JP3314801B2 - Dielectric filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a monolithic dielectric filter used in a high frequency band such as a microwave, and more particularly to a dielectric filter having improved attenuation characteristics of its third harmonic.

[0002]

2. Description of the Related Art As shown in FIG. 4A , a dielectric filter is formed at predetermined intervals in the outer surface of a rectangular parallelepiped dielectric block 1 and in the longitudinal direction of the dielectric block 1. A conductor film 4 is formed on the inner surfaces of the five through holes 2 and 3,
The λ / 4 resonator is formed by alternately forming upper and lower portions of the conductor film 5 at one end of the three inner through holes 3 to form a λ / 4 resonator, and the through holes 2 located outside the resonator are formed. 2 and 3. An interdigital dielectric filter (band-pass filter BPF) having input / output electrodes 7 formed by forming conductive film removed portions 6 at the upper and lower terminal portions of FIG. 2 and a rectangular parallelepiped as shown in FIG. The conductor film 4 is formed on the outer surface of the dielectric block 1 and the inner surfaces of five through holes 2 and 3 formed at predetermined intervals in the longitudinal direction of the dielectric block 1, and the three inner conductive films are formed. A λ / 4 resonator is formed by forming a conductor film removing portion 5 at the same end of the through hole 3 of the through hole 3, and conductors are provided at the upper and lower ends of the through holes 2, 2 located outside the resonator. The comb-line method of forming the input / output electrode 7 by forming the film removal portion 6 There is a collector filter. Fig. 5 (a),
(B) is a perspective view of each of them, which is 13 mm in length, 7.2 mm in width and 3.2 mm in height, for example. FIG. 6 is a diagram showing the attenuation characteristics of the dielectric filter of FIG. In this example, the third harmonic f of the λ / 4 resonance frequency
It can be seen that 3 has occurred. Conventionally, the filter characteristic has been improved by combining this band-pass filter BPF with a low-pass filter LPF to attenuate its harmonics or shift the generation point of the harmonics.

[0003]

However, BPF and LP
In the combination of F, the shape becomes larger, which is disadvantageous from the viewpoint of miniaturization. In addition, the insertion loss of the BPF characteristic is deteriorated, and impedance mismatch is caused by a connection method, so that insertion loss and return loss are reduced. It was the cause of further deterioration.

An object of the present invention is to provide a conventional λ / 4 dielectric filter with a single-stage resonator, and to reduce filter harmonics without deteriorating the filter characteristics (IL, RL). It is an object of the present invention to provide an inexpensive dielectric filter having a configuration with a small number of components by solving the problems of greatly improving the number of components due to the addition of an LPF and the difficulty of connection (impedance mismatch). .

[0005]

That is, in the present invention, a plurality of holes (2, 3) penetrating from the upper surface in the longitudinal direction to the bottom surface of the rectangular parallelepiped dielectric block (1) are provided. A conductor film (4) is formed on the inner surface of (2, 3) and the outer surface of the block, and a plurality of holes (3) inside the hole (2 ).
Is removed by removing one of the two end face conductors
Holes forming a） resonator and located at both ends in the longitudinal direction (2)
In the dielectric filter having the input / output electrode (7) formed by removing the upper and lower end surface conductors, a height (X0) is attached to one longitudinal end surface of the input / output electrode (7) of the λ / 4 resonator. ) Is reduced to an integral fraction of 2 or more of the height (X) of the λ / 4 resonator.
Then , a resonator (8) having a resonance frequency that is an integral multiple of the resonance frequency of the λ / 4 resonator is continuously formed,
It is characterized by being coupled by capacitive coupling.

Further, in the present invention, a plurality of holes (2, 3) penetrating from the upper surface in the longitudinal direction to the bottom surface of the rectangular parallelepiped dielectric block (1) are provided, and each of the holes (2, 3) is formed. forming a conductive film (4) on the inner and block outer surface, further wherein the holes
Two end faces of the plurality of holes (3) inside (2)
One end conductor of the conductor is removed to form a λ / 4 resonator, and the upper and lower end conductors at the holes (2) located at both ends in the longitudinal direction are removed to form an input / output electrode (7). In addition, the height (X0) is set to an integer of 2 or more of the height (X) of the λ / 4 resonator on both end faces in the longitudinal direction of the input / output electrode (7) of the λ / 4 resonator. 1 , wherein a resonator (8) having a resonance frequency that is an integral multiple of the resonance frequency of the λ / 4 resonator is continuously formed and coupled by capacitive coupling.

Further, in the present invention, the λ / 4 resonator is of a comb line type or an interdigital type.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG.
The conductor film 4 is formed on the entire inner surface of the entire outer surface, the plurality of through holes 3 for resonators, the holes 2 for input / output terminals, and the through holes 8 provided on the end faces of the mounting holes 2 for input / output terminals. Thereafter, the conductor film 4 around the through holes 3 and 8 and the periphery of the input / output terminal hole 2 is formed.
Is removed with a taper reamer, etc. to remove the conductive film 5,
6 and 9, a λ / 4 resonator (BPF) having a three-stage structure of the resonator 3 and a one-stage resonator 8 capacitively coupled to the resonator 3 are integrally formed. An induction filter of an interdigital type in which conductor film removal portions 5 around the hole 3 are alternately arranged on the upper and lower surfaces is shown.
In the figure, reference numeral 7 denotes an input / output electrode derived from a pin terminal for connecting an external circuit.

[0009] resonator 8 in FIG. 1 for the harmonic improvement, but is provided only on one side of the dielectric block 1, it may take a further damping may be provided in symmetrical engagement Ru resonator 8 on both sides It is possible to respond by.

FIG . 1 is a perspective view of a dielectric filter. The dimensions of the conventional dielectric filter shown in FIG. 5 are slightly larger than that of the conventional dielectric filter shown in FIG. FIG. 2 showing the damping characteristic thereof and FIG .
Compared with the above, the attenuation characteristic is greatly improved with respect to the third harmonic f3, and is hardly affected in other frequency regions. Therefore, the in-band loss due to the insertion of the resonator 8 occurs. It turns out there is no.

In the case of forming the single-stage resonator 8 of the third harmonic as in this embodiment, basically, the height X of the resonator 8 shown in FIG.
0 may be approximately 1/3 of the height X of the BPF. Therefore,
By changing the height X0, the resonance frequency of the resonator 8 can be set to an arbitrary frequency such as twice (second harmonic) or five times (fifth harmonic) the resonance frequency of the BPF. .

FIG . 3 illustrates a comb line type dielectric filter. The difference from FIG. 5B of the conventional type is that the above-mentioned single-stage resonator 8 is provided on one end face in the longitudinal direction of the dielectric filter, and the other configuration is the same. Of course,
Such a configuration also has the same harmonic improvement effect as the interdigital system.

As described above, by integrating the BPF and the single-stage resonator 8 for improving harmonics as described in the embodiment, mismatching of the impedance of each resonator is eliminated, and the lossless dielectric filter is improved. Realization becomes possible.
Further, in this embodiment, the BPF has a three-stage structure of the resonator 3, but is not limited to this.

[0014]

According to the present invention, as a means for improving the harmonic characteristics of the dielectric filter, a filter resonator is incorporated in the filter itself, thereby making it possible to compare the filter with a conventional LPF. It is possible to provide a small and inexpensive dielectric filter without deterioration in characteristics.

Further, desired filter characteristics can be easily realized by adjusting the height of the added harmonic improving resonator.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing characteristics of the dielectric filter of FIG.

FIG. 3 is a perspective view of a dielectric filter showing another embodiment.
is there.

FIG. 4 is a cross-sectional view of a conventional dielectric filter, and FIG.
Interdigital method, (b) Comline method
Things.

FIG. 5 shows a perspective view of a conventional dielectric filter, and FIG.
Is the interdigital system, (b) is the comb line system
It depends.

FIG. 6 is a diagram illustrating characteristics of the dielectric filter of FIG . 4;

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Makoto Hara 5-36-11 Shimbashi, Minato-ku, Tokyo Inside Fuji Electric Chemical Co., Ltd. (56) References JP-A-1-291501 (JP, A) JP-A Hei 6-338704 (JP, A) Japanese Utility Model 60-119103 (JP, U) Japanese Utility Model 61-304 (JP, U) Japanese Utility Model 57-146403 (JP, U) (58) Fields surveyed (Int) .Cl. ⁷ , DB name) H01P 1/20-1/219 H01P ^7/ 00-7/10

Claims (2)

(57) [Claims] A plurality of holes (2, 3) penetrating from a top surface in the longitudinal direction to a bottom surface of a dielectric block (1) having a rectangular parallelepiped shape are provided, and an inner surface of each hole (2, 3) and an outer surface of the block. A conductor film (4) is formed on the λ / 4 resonator, and one of the two end face conductors of the plurality of holes (3) inside the hole (2) is removed. In the dielectric filter, the conductors at the upper and lower ends of the holes (2) located at both ends in the longitudinal direction are removed to form the input / output electrodes (7), the input / output electrodes (7) of the λ / 4 resonator are provided. The height (X0) is set to one or more integral multiples of the height (X) of the λ / 4 resonator on one end face in the longitudinal direction, and the integer of the resonance frequency of the λ / 4 resonator A dielectric film characterized in that a resonator (8) having a double resonance frequency is continuously formed and coupled by capacitive coupling. Ta. 2. A plurality of holes (2, 3) penetrating from a top surface in a longitudinal direction to a bottom surface of a dielectric block (1) having a rectangular parallelepiped shape, and an inner surface of each hole (2, 3) and an outer surface of the block. A conductor film (4) is formed on the λ / 4 resonator, and one of the two end face conductors of the plurality of holes (3) inside the hole (2) is removed. In the dielectric filter, the conductors at the upper and lower ends of the holes (2) located at both ends in the longitudinal direction are removed to form the input / output electrodes (7), the input / output electrodes (7) of the λ / 4 resonator are provided. The height (X 0) is set to an integral multiple of 2 or more of the height (X) of the λ / 4 resonator on both end faces in the longitudinal direction, and an integer of the resonance frequency of the λ / 4 resonator is provided. A dielectric film characterized in that a resonator (8) having a double resonance frequency is continuously formed and coupled by capacitive coupling. Ta.