WO2010125806A1 - Waveguide filter and communication access device - Google Patents

Abstract

Disclosed is a waveguide filter provided with: a dielectric substrate that is provided on an E surface of a waveguide and has a first surface and a second surface; a conductive pattern that is provided on the first surface of the dielectric substrate and comprises a conductive material having a slit that extends in the direction of signal propagation; a plurality of through-holes that are filled with a conductive material and are provided along the aforementioned slit so as to connect the second surface of the dielectric substrate to the conductive pattern area on the first surface of the dielectric substrate; a ground pattern that comprises a conductive material and is provided on the second surface of the dielectric substrate, except for where the aforementioned through-holes are exposed; a plurality of switching elements that can electrically connect or disconnect the ground pattern to/from the plurality of exposed through-holes on the second surface; and a center-frequency correction unit that controls whether the plurality of switching elements are on or of, thereby increasing or decreasing the number of through-holes connected to the ground pattern and consequently correcting a center frequency.

Description

Waveguide filter, communication access device

The present invention relates to frequency adjustment of a high frequency filter, particularly a waveguide filter.

In a millimeter wave band wireless access device, a high frequency BPF (Band Pass Filter) is used for a high frequency input / output unit in order to remove unnecessary waves.
An example of the high frequency BPF will be described with reference to FIG. The high frequency BPF shown in FIG. 8 is also called an E-plane waveguide type BPF. The high-frequency BPF is configured by sandwiching thin metal fins 130 having a plurality of windows by split bodies 110 and 120 each having a rectangular cross section divided into two along the signal propagation direction at the center of the H plane. ing.

Such an E-plane waveguide type BPF has characteristics as a BPF determined by the shape of the metal fin 130 and the waveguide (particularly, the length of the long side (width) of the cross section of the rectangular waveguide). . For this reason, for example, in order to change the center frequency of the BPF, it is necessary to change the shape of the metal fin 130 or the cross-sectional shape of the rectangular waveguide.

On the other hand, for the purpose of expanding the frequency band that can be covered, a BPF in which the center frequency and the frequency bandwidth can be electrically adjusted is disclosed in Patent Document 1, for example.

Briefly, this BPF is formed by replacing the metal fin 130 shown in FIG. 8 with a three-layer substrate provided with a resonator, and mounting an active element in the resonator. In this BPF, the center frequency or bandwidth is adjusted by applying a bias voltage to the active element from the outside of the three-layer substrate through the line pattern on the inner layer of the three-layer substrate.

Japanese Unexamined Patent Publication No. 2007-88545

However, even with the BPF disclosed in Patent Document 1, dynamic frequency adjustment cannot be expected because the adjustable frequency range is narrow, and it is difficult to satisfy the characteristics actually required for the apparatus.

In addition, mechanical parts such as a waveguide constituting the BPF are generated within a range having a difference at the time of manufacture, thereby causing a problem that characteristics of the center frequency and reflection loss are deviated from design values. In particular, in the E-plane waveguide type BPF, the influence on the shift of the center frequency due to the manufacturing range of the mechanical parts is large. The center frequency deviation due to the manufacturing range of the mechanical parts depends on the manufacturing method, but in cutting, about ± 100 MHz occurs in the 22 GHz band. In addition, the mechanical component expands and contracts due to temperature, and the center frequency fluctuates by about several tens of MHz in the 22 GHz band due to the influence. When both of these deviations are combined, the maximum is about 300 Hz.
Conventionally, an adjustment screw for adjusting a shifted characteristic has been provided for this problem. However, this requires processing costs, component costs, and adjustment labor and costs. In addition, a design in which the deviation of the center frequency does not easily occur is made by tightening the manufacturing range or using a material having a small temperature fluctuation. In this case, the processing cost and material cost of the mechanism parts are required.

The present invention has been made based on such a technical problem. The center frequency can be easily changed without changing the shape of the metal fin and the waveguide, particularly the cross-sectional size, and the cost can be reduced. It is an object of the present invention to provide a waveguide filter or the like that can correct the center frequency shift while suppressing it.

The waveguide filter according to the present invention is provided on the E surface of the waveguide, and is provided on a dielectric substrate having a first surface and a second surface, and on the first surface of the dielectric substrate. A conductive pattern made of a conductive material having a slit extending in the propagation direction, and along the slit so as to pass from the region of the conductive pattern on the first surface of the dielectric substrate to the second surface of the dielectric substrate. Provided in a region excluding a plurality of through-hole portions that are a plurality of through-holes filled with a conductive material and a region where the through-hole portion is exposed on the second surface of the dielectric substrate. A ground pattern made of a conductive material, a plurality of through holes exposed on the second surface, and a plurality of slots that can electrically connect the ground pattern. Comprising a switching element, each of the on of the plurality of switching elements, by increasing or decreasing the number of the through-hole portion by controlling the off connected to the ground pattern, and a center frequency correcting unit for correcting the center frequency.

The communication access device of the present invention includes the above waveguide filter.

According to the present invention, the shift of the center frequency can be corrected by increasing / decreasing the number of through-hole portions connected to the ground pattern by controlling on / off of the plurality of switching elements. Therefore, the center frequency shifts according to the degree of manufacturing difference and temperature of the mechanical parts, while reducing the cost of the mechanical parts, without using adjustment screws, tightening manufacturing differences, and using materials with small temperature fluctuations. The structure which can correct | amend is realizable.

It is a perspective view of the E-plane waveguide type BPF in this embodiment. It is a perspective view which shows the metal fin which is a part of component of the E surface waveguide type BPF shown to FIG. 1A. It is the figure which looked at the dielectric substrate which is a part of component of the E surface waveguide type BPF shown by FIG. 1A from the inner surface side. It is the figure which looked at the dielectric substrate which is a part of component of the E surface waveguide type BPF shown by FIG. 1A from the outer surface side. FIG. 2C is a sectional view taken along line C-C ′ shown in FIG. 2B. It is a figure which shows the control circuit of the switching element provided in the dielectric substrate in this embodiment. It is sectional drawing of the dielectric substrate equivalent to the state which insulated all the through-hole parts from the ground pattern in this embodiment. It is sectional drawing of the dielectric substrate equivalent to the state which connected all the through-hole parts in this embodiment with the ground pattern. It is a figure which shows the attenuation | damping characteristic simulated in the 22 GHz band about BPF without a slit, and the E-plane waveguide type BPF in this embodiment. It is a figure which shows the result of having simulated about the difference in the center frequency of BPF by the difference in the slit width of the conductive pattern provided in a dielectric substrate about the E surface waveguide type BPF in this embodiment. It is a figure which shows the result of having simulated the difference in the center frequency of BPF when the number of the through-hole parts connected to a ground pattern is varied about E plane waveguide type BPF in this embodiment. It is a disassembled perspective view for demonstrating an example of the conventional E surface waveguide type BPF.

Hereinafter, an embodiment for carrying out a waveguide filter according to the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to only these examples.

1A and 1B illustrate an E-plane waveguide type BPF (waveguide filter) in the present embodiment.
In FIG. 1A, an E-plane waveguide type BPF (hereinafter abbreviated as BPF as appropriate) is composed of divided bodies 1 and 2 and metal fins 3. The divided bodies 1 and 2 are formed by dividing a rectangular waveguide into two along the signal propagation direction on the H plane hp. The metal fin 3 is sandwiched between these divided bodies 1 and 2. As shown in FIG. 1B, the metal fin 3 has a plurality of windows W1.

In each of the divided bodies 1 and 2, a portion corresponding to the E plane ep is formed by the dielectric substrates 10 and 20. The parts other than the dielectric substrates 10 and 20 in the divided bodies 1 and 2, that is, the parts corresponding to the upper and lower H surfaces hp are formed by metal walls 4, 4 ′, 5 and 5 ′. In FIG. 1A, the arrow D1 indicates the size in the width direction of the cross section of the waveguide, that is, the distance between two E surfaces ep facing each other. *

The dielectric substrate 10 will be described with reference to FIGS. 2A to 2C. The dielectric substrate 10 has a substrate body 11 made of a dielectric material. A conductive pattern 12 made of a conductive layer having a slit S10 having a width G extending in the signal propagation direction is formed on one surface of the dielectric substrate 10 on the inner surface side of the waveguide. A ground pattern 13 made of a conductor layer is formed on the remaining portion including the other surface on the outer surface side of the waveguide in the dielectric substrate 10.

When the dielectric substrates 10 and 20 are mounted on the metal walls 4, 4 ′, 5, and 5 ′, the dielectric substrates 10 and 20 become conductive with the conductive patterns 12. A method for attaching the dielectric substrates 10 and 20 to the metal walls 4, 4 ′, 5, and 5 ′ is not particularly limited, and various methods such as screwing, soldering, or conductive adhesive can be used.

The dielectric substrates 10 and 20 are formed with a plurality of through-hole portions TH1 on both sides facing each other with the slit S10 interposed therebetween and spaced from each other in the signal propagation direction along the slit S10. The through hole portion TH1 is configured by filling a through hole penetrating the substrate body 11 with a conductive material.
On the outer surface side of the dielectric substrates 10 and 20, the region corresponding to the through hole portion TH1 and the ground pattern 13 in the surrounding region are removed, and the exposed through hole portion TH1 and the ground pattern 13 are electrically insulated. It is said that.

As shown in FIG. 3, switching elements 30 are provided between the through-hole portions TH <b> 1 and the ground pattern 13 on the outer surface side of the dielectric substrates 10 and 20. Using this switching element 30, the conduction between each through-hole portion TH1 and the ground pattern 13 can be turned on (connected) and turned off (cut off). In the present embodiment, the diode 41 is used as the switching element 30, but is not limited to this. For example, a transistor may be used as the switching element 30. The cathodes of the diodes constituting the switching element 30 are connected to the through-hole portions TH1, and the anodes of the diodes are commonly connected to the ground (or the ground pattern 13). The diode has a threshold (for example, about several V) with respect to the reverse voltage, and the voltage of the DC power supply V is set to this threshold.

The control circuit (center frequency correction unit) 40 shown in FIG. 3 turns on / off the switching element 30. In the control circuit 40, each of the two through-hole portions TH1 is connected to the positive side of the DC power source V via a switch 42 for each set, and the opening and closing of each switch 42 is automatically controlled by a controller (not shown). It becomes the composition which is done.
A controller (not shown) controls the number of switching elements 30 to be turned on by controlling the opening and closing of each switch 42.
The number of switches 42 to be turned on may be controlled (changed) by a volume switch or the like. Alternatively, a controller (not shown) has a function of detecting the center frequency of the BPF, and the number of switches 42 to be closed is automatically increased or decreased so that the detected center frequency matches a predetermined specified value. Feedback control may be performed. Further, the controller (not shown) has a function of detecting the temperature of the BPF, and the temperature correction control that automatically increases or decreases the number of switches 42 to be closed based on a predetermined map or the like according to the temperature. May be performed.

According to such a control circuit 40, when all the switches 42 are turned off, all the switching elements 30 are turned off, and the through hole portion TH1, that is, the conductive pattern 12 on the inner surface side of the dielectric substrates 10 and 20, from the ground. Blocked. This state is equivalent to being in the state shown in FIG. 4A.

On the other hand, when all the switches 42 are turned on, all the switching elements 30 are turned on, and the through hole TH1, that is, the conductive pattern 12 on the inner surface side of the dielectric substrates 10 and 20, is short-circuited to the ground in the vicinity of the slit S10. The This state is equivalent to being in a state as shown in FIG. 4B.

As described above, according to the BPF of this embodiment, the dielectric substrates 10 and 20 have the conductive pattern 12 having the slit S10 on the inner surface side. A plurality of through-hole portions TH1 penetrating the substrate body 11 are electrically insulated from the ground pattern 13 on the outer surfaces of the dielectric substrates 10 and 20. Dielectric substrates 10 and 20 are installed in parallel to the two side surfaces (E surface) of the rectangular waveguide. Further, a switching element 30 is provided between each through-hole portion TH1 and the ground pattern 13, and the switch 42 can turn on (connect) and turn off (cut off) the conduction between each through-hole portion TH1 and the ground pattern 13.

[Description of Operation of Embodiment]
The operation of the BPF of this embodiment as described above will be described using simulation results. The simulation was performed by providing the through-hole portion TH1 on only one of the dielectric substrates 10 and 20 on both sides of the rectangular waveguide.
FIG. 5 shows a BPF (curve C1) having a conductive pattern without a slit S10 on the inner surface side, a BPF having a conductive pattern 12 with a slit S10 (curve C2: see FIG. 4A), and a conductive pattern 12 on the inner surface side with a slit S10. The frequency-attenuation characteristics are shown for three examples of BPF (curve C3: see FIG. 4B) in which the ground pattern 13 on the outer surface side is short-circuited with the through hole portion TH1. Here, the attenuation characteristics of an 8-stage BPF simulated in the 22 GHz band (eight windows W1 in the metal fin 3) are shown. In either example, a Teflon (registered trademark) substrate is used as the material of the substrate body 11.

As shown by a curve C2, a dielectric substrate 10 made of a Teflon (registered trademark) substrate body 11 having a conductive pattern 12 having a slit S10 formed on the inner surface side is provided in parallel to the E surface at a location corresponding to the E surface. This is equivalent to extending the length of the long side of the rectangular waveguide, which is the mechanical component of the BPF (width direction size D1: cross section of the rectangular waveguide, see FIG. 1), and the center frequency of the BPF is It shifts to the lower one.

As shown by a curve C3, the inner surface side on which the conductive pattern 12 having the slit S10 is formed and the outer surface side having the ground pattern 13 are short-circuited at a plurality of locations along the slit S10 by the through-hole portion TH1 provided in the substrate body 11. This is equivalent to the fact that the E planes of the waveguides are close to each other (the width direction size D1 of the cross section of the rectangular waveguide is reduced), and the center frequency of the BPF is shifted to the higher side.

FIG. 6 shows the result of simulating the change in the center frequency of the BPF due to the difference in the slit width G of the conductive pattern 12 having the slit S10. A curve E1 shows a simulation result when the slit width G is 0.8 mm. A curve E2 shows a simulation result when the slit width G is 1.2 mm. A curve E3 shows a simulation result when the slit width G is 1.6 mm. A curve E4 shows a simulation result when the slit width G is 2.0 mm. As can be understood from FIG. 6, if the slit width G is narrowed, the center frequency of the BPF is shifted to a lower side, and conversely, if the slit width G is increased, the center frequency can be shifted to a higher side.

FIG. 7 shows that in a configuration having a total of 16 switching elements 30 (8 switches 42 in total) in the 22 GHz band, the number of switches 42 and switching elements 30 to be turned on is different. This is the attenuation characteristic of the BPF simulated. A curve F1 shows the attenuation characteristics when all the conduction between the through-hole portion TH1 and the ground pattern 13 is turned on (when 16 switching elements 30 are turned on). A curve F2 shows the attenuation characteristic when only two (one set) conduction between the through-hole portion TH1 and the ground pattern 13 is turned off (when 14 switching elements 30 are turned on). A curve F3 shows attenuation characteristics when eight (four sets) conduction between the through-hole portion TH1 and the ground pattern 13 is turned off (when eight switching elements 30 are turned on). A curve F4 shows attenuation characteristics when 16 (all) conductions between the through-hole portion TH1 and the ground pattern 13 are turned off (when 0 switching elements 30 are turned on), respectively.
When the number of switching elements 30 turned off and the conduction between the through hole portion TH1 and the ground pattern 13 is reduced, the E planes of the waveguide are separated from each other (the width of the cross section of the rectangular waveguide). The direction size D1 becomes larger), and the center frequency of the BPF shifts to a lower side.

According to the configuration as described above, in the E-plane waveguide type BPF, the center frequency of the BPF can be made variable without changing the shape of the metal fins 3 and the waveguide, particularly the cross-sectional size. That is, the slit width G of the conductive pattern 12 formed on the dielectric substrate mounted on the waveguide is changed, or the inner surface side conductive pattern 12 and the outer surface side ground pattern 13 are through-holes in a region close to the slit S10. The center frequency of the BPF can be made variable by short-circuiting the part TH1.

Further, without increasing the dielectric constant of the substrate main body 11 in the dielectric substrates 10 and 20 mounted on the waveguide, or without increasing the thickness of the entire dielectric substrate 10 or 20, the conductive pattern 12 on the inner surface side is reduced. By narrowing the slit width G, the center frequency of the BPF can be lowered. As a result, if the BPF is the same frequency band, the BPF can be downsized by applying the present invention.

By switching on and off by the switching element 30, two attenuation characteristics of the curve C2 and the curve C3 described in FIG. 5, that is, switching of the center frequency can be realized. Further, the dielectric substrates 10 and 20 are provided on the two E surfaces ep of the rectangular waveguide, respectively, and all the switching elements 30 of the dielectric substrates 10 and 20 on both sides are turned on by the control circuit. The center frequency can be switched in three stages by performing control to turn on all the switching elements 30 of only one of the 20 and turn off all the switching elements 30 of the dielectric substrates 10 and 20 on both sides.

Further, the slit widths G of the conductive patterns 12 in the dielectric substrates 10 and 20 are made different from each other, the switching elements 30 of the dielectric substrates 10 and 20 on both sides are turned on, and only one switching element 30 of the dielectric substrates 10 and 20 is turned on. The center frequency can be switched in four steps by performing control to turn on, turn on only the other switching element 30 of the dielectric substrates 10 and 20, and turn off the switching elements 30 of the dielectric substrates 10 and 20 on both sides. . Thereby, it is possible to realize a broadband BPF of 1 GHz or more.

As described above, the E-plane waveguide BPF according to the present embodiment can dynamically change the center frequency, and can widen the variable range of the center frequency.

Further, by controlling the on / off of the switch 42 by a controller (not shown), the switching element 30 increases or decreases the number of conduction between the through-hole portion TH1 and the ground pattern 13, so that the center frequency of the BPF is increased. It can be corrected by fine adjustment.

For example, when the width direction size D1 of the cross section of the waveguide becomes large within the range of the manufacturing range, the center frequency of the BPF shifts to the lower side. Correction can be made by increasing the number of parts TH1. Conversely, when the width direction size D1 of the cross section of the waveguide is reduced, the center frequency is shifted to the lower side by turning off the switching element 30 and reducing the number of through-hole portions TH1 that are electrically connected to the ground pattern 13. Can correct the center frequency.

Also, the center frequency of the BPF shifts to the lower side as the temperature rises, and shifts toward the higher side as the temperature decreases. Therefore, a controller (not shown) turns on the switching element 30 to increase the number of through holes TH1 to be connected to the ground pattern 13 as the temperature increases. By reducing the number of hole portions TH1, it is possible to correct the shift of the center frequency due to temperature.

As described above, according to the E-plane waveguide type BPF in the present embodiment, the slit width G and the like are difficult to change after manufacture, but the number of through-hole portions TH1 that are electrically connected to the ground pattern 13 Thus, the shift of the center frequency can be corrected. In addition, when correcting the deviation, it is only necessary to adjust the number of switching elements 30 to be turned on by a controller (not shown), so that the correction can be easily performed. Further, since only the switching element 30, the switch 42, and the controller (not shown) are provided, and mechanical processing and high-precision manufacturing range are not required, the above effect can be obtained at low cost.

As mentioned above, although this invention was described about embodiment, this invention is not limited to the said embodiment. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the spirit and scope of the present invention described in the claims.
For example, in the above embodiment, the simulation was performed by providing the through-hole portion TH1 only on one side of the dielectric substrates 10 and 20. However, it is also possible to provide the through hole portion TH1 on both the dielectric substrates 10 and 20.
In the above embodiment, the dielectric substrate 20 has the same structure as the dielectric substrate 10, but only one of the two side walls may be replaced with the above-described dielectric substrate.
Further, by changing the thickness of the dielectric substrates 10 and 20, the dielectric constant, and the width of the slit S10, the variable range of the center frequency can be expanded and the center frequency can be finely controlled. For example, if the center frequency can be finely controlled, the BPF band can be narrowed to the minimum necessary, so that the number of BPF stages can be reduced in order to achieve the necessary attenuation.

This application claims priority based on Japanese Patent Application No. 2009-109794 filed on April 28, 2009, the entire disclosure of which is incorporated herein.

In a radio access device in the millimeter wave band, a high-frequency BPF is used for a high-frequency input / output unit in order to remove unnecessary waves. The high-frequency BPF is required to have a wide band, high attenuation, and low loss. For example, in a 23 GHz band device, the usable frequency band extends over 2 GHz, and it is impossible to cover this with one type of BPF. It corresponds by. Even in the same 23 GHz band apparatus, BPFs having different use bands are physically different, and therefore, there are a plurality of apparatuses for mounting the BPF.

On the other hand, if the E-plane waveguide type BPF according to the embodiment of the present invention is used, the 23 GHz band can be fully covered with one kind of BPF having a small number of stages. There are great benefits.

1 and 2 Divided bodies 3 Metal fins 10 and 20 Dielectric substrate 11 Substrate body 12 Conductive pattern 13 Ground pattern 30 Switching element 40 Control circuit (center frequency correction unit)
41 Diode 42 Switch

Claims (6)

1. A dielectric substrate provided on the E-plane of the waveguide and having a first surface and a second surface;
   A conductive pattern made of a conductive material provided on the first surface of the dielectric substrate and having a slit extending in a signal propagation direction;
   A plurality of through-holes provided along the slits extending from the region of the conductive pattern on the first surface of the dielectric substrate to the second surface of the dielectric substrate and filled with a conductive material; A plurality of through-hole portions,
   A ground pattern made of a conductive material provided in a region excluding a region where the through hole portion is exposed on the second surface of the dielectric substrate;
   Each of the plurality of through-hole portions exposed on the second surface and a plurality of switching elements capable of electrically interrupting the ground pattern,
   A waveguide filter comprising: a center frequency correction unit that corrects a center frequency by increasing / decreasing the number of through holes connected to the ground pattern by controlling on / off of each of the plurality of switching elements. .
2. 2. The waveguide filter according to claim 1, wherein the center frequency correction unit corrects the center frequency in accordance with a distance between two E surfaces facing each other of the waveguide.
3. The waveguide filter according to claim 1 or 2, wherein the center frequency correction unit corrects the center frequency according to temperature.
4. 4. The dielectric substrate according to claim 1, wherein the waveguide is a rectangular waveguide having a rectangular cross section, and the dielectric substrate is provided on at least one of two E surfaces facing each other in the rectangular waveguide. 5. 2. The waveguide filter according to item 1.
5. The waveguide filter according to any one of claims 1 to 4, wherein the center frequency is changed by changing a width of the slit.
6. A communication access device comprising the waveguide filter according to any one of claims 1 to 5.

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