JPS63311801A - Dielectric filter device - Google Patents

Abstract

PURPOSE:To attain miniaturization and low cost of the titled device with simple structure by fixing a dielectric filter directly on a board and forming an additional circuit onto the same board. CONSTITUTION:An outer conductor 12 and an earth electrode 18 of both dielectric filters 2a, 2b are soldered onto a board 14 on nearly the entire surface of which the earth electrode 18 is formed except the surrounding of prescribed land electrodes 24, 28 or the like on the surface of a dielectric plate 16, and conducted and adhered by a conductive adhesives or the like. Moreover, a low-pass filter 22a and a phase shift circuit 22b as the additional circuit are formed on said board 14. Then the inner conductors 10 at both ends of the dielectric filter 2a and one end of the phase shift circuit 22b are coupled electrically by coupling capacitors 32, 33 respectively. This, the structure is simplified and the miniaturization and low cost of the dielectric filter device are attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a dielectric filter device that combines a dielectric filter and an additional circuit.

[Conventional technology and its problems]

Conventionally, in this type of dielectric filter device, when storing and fixing the dielectric filter in a metal case,
In order to prevent the dielectric filter from being damaged by absorbing the difference in thermal expansion between the two, a metal spring or the like is used to establish electrical continuity between the two, rather than soldering. I tried to fix it to some extent. Therefore, there was a problem that the structure became complicated and the cost increased.

Additionally, additional circuits used in combination with the dielectric filter, such as low-pass filters and phase shift circuits, can be configured on the board alone or using cables, and housed in the same metal case as the dielectric filter. Was. Therefore, from this point of view as well, there was a problem that the structure became complicated and the cost increased.

[Purpose of the invention]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a dielectric filter device that has a simple structure, is smaller in size, and can be lowered in cost.

Means for Achieving Objective C] The dielectric filter device of the present invention comprises a dielectric block having a through hole provided therein, an inner conductor provided on the inner surface thereof, and an outer conductor provided at least on the west side of the dielectric block. placing the filter on a substrate comprising a ground electrode formed on the surface of a dielectric plate having the same or substantially the same coefficient of thermal expansion as that of the dielectric block, and conductively bonding the ground electrode and the outer conductor of the dielectric filter; Additionally, an additional circuit is formed on the same substrate and electrically coupled to the inner conductor of the dielectric filter, which is housed in a metal case and connected to the dielectric filter or additional circuit on the substrate. It is characterized by having input/output terminals pulled out.

[Effect]

The dielectric filter is mechanically fixed and electrically connected to the substrate by conductive bonding.

Therefore, the structure becomes simple. Of course, even in that case, since dielectrics with the same or almost the same coefficient of thermal expansion are used for both, there will be no problem due to the difference in thermal expansion.

Further, since the additional circuit is also formed on the same substrate as above, the structure is also simplified from this point of view. As a result of the above, it is possible to reduce the size and cost of the dielectric filter device.

〔Example〕

FIG. 1 is an exploded perspective view of a dielectric filter device according to an embodiment of the present invention, and FIG. 2 is an equivalent circuit diagram of the same device.

This dielectric filter device is an example of a duplexer used in a car phone, etc., and a transmitter is connected to the terminal 38a and a receiver is connected to the terminal 38c.
It is used to share the antenna connected to b.

Reference numeral 2a denotes a dielectric filter on the transmission side, such as that disclosed in Japanese Patent Laid-Open No. 58-9401, in which four through holes 6 are formed in a cubic dielectric block 4 made of ceramic, for example. Inner conductors 10 are arranged in parallel on the inner surface of each through hole 6, and outer conductors 12 are provided on the west side and, in this example, the bottom of dielectric block 4, thereby forming four resonant units. Furthermore, a cavity 8 is provided between adjacent through holes 6 of the dielectric block 4 in order to obtain coupling between each resonant unit. As a result, the dielectric filter 2a has four mutually coupled resonant units formed therein to constitute a bandpass filter. S is the outer conductor 12
Shows an open end surface without a

2b is a dielectric filter on the reception side, and has, for example, the same structure as the dielectric filter 2a described above. The dielectric filters 2a and 2b are arranged so that their open end surfaces S face oppositely to each other, thereby suppressing mutual interference as much as possible.

Then, such dielectric filters 2a and 2b are mounted on the surface of a dielectric plate 16 made of ceramic having the same or almost the same coefficient of thermal expansion as that of the dielectric block 4, except for the areas around predetermined land electrodes 24, 28, etc. Earth electrode 1 on almost the entire surface
The outer conductor 12 of both dielectric filters 2a, 2b and the ground electrode 18 are electrically connected to each other by soldering, conductive adhesive, or the like. Note that the ground electrodes 18 on the upper and lower surfaces of the substrate 14 are different from the ground electrodes 1 on the side surfaces.
8, and through hole 2.
0 is also connected in some places, thereby suppressing the occurrence of undesirable inductance as much as possible.

Further, on the same substrate 14, a low pass filter 22a and a phase shift circuit 22b are formed as examples of additional circuits.

The low-pass filter 22a includes a capacitance and an inductance 26 formed between the land electrode 24 on the upper surface of the substrate 14 and the ground electrode 18 on the lower surface. The phase shift circuit 22b also
Land electrode 28 on the top surface of the substrate 14 and ground electrode 1 on the bottom surface
It consists of a capacitance formed between 8 and an inductance 30.

Then, the inner conductors 10 on both ends of the dielectric filter 2a and one end of the low-pass filter 22a and the phase shift circuit 22b are electrically coupled by coupling capacitances 32 and 33, respectively, and the inner conductors 10 on both ends of the dielectric filter 2b are A capacitance 34.35 connects the other end of the low-pass filter 22b and the terminal 38c.
are electrically coupled to each other, and are further connected to a low-pass filter 22.
A terminal 38a is connected to the other end of the phase shift circuit 22b and one end of the phase shift circuit 22b.
and 38b are connected to each other.

And the metal case 4 is placed on top of the structure configured in this way.
0 (in other words, it is housed inside the metal case 40), and the metal case 40 and the ground electrode 18 of the board 14 are soldered and conductively joined using a conductive adhesive or the like, and the metal case 40 is The aforementioned input/output terminal 38
A to 38c are insulated and drawn out.

In this dielectric filter device, the dielectric filters 2a and 2b are conductively bonded directly onto the substrate 14, so the structure is simpler than the conventional case where they are fixed to a metal case using metal springs or the like. It gets easier. Of course, even in that case, since the dielectric filters 2a, 2b and the substrate 14 are made of ceramics with the same or almost the same coefficient of thermal expansion,
There are no adverse effects caused by the difference in thermal expansion.

Further, since the low-pass filter 22a and the phase shift circuit 22b are also formed on the same substrate 14, the structure is simpler than the conventional case where these are provided on separate substrates.

As a result of the above, it is possible to reduce the size and cost of the dielectric filter device.

Note that a structure may also be adopted in which a metal spring is inserted between the metal case 40 and the upper surfaces of the dielectric filters 2a and 2b to further ground the gap therebetween.

Moreover, if a drawn product is used for the metal case 40, the structure will be simpler.

Incidentally, the reason for providing the above-mentioned low-pass filter 22a and phase shift circuit 22b is as follows.

For example, when dielectric filters 2a and 2b with a center frequency of 835 MHz on the transmitting side, a center frequency of 880 MHz on the receiving side, and a bandwidth of 25 MH2 are used in such a duplexer, the passband characteristics of the individual dielectric filters 2a, 2b are as follows.
When the performance is satisfied in 2b, the problem on the transmitting side is mainly spurious characteristics.

However, it is generally difficult to suppress spurious waves only with an integrated dielectric filter 2a as in this example or a distributed constant type filter, so an external low-pass filter 22a as in this example or a third harmonic It is necessary to add a trap filter that attenuates only a specific frequency range.

On the other hand, regarding the dielectric filter 2b on the receiving side, normally in a dielectric filter device such as the present invention, the impedance in the transmission frequency band is low before spurious, and if left as is, it will be combined with the dielectric filter 2a on the transmitting side. That is, in this example, there is a problem that it cannot be directly connected to the antenna terminal 38b (incidentally, the impedance of the dielectric filter 2a on the transmitting side in the receiving frequency band is usually sufficiently high).

Therefore, in such a case, the dielectric filter 2 on the receiving side
It is necessary to add a phase shift circuit 22b to the input side of signal b, which rotates the phase angle θ so that the impedance becomes maximum at the transmission frequency. This phase shift circuit 22b may be constructed from a strip line instead of an LC.

Finally, although a duplexer having two dielectric filters 2a and 2b as dielectric filters and a low-pass filter 22a and a phase shift circuit 22b as additional circuits has been exemplified above, the present invention is not limited to such a structure. Of course.

〔Effect of the invention〕

As described above, according to the dielectric filter device of the present invention,
Since the dielectric filter is directly fixed on the substrate and the additional circuit is also formed on the same substrate, the structure is simplified, and as a result, the size and cost can be reduced.

[Brief explanation of drawings]

FIG. 1 is an exploded perspective view of a dielectric filter device according to an embodiment of the present invention. FIG. 2 is an equivalent circuit diagram of the dielectric filter device of FIG. 1.

Claims (1)

[Claims] (1) A dielectric filter consisting of a dielectric block with a through hole provided with an inner conductor on its inner surface and outer conductors on at least four sides of the dielectric block has the same coefficient of thermal expansion as that of the dielectric block. A ground electrode is formed on the surface of substantially the same dielectric plate, and the ground electrode and the outer conductor of the dielectric filter are electrically connected to each other, and an additional circuit is formed on the same board to connect the ground electrode to the dielectric filter. The filter is electrically coupled to the inner conductor of the filter, and is housed in a metal case, with input/output terminals connected to the dielectric filter or additional circuit on the board drawn out from the case. Dielectric filter device.