JP2007281603A - Antenna element, method for manufacturing the same and antenna unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna element operating stably in which the operating frequency band of an antenna can be varied by simple control. <P>SOLUTION: Each of a plurality of MEMS switches 4A1 (or 4B1) has a movable cut piece 4A (or 4B) of cantilever structure. One end of the movable cut piece is connected to a basic radiation conductor 2. Furthermore, a through-conductor 7 is formed for connecting the center of the basic radiation conductor 2 to a ground conductor 6. When a desired voltage is applied between a control line 5A (or 5B) and the through-conductor 7, the plurality of MEMS switches 4A1 (or 4B1) can be operated by electrostatic force. Furthermore, since the through-conductor 7 is located in the center of the basic radiation conductor 2, the movable cut pieces 4A and 4B can be moved without having impact on the characteristics of an antenna element 100. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an antenna element whose operating frequency is varied using a MEMS switch, an antenna device using the antenna element, and a method for manufacturing the antenna element.

  Micro Electro Mechanical Systems (MEMS) technology, which is a technology for manufacturing electrical or mechanical devices using semiconductor microfabrication technology, has recently been applied to the field of high frequencies. An example of an element formed using MEMS technology in the field of high frequency is a MEMS switch. The feature of the MEMS switch is that it can simultaneously realize low loss and high isolation over a very wide frequency band.

  A MEMS switch having such characteristics is preferably used in the front end of a high-frequency device. For example, US Pat. No. 6,1984,438 (Patent Document 1) discloses a configuration in which a plurality of MEMS switches are loaded on an antenna and the operating frequency of the antenna is switched by turning them on (conducting) / off (cutting off). .

There are various types of MEMS switches. For example, there are a switch for electrostatically driving a cantilever beam, a switch for energizing a membrane (film) by electrostatically driving and pulling, and the like.
US Pat. No. 6,1984,438

  FIG. 27 is a diagram showing a configuration of an antenna device disclosed in US Pat. No. 6,1984,438 (Patent Document 1).

  Referring to FIG. 27, antenna device 110 includes a plurality of radiating conductor elements 130 arranged in a matrix. Two adjacent radiating conductor elements 130 in the same row or the same column are connected by a connecting conductor 132. A MEMS switch 131 is disposed in the middle of the connection conductor 132.

  When power is supplied to one radiation conductor element 130, a radio wave having a resonance length equal to the length of one side of the radiation conductor element 130 is radiated. In a state where all the MEMS switches 131 included in the antenna device 110 are turned off, a radio wave having a resonance length equal to the length of one side of the radiation conductor element 130 is radiated from each of the plurality of radiation conductor elements 130.

  On the other hand, when all the MEMS switches 131 are turned on, the plurality of radiation conductor elements 130 are connected to each other. Thereby, the plurality of radiating conductor elements 130 become one rectangular radiating conductor as a whole. Since the resonance length in this case is longer than the resonance length in a state where all the MEMS switches 131 are turned off, the antenna device 110 radiates radio waves having a lower frequency. As described above, the antenna device 110 can switch the operating frequency by switching the MEMS switch on and off.

  However, in the antenna device 110, it is necessary to match the characteristic impedance both when the operating frequency is high and when the operating frequency is low. The feeding point of the antenna device 110 when the operating frequency is high is the feeding point 133, and the feeding point of the antenna device 110 when the operating frequency is high is the feeding point 134. Thus, in the antenna device 110, it is necessary to change the position of the feeding point between when the operating frequency is high and when the operating frequency is low.

  US Pat. No. 6,1984,438 (Patent Document 1) does not particularly disclose such a method for supplying power to a plurality of locations. However, when feeding points are provided at a plurality of different locations, there are generally problems that the arrangement of the feeding lines is complicated and the feeding efficiency is lowered.

  In addition, US Pat. No. 6,1984,438 (Patent Document 1) does not disclose a method for controlling a plurality of MEMS switches. However, when considering based on the configuration shown in FIG. 27, it is easily imagined that the control method becomes complicated.

  In US Pat. No. 6,1984,438 (Patent Document 1), as shown in FIG. 27, only one MEMS switch 131 is provided between two radiation conductor elements 130. For this reason, when the MEMS switch is turned on, a current accompanying power feeding flows in the MEMS switch 131 in a concentrated manner. When a current exceeding the allowable current of the MEMS switch 131 flows through the MEMS switch 131, a problem such as a contact (sticking) of the contact of the MEMS switch 131 occurs, and the operation of the antenna device 110 becomes defective.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide an antenna element that can change the operating frequency band of an antenna by simple control and can operate stably. .

  Moreover, the objective of this invention is providing the antenna device which mounts the above-mentioned antenna element, and the manufacturing method of an antenna element.

  In summary, the present invention is an antenna element formed on a substrate having first and second main surfaces, a first radiation conductor formed on the first main surface, and a first main surface. A second and third radiation conductors positioned so as to sandwich the first radiation conductor, and a plurality of first MEMS switches provided in parallel between the first radiation conductor and the second radiation conductor; A plurality of second MEMS switches provided in parallel between the first radiation conductor and the third radiation conductor, a ground conductor formed on the second main surface, and the first radiation penetrating the substrate A through conductor connecting the center of the conductor and the ground conductor;

  According to another aspect of the present invention, there is provided a method for manufacturing an antenna element, wherein a first radiation conductor is formed on a first main surface of a semiconductor substrate having first and second main surfaces, and the first Forming a second radiation conductor and a third radiation conductor on the main surface of the first radiation conductor so as to sandwich the first radiation conductor; selectively processing the first radiation conductor; A plurality of first MEMS switches provided in parallel with the first radiation conductor and a plurality of second MEMS switches provided in parallel between the first radiation conductor and the third radiation conductor. Forming a ground conductor on the second main surface; and forming a through conductor that penetrates the semiconductor substrate and connects the center of the first radiation conductor and the ground conductor.

  According to the antenna element and the antenna device of the present invention, the operating frequency band can be changed by simple control.

  Moreover, according to the method for manufacturing an antenna element of the present invention, it is possible to manufacture such an antenna element.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same reference numerals indicate the same or corresponding parts.

[Embodiment 1]
FIG. 1 is a perspective view showing a configuration of an antenna element according to the first embodiment.

FIG. 2 is a cross-sectional view taken along the line II-II in FIG.
FIG. 3 is a plan view showing the back surface of the antenna element of FIG.

  1 to 3, antenna element 100 includes a substrate 1 having a front surface 1A and a back surface 1B. The substrate 1 is, for example, a dielectric substrate or a high resistance silicon substrate.

  The antenna element 100 further includes a basic radiation conductor 2, extending radiation conductors 3A and 3B, a plurality of MEMS switches 4A1, and a plurality of MEMS switches 4B1. The basic radiation conductor 2, the extending radiation conductors 3A and 3B, the plurality of MEMS switches 4A1, and the plurality of MEMS switches 4B1 are formed on the surface 1A of the substrate 1.

  The shape of the basic radiation conductor 2 is a rectangle. The extending radiation conductors 3 </ b> A and 3 </ b> B are arranged symmetrically with respect to the basic radiation conductor 2. A plurality of MEMS switches 4A1 are arranged in parallel between the basic radiation conductor 2 and the extending radiation conductor 3A. A plurality of MEMS switches 4B1 are arranged in parallel between the basic radiation conductor 2 and the extending radiation conductor 3B.

  Each of the plurality of MEMS switches 4A1 and the plurality of MEMS switches 4B1 includes a movable piece having a cantilever structure and a control electrode. A cantilever is a beam that is fixedly supported at one end and free at the other end.

  The configuration of each of the plurality of MEMS switches 4A1 will be described. One end of the movable section 4A is fixed by being connected to the basic radiation conductor 2, and the other end of the movable section 4A extends to the extending radiation conductor 3A side. The other end of the movable section 4A is located above the surface 1A.

  When a predetermined voltage is applied to the control electrode, the MEMS switch 4A1 operates (turns on). During operation of the MEMS switch 4A1, the other end of the movable piece 4A comes into contact with the extending radiation conductor 3A. This control electrode is provided below the movable piece 4A. In the present embodiment, the control electrodes of the plurality of MEMS switches 4A1 are connected to each other and formed as a control wiring 5A. Therefore, the plurality of movable segments 4A operate simultaneously.

  The configuration of each of the plurality of MEMS switches 4B1 will be described. One end of the movable section 4B is fixed by being connected to the basic radiation conductor 2, and the other end of the movable section 4B extends to the extending radiation conductor 3B side. The other end of the movable piece 4B is located above the surface 1A.

  Similarly to the MEMS switch 4A1, when a predetermined voltage is applied to the control electrode, the MEMS switch 4B1 operates (turns on). During the operation of the MEMS switch 4B1, the other end of the movable piece 4B comes into contact with the extending radiation conductor 3B. This control electrode is provided below the movable piece 4B. In the present embodiment, the control electrodes of the plurality of MEMS switches 4B1 are connected to each other and formed as a control wiring 5B. Therefore, the plurality of movable segments 4B operate simultaneously.

  The antenna element 100 further includes a ground conductor 6 and a through conductor 7. The ground conductor 6 is formed on the back surface 1 </ b> B of the substrate 1. The through conductor 7 penetrates the substrate 1 and connects the center of the basic radiation conductor 2 and the ground conductor 6.

  The center of the basic radiating conductor 2 is the geometric center of the radiating conductor and means a position that is a reference potential of the electric field amplitude generated between the radiating conductor and the back-grounded conductor when the microstrip antenna is operated. .

  In the substrate 1, a feed through hole 8 that penetrates the substrate 1 is formed. For example, a device for supplying power to the basic radiation conductor 2 (for example, a coaxial connector or a power supply cable) is passed through the power supply through hole 8. The ground conductor 6 is formed with an opening 6 </ b> B that surrounds the power feed through hole 8 and has a diameter larger than that of the power feed through hole 8. As a result, it is possible to ensure insulation between the device passed through the feed through hole 8 and the ground conductor.

  The antenna element 100 functions as a so-called microstrip antenna. The operating principle of the antenna element 100 will be described below. The DC voltage described below means a potential difference when the potential of the ground conductor 6 is used as a reference.

  In FIG. 1, the basic radiation conductor 2 is connected to a ground conductor 6 through a through conductor 7. A DC voltage V (control voltage) is applied to the control wirings 5A and 5B by a control circuit (not shown). As a result, the plurality of MEMS switches 4A1 and 4B1 are turned on.

  FIG. 4 is a perspective view showing the antenna element 100 when the plurality of MEMS switches 4A1 and 4B1 are in the ON state.

  Referring to FIG. 4, the distal end portions (the other end described above) of each of the plurality of movable pieces 4A are in contact with the extending radiation conductor 3A. The front ends (the other end described above) of each of the plurality of movable segments 4B are in contact with the extending radiation conductor 3B. As a result, the basic radiation conductor 2 and the extending radiation conductor 3A are connected, and the basic radiation conductor 2 and the extending radiation conductor 3B are connected.

FIG. 5 is a cross-sectional view taken along line VV in FIG.
Referring to FIG. 5, since the movable piece 4A is connected to the basic radiation conductor 2 and given a direct current reference potential, when the potential of the control wiring 5A is set to the potential V, the movable piece 4A and the control wiring 5A. An electrostatic force corresponding to the DC voltage V is generated between the two. Since the movable piece 4A is attracted downward by the electrostatic force, the tip of the movable piece 4A comes into contact with the extending radiation conductor 3A.

  The same applies to the MEMS switch 4B1, and when the potential of the control wiring 5B is set to the potential V, an electrostatic force corresponding to the DC voltage V is generated between the movable piece 4B and the control wiring 5B. Since the movable piece 4B is attracted downward by an electrostatic force, the tip of the movable piece 4B comes into contact with the extending radiation conductor 3B.

  As described above, in this embodiment, the MEMS switch is turned on by applying the DC voltage V to the control wirings 5A and 5B with the potential of the basic radiation conductor 2 as the reference potential.

  In such a MEMS switch control method, since the center of the basic radiation conductor 2 is grounded at a high frequency (a reference potential of amplitude), the center of the basic radiation conductor 2 is set to a zero potential of DC. I'm taking advantage of the fact that there is no problem.

  The ground conductor 6 and the basic radiation conductor 2 constitute a microstrip line. In order for the basic radiating conductor 2 to function as an antenna, a large current needs to flow through the basic radiating conductor 2. This can be realized by utilizing the resonance phenomenon, for example, by setting the length of the basic radiation conductor 2 to a half wavelength. Here, “the length of the basic radiation conductor 2” means the length between the root of the movable segment 4A and the root of the movable segment 4B.

  When there is an antenna on the ground conductor 6, a coaxial line is suitable for feeding the antenna. The antenna element 100 is also fed by a coaxial line from below the ground conductor 6. During power feeding, the outer conductor of the coaxial line is connected to the ground conductor 6, and the inner conductor of the coaxial line is connected to the basic radiation conductor 2 through the feed through hole 8.

  Here, in order to operate the antenna, it is important not to connect the inner conductor of the coaxial line to the center of the basic radiation conductor 2 (position of the through conductor 7). Since both ends of the basic radiating conductor 2 are open, the current at both ends of the basic radiating conductor 2 must be zero. Moreover, since the length of the basic radiation conductor 2 is set to a half wavelength, the current distribution in the basic radiation conductor 2 is sinusoidal.

  It is widely known that when a standing wave current is generated by resonance, the voltage waveform is shifted in phase by 90 degrees with respect to the current waveform. That is, the magnitude of the voltage in the basic radiating conductor 2 is maximum at both ends, and is zero at the center, which is equal to the potential of the ground conductor 6.

  As can be seen from the above description, the electromagnetic field at the center of the basic radiating conductor 2 becomes 0. Therefore, even if the center of the basic radiating conductor 2 and the grounding conductor 6 are connected by the through conductor 7, the center of the basic radiating conductor 2 can be obtained. The electromagnetic field is not affected. If a place other than the center of the basic radiation conductor 2 and the ground conductor 6 are connected by the through conductor 7, the electromagnetic field between the basic radiation conductor 2 and the ground conductor 6 is disturbed. Problems such as the radiation pattern being disturbed and the deterioration of radiation efficiency occur.

  In this embodiment, in the MEMS switch having a cantilever structure, the potential of the movable piece (cantilever) is set to 0 V of direct current. By applying a desired voltage between the movable piece and the control wiring, an electrostatic force is generated between the movable piece and the control wiring. This makes it possible to suck the tip of the movable section downward. If the base of the movable section (the fixed end of the cantilever beam) is connected to the extending radiation conductor, the MEMS switch cannot be driven by the simple method as described above. The reason is that it is difficult to control so as to generate a desired voltage between the control wiring and the movable piece because the potential of the movable piece becomes a float.

  Next, the path of the current that flows on the radiation conductor when high-frequency power is fed to the basic radiation conductor 2 through the feed through hole 8 will be described.

  FIG. 6 is a diagram illustrating a path of a current flowing through the radiation conductor when all of the plurality of MEMS switches 4A1 and 4B1 are in the OFF state.

  Referring to FIG. 6, the broken-line frames indicate that the movable segments 4A and 4B are not connected to the extending radiation conductors 3A and 3B, that is, the plurality of MEMS switches 4A1 and 4B1 are all turned off. Indicates. However, FIG. 6 does not show the control wirings 5A and 5B for the sake of simplicity. When all of the plurality of MEMS switches 4A1 and 4B1 are in the OFF state, a current 9 flows on the basic radiating conductor 2 in the direction from the extending radiating conductor 3A to the extending radiating conductor 3B as indicated by an arrow. The length of the current path at this time is equal to the length L of the basic radiation conductor 2.

  FIG. 7 is a diagram illustrating a path of current flowing through the radiation conductor when all of the plurality of MEMS switches 4A1 and 4B1 are in the on state.

  Referring to FIG. 7, when all of the plurality of MEMS switches 4A1 and 4B1 are in the ON state, a current 10 flows through the extending radiation conductors 3A and 3B, the plurality of MEMS switches 4A1 and 4B1, and the basic radiation conductor 2. However, in FIG. 7, as in FIG. 6, the control wirings 5A and 5B are not shown in order to simplify the description.

  As indicated by the arrows, the direction in which the current 10 flows is from the extending radiation conductor 3A to the extending radiation conductor 3B. The lengths of the extending radiation conductors 3A and 3B are L1 and L2, and the lengths of the movable segments 4A and 4B are S1 and S2. The length of the current path when the plurality of MEMS switches 4A1 and 4B1 are all in the on state is (L + L1 + L2 + S1 + S2).

  As can be seen from FIG. 7, the current flowing between the basic radiating conductor and the extending radiating conductor is distributed to each of the plurality of MEMS switches. As a result, it is possible to prevent problems such as welding of the contacts of the MEMS switch caused by a current exceeding the allowable current flowing through the MEMS switch.

  Thus, in the present embodiment, the plurality of movable segments 4A are collectively operated by the control wiring 5A and the plurality of movable segments 4B are collectively operated by the control wiring 5B. Thereby, in this Embodiment, the reliability of a MEMS switch can be ensured.

  As can be seen by comparing FIG. 6 and FIG. 7, the current path length when the plurality of MEMS switches 4A1 and 4B1 are turned on is longer than the current path length when the plurality of MEMS switches 4A1 and 4B1 are turned off. It can be seen that the conductor lengths of the conductors 3A and 3B and the lengths of the movable segments 4A and 4B increase. Therefore, the resonance length of the radiation conductor is longer when the plurality of MEMS switches 4A1 and 4B1 are turned on than when the plurality of MEMS switches 4A1 and 4B1 are turned off. As a result, the frequency of radio waves radiated from the antenna element 100 is lower when the plurality of MEMS switches 4A1 and 4B1 are turned on than when the plurality of MEMS switches 4A1 and 4B1 are turned off.

  In the antenna element of the present embodiment, the extending radiation conductors 3A and 3B are arranged symmetrically with respect to the basic radiation conductor 2. Therefore, in the antenna element of the present embodiment, impedance matching can be performed without changing the position of the feeding point when changing the operating frequency. Therefore, in the antenna element according to the present embodiment, it is possible to prevent the arrangement of the feeder lines from becoming complicated and to suppress a reduction in the feeding efficiency.

  FIG. 8 is a diagram illustrating a result of calculating the reflection characteristics of the antenna element according to the first embodiment by electromagnetic field simulation. In the simulation, when the center wavelength of the radio wave radiated from the antenna element 100 is λg, the vertical and horizontal widths of the basic radiating conductor 2 are set to about 0.4 λg, and the length of the MEMS switch and the length of the extending radiating conductor are substantially set. The distance between the feeding point and the center of the basic conductor was set to about 0.07 λg.

  In FIG. 8, the horizontal axis of the graph represents a value obtained by normalizing the frequency of the radio wave radiated from the antenna element 100 with the resonance frequency when the radio wave is radiated only from the basic radiation conductor 2. The vertical axis of the graph represents the reflected power from the antenna.

  A curve C1 shows the reflection characteristics of the antenna element 100 when the plurality of MEMS switches 4A1 and 4B1 are turned on, and a curve C2 shows the reflection characteristics of the antenna element 100 when the plurality of MEMS switches 4A1 and 4B1 are turned off.

  It shows that the reflected power from the antenna is small at the standard frequency at the peaks of the curves C1 and C2, that is, electromagnetic waves are efficiently radiated from the antenna. It can be seen from FIG. 8 that the operating frequency of the antenna changes when the MEMS switch is turned on or off.

  As described above, the antenna element of Embodiment 1 includes a plurality of MEMS switches between the basic radiation conductor and the extending radiation conductor. Each of the plurality of MEMS switches has a movable piece having a cantilever structure and a control electrode for driving the movable piece. One end of the movable segment is connected to the basic radiation conductor. Further, the antenna element of the first embodiment includes a through conductor that connects the ground conductor and the center of the basic radiation conductor.

  As a result, the antenna element according to the first embodiment simultaneously operates the plurality of movable segments by applying a desired voltage between the control wiring formed so as to pass under the plurality of movable segments and the through conductor. It becomes possible. Furthermore, according to the first embodiment, the movable piece of the MEMS switch can be moved without affecting the characteristics of the antenna element.

  Moreover, according to Embodiment 1, the extending | stretching radiation conductor is arrange | positioned symmetrically on the right and left of a basic radiation conductor. Even if the overall size of the radiation conductor changes due to the switching of the MEMS switch, the position of the feeding point that can be matched at each operating frequency is constant, so only one feeding point is required. Thus, according to the first embodiment, the control of the MEMS switch and the power supply to the antenna element can be realized by a simple method.

  Furthermore, according to the first embodiment, by arranging a plurality of MEMS switches in parallel between the basic radiating conductor and the extending radiating conductor, the current flowing through each switch can be reduced. Can be prevented. Therefore, according to the first embodiment, the reliability of the operation of the antenna element can be ensured.

[Embodiment 2]
FIG. 9 is a perspective view showing an antenna device according to the second embodiment.

FIG. 10 is a cross-sectional view of the antenna device according to the second embodiment.
With reference to FIG. 9 and FIG. 10, antenna device 100A according to the second embodiment includes antenna element 100 of the first embodiment. The following description of the configuration of the antenna element 100 will not be repeated.

  The antenna device 100 </ b> A further includes a coaxial connector 11 and a metal plate 13. The coaxial connector 11 corresponds to the “power feeding device” of the present invention. The power supply device of the present invention is at least partially connected to the basic radiation 2 through a through hole provided in the substrate. Thereby, it becomes easy to feed the radiation conductor from the back surface of the substrate.

The metal plate 13 is used for grounding the antenna device 100A.
The antenna device 100A is formed by bonding the metal plate 13 and the coaxial connector 11 in this order from the back surface 1B side of the substrate 1. At this time, the insulating portion 11 </ b> C of the coaxial connector 11 is accommodated in the opening 13 </ b> B provided in the metal plate 13. As a result, the core wire 11 </ b> A (inner conductor) is accommodated in the feed through hole 8 of the antenna element 100. The insulating portion 11C is formed of a nonconductor, and insulates the core wire 11A of the coaxial connector and the external conductor 11B.

  The core wire 11A is electrically connected to the basic radiation conductor 2. In order to ensure electrical connection between the core wire 11A and the basic radiation conductor 2, the feed through hole 8 is covered with a meltable conductor 12 such as solder or conductive resin.

  Furthermore, the ground conductor 6 of the antenna element 100 is connected to the outer conductor 11B of the coaxial connector 11 via the metal plate 13. As a result, the potential of the ground conductor 6 and the potential of the outer conductor 11B of the coaxial connector 11 are equal to zero.

  The coaxial connector 11 is supplied with high-frequency power from, for example, an oscillator mounted on a MMIC (Monolithic Microwave Integrated Circuit). This facilitates power supply to the basic radiation conductor 2. The coaxial connector 11 is generally used to connect an antenna and a device that supplies power to the antenna. Therefore, by providing the coaxial connector 11 in the antenna device 100A, various power feeding devices other than the above-described oscillator can be connected to the antenna 100A.

  The operating principle of antenna device 100A according to the second embodiment is the same as the operating principle of antenna element 100 according to the first embodiment. That is, a DC voltage V is applied between the control wiring 5A and the outer conductor 11B of the coaxial connector 11 in order to operate the plurality of movable segments 4A. A DC voltage V is applied between the control wiring 5B and the outer conductor 11B of the coaxial connector 11 in order to operate the plurality of movable segments 4B. The outer conductor 11B is connected to the plurality of movable segments 4A and 4B through the metal plate 13, the ground conductor 6, the through conductor 7, and the basic radiation conductor 2. A desired electrostatic force acts between the movable piece 4A and the control wiring 5A and between the movable piece 4B and the control wiring 5B. Thereby, the plurality of MEMS switches 4A1 and 4B1 can be turned on and off.

  As described above, the antenna device of the second embodiment is provided with the grounding metal plate on the back surface of the antenna element of the first embodiment and the coaxial connector for feeding power to the antenna element. The core wire (inner conductor) of the coaxial connector passes through the feed through hole and is connected to the basic radiation conductor. As a result, according to the second embodiment, it is possible to efficiently supply high-frequency power to the basic radiation conductor of the antenna element.

[Embodiment 3]
FIG. 11 is a cross-sectional view of the antenna device according to the third embodiment.

  Referring to FIG. 11, antenna device 100B according to the third embodiment includes antenna element 100 of the first embodiment. The following description of the configuration of the antenna element 100 will not be repeated.

  The antenna device 100 </ b> B further includes a metal conductor 14 and a power feeding circuit 15. The metal conductor 14 is embedded in the feed through hole 8.

  The power feeding circuit 15 feeds high frequency power to the antenna element 100 through the metal conductor 14. One terminal of the feeder circuit is connected to the through conductor 7 and grounded. The other terminal of the feeder circuit is connected to the metal conductor 14. Feed circuit 15 is formed on substrate 1 (for example, surface 1A). The power feeding circuit 15 corresponds to the “power feeding device” in the antenna device of the present invention.

  According to the third embodiment, the power feeding circuit 15 and the antenna element 100 can be integrated. As a specific example, the power feeding circuit 15 and the antenna element 100 can be formed over one semiconductor substrate. As a result, the antenna device of the third embodiment can have a smaller number of parts than the antenna device of the second embodiment.

[Embodiment 4]
12 to 26 are views showing a method of manufacturing the antenna element 100 of FIG. The cross sections shown in FIGS. 12 to 26 (excluding FIG. 16) below correspond to the portions indicated by the broken line frame of the antenna element 100 shown in FIG.

FIG. 12 is a diagram showing a first step of the method for manufacturing the antenna element 100 of FIG.
Referring to FIG. 12, a high resistance silicon substrate is used for substrate 1. In consideration of high frequency characteristics and the like, the substrate 1 is preferably a dielectric substrate. However, high resistance silicon is used for the substrate 1 in order to utilize MEMS technology for processing such as forming a through hole. The specific resistance of silicon is, for example, 1000 Ω · cm or more.

  An insulating film 16 is formed on the surface 1A of the substrate 1 for insulation between the surface wirings. For the insulating film 16, for example, a silicon thermal oxide film is used.

FIG. 13 is a diagram showing a second step of the method for manufacturing the antenna element 100 of FIG.
Referring to FIG. 13, ground conductor 6 is formed on back surface 1 </ b> B of substrate 1. The ground conductor 6 includes a low resistance layer 17A and an adhesion reinforcing layer 17B. The low resistance layer 17A is, for example, a gold (Au) film. The adhesion reinforcing layer 17B is, for example, a chromium (Cr) film, and is formed between the low resistance layer 17A and the back surface 1B in order to prevent the low resistance layer 17A from being peeled off. Subsequently, a patterning process (photolithography and etching) is performed, and the ground conductor 6 existing at the place where the feed through hole 8 is formed on the back surface 1B is removed to form the opening A1.

FIG. 14 is a diagram showing a third step of the method for manufacturing the antenna element 100 of FIG.
Referring to FIG. 14, the insulating film 16 existing in the region where the power supply through hole 8 is formed on the surface 1A is removed to form the opening A2. By the patterning process at this time, the diameter of the opening A2 is formed to be slightly larger than the diameter of the power feed through hole 8 (see FIG. 22) to be formed later. In the manufacturing process, the center of the opening A2 and the center of the power feed through hole 8 may be slightly shifted. In such a case, the substrate 1 is damaged as will be described later. By making the diameter of the opening A2 about one time larger than the diameter of the opening A1, it is possible to prevent damage to the substrate 1 when the power supply through hole 8 is formed.

FIG. 15 is a diagram showing a fourth step of the method for manufacturing the antenna element 100 of FIG.
Referring to FIG. 15, base wiring layer 18 is formed on surface 1A. The underlying wiring layer 18 serves as both the control wirings 5A and 5B and the plating underlying film when forming the MEMS switch and the radiation conductor (the basic radiation conductor 2 and the extending radiation conductors 3A and 3B).

  The underlying wiring layer 18 includes a low resistance layer 18A and an adhesion reinforcing layer 18B. The low resistance layer 18A is, for example, a gold (Au) film. The adhesion reinforcing layer 18B is a metal film having a high resistance such as a titanium (Ti) film, and is formed between the low resistance layer 18A and the surface 1A in order to prevent the low resistance layer 18A from being peeled off. The

  FIG. 16 is a diagram showing a fifth step of the method for manufacturing the antenna element 100 of FIG. Note that FIG. 16 shows a cross section that does not pass through the MEMS switch and is parallel to the cross section indicated by the dashed frame in FIG.

  Referring to FIG. 16, by processing base wiring layer 18, base wiring layer 18 has only low adhesion layer 18 </ b> B by removing low resistance layer 18 </ b> A at locations other than the lower part of the MEMS switch.

  When the MEMS switch is turned on, a part of the high-frequency current flowing through the MEMS switch flows into the control electrode through the gap between the MEMS switch and the control electrode. For this reason, the pass rate is deteriorated (passage loss increases). However, if the control electrode is a resistor, high-frequency current can be prevented from flowing. For this reason, it is preferable that the control wirings 5A and 5B are made of only the adhesion strengthening layer 18B having high resistance except for portions other than the lower part of the MEMS switch.

FIG. 17 is a diagram showing a sixth step in the method for manufacturing antenna element 100 in FIG.
Referring to FIG. 17, sacrificial layer 19 is formed on surface 1A, and minute recesses 19A serving as contact molds are formed by patterning at positions corresponding to the contact portions of the MEMS switch. The sacrificial layer 19 is, for example, a nickel (Ni) film.

FIG. 18 is a diagram showing a seventh step in the method for manufacturing antenna element 100 in FIG.
Referring to FIG. 18, sacrificial layers 19B and 19C are formed by patterning sacrificial layer 19. The sacrificial layer 19B becomes a part for forming a gap of the MEMS switch. The sacrificial layer 19 </ b> C serves as a lid for the power feed through hole 8 in the process of forming the power feed through hole 8.

FIG. 19 is a diagram showing an eighth step of the method for manufacturing the antenna element 100 of FIG.
Referring to FIG. 19, the extending radiation conductor 3B, the movable piece 4B, and the basic radiation conductor 2 are formed of a plating film. A portion that is not desired to be plated when the plating film is formed is covered with a resist mask 20. The plated film needs to be a good conductor in order to suppress high-frequency conductor loss as much as possible. For this purpose, for example, gold (Au) or copper (Cu) is used as the material of the plating film. Although not shown in FIG. 19, in the eighth step, the extending radiation conductor 3A and the movable piece of the MEMS switch 4A1 are also formed of a plating film.

FIG. 20 is a diagram showing a ninth step of the method for manufacturing the antenna element 100 of FIG.
Referring to FIG. 20, resist mask 20 is removed. Thus, the basic radiation conductor 2 and the extending radiation conductors 3A and 3B are formed mainly by the eighth and ninth steps. When the ninth step is completed, the movable segments 4A and 4B are not clearly separated from the basic radiation conductor 2.

FIG. 21 is a diagram showing a tenth step of the method for manufacturing the antenna element 100 of FIG.
Referring to FIG. 21, a resist is applied to back surface 1B of substrate 1 and patterning is performed. Thereby, a resist mask 21 is formed on the back surface 1B. Note that an opening is formed in the resist mask 21 at the position of the opening A1. This opening is provided in order to form the feed through hole 8 in the substrate 1. In addition, an opening A3 is provided in the resist mask 21 in order to form a through hole in the substrate 1 for embedding the through conductor 7 in a later step.

FIG. 22 is a diagram showing an eleventh step of the method for manufacturing the antenna element 100 of FIG.
Referring to FIG. 22, on the back surface 1 </ b> B of the substrate 1, a through hole 22 for embedding the through conductor 7 and a feed through hole 8 are formed in the substrate 1 </ b> B by ICP-RIE (Inductively Coupled Plasma Reactive Ion Etching). . The sacrificial layer 19C serves as an ICP-RIE etching stop material when the power feed through hole 8 is formed. Similarly, when the through hole 22 is formed, the adhesion reinforcing layer 18B serves as an ICP-RIE etching stop material.

  As described above, in consideration of alignment accuracy, the diameter of the opening A2 is formed to be slightly larger than the diameter of the power supply through hole 8. In the case where the center position of the opening A2 and the center position of the feed through hole 8 are shifted, when the etching of the substrate 1 proceeds to the surface 1A, the sacrificial layer 19C and the insulating film 16 appear. In this state, when an ion species is introduced into the power feed through hole 8, the insulating film 16 is charged. Then, the ion species introduced one after another into the power feed through hole 8 are reflected to the substrate 1 side by the charged insulating film 16. For this reason, the substrate 1 is etched to cause damage (notches).

  As a result, the power supply through-hole 8 has a problem that the diameter on the surface 1A side is widened. In addition, the dielectric breakdown of the insulating film 16 may occur.

  The opening A1 is formed to be slightly larger than the opening A2. Even if the etching of the substrate 1 proceeds to the surface 1A by ICP-RIE, only the sacrificial layer 19C appears. When the ion species reaches the sacrificial layer 19C, the electric charge escapes to the sacrificial layer 19C side, so that the surface of the sacrificial layer 19C is not charged. As a result, the notch in the substrate 1 can be prevented.

FIG. 23 is a diagram showing a twelfth process of the method for manufacturing the antenna element 100 of FIG.
Referring to FIG. 23, the inner wall of through hole 22 is metallized with a solder underlayer 23 made of, for example, Cr / Ni / Au.

FIG. 24 is a diagram showing a thirteenth step of the method for manufacturing the antenna element 100 of FIG.
Referring to FIG. 24, through conductor 7 is inserted into through hole 22 covered with solder base film 23. The through conductor 7 is, for example, solder. The through conductor 7 is formed by a molten solder discharge method or the like. Thus, the through conductor 7 is formed mainly through the 11th to 13th steps.

FIG. 25 is a diagram showing a fourteenth step of the method for manufacturing the antenna element 100 of FIG.
FIG. 26 is another diagram showing a fourteenth step of the method of manufacturing antenna element 100 in FIG.

  Referring to FIGS. 25 and 26, sacrificial layers 19B and 19C are removed by etching to complete antenna element 100 according to the first embodiment. Note that FIG. 24 corresponds to a portion indicated by a broken-line frame in FIG. The part shown in FIG. 25 corresponds to the part shown in FIG.

  As shown in FIG. 25, a gap is formed below the tip of the basic radiation conductor 2 by removing the sacrificial layer 19B. That is, one of the both end portions of the basic radiation conductor 2 becomes the movable piece 4B of the MEMS switch 4B1. Although not shown in FIG. 25, at this time, one of both end portions of the basic radiation conductor 2 becomes the movable piece 4A of the MEMS switch 4A1. In the fourteenth step, so to speak, both end portions of the basic radiating conductor 2 are selected, and processing for forming a plurality of MEMS switches 4A1, 4B1 is performed on both end portions.

  As described above, according to the fourth embodiment, the antenna element according to the first embodiment can be manufactured.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 is a perspective view showing a configuration of an antenna element according to a first embodiment. It is sectional drawing along the II-II line of FIG. It is a top view which shows the back surface of the antenna element of FIG. It is a perspective view which shows the antenna element 100 when several MEMS switch 4A1, 4B1 is an ON state. It is sectional drawing along the VV line of FIG. It is a figure which shows the path | route of the electric current which flows through a radiation conductor when several MEMS switch 4A1, 4B1 is all an OFF state. It is a figure which shows the path | route of the electric current which flows through a radiation conductor when several MEMS switch 4A1 and 4B1 are all ON states. It is a figure which shows the result of having calculated the reflection characteristic of the antenna element of Embodiment 1 by electromagnetic field simulation. 6 is a perspective view showing an antenna device according to a second embodiment. FIG. 6 is a cross-sectional view of an antenna device according to a second embodiment. FIG. It is sectional drawing of the antenna device according to Embodiment 3. It is a figure which shows the 1st process of the manufacturing method of the antenna element 100 of FIG. It is a figure which shows the 2nd process of the manufacturing method of the antenna element 100 of FIG. It is a figure which shows the 3rd process of the manufacturing method of the antenna element 100 of FIG. It is a figure which shows the 4th process of the manufacturing method of the antenna element 100 of FIG. It is a figure which shows the 5th process of the manufacturing method of the antenna element 100 of FIG. It is a figure which shows the 6th process of the manufacturing method of the antenna element 100 of FIG. It is a figure which shows the 7th process of the manufacturing method of the antenna element 100 of FIG. It is a figure which shows the 8th process of the manufacturing method of the antenna element 100 of FIG. It is a figure which shows the 9th process of the manufacturing method of the antenna element 100 of FIG. It is a figure which shows the 10th process of the manufacturing method of the antenna element 100 of FIG. It is a figure which shows the 11th process of the manufacturing method of the antenna element 100 of FIG. It is a figure which shows the 12th process of the manufacturing method of the antenna element 100 of FIG. It is a figure which shows the 13th process of the manufacturing method of the antenna element 100 of FIG. It is a figure which shows the 14th process of the manufacturing method of the antenna element 100 of FIG. It is another figure which shows the 14th process of the manufacturing method of the antenna element 100 of FIG. It is a figure which shows the structure of the antenna apparatus disclosed by US Patent 6198438 (patent document 1).

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Board | substrate, 1A surface, 1B back surface, 2 Basic radiation conductor, 3A, 3B Extending radiation conductor, 4A, 4B Movable section, 4A1, 4B1 MEMS switch, 5A, 5B Control wiring, 6 Grounding conductor, 6B, 13B, A1 A3 opening, 7 through conductor, 8 feed through hole, 9, 10 current, 11 coaxial connector, 11A core wire, 11B outer conductor, 11C insulation, 12 meltable conductor, 13 metal plate, 14 metal conductor, 15 feeder circuit , 16 Insulating film, 17A, 18A Low resistance layer, 17B, 18B Adhesion strengthening layer, 18 Underlying wiring layer, 19 Sacrificial layer, 19A Micro recess, 19B, 19C Sacrificial layer, 20, 21 Resist mask, 22 Through hole, 23 Below Base film, 100 antenna element, 100A, 100B, 110 antenna device, 130 radiating conductor element, 131 MEMS switch , 132 connecting conductor, 133,134 feeding point.

Claims (9)

A substrate having first and second major surfaces;
A first radiation conductor formed on the first main surface;
Second and third radiation conductors formed on the first main surface and positioned so as to sandwich the first radiation conductor;
A plurality of first MEMS switches provided in parallel between the first radiation conductor and the second radiation conductor;
A plurality of second MEMS switches provided in parallel between the first radiation conductor and the third radiation conductor;
A ground conductor formed on the second main surface;
An antenna element comprising a through conductor that penetrates through the substrate and connects the center of the first radiation conductor and the ground conductor.   The antenna element according to claim 1, wherein the second and third radiating conductors are arranged symmetrically with respect to the first radiating conductor. Each of the plurality of first MEMS switches includes:
A first movable piece having one end connected to the first radiating conductor and the other end extending toward the second radiating conductor and positioned above the first main surface;
A first control electrode provided below the movable section,
The first control electrodes of each of the plurality of first MEMS switches are connected to each other;
Each of the plurality of second MEMS switches includes:
A second movable piece having one end connected to the first radiation conductor and the other end extending toward the third radiation conductor and positioned above the first main surface;
A second control electrode provided below the movable section,
The antenna element according to claim 2, wherein the second control electrodes of each of the plurality of second MEMS switches are connected to each other. An antenna device,
An antenna element according to claim 1,
The antenna element is formed with a through-hole penetrating the substrate and the first radiating conductor and opened at a position different from the center of the first radiating conductor in the first radiating conductor,
The antenna device is
An antenna device, further comprising: a power feeding device at least partially passing through the through hole and electrically connected to the first radiation conductor. The power supply device
The antenna according to claim 4, comprising a coaxial connector having an inner conductor electrically connected to the first radiation conductor through the through hole and an outer conductor electrically connected to the ground conductor. apparatus. The power supply device
A metal conductor inserted into the through hole;
The antenna device according to claim 4, further comprising a power supply circuit connected to the metal conductor. A method for manufacturing an antenna element, comprising:
A first radiating conductor is formed on the first main surface of the semiconductor substrate having the first and second main surfaces, and the first radiating conductor is sandwiched between the first main surfaces. Forming second and third radiation conductors;
A plurality of first MEMS switches provided in parallel between the first radiation conductor and the second radiation conductor by selectively processing the first radiation conductor; and the first radiation conductor. Forming a plurality of second MEMS switches provided in parallel between the first radiation conductor and the third radiation conductor;
Forming a ground conductor on the second main surface;
Forming a through conductor that penetrates the semiconductor substrate and connects the center of the first radiation conductor and the ground conductor.   The method of manufacturing an antenna element according to claim 7, wherein the second and third radiating conductors are arranged symmetrically with respect to the first radiating conductor. Each of the plurality of first MEMS switches includes:
A first movable piece having one end connected to the first radiating conductor and the other end extending toward the second radiating conductor and positioned above the first main surface;
A first control electrode provided below the movable section,
The first control electrodes of each of the plurality of first MEMS switches are connected to each other;
Each of the plurality of second MEMS switches includes:
A second movable piece having one end connected to the first radiation conductor and the other end extending toward the third radiation conductor and positioned above the first main surface;
A second control electrode provided below the movable section,
The method for manufacturing an antenna element according to claim 8, wherein the second control electrodes of each of the plurality of second MEMS switches are connected to each other.

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