JPH0444401A - Dielectric filter device - Google Patents

Abstract

PURPOSE:To obtain a stable characteristic even at a high frequency band by making plural throughholes whose length is 1/2 of a resonance wavelength in parallel, providing a dielectric layer which is formed to an outer circumferential face of a dielectric block and a conductor layer whose both ends are short- circuited formed to an inner circumferential face of a throughhole except the part of the dielectric block. CONSTITUTION:A dielectric block 20 is lambda/2 long and both ends are short- circuited, then the dielectric block 20 is resonated at a frequency equivalent to the resonance wavelength lambda/2. In such a case, a standing wave exists in the dielectric block 20 such that the voltage is zero and the current is maximum at short-circuit conductors 26a, 26b and the voltage is maximum and the current is zero in the middle of an inner conductor 24. That is, a coupling pin 27 is extended up to the middle of a throughhole 21 to obtain a capacitive coupling between a center conductor 29 and the inner conductor 24. Thus, deep insertion of the coupling pin 27 into the throughhole 21 is allowed thereby ensuring the coupling pin 27 to be supported by the dielectric block 20.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an integrally molded dielectric filter device suitable for use mainly in a high frequency band.

[Prior Art] In a conventional integrally molded filter, as shown in Fig. 4,
The dielectric block 1 has two through holes 2 and 3 having a length of 1/4 of the resonance wavelength λ and are parallel to each other.

A short circuit conductor 4a is formed on one end surface of the outer circumferential surface of the dielectric block 1, where the through hole 2.3 opens, to serve as a short circuit end surface, and an outer conductor 4b is formed on the side wall surface. Furthermore, inner conductors 5 and 6 are formed on the inner peripheral surfaces of the through holes 2 and 3. The opening of the through hole 2゜3 on the side where the outer conductor 4 is not formed is an open end surface, and an input/output coupling pin consisting of a dielectric tube 7 and a center conductor 8 placed at the center of the dielectric tube 7 is formed. 9.10 is inserted and fixed.

[Problem to be solved by the invention] In the conventional dielectric filter device, the resonant frequency is 2G.
At high frequencies of about Hz to 3 GHz, the center conductor 8
It becomes necessary to reduce the external coupling capacitance generated between the inner conductor 5 or 6 and the inner conductor 5 or 6.

For this purpose, it is necessary to shallowly insert the coupling pins 9, 10 into the through holes 2, 3. For this reason, the coupling pin 9
．． The holding by the through hole 2.3 of No. 10 becomes unstable. In addition, the capacitance value easily changes due to slight differences in the degree of insertion of the coupling pins 9 and 10 into the through holes 2°3.
It becomes difficult to obtain the desired capacitance. Therefore, in the conventional configuration, the characteristics become unstable and a highly reliable dielectric filter device cannot be obtained.

One way to improve the above problem is to increase the dielectric constant of the dielectric block 1, but in that case, the cutoff frequency in higher-order modes will be lowered and will be observed as a spurious response. The influence of next mode spurious can no longer be ignored.

An object of the present invention is to provide a highly reliable dielectric filter device that can obtain stable characteristics even in a high frequency band.

[Means for Solving the Problems] A dielectric filter device according to the present invention has a resonant wavelength of 172
A dielectric block in which a plurality of through holes having a length of The short-type conductor layer and the input/output layer inserted into the through hole.
It has an output coupling pin.

[In a dielectric block in which a through hole with a length of 1/2 of the resonant wavelength is formed, the conductor layer formed on the outer peripheral surface is short-circuited at both ends, so the resonant operation is expressed as follows. It will be done. In other words, since the conductor layer is short-circuited at both ends of the dielectric block at both ends of the through hole, the voltage is zero and the current is maximum at the resonant frequency, while the voltage is maximum and the current is maximum at the center of the dielectric block. There is a standing wave that causes the current to become zero. Therefore, in order to capacitively couple the coupling pin to such a dielectric block, the dielectric filter device according to the present invention allows the coupling pin to be inserted into the vicinity of the center of the through hole.

Therefore, in the dielectric filter according to the present invention, the coupling pin can be inserted sufficiently deeply into the through-hole of the dielectric block, and the coupling pin can be reliably held by the through-hole. Furthermore, the capacitance value is stabilized and the reliability of the dielectric filter device is improved.

As a result, in the dielectric filter device according to the present invention,
without the negative effects of higher-order mode spurs.
Stable characteristics can be obtained even in a relatively high frequency band, making it possible to obtain a highly reliable dielectric fill device.

Furthermore, compared to the conventional λ/4 type dielectric filter device,
Since the area of the outer peripheral surface of the dielectric block covered by the conductor layer is large, RF leakage is reduced.

[Example 2] As shown in FIG. 1, the dielectric filter device according to this example has a dielectric block 20 having a generally rectangular parallelepiped shape. As shown in the figure, the length of a certain side of the dielectric block 20 is set to 1/2 of the resonance wavelength λ,
The dielectric block 20 has a pair of through holes 21 and 22 extending in the length direction of /2 and parallel to each other. In addition, a through hole 21 is provided in the center of the dielectric block 20.
A coupling hole 23 parallel to the angle 22 is formed.

An inner conductor 24. is provided on the inner peripheral surface of the through hole 21.22 for both pages.
25 is formed. Further, on the outer peripheral surface of the dielectric block 20, an outer conductor 26, a short circuit conductor 26a,
26b is formed.

That is, the entire surface of the dielectric block 20 is substantially covered with the conductive layer except for the inner wall surface of the coupling hole 23. Further, the side inner conductors 24 and 25 and the outer conductor 26 constitute a resonance unit, that is, a λ/2 type double-ended short TEM coaxial resonance unit. Note that these conductor layers are formed by baking or plating a metal film. The coupling hole 23 is provided to couple both resonance units, and constitutes the main body portion of the dielectric filter device.

Connecting pins 27 and 28 are press-fitted and fixed into both prize holes 21 and 22, respectively. Each coupling pin 27.28 has a center conductor 29.30 and a center conductor 29.30, respectively. Dielectric tubes 31 and 32 made of synthetic resin are fixed around the go.
It has By press-fitting the dielectric tubes 31, 32 into the through holes 21.22, the coupling pins 27.2
8 is fixed to the dielectric block 20, and the center conductor 29.30 is capacitively coupled to the inner conductor 24.25. However, if the entire inner peripheral surface of the through hole 21.22 is covered with the inner conductor 24.25, the first and final stage resonators are not coupled to the external circuit. In a region where the electric field energy distribution is dominant between the inner conductor and the outer conductor, such as near the center in the axial direction, the inner conductor 24, 25 may be spread over the entire circumference of the inner conductor 24, 25, or may not be spread over the entire circumference, but with a certain width. Remove to expose the dielectric. The point is to open coupling windows in the inner conductors 24 and 25 so as to provide the required amount of coupling. The form of the coupling window is arbitrary.

Rain center conductor 29.30 and both dielectric tubes 31. What is 32?
Both extend toward the center inside the through holes 21 and 22, and their tips reach the longitudinal center of the through hole 21.

Incidentally, an overall outline of such a dielectric filter device is shown in FIG. Further, an equivalent circuit of such a dielectric filter device is shown in FIG. In FIG. 3, a pair of resonant units 35
, 36 correspond to a pair of resonance units configured in the through hole 21 and 22 portions of FIG. Both ends of both resonant units 35, 36 are grounded, and the inner conductor 24, 25 and the outer conductor 26 are connected by short-circuit conductors 26a, 26b formed on both end faces of the dielectric block 20 in FIG. This corresponds to the state where is shorted. Furthermore, the resonance unit 35 in FIG. Capacitances 37 and 38 are connected to the center of the inner conductor 24 and 36, and the center of the inner conductor 24 and 25 in FIG.
This corresponds to the fact that it is capacitively coupled to the tip of the Therefore, the tip of the center conductor 29.30 protruding from the dielectric block 20 corresponds to the connection terminal 39.40 in FIG. Further, both resonant units 35, 36 are magnetically coupled to each other, which corresponds to the coupling hole 2 in FIG.
3.

Next, the operation of this embodiment will be explained.

For example, when a high frequency wave with a bandwidth consisting of one center conductor 29 is introduced, it is transmitted to the inner conductor 24 by capacitive coupling between the center conductor 29 and the inner conductor 24 . At this time, the dielectric block 20 has a length of λ/2 and is short-circuited at both ends, so the dielectric block 20 resonates corresponding to the resonant wavelength λ/2. At this time, a standing wave is generated in which the voltage is at a maximum and the current is at a maximum in the short-circuited conductors 26a and 26b, and the voltage is at a maximum and the current is at a maximum at the center of the inner conductor 24. That is, the capacitive coupling between the center conductor 29 and the inner conductor 24 is mainly performed at the center portion of the through hole 21 where the electric field is strongest. In other words, the center conductor 29 and the inner conductor 24
In order to obtain capacitive coupling between the coupling pin 27 and the through hole 21, a configuration may be adopted in which the coupling pin 27 extends to the center of the through hole 21. Therefore, the coupling pin 27 can be inserted deeply into the through hole 21, and thereby the coupling pin 27 can be reliably held by the dielectric block 20. Moreover, the capacitance characteristics between the inner conductor 24 and the coupling pin 27 are stabilized, resulting in high reliability.

The dielectric block 20 is connected by input from the coupling pin 27 side.
When it resonates, the dielectric block 20 on the through hole 22 side also resonates based on the magnetic field coupling between the pair of resonance units. Based on the capacitive coupling between the center conductor 30 and the inner conductor 25 of the coupling pin 28, the a force in the desired band is applied to the center conductor 3.
It will be obtained from 0. On the coupling pin 28 side, the tip extends to the center of the through hole 22 for the same reason as on the coupling pin 27 side, so that the coupling pin 28
The retention by the dielectric block 20 is ensured, and stable capacitance characteristics can be obtained.

On the other hand, since the outer peripheral surface of the dielectric block 20 is covered with the outer conductor 26 over the entire circumference, R
F leak can be reliably prevented. Furthermore, the length of the dielectric block 20 is larger than that of the conventional λ/4 type dielectric resonator device, which is λ/2.

However, when the specifications are for a high frequency band, the absolute value of the resonant wavelength λ is small, so the problem of increasing the size of the dielectric block 20 and limiting the locations where it can be used does not occur. Rather, by making the dielectric block 20 larger than before, the dielectric filter device does not become too small.
There is also a secondary benefit of convenient handling.

In the above embodiment, a dielectric filter device having a pair of through holes 21 and 22 was described, but the present invention can be similarly implemented in a dielectric filter device having more than one pair of through holes.

In addition, it is also possible to configure a half-wavelength dielectric filter device with both ends open, without providing the shorting conductors 26a and 26b. In this case, the insertion position of the coupling pins 27 and 28 needs to be shallow as in the conventional case, and there is no effect of reducing RF leakage.

However, with that configuration, Qo increases by 20 to 30%, so if you want to reduce insertion loss as much as possible,
Insertion loss can be reduced in inverse proportion to Qo.

[Effects of the Invention] According to the dielectric filter device of the present invention, the coupling pin can be inserted up to the center of the through hole of the dielectric block, so that the coupling pin can be held by the dielectric block. Become certain. Moreover, the capacitance characteristics of the coupling pin are stabilized, and a highly reliable dielectric filter device can be obtained. Furthermore, since the area covered by the conductor layer of the dielectric block becomes larger, RF leakage can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of a dielectric filter device according to the present invention;
FIG. 2 is a perspective view thereof, FIG. 3 is an equivalent circuit thereof, and FIG. 4 is a diagram corresponding to the first diagram of a conventional dielectric filter device. 20 is a dielectric block, 21.22 is a through hole, 24.2
5 is an inner conductor, 26 is an outer conductor, and 27 and 28 are coupling pins.

Claims (1)

[Claims] A dielectric block in which a plurality of through holes having a length of 1/2 of a resonant wavelength are formed in parallel to each other, a conductor layer formed on the outer peripheral surface of the dielectric block, and a portion of the through holes formed on the inner peripheral surface of the through hole. A conductor layer with shorted ends formed except for the
A dielectric filter device comprising an input/output coupling pin inserted into the through hole.