JP3439985B2 - Waveguide type bandpass 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 waveguide type bandpass filter using a dielectric waveguide line that mainly transmits high frequency signals such as microwaves and millimeter waves.

[0002]

2. Description of the Related Art In recent years, research on mobile communication and inter-vehicle radar using high frequencies such as microwaves and millimeter waves has been actively pursued. A technology using these high frequencies requires a bandpass filter that passes only high frequency signals of a specific frequency.

There are various configurations of bandpass filters for high frequencies, and a waveguide type bandpass filter using a rectangular waveguide is known as one having good bandpass characteristics. This includes, for example, a structure shown in schematic perspective views in FIGS. 4 and 5.

The structure shown in FIG. 4 has a rectangular waveguide 1
The short pins 2 (2a to 2e) such as a plurality of metal rods forming an inductive window are vertically arranged at a half of the guide wavelength λg.
A bandpass filter is formed by arranging in the signal transmission direction with a spacing d (d <λg / 2) of less than.

According to this structure, the short pin 2c or the short pin group 2a, which is located substantially at the center of the waveguide 1, is formed.
2e divides the width of the waveguide 1 into a half or less of the cutoff wavelength. As a result, the waveguide 1
Since the electromagnetic wave propagating in the area is reflected, the regions L _{1 to} L ₄ shown in the figure can be regarded as an electrically closed space. This closed space has an inherent resonance mode and functions as a resonator that resonates at the lowest frequency when its length d is λg / 2. In the case of the structure shown in FIG. 4, it can be considered that four resonators formed by the wall formed by the short pins 2 are coupled in series to the waveguide 1.

As described above, the electromagnetic wave propagating through the waveguide 1 from the input side on the left side in FIG.
However, when the frequency of the electromagnetic wave coincides with the inherent resonance frequency of the resonator described above, energy is transferred from between the short pins 2a (inductive window) to the resonance region L ₁ by electromagnetic coupling. Flows in. Similarly, L ₁ to L ₂ , L ₂ to L ₃ , L ₃ to L ₄
Energy propagates to the waveguide 1 and propagates again as an electromagnetic wave from the output side of the waveguide 1 on the right side in FIG. Therefore, only the electromagnetic wave having a natural frequency can pass through the region formed by these structures, and thus the electromagnetic wave operates as a bandpass filter.

Since the above-mentioned resonance regions L _{1 to} L ₄ have inductive windows for coupling, their length d is generally shorter than λg / 2.

In the structure shown in FIG. 5, the short-wave plate 3 such as a plurality of metal plates forming inductive windows (inductive walls) in the rectangular waveguide 1 is also vertically arranged in the guide wavelength λg. The band pass filter is formed by arranging in the signal transmission direction at an interval d (d <λg / 2) that is less than ½ of the above.

According to this, the short-circuit plate 3 and the inductive window resulting therefrom function in exactly the same manner as the above-described short-pin 2 and the gap therebetween, thereby forming a band-pass filter.

[0010]

However, although the conventional bandpass filter using the rectangular waveguide having such a structure has excellent bandpass characteristics for high frequency signals, it is difficult to process during fabrication. there were. Therefore, there is a problem that the productivity is low and, as a result, the cost is high.

Further, since the rectangular waveguide itself is large in size, the band pass filter using the same is also large, and it is difficult to make it compact for use in mobile communication and inter-vehicle radar. there were.

The present invention has been devised in view of the above circumstances, and an object of the present invention is to provide a waveguide band-pass filter which has high productivity and is compatible with miniaturization.

[0013]

As a result of repeated studies on the above-mentioned problems, the present inventor has replaced a conventional rectangular waveguide with a pair of pairs as shown in a schematic perspective view in FIG. In the dielectric substrate sandwiched between the main conductor layers, the signal wavelength of 2
A pair of sidewall through conductor groups formed by electrically connecting the main conductor layers at intervals of less than one-half, and between the sidewall through conductor groups formed between the main conductor layers in parallel with the main conductor layer. A dielectric waveguide line (see Japanese Patent Application No. 8-229925) in which a side wall of the waveguide is formed by a sub-conductor layer that is electrically connected is used, and an inductive window is formed inside the dielectric waveguide line. By forming a plurality of short-circuit conductors corresponding to the short-pins forming the and arranging them in the signal transmission direction at intervals of less than one half of the guide wavelength,
It has been found that a waveguide type bandpass filter similar to the structure shown in FIGS. 4 and 5 can be manufactured using a dielectric waveguide line.

The waveguide type bandpass filter of the present invention electrically connects a pair of main conductor layers sandwiching a dielectric substrate and the main conductor layers at intervals of less than ½ of the signal wavelength in the signal transmission direction. And two rows of side wall through conductor groups connected to each other, and a sub-conductor layer formed between the main conductor layers in parallel with the main conductor layer and electrically connected to the side wall through conductor groups. Formed in parallel with the main conductor layer, inside the dielectric waveguide line that transmits a high-frequency signal by a region surrounded by the main conductor layer, the sidewall through conductor group, and the sub conductor layer, A plurality of short-circuit conductors that electrically connect the sub-conductor layers to form an inductive window are arranged in the signal transmission direction at intervals of less than half the guide wavelength. is there.

In the waveguide band pass filter of the present invention, in the above structure, the short-circuit conductor and another short-circuit conductor or the main conductor layer are electrically provided inside the dielectric waveguide line. A through conductor which is connected and forms the inductive window together with the short-circuit conductor is formed.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION A waveguide type bandpass filter of the present invention will be described below with reference to the drawings.

FIG. 3 is a schematic perspective view showing the structure of a dielectric waveguide line used in the waveguide type bandpass filter of the present invention. In FIG. 3, 11 is a dielectric substrate, 12 and 13 are a pair of main conductor layers sandwiching the dielectric substrate 11, and 14 is a lead in the signal transmission direction at intervals of less than ½ (1/2) of the signal wavelength. Body layer 12
It is a group of two side wall through conductors formed by electrically connecting 13 between them. Further, 15 is a main conductor layer 12 for electrically connecting the through conductors forming each row of the sidewall through conductor group 14 to each other.
It is a sub-conductor layer formed in parallel with 13.

According to FIG. 3, a dielectric substrate having a predetermined thickness a.
A pair of main conductor layers 12 and 13 are formed at positions sandwiching 11, and the main conductor layers 12 and 13 are formed on the upper and lower surfaces of the dielectric substrate 11 at least sandwiching the waveguide line formation position. Also,
A large number of through conductors such as through-hole conductors and via-hole conductors for electrically connecting the main conductor layers 12 and 13 are provided between the main conductor layers 12 and 13 to form two rows of side wall through conductor groups 14. Further, the sub conductor layer 15 is formed in parallel with the main conductor layers 12 and 13 so as to electrically connect the through conductors in each row.

The two rows of side wall penetrating conductor groups 14 have a predetermined spacing (width) b and are ½ of the signal wavelength in the signal transmission direction.
The sub-conductor layer 15 and the sub-conductor layer 15 form a side wall of the dielectric waveguide line 16. Further, by forming the sub conductor layer 15, when viewed from the inside of the dielectric waveguide line 16, the side wall of the line becomes a fine grid shape by the side wall through conductor group 14 and the sub conductor layer 15, The electromagnetic wave shielding effect can be further enhanced.

Here, there is no particular limitation on the thickness a of the dielectric substrate 11, that is, the distance between the pair of main conductor layers 12 and 13, but when the single mode is used, the distance b is 2 times.
In the example of FIG. 3, the portions corresponding to the E surface and the H surface of the dielectric waveguide are formed by the main conductor layers 12 and 13, the sidewall through conductor group 14 and the sub conductor layer 15, respectively. . Moreover, the side wall through conductor group 14 forms an electrical wall together with the sub conductor layer 15 by setting the distance c to be less than half the signal wavelength.

The magnetic field of the electromagnetic wave propagating through the line 16 is parallel to the side walls formed by the side wall through conductor group 14 and the sub conductor layer 15 and arranged in parallel. Therefore, if the gap formed between the through conductor group 14 and the sub conductor layer 15 is larger than ½ of the signal wavelength, the gap acts as a slot to leak an electromagnetic wave. Even if the line 16 is fed with an electromagnetic wave, the electromagnetic wave does not propagate along the pseudo waveguide formed here. However, if the gap is smaller than 1/2 of the signal wavelength, the electromagnetic wave propagates along this pseudo waveguide without leaking. As a result, according to the configuration of FIG. 3, the cross-sectional area surrounded by the pair of main conductor layers 12 and 13, the two-row sidewall through conductor groups 14 and the sub conductor layer 15 is a × b.
The area of size is the dielectric waveguide line 16.

Further, in these embodiments, the side wall through conductor group is provided.
Although 14 are formed in two rows, the side wall through conductor groups 14 are arranged in four rows or six rows to form a pseudo conductor wall by the side wall through conductor groups 14 in double or triple layers. As a result, it is possible to more effectively prevent the leakage of electromagnetic waves from the conductor wall.

According to the above-mentioned dielectric waveguide line, since it becomes a transmission line by a dielectric waveguide, its waveguide size is an ordinary waveguide when the relative permittivity of the dielectric substrate 11 is ε. Of 1
It becomes the size of / √ε. Therefore, as the dielectric substrate 11 is made of a material having a higher relative permittivity ε, the waveguide size can be made smaller, and the wiring can be formed at high density. It becomes a size that can be used as a transmission line.

As described above, the through conductors forming the sidewall through conductor group 14 have an interval c of less than half the signal wavelength λ.
It is desirable that the interval c be a constant repeating interval in order to realize good transmission characteristics, but it may be changed appropriately if it is less than half the signal wavelength λ. It goes without saying that some values may be combined.

The dielectric substrate 11 constituting such a dielectric waveguide line is not particularly limited as long as it functions as a dielectric and has characteristics that do not hinder the transmission of high frequency signals. It is desirable that the dielectric substrate 11 be made of ceramics from the viewpoints of accuracy and ease of manufacturing when forming the transmission line.

Ceramics having various relative dielectric constants have been known as such ceramics.
In order to transmit a high frequency signal by the dielectric waveguide line according to the present invention, a paraelectric material is desirable. This is because ferroelectric ceramics generally have large dielectric loss and high transmission loss in the high frequency region. Therefore, it is suitable that the dielectric constant ε _r of the dielectric substrate 11 is about 4 to 100.

Further, generally, the thickness of one layer of the dielectric layer formed on the multilayer wiring board, the package for housing the semiconductor element or the inter-vehicle radar is about 1 mm at the maximum,
When a material with a relative permittivity of 100 is used and the side wall has an H plane, that is, a magnetic field is an electromagnetic field distribution winding parallel to the side wall surface, the minimum frequency that can be used is calculated to be 15 GHz, It will also be available in the obi area. On the other hand, a dielectric made of a resin that is generally used as the dielectric substrate 11 has a relative permittivity ε _r of about 2. Therefore, if the thickness of the dielectric layer is 1 mm, it should be about 100 GHz or more. Will not be possible.

Although many paraelectric ceramics such as alumina and silica have a very small dielectric loss tangent, not all paraelectric ceramics can be used. In the case of the dielectric waveguide line, there is almost no loss due to the conductor, and most of the loss during signal transmission is due to the dielectric.
(DB / m) is expressed as follows. α = 27.3 × tan δ / [λ / {1- (λ / λc) ² }
^1/2 ] In the formula, tan δ: dielectric loss tangent of the dielectric λ: wavelength in the dielectric λc: cutoff wavelength According to the standardized rectangular waveguide (WRJ series) shape, {1- ( λ / λc) ² } ^1/2 is about 0.75.

Therefore, this is a transmission loss that can be put to practical use-
In order to achieve 100 dB / m or less, it is necessary to select a dielectric material so that the following relationship holds. f × ε _r ^1/2 × tan δ ≦ 0.8 In the formula, f is a frequency (GHz) to be used.

Examples of such a dielectric substrate 11 include alumina ceramics, glass ceramics, aluminum nitride ceramics, etc. For example, ceramic raw material powder is mixed with an appropriate organic solvent / solvent to form a sludge-like material. A plurality of ceramic green sheets are obtained by forming a sheet shape by adopting a conventionally known doctor blade method, calendar roll method, etc. After that, each of these ceramic green sheets is appropriately punched and laminated. It is manufactured by firing at a temperature of 1500 to 1700 ° C for alumina ceramics, 850 to 1000 ° C for glass ceramics, and 1600 to 1900 ° C for aluminum nitride ceramics.

As the pair of main conductor layers 12 and 13 and sub conductor layer 15, for example, when the dielectric substrate 11 is made of alumina ceramics, oxides such as alumina, silica, magnesia, etc. suitable for metal powder such as tungsten. And organic solvents
A paste is prepared by adding and mixing a solvent etc. on a ceramic green sheet so as to completely surround at least the transmission line by a thick film printing method, followed by firing at a high temperature of about 1600 ° C and a thickness of 10 ~ It is formed to have a thickness of 15 μm or more. As the metal powder, copper / gold / silver is suitable for glass ceramics, and tungsten / molybdenum is suitable for aluminum nitride ceramics. The thickness of the main conductor layers 12 and 13 is generally about 5 to 50 μm.

The penetrating conductors forming the side wall penetrating conductor group 14 may be formed of, for example, via-hole conductors or through-hole conductors, and the cross-sectional shape thereof is circular, which is easy to manufacture, or rectangular or rhombic. It may be polygonal. These through conductors are formed by, for example, punching a ceramic green sheet into a through hole, and embedding a metal paste similar to that of the main conductor layers 12 and 13 in the through hole.
Formed by firing at the same time as 11. The diameter of these through conductors is preferably 50 to 300 μm.

Next, an example of an embodiment of the waveguide type bandpass filter of the present invention using such a dielectric waveguide line will be described with reference to FIG.

FIG. 1 is a schematic perspective view showing an example of an embodiment of a waveguide type bandpass filter of the present invention. In the figure, 21 is a dielectric substrate having a thickness a, 22 and 23 are a pair of main conductor layers formed by sandwiching the dielectric substrate 21, and 24 is a signal wavelength in the signal transmission direction with a predetermined interval (width) b. Half of
Two groups of side wall through conductors formed by electrically connecting the main conductor layers 22 and 23 with a spacing c of less than 25, and 25 between the through conductors forming each row of the side wall through conductor group 24 are electrically connected to each other. A sub-conductor layer formed in parallel with the main conductor layers 22 and 23, which is electrically connected to each other, and is surrounded by a pair of main conductor layers 22 and 23, two rows of side wall through conductor groups 24, and a sub-conductor layer 25. It is a dielectric waveguide line constituted by a region. A part of the side wall in front of the dielectric waveguide line 26 is omitted for convenience of explanation.

The dielectric substrate 21, the main conductor layers 22 and 23, the side wall through conductor group 24, and the sub conductor layer 25 are formed in the same manner as in the dielectric waveguide line 16 used in the present invention. It

Further, 27 is a space d within the dielectric waveguide line 26 in the signal transmission direction, which is less than half the guide wavelength λg.
A short circuit in which an inductive window is formed by electrically connecting sub-conductor layers 25, which are formed in parallel with the main conductor layers 22 and 23 and which form side walls on both sides, arranged at (d <λg / 2). It is a conductor. A plurality of the short-circuit conductors 27 are formed in accordance with the specifications of the filter, which correspond to the short pins 2 in the waveguide type bandpass filter using the conventional rectangular waveguide.

The short-circuit conductor 27 may be formed of a conductor layer or the like. For example, when the dielectric substrate 21 is a ceramic substrate, the conductor pattern of the sub conductor layer 25 is printed on the ceramic green sheet forming the dielectric layer of the dielectric substrate 21, and at the same time the conductor pattern of the short-circuit conductor 27 is printed. It may be formed by

According to the present invention, the plurality of short-circuit conductors 27 forming the inductive window inside the dielectric waveguide line 26 are arranged at a predetermined distance d which is less than half the guide wavelength λg. By providing the short-circuit conductors 27 and adjusting the number, size, interval, etc. of the short-circuit conductors 27, a dielectric structure composed of a pair of main conductor layers 22 and 23, two rows of side wall through conductor groups 24, and sub conductor layers 25 is formed. The body waveguide line 26 corresponds to the rectangular waveguide 1 shown in FIG. 4, and the plurality of short-circuit conductors 27 correspond to the short pins 2 shown in FIG. A waveguide type band pass filter similar to the waveguide type band pass filter using the wave guide 1 can be formed according to the same principle.

According to the waveguide type band pass filter of the present invention as described above, the waveguide type band pass filter is a dielectric waveguide and is smaller than the conventional waveguide type band pass filter using the rectangular waveguide. Since it can be manufactured, it can be built in a dielectric substrate that constitutes a multilayer wiring substrate or a package for housing a semiconductor element, and it is a waveguide band pass filter that can easily be made smaller. Moreover, since it can be easily manufactured by a sheet laminating technique such as a green sheet laminating method, the waveguide band pass filter has high productivity and can be manufactured at low cost.

When arranging the short-circuit conductors 27 forming the inductive window in the waveguide type bandpass filter of the present invention, the intervals, the number and the size of the short-circuit conductors 27 functioning as short-circuit pins are the filter characteristics. Be involved in a complicated way. Therefore, it is possible to obtain a waveguide band pass filter having a desired band pass characteristic by repeatedly performing calculation by electromagnetic field analysis so as to satisfy the required filter characteristic.

Next, FIG. 2 shows another example of the embodiment of the waveguide type band pass filter of the present invention in a schematic perspective view similar to FIG. In this example, the configuration of the conventional waveguide type bandpass filter shown in FIG. 5 is realized by using the dielectric waveguide line 16 shown in FIG. 2 shows the internal structure of the waveguide type bandpass filter of the present invention as in FIG. 1. In FIG. 2, the same parts as those in FIG. 1 are designated by the same reference numerals. In addition, as in FIG. 1, the dielectric waveguide line 26
For convenience of explanation, a part of the side wall in front of is omitted for illustration.

In FIG. 2, reference numeral 28 denotes a short-circuit conductor 27 and another short-circuit conductor 27 which are arranged inside the dielectric waveguide line 26 at a distance d which is less than half the guide wavelength λc in the signal transmission direction. These are through conductors that electrically connect to the main conductor layers 22 and 23 and form an inductive window together with the short-circuit conductor 27. The plurality of through-conductors 28 are induction conductors similar to the short-circuit plate 3 shown in FIG. A plurality of flexible windows are formed in accordance with the specifications of the filter and are disposed in the waveguide so as to form a flexible window.

As described above, the plurality of short-circuit conductors 27 extending inside the dielectric waveguide line 26, and the short-circuit conductors 27 and other short-circuit conductors 27 or the main conductor layers 22 and 23 are electrically connected. By disposing the inductive window formed by the plurality of through conductors 28 connected to each other at a predetermined distance d which is less than one half of the in-tube wavelength λg, a pair of main conductor layers 22 and 23 and two rows of side walls are provided. Through conductor group
Dielectric waveguide line 26 composed of 24 and sub-conductor layer 25
Corresponds to the rectangular waveguide 1 shown in FIG. 5, and includes a plurality of short-circuit conductors.
The inductive window formed by 27 and the through conductor 28 corresponds to the short-circuit plate 3 shown in FIG. 5, and the same principle as the waveguide band pass filter shown in FIGS. 4 and 5 is obtained. Thereby, a waveguide band pass filter similar to the waveguide band pass filter using the rectangular waveguide shown in FIG. 5 can be formed.

The waveguide-type bandpass filter of the present invention as described above also becomes a waveguide-type bandpass filter which can be easily downsized, has high productivity, and can be manufactured at low cost.

When the short-circuit conductor 27 and the through conductor 28 forming the inductive window are arranged as in this example, the analysis simulator is designed to satisfy the required filter specifications as in the case of the short-circuit conductor 27 described above. Is used to obtain a waveguide bandpass filter having a desired bandpass characteristic.

The through conductors 28 are the side wall through conductor groups 24.
It may be formed as described above similarly to the through conductor.
Moreover, the cross-sectional shape is not limited to a circular shape, and may be an elliptical shape, a triangular shape, a quadrangular shape, a polygonal shape, or a flat plate shape depending on a desired bandpass characteristic.

The present invention is not limited to the examples of the above embodiments, and various modifications and improvements can be made without departing from the gist of the present invention. For example, in the above example, the resonance part has four stages (L _{1 to} L ₄ ), but a multistage filter may be used according to the specifications of the filter.

[0048]

As described above in detail, according to the waveguide type bandpass filter of the present invention, the inside of the dielectric waveguide line is
A short-circuit conductor which is formed by electrically connecting the sub-conductor layers in parallel with the main conductor layer, and electrically connects the side walls formed by the sidewall through conductor group and the sub-conductor layer to form an inductive window. Since the waveguides are arranged in the signal transmission direction at intervals of less than one half of the guide wavelength λg, the waveguide serves as a dielectric waveguide and a waveguide type bandpass using a conventional rectangular waveguide. Since it can be made smaller than a filter, it can be made in a dielectric substrate such as a multilayer wiring board, and it is a waveguide bandpass filter that can easily be made smaller, and moreover, it is a green sheet laminate. Since it can be easily manufactured by a sheet laminating technique such as a method, it is a waveguide type bandpass filter which has high productivity and can be manufactured at low cost.

Further, according to the waveguide type bandpass filter of the present invention, the short-circuit conductor is electrically connected to the other short-circuit conductor or the main conductor layer inside the dielectric waveguide line, and the short-circuit conductor is formed. When the through conductor forming the inductive window is formed together with the short-circuit conductor and the through conductor to form the inductive window, the conductor becomes an electrical wall to form the inductive window. Since the number of portions is increased, the concentration of current on the conductor is alleviated, and the energy loss due to the conductor is reduced, resulting in less loss of electromagnetic waves and better filter characteristics.

As described above, according to the present invention, as a waveguide type bandpass filter using a dielectric waveguide line, there is provided a waveguide type bandpass filter which has high productivity and can be made compact. I was able to.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing an example of an embodiment of a waveguide type bandpass filter of the present invention.

FIG. 2 is a schematic perspective view showing another example of the embodiment of the waveguide type bandpass filter of the present invention.

FIG. 3 is a schematic perspective view for explaining a dielectric waveguide line related to a waveguide band pass filter of the present invention.

FIG. 4 is a schematic perspective view showing an example of a conventional waveguide type bandpass filter.

FIG. 5 is a schematic perspective view showing another example of a conventional waveguide type bandpass filter.

[Explanation of symbols]

11, 21 ... Dielectric substrate 12, 13, 22, 23 ... Main conductor layer 14, 24 ... Side wall through conductor group 15、25 ・ ・ ・ ・ ・ ・ ・ ・ Sub conductor layer 16, 26 ... ・ ・ ・ Dielectric waveguide line 27 ... Short-circuit conductor 28 ...

Claims (2)

(57) [Claims] 1. A pair of main conductor layers sandwiching a dielectric substrate and two columns formed by electrically connecting the main conductor layers at an interval of less than one-half of a signal wavelength in a signal transmission direction. The side wall through conductor group and a sub conductor layer which is formed between the main conductor layers in parallel with the main conductor layer and is electrically connected to the side wall through conductor group. Is formed in parallel with the main conductor layer inside the dielectric waveguide line that transmits a high frequency signal by a region surrounded by the through conductor group and the sub conductor layer, and electrically connects the sub conductor layers. A waveguide band-pass filter, wherein a plurality of short-circuit conductors forming an inductive window are arranged in the signal transmission direction at intervals of less than ½ of the guide wavelength. 2. A through conductor that electrically connects the short-circuit conductor to another short-circuit conductor or the main conductor layer inside the dielectric waveguide line, and forms the inductive window together with the short-circuit conductor. The waveguide type band pass filter according to claim 1, wherein the band pass filter is formed.