JPH11284409A - Waveguide type bandpass filter - Google Patents

Abstract

(57) [Summary] [PROBLEMS] In a waveguide type bandpass filter using a rectangular waveguide, miniaturization cannot be achieved and productivity is low. A pair of main conductor layers sandwiching a dielectric substrate (21)
22 formed by electrically connecting the main conductor layers 22 and 23 at an interval of less than half the signal wavelength in the signal transmission direction.
A main conductor layer 22
An electrically inductive window is formed by electrically connecting the main conductor layers 22 and 23 inside the dielectric waveguide line 25 for transmitting a high-frequency signal by the region surrounded by 23 and the through conductor group 24 for the side wall. The plurality of through conductors 26 in the signal transmission direction make up a half of the guide wavelength.
And a waveguide-type band-pass filter disposed at an interval of less than. A waveguide-type bandpass filter having a small size, high productivity, and good characteristics is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveguide band-pass filter using a dielectric waveguide for transmitting 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. These high-frequency techniques require a band-pass filter that passes only a high-frequency signal of a specific frequency.

There are various types of high-frequency band-pass filters, and a waveguide-type band-pass filter using a rectangular waveguide is known as having a good band-pass characteristic. These include, for example, those having the structure shown in schematic perspective views in FIGS.

[0004] The structure shown in FIG.
The short pins 2 (2a to 2e) such as a plurality of metal rods forming an inductive window inside the inside are vertically connected to a half of the guide wavelength λg.
A bandpass filter is formed by arranging in the signal transmission direction at an interval d (d <λg / 2) less than.

According to this structure, the short pin 2c or the short pin groups 2a to 2
By e, the width of the waveguide is divided into half or less of the cutoff wavelength. As a result, the electromagnetic wave propagating through the waveguide by short pins 2 is reflected, region L ₁ ~L ₄ shown in the figure may be regarded as electrically closed space. This closed space has a unique resonance mode, and functions as a resonator that resonates at the lowest frequency when the length d is λg / 2. In the case of the structure shown in FIG. 6, it can be considered that four resonators formed by the wall by the short pins 2 are coupled in series to the waveguide.

As described above, the electromagnetic wave propagating through the waveguide 1 from the left input side in FIG.
Although it can not be transmitted by a, natural resonance frequency as the energy from between the short pins 2a in the case of a match (inductive window) in the resonance region L ₁ by electromagnetic coupling with the frequency of the electromagnetic waves of the resonator mentioned above Flows in. Similarly, from L ₁ to L _2, from L ₂ to L _3, L ₄ from L ₃
Energy propagates from the right output side in FIG. 6 of the waveguide 1 again as an electromagnetic wave. Therefore, only the electromagnetic wave having a specific frequency can pass through the region of these structures, thereby operating as a band-pass filter.

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

In the structure shown in FIG. 7, a short plate 3 such as a plurality of metal plates forming an inductive window (inductive wall) inside a rectangular waveguide 1 is similarly vertically arranged with a guide wavelength λg. Are arranged in the signal transmission direction at an interval d (d <λg / 2) of less than one half of the bandpass filter to form a band-pass filter.

According to this, the short plate 3 and the inductive window formed by the short plate 3 function in exactly the same manner as the short pins 2 and the gaps therebetween, thereby forming a bandpass filter.

[0010]

A conventional band-pass filter using a rectangular waveguide having such a structure has a problem that although it has excellent band-pass characteristics for high-frequency signals, it is difficult to process at the time of fabrication. . For this reason, there was a problem that productivity was low and as a result the cost was high.

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

SUMMARY OF THE INVENTION The present invention has been made 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 can cope with miniaturization.

[0013]

The present inventors have repeatedly studied the above problems, and as a result, are shown in schematic perspective views in FIGS. 4 and 5, respectively, in place of the conventional rectangular waveguide. For two rows of side walls formed by electrically connecting the main conductor layers at intervals of less than half the signal wavelength in the signal transmission direction in the dielectric substrate sandwiched between a pair of main conductor layers A dielectric waveguide line having a waveguide sidewall formed by a group of through conductors (see Japanese Patent Application Laid-Open No. 6-53711 and Japanese Patent Application No. 8-229925).
And a plurality of through conductors corresponding to short pins forming an inductive window are formed inside the dielectric waveguide line, and are disposed at intervals of less than half the guide wavelength in the signal transmission direction. As a result, it has been found that a waveguide type bandpass filter similar to the structure shown in FIGS. 6 and 7 can be manufactured using the dielectric waveguide line.

The waveguide band-pass filter according to the present invention is characterized in that a pair of main conductor layers sandwiching a dielectric substrate are electrically connected between the main conductor layers at an interval of less than half the signal wavelength in the signal transmission direction. And a two-row side wall penetrating conductor group formed to be connected to the main conductor layer and a region surrounded by the side wall penetrating conductor group. Inside, a plurality of through conductors that electrically connect the main conductor layers to form an inductive window are arranged at intervals of less than half a guide wavelength in the signal transmission direction. Is what you do.

In the above-mentioned structure, a sub-conductor layer electrically connected to the side wall penetrating conductor group may be parallel to the main conductor layer between the main conductor layers. It is characterized by being formed in.

Further, in the waveguide type band pass filter according to the present invention, in the waveguide type band pass filter having the above-mentioned structure, wherein the sub conductor layer is formed, the sub conductor layer is formed of the dielectric waveguide line. It extends inside and is electrically connected to the through conductor, and forms the inductive window together with the through conductor.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a waveguide type bandpass filter according to the present invention will be described with reference to the drawings.

FIGS. 4 and 5 are schematic perspective views showing the structure of a dielectric waveguide used in the waveguide type bandpass filter of the present invention. In these figures, reference numeral 11 denotes a dielectric substrate, 12 and 13 denote a pair of main conductor layers sandwiching the dielectric substrate 11, and 14 denotes a main conductor layer 12 and 12 at an interval of less than half the signal wavelength in the signal transmission direction. 13 are two rows of through-hole conductor groups for side walls formed by electrically connecting between 13.

According to FIGS. 4 and 5, a pair of main conductor layers 12 and 13 are formed at positions sandwiching a dielectric substrate 11 having a predetermined thickness a. 11 are formed on the upper and lower surfaces sandwiching at least the waveguide line forming position. 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, forming two rows of side wall through conductor groups 14. doing.

The two rows of penetrating conductor groups 14 for the side walls have a predetermined interval (width) b and are １ of the signal wavelength in the signal transmission direction.
It is formed with a predetermined distance c smaller than the above, thereby forming a side wall in the dielectric waveguide line.

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.
4 and 5, the portions corresponding to the H and E planes of the dielectric waveguide are the main conductor layers 12 and 13 and the through conductor groups 14 for the side walls, respectively. If the thickness a is about twice as large as the interval b, the portions corresponding to the E-plane and the H-plane of the dielectric waveguide are respectively the main conductor layers.
12 and 13 and the through conductor group 14 for the side wall.
Further, the interval c is set to be less than half the signal wavelength (cutoff wavelength), so that the side wall through conductor group 14 forms an electrical wall.

Since a TEM wave can propagate between a pair of main conductor layers 12 and 13 arranged in parallel, if the distance c between the side wall penetrating conductor groups 14 is larger than the signal wavelength, that is, the cutoff wavelength λc, this waveguide is formed. Even if an electromagnetic wave is supplied to the pipe line, the electromagnetic wave does not propagate along the pseudo waveguide formed here. However, if the distance c between the side wall through conductor groups 14 is smaller than the cutoff wavelength λc, the electromagnetic wave cannot propagate in a direction perpendicular to the waveguide line, and reflects while transmitting the signal in the signal transmission direction of the waveguide line. Is propagated to As a result, according to the configurations shown in FIGS. 4 and 5, a region having a cross-sectional area of a × b size surrounded by the pair of main conductor layers 12 and 13 and the two rows of penetrating conductor groups for side walls 14 is a dielectric waveguide. It becomes the pipe line 15.

In FIG. 5, reference numeral 16 denotes a through conductor group for a side wall.
Electrically connecting through conductors forming each row of 14,
This is a sub-conductor layer formed in parallel with the main conductor layers 12 and 13, and is appropriately formed as desired. By forming such a sub-conductor layer 16, when viewed from the inside of the dielectric waveguide line 15, the side wall of the line becomes a fine lattice shape by the side wall through conductor group 14 and the sub-conductor layer 16, and The effect of shielding electromagnetic waves from the object can be further enhanced.

In these embodiments, the through conductor group for the side wall is used.
Although 14 is formed in two rows, the through conductor groups 14 for side walls are arranged in four rows or six rows, and pseudo conductor walls formed by the through conductor groups 14 for side walls are formed in two or three layers. Thereby, leakage of electromagnetic waves from the conductor wall can be more effectively prevented.

According to the above-described dielectric waveguide line, since the transmission line is formed by a dielectric waveguide, the size of the waveguide is determined by setting the relative permittivity of the dielectric substrate 11 to ε. Of 1
/ √ε. Therefore, as the dielectric substrate 11 is made of a material having a large relative permittivity ε, the waveguide size can be reduced, and a multilayer wiring board, a semiconductor element housing package, or an inter-vehicle radar on which wiring is formed at high density The transmission line has a size usable as a transmission line.

As described above, the through conductors forming the side wall through conductor group 14 are arranged at an interval c smaller than half the cutoff wavelength λc, and this interval c realizes good transmission characteristics. In order to achieve this, it is desirable to have a constant repetition interval, but it goes without saying that the interval may be appropriately changed or some value may be combined as long as the interval is less than half the cutoff wavelength λc.

The dielectric substrate 11 constituting such a dielectric waveguide is not particularly limited as long as it functions as a dielectric and has a characteristic that does not hinder transmission of high-frequency signals. The dielectric substrate 11 is desirably made of ceramics from the viewpoint of accuracy in forming the transmission line and easiness of manufacturing.

As such ceramics, ceramics having various relative dielectric constants have been known.
In order to transmit a high-frequency signal by the waveguide line of the present invention, it is desirable that the waveguide line be a paraelectric substance. This is because ferroelectric ceramics generally have large dielectric loss and high transmission loss in a high frequency range. Therefore, the dielectric substrate
It is appropriate that the relative permittivity ε _r of 11 is about 4 to 100.

In general, the line width of a wiring layer formed on a multilayer wiring board, a package for housing semiconductor elements or an inter-vehicle radar is at most about 1 mm, so that a material having a relative dielectric constant of 100 is used, and If the plane, ie the magnetic field is used so as to form an electromagnetic field distribution parallel to the upper plane, the minimum frequency that can be used is calculated as 15 GHz,
It can also be used in the microwave band. On the other hand, a dielectric made of a resin generally used as the dielectric substrate 11 has a relative permittivity ε _r of about 2, and therefore cannot be used unless the line width is 1 mm or more than about 100 GHz. Becomes

Further, among such paraelectric ceramics, many have very small dielectric loss tangents, such as alumina and silica, but not all paraelectric ceramics can be used. In the case of a 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, and the loss due to the dielectric α
(DB / m) is expressed as follows. α = 27.3 × tan δ / [λ / {1- (λ / λc) ² }
^1/2 ] where tan δ: dielectric loss tangent of the dielectric λ: wavelength in the dielectric λc: cut-off wavelength According to the standardized rectangular waveguide (WRJ series) shape, ｛1- ( λ / λc) ² ｝ ^1/2 is about 0.75.

Therefore, the transmission loss is practically usable.
In order to make it 100 dB / m or less, it is necessary to select a dielectric so that the following relationship is satisfied.

F × ε _r ^1/2 × tan δ ≦ 0.8 where f is a frequency (GHz) to be used.

Examples of such a dielectric substrate 11 include alumina ceramics, glass ceramics, and aluminum nitride ceramics. For example, an appropriate organic solvent and a solvent are added to and mixed with ceramic raw material powder to form a slurry. A plurality of ceramic green sheets are obtained by forming a sheet by employing a conventionally known doctor blade method or calender roll method, and thereafter, each of these ceramic green sheets is subjected to appropriate punching 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.

When the dielectric substrate 11 is made of alumina ceramics, for example, an oxide such as alumina, silica, magnesia, or an organic solvent or a solvent suitable for a metal powder such as tungsten is used as the pair of main conductor layers 12 and 13. What was added and mixed into a paste was printed on a ceramic green sheet by a thick film printing method so as to completely cover at least the transmission line, and then fired at a high temperature of about 1600 ° C.
It is formed so as to have a thickness of 10 to 15 μm or more. In addition,
As the metal powder, copper / gold / silver is preferable for glass ceramics, and tungsten / molybdenum is preferable for aluminum nitride ceramics. The main conductor layer 12
The thickness of 13 is generally about 5 to 50 μm.

The through conductor constituting the side wall through conductor group 14 may be formed by, for example, a via-hole conductor or a through-hole conductor. It may be a polygon. These through conductors are, for example, filled with the same metal paste as the main conductor layers 12 and 13 in through holes produced by punching a ceramic green sheet, and then a dielectric substrate
Simultaneously with 11 to form. These through conductors preferably have a diameter of 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 will be described with reference to FIGS. 1 and 2. FIG.

FIG. 1 is a schematic perspective view showing an example of an embodiment of a waveguide band-pass filter of the present invention, and FIG. 2 is a plan view. In these figures, reference numeral 21 denotes a dielectric substrate having a thickness a, 22 and 23 denote a pair of main conductor layers formed to sandwich the dielectric substrate 21, and 24 denotes a signal at a predetermined interval (width) b in a signal transmission direction. Two rows of side wall penetrating conductor groups formed by electrically connecting the main conductor layers 22 and 23 at an interval c of less than half the wavelength (cutoff wavelength λc), 25 is a pair of main conductor layers 22 A dielectric waveguide line portion defined by a region surrounded by 23 and two rows of through-hole conductor groups 24 for side walls.

The dielectric substrate 21, the main conductor layers 22 and 23, and the through conductor group 24 for the side wall are configured in the same manner as the above-described dielectric waveguide line used in the present invention.

In these figures, diagonal lines are shown.
Reference numeral 26 designates a gap between the main conductor layers 22 and 23 which is disposed in the dielectric waveguide line 25 in the signal transmission direction at an interval d (d <λg / 2) of less than half the guide wavelength λg. A plurality of through conductors that are electrically connected to form an inductive window.

According to the present invention, a plurality of through conductors 26 forming an inductive window inside the dielectric waveguide line 25 are arranged at a predetermined interval d less than half the guide wavelength λg. By adjusting the number of the through conductors 26 and adjusting the number of the through conductors 26, a dielectric waveguide line 25 composed of a pair of main conductor layers 22 and 23 and two rows of side wall through conductor groups 24 is shown in FIG. 6 and the plurality of through conductors 26 correspond to the short pins 2 shown in FIG. 6, and a waveguide band pass using the rectangular waveguide shown in FIG. A similar waveguide type bandpass filter can be formed by the same principle as that of the filter.

According to such a waveguide band-pass filter of the present invention, a dielectric waveguide is used, which is smaller than a conventional waveguide band-pass filter using a rectangular waveguide. Since it can be manufactured, it can be built in a dielectric substrate that constitutes a multilayer wiring board or a package for accommodating a semiconductor element, and a waveguide-type bandpass filter that can be easily adapted to miniaturization can be obtained. In addition, since it can be easily manufactured by a sheet laminating technique such as a green sheet laminating method, a waveguide type bandpass filter which has high productivity and can be manufactured at low cost can be obtained.

When a plurality of through conductors 26 forming an inductive window are provided in the waveguide type bandpass filter of the present invention, the distance, number, size, etc., of the through conductors 26 functioning as short pins are determined. Complexly involved in filter characteristics. Therefore, by repeatedly performing calculations by electromagnetic field analysis so as to satisfy the required filter characteristics, a waveguide band-pass filter having desired band-pass characteristics is obtained.

In the waveguide type bandpass filter shown in FIGS. 1 and 2, a plurality of through conductors 26 forming an inductive window with respect to the dielectric waveguide line shown in FIG. 4 are provided. The main conductor layers 22 and 23 are further provided between the main conductor layers 22 and 23, as in the dielectric waveguide line shown in FIG.
May be formed in parallel with the sub-conductor layer electrically connected to the side wall through conductor group 24. When the sub-conductor layer is formed in such a manner, the pseudo conductor wall formed by the side wall through conductor group 24 is further strengthened as an electric wall, so that the electromagnetic wave transmission characteristics and shielding effect are further enhanced. Thus, a waveguide-type band-pass filter having good band-pass characteristics can be obtained.

Next, FIG. 3 shows another embodiment of the waveguide band-pass filter of the present invention in a plan view similar to FIG. FIG. 3 is a plan view showing the internal structure of the waveguide band-pass filter of the present invention as in FIG. 2, and the same reference numerals in FIG. 3 denote the same parts as in FIG.

FIG. 3 shows a conventional waveguide type band shown in FIG. 7 using the dielectric waveguide line according to the present invention having the sub-conductor layer 16 shown in FIG. 5 as the dielectric waveguide line. This realizes a configuration of a pass filter. In FIG. 3, reference numeral 27 denotes the inside of the dielectric waveguide 25 in the signal transmission direction, and
A plurality of through conductors, which are arranged at an interval d of less than one part and form an inductive window by electrically connecting between the main conductor layers 22 and 23, and the plurality of through conductors 27 are shown in FIG. Are arranged in the waveguide so as to form an inductive window similar to the short plate 3 shown in FIG.

Reference numeral 28 denotes a sub-conductor layer. In this example, the sub-conductor layer 28 is electrically connected to the two rows of side wall penetrating conductor groups 24 in each row, and includes a pair of main conductor layers. A plurality of through conductors 27 extending inside a dielectric waveguide line 25 formed by a region surrounded by 22 · 23 and two rows of side wall through conductor groups 24 to form an inductive window; Are electrically connected to each other on the side of the side wall through-conductor group 24, and the extended portion forms an inductive window together with the through-conductor 27.

As described above, the inductive window formed by the plurality of through conductors 27 and the sub-conductor layer 28 extended inside the dielectric waveguide 25 and electrically connected to the through conductors 27 is formed. Are arranged at a predetermined interval d that is less than half of the guide wavelength λg, whereby a dielectric waveguide composed of a pair of main conductor layers 22 and 23 and two rows of side wall through conductor groups 24 is formed. The line 25 corresponds to the rectangular waveguide 1 shown in FIG. 7, and the inductive window formed by the plurality of through conductors 27 and the sub-conductor layers 28 corresponds to the short plate 3 shown in FIG. 6 and 7
A waveguide-type bandpass filter similar to the waveguide-type bandpass filter using the rectangular waveguide shown in FIG. 7 is formed on the same principle as the waveguide-type bandpass filter shown in FIG. Can be.

The waveguide band-pass filter of the present invention as described above also provides a waveguide band-pass filter that can be easily adapted to miniaturization, has high productivity, and can be manufactured at low cost.

In the case where a plurality of through conductors 27 and sub-conductor layers 28 forming an inductive window are provided as in this example, as in the case of the above-described through conductor 26, the required filter specifications are satisfied. By using an analysis simulator, a waveguide band-pass filter having desired band-pass characteristics is obtained.

The plurality of through conductors 26 and 27 may be formed as described above, similarly to the through conductors of the side wall through conductor group 24. Further, the cross-sectional shape is not limited to a circle, but may be an ellipse, a triangle, a square, a polygon, or a flat plate according to a desired band-pass characteristic.

It should be noted that the present invention is not limited to the above-described embodiments, and that various changes and improvements can be made without departing from the scope of the present invention. For example, in the above example, the filter has four stages (L _{1 to} L ₄ ) of the resonance unit, but a multi-stage filter may be used according to the specifications of the filter.

[0052]

As described above in detail, according to the waveguide band-pass filter of the present invention, the inside of the dielectric waveguide line is
Because a plurality of through conductors that electrically connect the pair of main conductor layers sandwiching the dielectric substrate to form an inductive window are arranged in the signal transmission direction at an interval of less than half the guide wavelength λg. Since it is a dielectric waveguide, it can be made smaller than a conventional waveguide type band-pass filter using a rectangular waveguide, so that it can be built in a dielectric substrate such as a multilayer wiring board. It is a waveguide bandpass filter that can be easily adapted to miniaturization, and can be easily manufactured by a sheet laminating technique such as a green sheet laminating method, so that high productivity and inexpensive manufacturing are possible. It becomes a waveguide type band pass filter.

According to the waveguide bandpass filter of the present invention, when the sub-conductor layer electrically connected to the side wall through conductor group is formed between the main conductor layers in parallel with the main conductor layer. Since the pseudo conductor wall formed by the through conductor group for the side wall is further strengthened as an electrical wall, the transmission characteristics and shielding effect of the electromagnetic wave can be further enhanced, and the waveguide having a good bandpass characteristic can be obtained. It becomes a tubular band-pass filter.

Further, according to the waveguide type bandpass filter of the present invention, the sub-conductor layer extends inside the dielectric waveguide line and is electrically connected to the through conductor forming the inductive window. In the case where an inductive window is formed together with the through conductor,
Since the number of conductors forming the inductive window is increased, current concentration on the conductors is reduced, and energy loss due to the conductors is reduced, resulting in more excellent characteristics.

As described above, according to the present invention, there is provided a waveguide type band pass filter which is highly productive and can be miniaturized as a waveguide type band pass filter using a dielectric waveguide line. I was able to.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of an embodiment of a waveguide band-pass filter of the present invention.

FIG. 2 is a plan view showing an example of an embodiment of a waveguide band-pass filter according to the present invention.

FIG. 3 is a plan view showing another example of the embodiment of the waveguide band-pass filter of the present invention.

FIG. 4 is a perspective view for explaining a dielectric waveguide line according to the waveguide band-pass filter of the present invention.

FIG. 5 is a perspective view illustrating a dielectric waveguide line according to the waveguide band-pass filter of the present invention.

FIG. 6 is a perspective view showing an example of a conventional waveguide band-pass filter.

FIG. 7 is a perspective view showing another example of a conventional waveguide band-pass filter.

[Explanation of symbols]

 11, 21 ... Dielectric substrate 12, 13, 22, 23 ... Main conductor layer 14, 24 ... Through-hole conductor group for side wall 15, 25 ... ..... Dielectric waveguide lines 26, 27 ...

Claims (3)

[Claims] A pair of main conductor layers sandwiching a dielectric substrate, and two rows of main conductor layers formed by electrically connecting the main conductor layers at intervals of less than half the signal wavelength in a signal transmission direction. A side wall penetrating conductor group, and electrically connects the main conductor layer to the inside of a dielectric waveguide line transmitting a high-frequency signal by a region surrounded by the main conductor layer and the side wall penetrating conductor group. A plurality of through conductors that are connected to each other to form an inductive window are disposed in the signal transmission direction at an interval of less than half the guide wavelength. 2. The conductor according to claim 1, wherein a sub-conductor layer electrically connected to said side wall through conductor group is formed between said main conductor layers in parallel with said main conductor layer. Wave tube type band pass filter. 3. The sub-conductor layer extends inside the dielectric waveguide and is electrically connected to the through conductor.
3. The waveguide band-pass filter according to claim 2, wherein said inductive window is formed together with said through conductor.