JPH11274816A - Dielectric filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize a dielectric filter usable in a frequency band higher than 5 GHz. SOLUTION: The proposed filter is composed of bonded parallelopiped dielectrics 11 and 12, and input/output electrodes 13 and 14 are formed with the three sides surrounded by ground electrodes in contact with one side on one surface of each dielectric. Grounding electrodes 15 and 16 are formed as well on the other surfaces excepting for the bonding surface of the dielectrics 11 and 12 and the surface in contact with the input/output electrodes 13 and 14, and the filter is constituted by connecting the resonators on the bonding surface exposing the dielectrics. On the bonding surface, a conductor film 17 is formed for adjusting a connection between the resonators.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a dielectric filter suitable for use in a high frequency band of 5 GHz or more, and more particularly to a dielectric filter which can be reduced in size.

[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, it becomes difficult to obtain input / output coupling due to the reduced size defined by the frequency,
Also, in order to secure a high Q, it is necessary to increase the outer diameter. 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.

The inventor has proposed a dielectric filter in Japanese Patent Application No. 9-368254, 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. did. FIG. 5 is an exploded perspective view of an example of such a dielectric filter, in which an island-shaped electrode 53 is formed on the surface of a dielectric 51 and a conductor film 55 serving as a ground electrode is formed therearound. An island-shaped electrode 54 is formed on the surface, and a conductor film 56 serving as a ground electrode is formed around the electrode 54. The conductor film 57 is formed on the joint surface to adjust the coupling.

[0005]

However, since the above-mentioned dielectric filter is a half-wavelength dielectric filter, the size of the dielectric must be matched to it. When used for mobile communication equipment, it is required to be small and lightweight. The present invention provides a dielectric filter that meets the demand for miniaturization.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems by adopting a structure completely different from the conventional structure and adjusting the connection thereof.

That is, in a dielectric filter in which two rectangular parallelepiped dielectrics are joined, one surface of each dielectric is provided with an input / output electrode made of an island-shaped conductive film in contact with a long side of the surface. An earth electrode made of a conductive film separated and insulated from the input / output electrode is provided on the entire surface except for the surface adjacent to the end of the electrode and the surface facing the electrode, and at least one of the bonding surfaces has a ground formed on a part of the bonding surface. It is characterized by having a conductive film connected to the electrode.

[0008]

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. The above-described conventional dielectric filter is divided in half, and a quarter-wavelength filter can be realized with a half substrate size.

[0009]

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

A conventional dielectric filter shown in FIG. 5 will be described for comparison with the present invention. FIG. 5 is a perspective view of the dielectric filter as described above. 6.0 × 6.0 × 1.7m
m rectangular parallelepiped dielectric (dielectric constant 37) 51, 52 6.0 × 6.0mm
1.2 × 1.2 mm electrodes 53 and 54 are formed in the center of the surface of
In this case, electrodes 55 and 56 of a conductive film surrounding this are formed. A dielectric is exposed on the joining surface, and a conductive film that is electrically connected to the conductive films 55 and 56 is formed on the other surface. This was bonded at a bonding surface where a conductive film 57 was formed on a part of the dielectric surface.

FIG. 1 is an exploded perspective view of an embodiment of a dielectric filter according to the present invention. The island-shaped conductor films 13 and 14 are formed so as to be in contact with the long sides of one surface of the rectangular parallelepiped dielectrics 11 and 12 to be input / output electrodes. And a conductor film 1 around the input / output electrodes
5 and 16 are formed to serve as ground electrodes. I / O electrode 1
A dielectric material is exposed on the surfaces in contact with 3 and 14 and on the bonding surface facing the surfaces, and on the other surfaces, a conductive film electrically connected to the conductive films 15 and 16 is formed on the entire surface. In this example, the conductor film 17 is formed on the joint surface and is connected to the ground electrode.

A dielectric 1 having a relative dielectric constant of 37 in the structure shown in FIG.
1 and 12 are 3.0 × 6.0 mm and 1.0 mm thick, and 3.0 × 6.0 mm
Input / output electrodes 13 and 14 of 0.9 × 0.45 mm were formed along the center of the 6.0 mm 2 side of the surface of the substrate. The distance between the input / output electrodes 13 and 14 and the ground electrodes 15 and 16 was 0.5 mm. Conductive film 17 on bonding surface
A sample having a width of 2.6 mm was prepared.

FIG. 2 shows the characteristics of the dielectric filter having the above-mentioned size. The center frequency is 6.62 GHz, the 3 dB bandwidth is 380 MHz, and the insertion loss at the peak point is 0.78 dB. In the case shown in FIG. 5, the center frequency is 5.88 GH
z, 3dB bandwidth 135MHz, peak insertion loss 1.51
dB.

The dielectric filter shown in FIG.
37 dielectrics 31 and 32 are 3.0 × 6.0 mm and 1.0 mm thick, and 3.
0.9 × along the center of the 6.0 mm side of the 0 × 6.0 mm surface
0.45 mm input / output electrodes 33 and 34 were formed. Input / output electrode 33,
The distance between 34 and the ground electrodes 35 and 36 was 0.5 mm. The structure was such that the dielectric was exposed with a width of 1.0 mm at the center of the conductive film 37 on the bonding surface.

FIG. 4 shows the characteristics of the dielectric filter shown in FIG. 3, in which the center frequency is 6.63 GHz and the 3 dB bandwidth is 34.
At 5 MHz, the insertion loss at the peak point was 0.74 dB, and a dielectric filter having substantially the same characteristics as in FIG. 1 was obtained.

The center frequency can be changed by selecting the permittivity and size of the dielectric substrate, and the bandwidth between the resonators is adjusted by adjusting the coupling state between the resonators according to the shape and size of the conductor film on the bonding surface. Can be arbitrarily set.

[0017]

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. The size of the dielectric filter in the same frequency band can be reduced, and its characteristics can be easily adjusted.

Further, not only the size and thickness can be reduced, but also the dielectric filter can be obtained simply 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 is 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 another embodiment of the present invention.

FIG. 5 is a perspective view of a conventional dielectric filter.

[Explanation of symbols]

 11, 12, 31, 32: dielectric 13, 14, 33, 34: input / output electrode 15, 16, 35, 36: ground electrode 17, 37: conductive film

Claims (3)

[Claims] 1. A dielectric filter in which two rectangular parallelepiped dielectrics are joined to each other, the input / output electrodes being formed on one surface of each dielectric by an island-shaped conductive film contacting a long side of the surface. An earth electrode made of a conductor film separated and insulated from the input / output electrode is provided on the entire surface except for the surface adjacent to the end of the electrode and the surface facing the electrode. At least one of the joint surfaces is formed on a part of the joint surface, A dielectric filter comprising a conductive film connected to an electrode. 2. A dielectric filter in which two rectangular parallelepiped dielectrics are joined to each other, and each of the dielectrics has an input / output electrode formed of an island-shaped conductor film in contact with a long side of the surface. An input / output electrode was formed on at least one of the joining surfaces, including a ground electrode made of a conductive film separated and insulated from the input / output electrode on the entire surface except the surface adjacent to the end of the electrode and the surface facing the electrode. A dielectric filter comprising a conductive strip extending from a surface ground electrode to an opposing surface ground electrode. 3. A dielectric filter in which two rectangular parallelepiped dielectrics are joined to each other, the input / output electrodes being formed on one surface of each dielectric by an island-shaped conductive film contacting a long side of the surface. A ground electrode made of a conductive film separated and insulated from the input / output electrode is provided on the entire surface except for the surface adjacent to the end of the electrode and the surface facing the electrode, and a conductor formed on at least one of the bonding surfaces and connected to the ground electrode A dielectric filter comprising a film and having a dielectric exposed at a part of a bonding surface.