JPH02264501A - Dielectric filter - Google Patents

Abstract

PURPOSE:To obtain a dielectric filter with a structure offering ease of manufacture by manufacturing a dielectric block while dividing it into two blocks and bonding both the blocks after the manufacture. CONSTITUTION:An inner conductor 112 is placed in the center of two outer conductors 110 in parallel with the inner conductor 112 to form the center conductor of a tri-plate line. The tri-plate line is short-circuited by a short-circuit conductor 104 and acts like a 1/lambda resonator in the TEM mode having the resonance frequency in the height direction. Since a slit 115 is surrounded by a dielectric substance having a different dielectric constant from that of the dielectric block 101, a difference from the effective dielectric constant in even and odd modes is caused due to the slit 115 between the resonators 122 at the resonance frequency (f). Thus, a gyrator impedance Z(j) is obtained by equations I-III to attain the design of the dielectric filter with a desired characteristic, where epsilon(ro), epsilon(re), Z(oo), Z(oe) are respectively even and odd mode effective dielectric constants and even and odd impedance and Z(j) is a gynrator impedance.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a dielectric filter, and particularly to a structure of a dielectric filter that is easy to manufacture.

[Prior Art] Fig. 4 is a diagram showing an example of a conventional dielectric filter.
FIG. 4(a) is a perspective view showing the structure, and FIG. 4(b) is a block diagram showing an equivalent circuit.

In these figures, 401 is a dielectric block, and 402 is an outer conductor obtained by metallizing the dielectric block 401.

In this specification, for convenience of explanation, the outer conductor formed on the bottom surface of the dielectric block 401 will be particularly referred to as a short-circuit conductor. The outer conductor 402, including the shorting conductor, is normally connected to ground potential. 403 is a dielectric block 401
The inner conductor 404 is a slit provided in the dielectric block 401.

Each inner conductor 403 constitutes a distributed constant circuit together with the outer conductor 402, and the inner conductor 403 connects the outer conductor 40 with a short-circuited conductor at the bottom.
It is shorted to 2. For example, the length of the inner conductor 403 from the short-circuit point is ^/4 (however, ^ is the dielectric block 40 of the radio wave used).
1), a resonator is constructed. This resonator is shown at 413 in FIG. 4(b).

Furthermore, the dielectric constant within the slit 404 is the same as that of the dielectric block 40.
Since the dielectric constant is different from 1, this portion constitutes a gyrator. This gyrator is 41 in Fig. 4(b).
Indicated by 4. That is, due to the structure of FIG. 4<a), the structure shown in FIG. 4(b)
An equivalent circuit is constructed, and coupling between adjacent resonators 413 is performed by a gyrator 414, thereby constructing a multi-element filter.

[Problems to be Solved by the Invention] Since the conventional dielectric filter as described above has the above structure, there is a problem in that it is difficult to manufacture. That is, the dielectric block 401 is formed by cutting out a high dielectric constant material using a die as shown in FIG. It is necessary to provide a large protrusion of the inner conductor 404, and if the operating frequency is low and ^ is therefore long, the large protrusion of the inner conductor 403 must be lengthened, which makes die cutting difficult. Furthermore, in order to manufacture a broadband filter, it is necessary to increase the coupling, that is, to enlarge the slit 404, which also makes die cutting difficult and the inner conductor 40
3 and the space of slit 4Q4 are too close together, which causes a problem in terms of strength.

Also, after molding, the outer conductor 402. Paste silver is applied to the inner conductor 403 and fired, but the inner conductor 4, which is a long and narrow hole,
It is necessary to apply paste silver to the inner surface of 03, and in order to avoid conductor loss in this part, paste silver must be applied relatively thickly, and there are manufacturing problems such as this work is not easy. was there.

The present invention was made to solve this problem, and its purpose is to obtain a dielectric filter having an easy-to-manufacture structure.

[Means for Solving the Problems] A dielectric filter according to the present invention is manufactured by dividing a dielectric block into two blocks, and after manufacturing, the two blocks are joined.

[Operations] In this invention, the dielectric block is manufactured in two blocks, and the two blocks are joined after manufacturing, so that the dielectric block can be easily formed.

[Examples] Examples of the present invention will be described below with reference to the drawings. 1st
The figure shows one embodiment of this invention, and FIG. 1(a) shows two
FIG. 1(b) is a perspective view showing one of the blocks, FIG. 1(b) is a perspective view showing the two blocks joined together, and FIG. 1(c) is a block diagram showing an equivalent circuit.

In these figures, 101 is a dielectric block, 102 is an abutting plane (on the abutting plane, a conductor surface constituting the inner conductor is formed, so this is also called a conductor plane), 103 is a back conductor, and 104 is a back conductor. The bottom conductor (also referred to as a short-circuit conductor since the bottom conductor constitutes a short-circuit conductor), 105 is a slit.

First, the dielectric block 101 is formed by die cutting using a die having projections for the slits 105. The die used for this die cutting can have a simpler shape than conventional dies, making the die cutting process easier.

Next, a conductor is formed on the entire surface of the contact plane 1.02, the back surface, and the bottom surface, and the conductor surface 102. Back conductor 103. Bottom conductor 10
4 and connect the conductors on each side to each other. Conductor surface 10
By connecting the conductor No. 2 and the bottom conductor 104,
The bottom conductor 104 shorts the inner conductor 112. These conductors are generally formed by applying silver paste and firing it.

In this way, two blocks shown in FIG. 1(a) are made, the contact planes 102 are brought into contact with each other, and the contacting conductor surfaces are joined using, for example, silver paste. The thus bonded product is housed in an outer conductor case as shown in FIG. 1(b). In FIG. 1(b), 110 is an outer conductor, 1
11 is a space, ] 12 is an inner conductor, and 115 is a slit. Further, the space 111 is approximately half the distance between the inner conductors 112 that are in contact with each other.

Further, while the conventional inner conductor 403 shown in FIG. 4 constitutes a coaxial inner conductor, the inner conductor 112 is located at the center of the two outer conductors 110 parallel to the inner conductor 112, and is arranged along a triplate line. 1ine), this is also called the center conductor.

This triplate line is short-circuited by a short-circuit conductor 104, and operates as a TEM mode 1/λ resonator whose resonant frequency is in the height direction in the figure.

Since the slit 115 is made of a dielectric (usually air) having a dielectric constant different from that of the dielectric block 101, electrical coupling is established between the adjacent resonators 122, as shown in FIG. occurs. That is, at the resonance frequency f, this coupling slit 115 is formed between the resonators 122.
Therefore, there is a difference in effective permittivity between even mode and odd mode, and the effective permittivity in even mode is ε(ro), the effective permittivity in odd mode is ε(re), and the coupling coefficient is is K, then K=2(ε(ro)−ε(re))/(ε(ro>+
ε<re>>...(1) is obtained.

Further, the characteristic impedance Z of the resonator 122 is the characteristic impedance Z (oo) in the even mode.

From the characteristic impedance Z (oe) in odd mode, Z = 2Z (oe) Z (oo) / (Z (oe) +
Z (00)) ...(2).

Here, if the gyrator impedance is Zl), then Z(j)=(4/π)Z(1/K) (3).

Therefore, a dielectric filter with desired characteristics can be designed from these equations.

FIG. 2 is a perspective view showing another embodiment of the present invention, in which the same reference numerals as in FIG. 1 indicate the same or corresponding parts, and an inner conductor 112a
indicates that the conductor extends outside the contact plane 102 and is also formed on a part of the side surface of the slit 1.05. This configuration has the advantage that the difference between ε(rO) and ε(re) increases, and K can be increased.

FIG. 3 is a perspective view showing the connection between the dielectric filter according to the present invention and an external circuit, in which the same reference numerals as in FIG. 1 indicate the same or corresponding parts, and 116 is a coaxial cable.

The characteristic impedance of the coaxial cable 116 (for example, 50
ohm) is smaller than Z in equation (2), so Z (r)=Zs i n2 (r −2yr/λ)(
4) Connect the coaxial cable 116 to a point r (distance from the shorting conductor 104).

In the above embodiment, the bottom surface is used as a short-circuit surface to form a λ/4 resonator, but the bottom surface is used as an open surface to form a λ/4 resonator.
/2 resonator may be formed. in this case,
At high frequencies, the resonator length becomes short, so dimensional accuracy with respect to frequency is strictly required, but by using a λ/2 resonator, the dimensional accuracy can be reduced to 1/2.

[Effects of the Invention] As described above, according to the present invention, it is possible to construct a dielectric filter that is easy to manufacture and can be processed in detail, and it is also possible to form blocks easily even for relatively low frequencies. This has the effect that a dielectric filter can be obtained.

[Brief explanation of drawings]

FIG. 1 is a diagram showing one embodiment of the invention, FIG. 2 is a perspective view showing another embodiment of the invention, FIG. 3 is a perspective view showing the connection between the filter according to the invention and an external circuit, and FIG. FIG. 4 is a diagram showing an example of a conventional dielectric filter. 101... Dielectric block, 102... Contact plane,
104... Short circuit conductor, 105... Slit, 110
...outer conductor, 112...inner conductor, 122...resonator, 125...gyrator. Note that the same reference numerals in each figure indicate the same or corresponding parts. Figure 2 (b) (c) Figure 1 (a) (b)

Claims (1)

[Claims] A short-circuit conductor is formed on the bottom surface of the dielectric block, an outer conductor is formed on the side surface, and this outer conductor is connected to the short-circuit conductor, and each of the above-mentioned short-circuit conductors reaches the bottom surface from a plurality of locations on the top surface. Each inner conductor and the outer conductor constitute each resonator, and a dielectric having a dielectric constant different from that of the dielectric block is provided between adjacent resonators. In a dielectric filter in which a gyrator is constructed by inserting a Each of the blocks is provided with a contact plane and each slit at a position opposite to each contact plane and each slit of the other block, and each contact plane and each slit are connected to the top surface of the dielectric block. The inner conductors are arranged alternately so as to reach the bottom surface, and the inner conductors are formed on each abutment plane, and the inner conductors on the abutment planes facing each other of the two blocks are joined to each other to form the two blocks. A dielectric filter characterized in that the gyrator is constituted by slits that face each other when connected.