JPH11289202A - Dielectric filter and its characteristic adjustment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized dielectric filter usable in a high frequency band and having an attenuation pole whose pass band characteristics can be easily adjusted. SOLUTION: Island-shaped input / output electrodes 11 and 12 are formed on one surface of a rectangular parallelepiped dielectric block 10, and ground electrodes 13 are formed around the input and output electrodes 11 and 12 on the whole other surface. Input / output electrode 1
A through-hole 15 is formed between the surface where the input / output electrodes 11 and 12 are formed and a surface opposite to the surface where the input / output electrodes 11 and 12 are formed. Input / output electrode 11,
The periphery of the through hole 15 on the front side facing the surface on which the 12 is formed exposes the dielectric, and the attenuation pole is formed at a predetermined frequency by changing the area.

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. Conventional mobile communication uses frequencies up to about 2 GHz band, and as a filter used in a mobile station, a combination of a dielectric coaxial resonator and a filter is mainly used.

However, when an attempt is made to use a dielectric coaxial resonator at a higher frequency, the size defined by the frequency becomes thin, so that it is difficult to obtain input / output coupling, and high Q
It is necessary to increase the outer diameter in order to maintain For example,
To ensure the required Q at a frequency of 5 GHz, 10
An outer diameter of several millimeters is required. Alternatively, a TE mode resonator is used, but the structure becomes large,
The input / output coupling structure is also 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.

It is another object of the present invention to provide a dielectric filter whose pass band characteristics can be easily adjusted. Further, the present invention provides a dielectric filter having an attenuation pole.

[0006]

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

That is, in a dielectric filter integrally formed with a rectangular parallelepiped dielectric block, an input / output electrode made of an island-shaped conductive film formed on a surface having the largest area of the dielectric block at intervals in the longitudinal direction. And a ground electrode formed of a conductive film which is separated and insulated from the conductive film of the input / output electrode and is formed on almost the entire remaining surface and substantially the entire other surface. It has a through hole extending from the surface on which the electrode is formed to the surface opposite to the surface, the conductor film is also formed on the through hole, connected to the ground electrode, and the through hole on the surface facing the surface on which the input / output electrode is formed is provided. It is characterized in that the dielectric is exposed around the opening.

An input / output electrode formed of an island-shaped conductive film formed on the surface of the dielectric block having the largest area and spaced apart in the longitudinal direction is provided, and the surface of the input / output electrode is separated and insulated from the conductive film of the input / output electrode. A ground electrode made of a conductive film formed on almost the entire surface of the remaining surface and on the entire surface of the other surface, and a through hole located between the input / output electrodes and extending from the surface on which the input / output electrodes are formed to the opposite surface. In the method for adjusting the characteristics of a dielectric filter in which a conductive film is also formed in the through hole and connected to the ground electrode, the conductive film around the opening of the through hole on the surface facing the surface on which the input / output electrode is formed is removed. The feature is that the dielectric is exposed by cutting.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Although the resonance mode of a dielectric filter according to the present invention has not been completely analyzed, it has the same function as a waveguide, and has a structure in which a dielectric is filled inside the waveguide. It is considered that It is considered that a resonator is formed by the input and output electrode portions, and a filter characteristic can be obtained by the combination of these resonators.

In the present invention, the conductor connected to the ground potential is arranged between the resonators, whereby the coupling of the resonators is adjusted to form an attenuation pole having a predetermined frequency. That is, the frequency of the attenuation pole is adjusted by the inductance and the capacitance of the conductor.

[0011]

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

1A and 1B show an embodiment of the present invention, in which FIG. 1A is a perspective view and FIG. 1B is a plan view. I / O electrodes 11 and 12 of island-shaped conductive film are formed at intervals on the widest surface of the area of a rectangular parallelepiped dielectric block 10 of 12.0 × 6.0 × 2.5 mm,
These are input / output electrodes. The dimensions of the input and output electrodes are 1.4 ×
It is 1.4 mm.

A conductor film 13 surrounding the input / output electrodes 11 and 12 at a distance of 0.1 mm is formed on almost the entire remaining surface of the surface. In addition, almost all surfaces other than the surface on which the input / output electrodes 11 and 12 are formed are formed with a conductive film, and are electrically connected to the conductive film 13 surrounding the input / output electrodes 11 and 12, so that the whole becomes a ground electrode. The input / output electrodes 11 and 12 are connected to input / output signal lines.

In the present invention, a through hole 15 is formed between the input / output electrodes 11 and 12 and extends from the surface where the input / output electrodes are formed to the opposite surface. In this example, the size of the through hole 15 is 0.3 × 0.5 mm. A conductor film is also formed in the through hole 15, and a conductor layer is arranged between the resonators. On the surface around the through-hole 15 on the surface facing the surface on which the input / output electrodes are formed, the dielectric is exposed without forming a conductor film. In this example, a gap of 0.1 mm is formed between the conductor film on the edge of the through hole and the surrounding conductor film.

FIG. 2 shows the bandpass characteristics of the dielectric filter manufactured using the dielectric having a relative permittivity of 37 according to the embodiment shown in FIG. Center frequency is 6.01GHz, 3dB bandwidth is
15.60 MHz, the insertion loss at the peak was 0.66 dB, and it was confirmed that it could be used as a 6 GHz band band-pass filter. And 5. on the lower side of the passband.
An attenuation pole was obtained around 23 GHz.

FIG. 3 is a plan view showing another embodiment of the present invention. The size of the dielectric block is the same as in FIG. 1, and the input / output electrodes are also the same size. Through hole between input and output electrodes
The size of 35 is the same, but the width (gap) where the dielectric around the through hole is exposed is set to 0.7 mm.

The characteristics shown in FIG. 4 show the bandpass characteristics of the dielectric filter shown in FIG. The center frequency was 6.08 GHz, the 3 dB bandwidth was 19.41 MHz, and the insertion loss at the peak was 0.51 dB, confirming that the filter can be similarly used as a 6 GHz band band-pass filter. In this example, an attenuation pole was obtained near 6.78 GHz on the higher side of the passband.

As described above, according to the present invention, the characteristics such as the bandwidth are adjusted by utilizing the fact that the pass band characteristics change depending on the width (gap) of the dielectric exposed around the through hole. Can be. In the example of FIG. 1, an attenuation pole was obtained on the lower side of the pass band, but in the example of FIG. 3, an attenuation pole was obtained on the higher side of the pass band.

The conductor formed in the through hole between the input / output electrodes adds inductance and capacitance by the conductor from the surface facing the surface where the input / output electrodes are formed to the surface where the input / output electrodes are formed. The gap in the film adds capacitance. By selecting the inductance and the capacitance value, the frequency of the attenuation pole can be adjusted.

[0020]

According to the present invention, it is possible to obtain a dielectric filter which can be used in a frequency band of 5 GHz or more and whose characteristics can be easily adjusted. A damping characteristic can be added to the filter characteristic by the gap between the conductors of the through holes between the resonators.

Further, not only the size and thickness can be reduced, but also the dielectric filter can be manufactured only by forming a conductor 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. 1A is a perspective view showing an embodiment of the present invention, and FIG.
Plan view

FIG. 2 is an explanatory diagram of characteristics of a dielectric filter according to the present invention.

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

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

[Explanation of symbols]

 10: Dielectric block 11, 12: I / O electrode 13: Conductor film (earth electrode) 15, 35: Through hole

Claims (3)

[Claims] 1. A dielectric filter integrally formed with a rectangular parallelepiped dielectric block, wherein the input / output electrodes are formed by island-shaped conductive films formed at intervals in the longitudinal direction on the surface of the dielectric block having the largest area. And a ground electrode formed of a conductive film which is separated and insulated from the conductive film of the input / output electrode and is formed on almost the entire remaining surface and substantially the entire other surface. It has a through hole extending from the surface on which the electrode is formed to the surface opposite to the surface, the conductor film is also formed on the through hole, connected to the ground electrode, and the through hole on the surface facing the surface on which the input / output electrode is formed is provided. A dielectric filter, wherein a dielectric is exposed around an opening. 2. An input / output electrode comprising an island-shaped conductor film formed at intervals in the longitudinal direction on the surface of the dielectric block having the largest area, and the surface thereof is separated and insulated from the conductor film of the input / output electrode. A ground electrode made of a conductive film formed on almost the entire surface of the remaining surface and on the entire surface of the other surface, and a through hole located between the input / output electrodes and extending from the surface on which the input / output electrodes are formed to the opposite surface. In the method for adjusting the characteristics of a dielectric filter in which a conductive film is also formed in the through hole and connected to the ground electrode, the conductive film around the opening of the through hole on the surface facing the surface on which the input / output electrode is formed is removed. A method for adjusting characteristics of a dielectric filter, characterized by exposing a dielectric by cutting. 3. The method according to claim 2, wherein the coupling between the resonators is adjusted by cutting the conductive film.