JPS58105602A - Dielectric filter - Google Patents

Abstract

PURPOSE:To obtain optical characteristics of the titled dielectric filter by accommodating plural resonant elements each of which is obtained by fitting a resonant conductor on the surface of a dielectric plate, covering the rear surface of said plate with a shielding conductor and forming a window for electromagnetic coupling on the shielding conductor in parallel in a metallic box and by changing the areas of the windows. CONSTITUTION:A resonant conductor 2 is fitted on the surface of a dielectric plate 1. The rear surface of said plate 1 is covered with an electromagnetic shielding conductor 3 to be used also as an earthing conductor. A window 4 is formed on the lower part of the electromagnetic shielding conductor 3 and the conductor is removed from the part. The upper and lower end surfaces and the right and left sides of the dielectric plate 1 are covered with the conductor. The resonant conductor 2 is electrically short-circuited with the rear surface conductor 3 through the lower surface conductor of the dielectric plate 1. The upper end of the resonant conductor 2 is an opened end part, the lower end is a short-circuited end part connected with the earthing conductor and the length of the conductor 2 is fixed so that the conductor 2 resonates with the wavelength of odd tomes 1/4 resonant wavelength. Plural resonant elements 10 each of which consists of said dielectric plate 1 are accommodated in a metallic box 5. Optional filter characteristics are obtained by changing the size of the windows 4.

Description

DETAILED DESCRIPTION OF THE INVENTION <1) Technical Field of the Invention The present invention relates to a dielectric filter used in the microwave band.

(2) Technical background Filters used in microwave circuits have a lumped constant L.
There are those that use a C circuit and those that are coaxial, but the former has a large loss, and the latter has the disadvantage of being large in size. However, recently, a dielectric material with a high dielectric constant has been developed, and a coaxial deaf filter filled with this dielectric material has been put into practical use, and a microstrip line type filter with a lighter weight filter has also been developed. However, especially in devices that require miniaturization, such as in-vehicle radios or portable wireless devices, dielectric filters are still large-sized compared to other electronic components and account for a large proportion of non-devices.

There is a need for a round, lightweight dielectric filter for microwave circuits.

(3) Prior art and problems A coaxial dielectric filter has holes for the inner conductor formed at predetermined intervals corresponding to the filter characteristics in a dielectric body which is an outer conductor placed inside the housing, and holes for the inner conductor are formed in the holes for resonance. A conductor is provided, and a hole tube for adjusting the coupling between each resonance is formed between each hole. Such a coaxial deaf filter is generally large and heavy, and is not easy to manufacture because it requires drilling holes for the inner conductor in the dielectric material, which is a sintered body, with four precision precision. A microstrip line type filter has been developed in which a plurality of resonant conductors are provided in parallel on the surface of a dielectric material that leaves such points unaddressed. The coupling between each resonant conductor of such a microstrip line type filter is determined by the distance between each resonant conductor, p, which is also determined by the distance O between each resonant conductor @
The coupling between the resonant conductors of a coaxial filter is weaker than that of a coaxial filter. Therefore, if dielectric filters with the same filter characteristics are to be obtained, the distance between the resonant conductors of the microstripline filter must be shorter than the distance between the resonant conductors of the coaxial filter. For this reason, microstripline filters are smaller than coaxial filters. However, in such microstrip line type filters, especially when manufacturing multi-stage electric filters in which many resonant conductors are arranged in parallel,
- The electric body becomes elongated and warps occur during firing, resulting in poor productivity. Further, since the distance between each resonance conductor cannot be reduced below a predetermined value corresponding to the filter characteristics, there is a limit to the wrinkle formation. In addition, in such an IJ tube line reduction filter, each resonant conductor is provided in parallel on the dielectric surface, so in addition to coupling between adjacent resonant conductors, it is also possible to jump over one resonant conductor. Since the resonant conductors at different positions are coupled to each other, the coupling characteristics become unstable, and good filter characteristics cannot be obtained, such as the attenuation of the p-filter being unable to exceed a certain value.

(4) Purpose of the Invention The present invention has been made in view of the above points, and is a dielectric filter with excellent filter characteristics, which is small in size,
The purpose of this invention is to provide a dielectric filter that is lightweight.

(5) Structure of the Invention In order to achieve this object, in the present invention, a resonant conductor is provided on the front surface of a dielectric plate, the back surface is covered with an electromagnetic shielding conductor, and a window for electromagnetic coupling is formed on the electromagnetic shielding conductor. A plurality of resonant elements are housed in parallel in a metal housing, and the electromagnetic shielding conductor of the resonant element and the metal housing are electrically connected.

(6) Embodiment of the Invention The irises 11g1 and 2111 are perspective views seen from the front and back sides of a resonant element 100 including a dielectric filter Kj according to the present invention, respectively. Resonant conductor 2 on the surface of dielectric 1 [1]
is provided. The back surface of the dielectric I[l is covered with an electromagnetic shielding conductor 3 that also serves as a grounding conductor. A window 4 is formed in the lower part of this electromagnetic shielding conductor 3, and no conductor is provided in this portion. Both upper and lower end surfaces and both left and right side surfaces of the dielectric plate l are also covered with a conductor. The resonance conductor 2Fi is electrically short-circuited to the electromagnetic shielding conductor 3 on the back surface via the conductor on the lower surface of the dielectric $1. Further, as long as the resonance conductor 2 and the electromagnetic shielding conductor 3 are electrically short-circuited, the conductors on the top surface and both left and right side surfaces of the dielectric plate 1 may be omitted.

The upper end of the resonance conductor 2 is an open end, and the lower end is a short-circuited end connected to the grounding conductor (electromagnetic shielding conductor 3), and its length is an odd multiple of a quarter wavelength of the resonant wavelength. The length is formed to resonate. A plurality of resonant elements 10 made of such dielectric plates 1 are arranged in parallel and housed in a metal casing 5 shown in FIG. 3 with an interval of several inches between them. resonant element l
O is inserted into the inside through the nine long holes 6 on the side surface of the metal casing 6, and as shown in the horizontal cross-sectional view and vertical cross-sectional view of the 4th W and the Or, it can be fixed using an appropriate method such as soldering.

Both ends of the metal casing 5 serve as input/output terminals for a filter consisting of a collection of resonant elements 10! [2) Clause II 7 is provided. 8 is a connector.

As shown in FIG. 6, the common Jll conductor 2' is made by first forming a conductor pattern 2a in the shape of a resonant conductor in close contact with the dielectric layer l, and then soldering a metal plate having the same shape on the conductor pattern 2a. It may be formed by bonding or adhering with conductive paste or the like. The conductor pattern 2a can be formed by etching the dielectric layer 11 into a desired shape after electroless plating, or by closely contacting the conductor pattern 21 with the desired shape on the dielectric plate l. Figure 7 shows a half-resonant conductor 2It- on the dielectric [l].
This shows an example of the formation. In this case, the resonance conductor f
Both ends are open ends, and the length is formed to be an integral multiple of 1/2 of the resonant wavelength. In order to effectively occupy the surface area of the dielectric material 1 and to downsize the dielectric material 1, the resonance conductor f is formed in a bent manner, but it may have a straight shape.

(7) As described in detail of the invention, in the dielectric filter that emits zero @Vc-, a resonance conductor tube is provided on the surface of the dielectric layer, the back surface is covered with an electromagnetic shielding conductor, and the electromagnetic shielding conductor is A plurality of resonant elements provided with coupling windows are housed in parallel in a metal housing. Electromagnetic coupling between the resonance conductors is performed through the coupling window, and the coupling strength is determined by the area of this window, and arbitrary filter characteristics can be obtained by changing the area of the window. In addition, by changing the position of the window, it is possible to reliably prevent the resonant conductors from jumping over adjacent resonant conductors and joining together. Therefore, the resonance conductors can be disposed close to each other, and the resonance element can be disposed compactly within the metal casing, resulting in a small and lightweight filter. Also, since the coupling position between each resonant conductor is arbitrarily selected, unnecessary spurious waves such as higher-order modes are not passed through, and the filter characteristics are improved. If each resonant conductor is constructed from a conductor pattern closely formed on a dielectric plate and a P-shaped metal plate laminated on top of the conductor pattern, a sufficient thickness for high-frequency current can be obtained, so the passband of the filter can be obtained. loss is reduced. If each resonant conductor is appropriately bent, the shape of the dielectric layer 1 can be made smaller, and the filter can be further reduced in weight.

Since the electromagnetic shielding conductor of each resonant element is connected to the metal casing, grounding is performed through the metal casing, and the entire filter is reliably shielded and the filter characteristics are stabilized. To give an example of an experiment, in a 6-stage pass filter with an 800 MHz band of 2%, the total volume of the filter with the configuration of the present invention is 8.2 Ce, and the total volume of the microstrip line type filter with the conventional configuration is 18.3 Ce,
A coaxial filter has a low C of 34.3CC.

[Brief explanation of drawings]

1 and 2 are perspective views of a resonant element used in a dielectric filter according to the present invention, seen from the front and back surfaces, respectively, and FIG. 3 is a dielectric filter according to the present invention. Rino! A perspective view of & section, Fig. 4 is a sectional view of ff4 in Fig. 3,
FIG. 5 is a sectional view taken along the line -■ in FIG. 4, FIG. 6 is a perspective view of another example of the resonant element according to the present invention, and FIG. 7 is a front view of still another example of the resonant element. l... Dielectric layer, 2... Resonance conductor, 3... Electromagnetic shielding conductor, 4... Window, 5... Metal casing. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] 1. A plurality of resonant elements are arranged in parallel, with a resonant conductor provided on the surface of a dielectric plate, covered with a gold electromagnetic shielding conductor on the back side, and a window for electromagnetic coupling formed on the electromagnetic shielding conductor. and a dielectric filter that is housed in a metal housing and electrically connects the electromagnetic shielding conductor of the resonant element and the metal housing. 2. In the dielectric filter according to claim 1, one end of each resonance conductor is an open end, and the other end is a short-circuited end electrically connected to the electromagnetic shielding conductor at a quarter wavelength. A dielectric filter characterized by a resonant conductor. 3. The dielectric filter according to claim 1, wherein the half-wavelength resonant conductor is configured with both ends of each resonant conductor being open ends or short-circuited portions. 4. In the dielectric filter according to any one of claims 1 to 3, there is provided a thin film conductor pattern in which each resonance conductor is formed in close contact with a dielectric plate, and a droplet conductor pattern laminated thereon. 1. A dielectric filter comprising: and a metal plate having the same shape.