JP4076475B2 - Method for manufacturing dielectric line filter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a dielectric line filter, and more particularly to a method for manufacturing a dielectric line filter such as an NRD guide filter suitable for transmission of an ultrahigh frequency signal of quasi-millimeter wave or higher.
[0002]
[Prior art]
Conventionally, a microstrip line, a waveguide line, and a dielectric line are mainly used for millimeter wave band integrated circuits. Here, a printed line such as a microstrip line is not suitable for a millimeter-wave band transmission line because the conductor loss rapidly increases as the frequency increases. In addition, the waveguide line is not suitable for mass production because it needs to form a three-dimensional solid structure.
For this reason, dielectric lines are attracting attention as transmission lines in the ultrahigh frequency band. However, the dielectric line has a large radiation loss at the bends and discontinuities, which causes a problem that the inherent low loss characteristic of the dielectric line is impaired.
With respect to this problem, a nonradiative dielectric line (NRD guide) as shown in Patent Document 1 has been proposed and implemented.
As shown in FIG. 4, the NRD guide is configured to insert a dielectric strip 104 as a transmission line into a dielectric medium (usually air) 103 between two parallel conductive plates 101 and 102 while conducting the transmission. It is assumed to be interposed between the plates 101 and 102. Here, the gap between the conductor plates 101 and 102 is set to be not more than half of the wavelength in the medium of the transmission signal (main signal), so that the transmission signal cannot exist in the dielectric medium 103, so that unnecessary radiation can be suppressed. .
Conventionally, as a millimeter wave filter using an NRD guide, a resonance-type bandpass filter and a band rejection filter as shown in Non-Patent Document 1 have been proposed.
[0003]
[Patent Document 1]
Japanese Patent Publication No.62-35281 [Non-patent Document 1]
IEICE Transactions '85 / 2 Vol.J68-B No.2, “Experimental Design of Millimeter-Wave Filters Using Nonradiative Dielectric Lines”
[0004]
[Problems to be solved by the invention]
However, the NRD guide filter described in Non-Patent Document 1 requires that a circular resonator having a predetermined diameter made of a dielectric material be precisely arranged in a positional relationship corresponding to a pass band and a stop band. It's not easy. In addition, special processing is required to prevent deviation of the dielectric strip and the circular resonator in operation, which is not suitable for mass production.
Furthermore, the conventional NRD guide filter generally has a drawback that it lacks strength and robustness because the dielectric medium other than the dielectric strip is generally air, and this portion is a gap.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method of manufacturing a dielectric line filter that is easy to process, suitable for mass production, and has high strength and robustness. .
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the present invention comprises a dielectric medium between two substantially parallel conductive plates, a filter unit and a normal transmission unit having different porosity and dielectric constant, and the filter unit and the Usually, a transmission line is provided with a dielectric strip formed of a porous material made of the same raw material and material, and a dielectric line filter using a dielectric line configured to transmit a signal through the dielectric strip . A manufacturing method,
Forming a dielectric material film on one of the conductor plates;
When irradiating any one of an electron beam, an X-ray, and an ion beam on the dielectric strip shape portion of the dielectric material film, the irradiation amount of the filter portion corresponding portion included in the dielectric strip shape portion is determined. A step of making it smaller than the irradiation amount of the portion corresponding to the normal transmission part;
Making the entire dielectric material film porous,
It is characterized by having.
By such a patterning process , as in Non-Patent Document 1, a large number of circular resonators are created, and they are simply dielectric without using a relatively difficult manufacturing method such as arranging them in a precise positional relationship. The desired frequency selectivity is imparted to the dielectric line by a simple method such that the dielectric constant of the filter part of the body strip is made different from the dielectric constant of the normal transmission part , thereby forming a dielectric line filter. It becomes possible. Therefore, mass productivity is improved.
[0006]
Also, the filter unit and the normal transmission unit and the same raw material dielectrics strip, while so as to form a porous material comprising a material, a signal of a desired frequency band only by differences of the porosity of both It becomes possible to block.
That is, in general, it is necessary to prepare a different material in order to change the dielectric constant of the dielectric material. However, in a porous material, it is possible to change the dielectric constant by adjusting the porosity. For this reason, the dielectric constant is made different from other parts while using a dielectric material made of the same raw material and material. It becomes possible. In other words, the dielectric strip filter and the normal transmission section can be formed using substantially the same material, which facilitates the production of the dielectric line filter.
[0007]
In addition, the porous material has a lower dielectric constant and dielectric loss by increasing the porosity, and can obtain characteristics that are as close to air as possible. For this reason, it is possible to achieve transmission characteristics with very low loss compared to Teflon (registered trademark) which has been conventionally used as a material for the dielectric strip.
[0008]
In addition, the multi-porous material can be easily processed into complex shapes because it can be formed to the conductor plates using a patterning process of the present invention. This facilitates production and increases the degree of design freedom.
[0009]
It is also conceivable to form a reflection suppressing part whose dielectric constant is adjusted so as to suppress signal reflection between the filter part of the dielectric strip and the normal transmission part .
By this method , it is possible to suppress the reflection of the main signal at the boundary surface between the two due to the dielectric constant of the filter portion of the dielectric strip being different from the dielectric constant of the normal transmission portion . Therefore, transfer characteristics are improved.
[0010]
At this time, it is also conceivable that the reflection suppressing portion is made of a porous material, and the dielectric constant of the reflection suppressing portion is adjusted so as to adjust the porosity of the porous material.
As a result, the reflection suppressing portion can be formed from substantially the same material as the filter portion and the normal transmission portion of the dielectric strip, and thus manufacturing is facilitated.
[0011]
As a specific mode for adjusting the dielectric constant of the reflection suppressing portion, the dielectric constant of the reflection suppressing portion is adjusted to a predetermined dielectric constant between the dielectric constant of the filter portion of the dielectric strip and the dielectric constant of the normal transmission portion. Adjusting the dielectric constant of the reflection suppression unit so that it continuously changes between the dielectric constant of the filter portion of the dielectric strip and the dielectric constant of the normal transmission unit , and the dielectric constant of the reflection suppression unit It can be considered to adjust the dielectric constant of the filter part of the body strip so as to change stepwise between the dielectric constant of the normal transmission part .
[0012]
It is also conceivable that the gap between the conductor plates is set to be equal to or less than a half wavelength of the main signal in the dielectric medium.
As a result, the dielectric line can be configured as an NRD guide without unnecessary radiation of the main signal (transmission signal) in the dielectric medium, and more efficient signal transmission can be performed.
[0013]
At this time, it is conceivable that the dielectric medium is made of a porous material, and the dielectric constant of the dielectric medium is adjusted by adjusting the porosity of the porous material.
As a result, compared with the conventional dielectric line (see Patent Document 1) where the portion other than the dielectric strip is a gap, the dielectric strip is less likely to be displaced, and the strength is dramatically improved. A stable structure can be obtained.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments and examples of the present invention will be described with reference to the accompanying drawings for understanding of the present invention. It should be noted that the following embodiments and examples are examples embodying the present invention, and do not limit the technical scope of the present invention.
[0015]
Embodiment 1
FIG. 1 shows the configuration of a dielectric line filter X according to Embodiment 1 of the present invention.
As shown in the figure, a dielectric line filter (hereinafter simply referred to as a filter) X according to the first embodiment is a dielectric between two conductor plates 1 and 2 arranged in parallel with each other with a predetermined gap α. A medium 3 is disposed, and a dielectric strip 4 as a transmission path is interposed between the conductor plates 1 and 2 so as to be inserted into the dielectric medium 3.
[0016]
Here, the gap α between the conductor plates 1 and 2, that is, the thickness of the dielectric strip 4 is made smaller than 1/2 of the wavelength when the main signal (transmission signal) is radiated into the dielectric medium 3. Has been. As a result, no transmission signal can exist in the dielectric medium 3, and unnecessary radiation can be suppressed. That is, in the first embodiment, the filter X is configured as a filter using a nonradiative dielectric line (NRD guide).
[0017]
The dielectric constant of the dielectric strip 4 is larger than the dielectric constant of the dielectric medium 3 so that half of the wavelength of the transmission signal in the dielectric strip 4 is smaller than the gap α between the conductor plates 1 and 2. It has been enlarged.
Here, both the dielectric medium 3 and the dielectric strip 4 are made of a porous material made of, for example, a dry airgel material.
[0018]
That is, in the conventional NRD guide, the dielectric medium 3 is generally air, and the portion is therefore a gap. For this reason, there is a problem that the dielectric strip 4 is displaced. Therefore, in the first embodiment, the dielectric medium 3 is made of a porous material together with the dielectric strip 4, and thereby the dielectric strip 4 is displaced. Is prevented.
As described above, the portion of the dielectric medium 3 which has been a void in the past is filled with the porous material, so that the strength and the robustness are remarkably improved.
And such a porous material can adjust a dielectric constant by adjusting a porosity. Accordingly, a transmission signal can exist only inside the dielectric strip 4 while forming the dielectric medium 3 and the dielectric strip 4 by applying a porous material made of the same raw material and material. The dielectric constants of the dielectric medium 3 and the dielectric strip 4 can be adjusted.
[0019]
Next, the dielectric strip 4 will be described in more detail.
The dielectric strip 4 is provided with a filter unit 5 that blocks a signal in a predetermined frequency band so that a dielectric constant of a part of the dielectric strip 4 is different from a dielectric constant of another part.
That is, in the filter X of the first embodiment, the dielectric constant ε ₅ of the filter unit 5 that is a part of the dielectric strip 4 is smaller than the dielectric constant ε _{6 of the} other portion (hereinafter referred to as a normal transmission unit) 6. Thus, the porosity of the part corresponding to the filter unit 5 is made larger than that of the other parts, and the dielectric line functions as a filter having frequency selectivity.
Here, each dielectric constant ε _3, ε ₅ , ε ₆ of the dielectric medium 3, the filter unit 5, and the normal transmission unit 6 has the relationship of the following inequality 1 and, as a result, can exist in each unit 3, 5, 6. The relationship between the lower limit frequencies F _D3 , F _D5 , and F _D6 of the correct signal is as shown in inequality 2 below.
ε ₃ <ε ₅ <ε ₆ (1)
F _D3 > F _D5 > F _D6 (2)
However, the lower limit frequencies F _D3 , F _D5 , and F _D6 are frequencies when the half wavelength of the transmission signal is equal to the plate gap α in the dielectric medium 3, the filter unit 5, and the normal transmission unit 6. As a result, a signal whose frequency F is F _D5 >F> F _D6, that is, a signal having a frequency between F _{D6 and} F _D5 is cut off without passing through the filter unit 5.
[0020]
Next, a method for forming the dielectric medium 3 and the dielectric strip 4 made of a porous material between the conductor plates 1 and 2 will be described in detail (refer to Japanese Patent Application No. 2003-19344).
[0021]
First, a predetermined dielectric material is applied on one conductor plate 1 so as to have the gap α described above.
The dielectric material used here is 2 g of tetramethoxysilane (metal alkoxide) Si (CH ₃ O) ₄ , which is an example of an organometallic material, 10 g of ethanol, 2 g of butanol, 1 g of methyl 3-methoxypropionate, After 1.2 g of water having a pH of 3 was mixed and stirred, the mixture was allowed to react at 60 ° C. for about 6 hours, and this solution was reacted with IBCF (manufactured by Sanwa Chemical Co., Ltd.) as a photoacid generator. Is prepared by mixing 10 cc of this solution with 0.2 g of hexadecyltrimethylammonium chloride (an example of a surfactant) and stirring the solution. is there.
[0022]
Next, the portion coated with the above dielectric material is heated (baked) at 80 ° C. in the atmosphere and dried to form a film. This heating is performed for a sufficient time (for example, about 1 to 5 minutes) to remove the solvent such as ethanol contained in the raw material solution and increase the viscosity of the film to stabilize it on the substrate.
Subsequently, only the portion corresponding to the dielectric strip 4 in the dielectric material film is irradiated with an electron beam. As such an electron beam, for example, an electron beam having an acceleration voltage of 50 keV and a dose of 10 μC / cm ² is used.
Thereby, the Si-OH state formed from tetramethoxysilane forms a Si-O bond (so-called cross-linking reaction).
[0023]
Next, the dielectric material film is heated (baked) at 100 ° C. in the air. This step is a step for promoting the cross-linking reaction of the non-irradiated portion of the electron beam, and is performed for about 1 to 5 minutes, for example.
[0024]
Next, extraction processing of hexadecyltrimethylammonium chloride, which is a surfactant, is performed using supercritical CO ₂ at 15 MPa and 80 ° C. to remove organic components remaining in the dielectric material film. In this step, for example, first, a dielectric material is put into a predetermined pressure vessel, and then CO ₂ that is not in a supercritical state is introduced into the pressure vessel, and then the temperature and / or pressure in the pressure vessel is increased to increase CO _2. Is in a supercritical state. Alternatively, a supercritical fluid may be introduced into a pressure vessel containing a dielectric material.
[0025]
Next, the dielectric material after the extraction treatment is heated at 200 ° C. in the atmosphere. This heating is performed for about 5 to 30 minutes, for example.
Through the above steps, the portion of the dielectric material layer where the removed organic component was present becomes a void, and a porous material layer made of a so-called dry airgel material is formed on one conductor plate 1. Will be. As a result, the porosity of the portion corresponding to the dielectric medium 3 is higher than the porosity of the portion corresponding to the dielectric strip 4 irradiated with the electron beam, and the dielectric constant of the dielectric strip 4 is less than that of the dielectric medium 3. It becomes higher than the dielectric constant.
In the dielectric strip 4, the electron beam irradiation amount at the portion corresponding to the filter unit 5 is made smaller than the irradiation amount at the portion corresponding to the normal transmission unit 6. Thus, the porosity of the filter unit 5 corresponding parts is higher than the porosity of the normal transmission unit 6 corresponding parts, as a result, the dielectric constant epsilon ₅ of the filter unit 5 than the dielectric constant epsilon ₆ of normal transmission portions 6 Is also formed to be low.
The dielectric line filter X can be manufactured by adhering the other conductor plate 2 onto the dielectric strip 4 and the dielectric medium 3 formed as described above.
[0026]
The manufacturing method described above is suitable for mass production of dielectric lines because it can be manufactured by patterning rather than a manufacturing method in which each component is manufactured individually as in the prior art and then assembled.
Further, instead of the electron beam irradiation, irradiation with X-rays (for example, electron energy 1 GeV) or ion beam irradiation (for example, Be ²⁺ with an energy of 200 keV, ion dose 1e ¹³ / cm ^{2 to} 1e ¹⁴ / cm ²⁾ . Similar results are obtained when irradiation is performed.
In addition, as a supercritical fluid used for the extraction treatment of hexadecyltrimethylammonium chloride, at least two kinds of substances including at least one of carbon dioxide, ethanol, methanol, water, ammonia, and fluorocarbon substances are mixed. Similar results can be obtained.
[0027]
As described above, in the filter X of Embodiment 1, in the filter using a so-called NRD guide, the dielectric strip 4 is formed of a porous material, and the porosity of the filter unit 5 is adjusted by the manufacturing method described above. This cuts off the signal in the desired frequency band. Therefore, it is much simpler than the resonance type filter of Non-Patent Document 1 mentioned in the prior art, that is, a large number of circular resonators having a predetermined diameter corresponding to the pass band and the stop band are prepared, and these are precisely sized. It is possible to configure a dielectric line filter having a desired frequency selectivity without going through a complicated process of arranging at predetermined intervals under management.
Further, unlike the conventional Teflon (registered trademark) or the like, the dielectric material constituting the dielectric strip 4 is a porous material made of, for example, tetramethoxysilane. It is possible to achieve very low loss dielectric characteristics.
Further, in the filter X of the first embodiment, the dielectric medium 3 that is normally a gap is made of a porous material like the dielectric strip 4. Therefore, displacement of the dielectric strip 4 is prevented and the strength and robustness of the filter X are improved.
The dielectric medium 3 and the dielectric strip 4 are suitable for mass production because they are manufactured by patterning rather than by a manufacturing method in which the dielectric medium 3 and the dielectric strip 4 are individually manufactured and then assembled.
Furthermore, each part 3, 4, 5, 6 is manufactured from the same raw material by comprising the dielectric medium 3 and the dielectric strip 4 (filter part 5, normal transmission part 6) with substantially the same material. This makes it easier to manufacture. Therefore, the manufacturing cost can be reduced.
[0028]
Embodiment 2
Next, Embodiment 2 of the present invention will be described with reference to FIG.
The filter X1 of the second embodiment is obtained by modifying the dielectric strip 4 of the filter X of the first embodiment, and other parts are the same as those of the first embodiment. Therefore, only different parts will be described below.
The dielectric strip 4 </ b> A of the filter X <b> 1 is configured to form a reflection suppression unit 7 that suppresses reflection of the main signal at the boundary between both ends of the filter unit 5 and the normal transmission unit 6.
That is, in the dielectric strip 4A, the filter unit 5 is formed so that the dielectric constant ε ₅ is different from the dielectric constant ε ₆ of the normal transmission unit 6 so as to block a signal in a predetermined frequency band. Here, when the difference between the dielectric constants ε ₅ and ε ₆ changes greatly and suddenly, a large reflection may occur in the main signal at the boundary surface between the filter unit 5 and the normal transmission unit 6. . The reflection suppression unit 7 is used for matching that connects the filter unit 5 and the normal transmission unit 6 while suppressing the reflection of the signal due to the difference in dielectric constant between the filter unit 5 and the normal transmission unit 6. It is supposed to be provided as a track.
Here, the dielectric constant epsilon ₇ reflection-inhibiting portion 7, a predetermined capable of effectively suppressing the occurrence of reflections between the dielectric constant epsilon ₆ permittivity epsilon ₅ and normal transmission portion 6 of the filter unit 5 Set to dielectric constant. Further, such a dielectric constant ε ₇ can be set as experimentally obtained.
[0029]
The dielectric constant ε ₇ of the reflection suppressing unit 7 is not limited to a constant value, and the dielectric constant of the filter unit 5 increases from the junction end surface between the reflection suppression unit 7 and the filter unit 5 toward the junction end surface with the normal transmission unit 6. The dielectric constant ε ₅ may be continuously changed between the dielectric constant ε ₆ of the normal transmission unit 6.
Further, while towards the joining end face of the normal transmission unit 6 dielectric constant from the joining end faces of the reflection suppressing portion 7 and the filter unit 5 and the dielectric constant epsilon ₆ permittivity epsilon ₅ and normal transmission portion 6 of the filter unit 5 It may be changed step by step.
In the second embodiment, the reflection suppressing unit 7 is formed of a porous material made of the same raw material as the porous material constituting the filter unit 5 and the normal transmission unit 6. That is, in the porous material forming method referred to in Embodiment 1, the electron beam irradiation amount to the reflection suppressing unit 7 is a predetermined value between the irradiation amount in the portion corresponding to the filter unit 5 and the irradiation amount in the portion corresponding to the normal transmission unit 6. The dielectric constant ε ₇ of the reflection suppressing unit 7 can be adjusted by adjusting the amount of irradiation.
[0030]
As described above, in the filter X1 of the second embodiment, since the reflection suppressing portion 7 that suppresses the reflection of the signal is formed between the filter portion 5 and the normal transmission portion 6 of the dielectric strip 4, the dielectric constant of both of them. The reflection of the main signal due to the difference between ε ₅ and ε ₇ can be prevented. Therefore, transmission characteristics are improved.
Moreover, since the reflection suppression part 7 is comprised from the material substantially the same as the porous material which comprises the filter part 5 and the normal transmission part 6, manufacture becomes easy.
[0031]
【Example】
Hereinafter, an example of the dielectric line filter of the embodiment will be described with reference to FIG. FIG. 3A is a block diagram illustrating a frequency division wireless communication system B to which the filters X and X1 of the embodiment are applied.
The wireless communication system B includes an antenna 11, a reception-side frequency converter 12, a transmission-side frequency converter 13, and a branch 14 (eg, a diplexer or a circulator), and transmits a reception signal from the branch 14 to the reception-side frequency converter 12. and transmitting-side transmission line 22 for transmitting a transmission signal and a reception side transmission line 21 from the transmission side frequency converter 13 to the branch 14, to apply the transmission line 23 and Niso respectively NRD guide between the antenna 11 branches 14 Configured.
[0032]
In this wireless communication system B, a part of the transmission signal having a large output wraps around the reception side transmission path 21 via the branch 14, and as a result, the spectrum in the reception side transmission path 21 is, for example, FIG. ) As shown. That is, the level of such a sneak signal (transmission signal) 32 is higher than the level of the reception signal 31.
As described above, when a large level of sneak signal (transmission signal) is input to the reception-side frequency converter 12, a problem such as saturation of the reception amplifier occurs. Therefore, in the radio communication system B, the reception side transmission path 21 is configured by the filters X and X1 of the embodiment.
In other words, a filter portion (5) having a low dielectric constant is formed in a part of a dielectric strip (4) (not shown) of the reception side transmission line 21 made of an NRD guide, so that the reception side transmission line 21 blocks a sneak signal. It is supposed to function as.
[0033]
At this time, the frequency F _{RX of the} reception signal, the frequency F _{TX of the} transmission signal, and the above-described lower limit frequency F _CUT in the filter unit (5) are set so as to have a relationship represented by the following inequality 3, for example.
F _RX > F _CUT > F _TX (3)
As a result, a filter characteristic as indicated by a broken line 40 in FIG. 3B is achieved, so that the sneak signal 32 can be sufficiently attenuated in the reception-side transmission path 21 as shown in FIG. 3C. It becomes.
[0034]
【The invention's effect】
As described above, according to the present invention, it is possible to realize a dielectric line filter having excellent transmission characteristics, easy processing, excellent mass productivity, and good strength and robustness.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a configuration of a dielectric line filter according to a first embodiment of the present invention.
FIG. 2 is a perspective view showing a configuration of a dielectric line filter according to a second embodiment of the present invention.
FIG. 3 is a block diagram illustrating a configuration of a wireless communication system as an example to which the dielectric line filter according to the embodiment is applied.
FIG. 4 is a perspective view showing a configuration of a conventional general dielectric line.

Claims (8)

A dielectric medium between two substantially parallel conductor plates, a filter part and a normal transmission part having different porosity and dielectric constant, and the filter part and the normal transmission part are made of the same raw material and material. A dielectric strip formed of a porous material, and a dielectric line filter using a dielectric line configured to transmit a signal through the dielectric strip ,
Forming a dielectric material film on one of the conductor plates;
When irradiating any one of an electron beam, an X-ray, and an ion beam on the dielectric strip shape portion of the dielectric material film, the irradiation amount of the filter portion corresponding portion included in the dielectric strip shape portion is determined. A step of making it smaller than the irradiation amount of the portion corresponding to the normal transmission part;
Making the entire dielectric material film porous,
A method of manufacturing a dielectric line filter, comprising: 2. The dielectric line filter according to claim 1, wherein a reflection suppressing portion whose dielectric constant is adjusted so as to suppress signal reflection is formed between the filter portion of the dielectric strip and the normal transmission portion. Manufacturing method . 3. The method of manufacturing a dielectric line filter according to claim 2, wherein the reflection suppressing portion is made of a porous material, and a dielectric constant of the reflection suppressing portion is adjusted so as to adjust a porosity of the porous material. According to claim 2 or 3 formed by adjusting the predetermined dielectric constant between the dielectric constant and the normal transmission part of the dielectric constant of the filter part of the dielectric constant of the reflection suppressing portion is the dielectric strips Of manufacturing a dielectric line filter . To claim 2 or 3 dielectric constant of the reflection suppressing portion is configured continuously varying as between the dielectric constant and the normal transmission part of the dielectric constant of the filter portion of the dielectric strip The manufacturing method of the dielectric-line filter of description . To claim 2 or 3 consisting configured to change stepwise between the dielectric constant and the normal transmission part of the dielectric constant of the filter part of the dielectric constant of the reflection suppressing portion is the dielectric strips The manufacturing method of the dielectric-line filter of description . The method for manufacturing a dielectric line filter according to claim 1, wherein a gap between the conductor plates is set to be equal to or less than a half wavelength of a main signal in the dielectric medium. 8. The method of manufacturing a dielectric line filter according to claim 7, wherein the dielectric medium is made of a porous material, and a dielectric constant of the dielectric medium is adjusted so as to adjust a porosity of the porous material.

Images