielectrics are joined to each other, each of which has an input / output electrode made of an island-shaped conductor film at the center of one surface of the dielectric, and is separated from the input / output electrode. A ground electrode made of a conductive film surrounding the input / output electrodes insulated is provided on the entire surface, and a ground electrode made of a conductive film is provided on the entire surface except for the bonding surface, and a ground electrode is provided on at least one part of the bonding surface. 1. A dielectric filter, comprising: a conductive film connected to an input / output signal line; 5. A dielectric filter in which two rectangular parallelepiped dielectrics are joined, comprising an input / output electrode formed of an island-shaped conductor film at the center of one surface of each dielectric, and separated from the input / output electrode. A ground electrode made of a conductive film surrounding the input / output electrodes insulated is provided on the entire surface, and a ground electrode made of a conductive film is provided on the entire surface except for the bonding surface, and a ground electrode is provided on at least one part of the bonding surface. 1. A dielectric filter, comprising: a conductive film connected to the dielectric film, wherein the coupling is adjusted by the conductive film.