JP2007124308A - Antenna device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna device of lowered input impedance. <P>SOLUTION: In the antenna device 1, a set of radiation boards 2, 2 are arranged with a prescribed gap, the radiation board 2 is provided with an impedance matching means 3a for adjusting the input impedance, and a power supply part 5 electrically connected to the radiation board 2 is included. The impedance matching means 3a is conductor members 4, 4 provided in the respective radiation boards 2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an antenna device, and more particularly to an antenna device including a flat plate-shaped radiation plate.

  2. Description of the Related Art Conventionally, an antenna device for UWB that can use an ultra-wide frequency band in an antenna device including a flat radiation plate is known. For example, there is a known antenna device 50 as shown in FIG. 15, and the antenna device 50 is provided with a pair of radiation plates (conductor plates) 51 and 51. The radiation plates 51 have a trapezoidal shape in plan view, and the upper sides of the radiation plates 51 are arranged substantially in parallel with a gap having a predetermined width. A transmission line 53 is connected to a power feeding section 52 provided on the upper side of each radiation plate 51 so that a predetermined voltage is applied and a predetermined current is supplied. When power is supplied via the power supply unit 52 and the transmission line 53, resonance occurs based on the voltage and current, and radio waves are radiated from the radiation plates 51.

Also, in UWB antenna devices, there is known an antenna device in which a pair of radiation plates are arranged close to each other while forming a gap of a predetermined width, and power is fed from a predetermined position near the open end of the gap (patent) Reference 1). According to such an antenna device, by supplying power from a predetermined position of the radiation plate, current is transmitted in a direction in which a geometrical similarity is easily formed in the radiation plate. Then, since the VSWR characteristic is similar to that when using a radiation plate having a similar structure with the power feeding portion as a base point, a wide-band characteristic is realized by downsizing while using a radiation plate having a high degree of freedom. ing.
JP 2005-117363 A

  However, the conventional UWB antenna device shows a wide band characteristic, but since the input impedance is as high as about 200 to 300Ω, when the power is fed by connecting a commonly used 50Ω transmission line, the impedance is There is a problem in that the electric power cannot be effectively transmitted / received because most of the electric power supplied cannot be matched and is fed.

  Here, in general, the input impedance of the dipole antenna device is determined based on the input resistance and the input reactance. It is known that the input resistance decreases as the gap width between the radiation plates decreases, and in order to reduce the input impedance, the antenna device is configured by reducing the gap width between the radiation plates. However, in the conventional antenna device, since the upper side is arranged on the gap side in the case of the trapezoidal radiation plate and the apex is arranged on the gap side in the case of the triangular radiation plate, the length dimension of the portion in contact with the gap of the radiation plate is small. Even if the gap width is reduced, the amount of charge stored on the gap side of the radiation plate cannot be increased efficiently. Therefore, there is a problem that the input impedance cannot be sufficiently reduced even if the gap width between the radiation plates is reduced to the structural limit.

  In addition, in order to connect a 50Ω transmission line, it is necessary to connect with an impedance conversion circuit interposed therebetween, and there is a problem that the entire antenna device becomes large.

  The present invention has been made in view of these points, and an object of the present invention is to provide an antenna device with reduced input impedance.

In order to solve the above problem, the invention according to claim 1 is:
An antenna device in which a set of radiation plates is arranged with a predetermined gap, and the radiation plate includes impedance matching means for adjusting an input impedance, and a feeding unit electrically connected to each of the radiation plates. In
The antenna device according to claim 1, wherein the impedance matching means is a conductor member provided in each of the radiation plates.

According to the first aspect of the present invention, the radiation plate is provided with the impedance matching means, and the input reactance is reduced by using a set of conductor members. Further, by providing the conductor member, the capacitance of the antenna device increases and the input resistance decreases. Therefore, since both input reactance and input resistance are reduced, the input impedance is efficiently reduced.
Further, by providing a conductor member for each of the radiation plates, the capacitance of the antenna device can be greatly increased, and the input impedance is efficiently reduced.

The invention according to claim 2 is the antenna device according to claim 1,
One of the radiation plates is grounded by a grounding means.

  According to the second aspect of the present invention, since one of the radiation plates including the conductor member is grounded, the capacitance of the impedance matching means is greatly increased. The radiation plate also functions as a ground plate by being grounded.

The invention according to claim 3 is the antenna device according to claim 1 or 2,
The impedance matching means is characterized in that the conductor members are flat and are arranged so as to face each other.

  According to the third aspect of the present invention, the impedance matching means is configured such that the conductor members have a flat plate shape and are arranged so that they face each other, whereby charges are accumulated in the conductor member.

The invention according to claim 4 is the antenna device according to any one of claims 1 to 3,
The impedance matching means includes protrusions on mutually facing surfaces of the conductor member, and the conductor members are arranged so that the protrusions are staggered.

  According to the fourth aspect of the present invention, since the conductor member of the impedance matching means is provided with the protrusion, the facing area of the conductor member is increased and the capacitance is increased. That is, the input impedance is further reduced without increasing the size of the conductor member.

The invention according to claim 5 is the antenna device according to claim 1,
The radiation plate is disposed on a support substrate;
The impedance matching means includes a hole formed as the conductor member on the gap side of the radiation plate, and the hole penetrates the support substrate and is metal-plated on the inner periphery. And

  According to the invention described in claim 5, the hole as the conductor member of the impedance matching means is formed in the radiation plate so as to penetrate the support substrate, and the capacitance is increased by the metal plating portion on the inner periphery. As a result, the input resistance and input reactance of the antenna device are reduced. Therefore, since both input reactance and input resistance are reduced, the input impedance is efficiently reduced.

According to the first aspect of the present invention, since both the input resistance and the input reactance of the antenna device can be reduced, the input impedance can be efficiently reduced. Therefore, it is possible to directly connect a 50Ω transmission line with low characteristic impedance to the power feeding unit, and it is not necessary to provide an impedance conversion circuit or the like, so that the antenna device can be simplified and downsized.
In addition, the power supply efficiency is good, and the use band of the antenna device can be further widened.

  According to the second aspect of the present invention, since the capacitance of the impedance matching means is significantly increased, the input impedance of the antenna device can be efficiently reduced. Further, since the radiation plate can also function as a ground plate, it can be applied to a monopole antenna device.

  According to the invention described in claim 3, since the flat conductor members are arranged so as to face each other and accumulate electric charges, both the input reactance and the input resistance are reduced with a simple configuration, and the input impedance is easily reduced. Can be made.

  According to invention of Claim 4, it is possible to reduce input impedance more efficiently.

According to the invention described in claim 5, since the input reactance of the antenna device is reduced and the input resistance is reduced, the input impedance can be effectively reduced. Therefore, it is possible to directly connect a 50Ω system line and there is no need to provide an impedance conversion circuit or the like, so that the antenna device can be simplified and downsized.
In addition, the power supply efficiency is good, and the use band of the antenna device can be further widened.

  Embodiments of an antenna device according to the present invention will be described below with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples.

[First embodiment]
First, the configuration of the antenna device 1 according to the first embodiment will be described.
As shown in FIG. 1, in the antenna device 1 of the present embodiment, the radiation plates 2 and 2 having a trapezoidal shape in plan view are provided with a gap having a predetermined width and are arranged symmetrically about the center of the gap as a reference axis. . The radiation plate 2 is arranged such that the upper side thereof is disposed on the gap side and the upper sides of the pair of radiation plates 2 and 2 are substantially parallel to each other. Here, the length of each side of the radiation plate 2 is such that the upper side is 15 mm, the lower side is 32.5 mm, and the height is 15 mm. In order to use the antenna device for UWB, the length of each side of the radiation plate 2 is preferably about 8 to 12 mm on the upper side, 20 to 45 mm on the lower side, and about 10 to 25 mm on the height.

  The radiation plate 2 is made of a conductive material such as aluminum or copper. Moreover, there is no restriction | limiting in particular about the planar view shape of the radiation plate 2, It is good also as forming by any of a straight line, a curve, or these combination. In order to make the radiation pattern of radio waves uniform, an axially symmetric shape with the vertical bisector of the upper side as the reference axis is preferable. Here, the lowest frequency of the use band is determined according to the length dimension from the lower side of the radiation plate 2 to the lower side of the other radiation plate 2.

  Impedance matching means 3a for adjusting the input impedance is provided on the gap side of each radiation plate 2. As shown in FIGS. 2 and 3, the impedance matching means 3 a includes a pair of conductor members 4 and 4 having the same area. Each conductor member 4 has a flat plate shape and is disposed along the upper side of the radiation plate 2. The conductor member 4 is made of a conductive material such as metal, and is disposed so as to face each other with a gap therebetween, so that it functions as a capacitor and accumulates electric charges. The conductor member 4 is formed in a rectangular shape when viewed from the side, and has outer dimensions of a short side of 2 mm, a long side of 18 mm, and a thickness of 0.5 mm. Although there is no restriction | limiting in particular in the shape and magnitude | size of the conductor member 4, From a viewpoint of a connection with the radiation plate 2, it is 1 to 1.5 times the upper side (side which contacts the conductor member 4) about a long side about a long side. Is preferred. The short side of the conductor member 4 is preferably 0.1 to 10 mm, and the upper limit of the thickness is preferably 5 mm. In addition, as shown in FIG. 4, FIG. 5, it is good also as forming the edge part of the conductor member 4 with a curve.

  The gap between the radiation plates 2 affects the input impedance of the antenna device 1. The input impedance is lowered as the width of the gap is reduced, but the limit is about 0.5 mm from the viewpoint of mounting the antenna device 1, and generally about 0.5 to 1 mm. Has been. In the present embodiment, the gap between the conductor members 4 is the gap between the radiation plates 2 and the width thereof is 0.5 mm.

  A power feeding portion 5 that is electrically connected to the radiation plate 2 is provided at a substantially central position of the conductor member 4. One end of a transmission line 6 that supplies a current with a predetermined amplitude and phase is connected to the power supply unit 5. Connected to the other end of the transmission line 6 is an electronic component or a signal processing device (both not shown) for processing electrical signals based on transmitted and received radio waves.

Next, a radio wave transmission / reception method by the antenna device 1 of the present embodiment will be described.
When the antenna device 1 transmits radio waves, current is supplied to each radiation plate 2 through the transmission line 6 with a predetermined amplitude and phase based on an electrical signal from an electronic device or a signal processing device. The current fed to the radiation plate 2 is transmitted from the power feeding unit 5 to the lower side along the side of each radiation plate 2. Then, radio waves are transmitted mainly from the side and bottom sides of the radiation plate 2. Here, when power is supplied to the radiation plate 2, if the conductive member 4 is not provided, a part of the current is easily reflected by the power supply unit 5, but by providing the conductive member 4, the capacitance of the antenna device 1 is increased and the reflected wave is reflected. Is reduced. That is, the input reactance is reduced.

  When the antenna device 1 receives a radio wave, when a radio wave having a predetermined frequency is received from the radiation plate 2, a current flows through the radiation plate 2, and a current corresponding to the resonance frequency is transmitted to the power feeding unit 5. . The current transmitted in this way is transmitted to the electronic device or the signal processing device via the transmission line 6. Here, since the radiation plate 2 is provided with the impedance matching means 3a, the electric signal input from the power feeding unit 5 to the transmission line 6 is efficiently transmitted.

  Here, the input impedance Z of the antenna device 1 is represented by the sum of the input resistance R and the input reactance jX. The input resistance R is a value obtained by dividing the voltage vector amount at the power feeding unit 5 by the current vector amount, and the input reactance jX is a value obtained by the reflection amount of the current incident on the power feeding unit 5. is there. The state where impedance matching is achieved in the antenna device 1 is a state where the input impedance of the antenna device 1 is equal to the characteristic impedance of the feed line connected to the feed unit 5. For example, when the input reactance is completely removed, no reflected wave exists in the vicinity of the power supply unit 5 and the supply current is completely supplied to the radiation plate 2, so that the input resistance and the characteristic impedance of the power supply line become equal. Impedance matching can be obtained by connecting to.

続いて、以下の数式２のようにして、アドミッタンスＹ_antをインピーダンスＺ_antに変換する。

As shown in FIG. 7A, the antenna device 1 of the present embodiment is provided with impedance matching means 3a that functions as a capacitor. Thus, expressed in the circuit diagram shown in FIG. 7 (b), the radiation plate 2 to a radio wave transmitting and receiving means comprising a state equivalent to the impedance matching means 3a are connected in parallel as a capacitor of a capacitance C _r is there. In such an antenna device 1, the impedance of the capacitor is represented by 1 / jωC _r , and the impedance of the radio wave transmission means including the radiation plate 2 is represented by (R _r + jX _r ). Therefore, the admittance Y _ant, which is the reciprocal of the input impedance Z _ant of the antenna device 1, is obtained as shown in Equation 1 below.

Subsequently, the admittance Y _ant is converted into the impedance Z _ant as shown in Equation 2 below.

In the impedance Z _ant thus determined, the real part R _ant, when the imaginary part and X _ant, the real part R _ant and the imaginary part X _ant contains imaginary part B _ant admittance Y _ant. From Equation 1, since B _ant is a value that increases as the capacitance C _r of the capacitor increases, the value of both the real part R _ant and the imaginary part X _ant increases as C _r increases. Therefore, it is theoretically shown that the input resistance R _ant and the input reactance jX _{ant of} the antenna device 1 become smaller as C _r becomes larger.
In the present embodiment, since an increase in the opposing area of the conductor member 4 capacitance C _r of the impedance matching means 3a increases, it is possible to reduce the more input impedance Z _ant. Further, if the conductive member 4 as in the present embodiment is provided in the radiation plate 2, by grounding the grounding means of the radiation plate 2, significantly increase the capacitance C _r of the conductive member 4 Is possible. In this case, since the grounded radiation plate 2 also functions as a ground plate, it can be applied to a so-called monopole antenna device.

  In the antenna device 1 of the present embodiment, since the conductor member 4 is provided on the power feeding unit 5 side of the radiation plate 2, the reflected wave of the supply current of the radiation plate 2 is reduced. That is, the input reactance of the radiation plate 2 is reduced. Further, the conductor member 4 increases the capacitance of the antenna device 1 and decreases the input resistance. Thus, since the conductor member 4 can reduce the input reactance and the input resistance, the input impedance can be effectively reduced.

  Here, in order to determine whether or not the input reactance is reduced, the return value at each frequency was measured. The return value is represented by the ratio of the incident wave and the reflected wave of the current supplied to the radiation plate 2, and is 0 dB when all the current returns after being totally reflected by the power feeding unit 5. Is not returned at all, −∞ dB is indicated. The smaller the return value, the smaller the amount of reflection at that frequency, indicating that impedance matching is achieved. In general, a range showing a return value of about −10 dB or less is a use band of the antenna device.

  As shown in FIG. 6, the antenna device 1 of the present embodiment includes the impedance matching means 3 a, whereby the input reactance is reduced and the return value is significantly reduced, and the frequency band used is higher than that of the conventional antenna device 1. Has become wider.

  In addition, the change in input impedance due to the reduction in input reactance was measured at each frequency. Here, the characteristic impedance of the transmission line 6 is generally about 50Ω, and if the input impedance of the antenna device 1 is about 50Ω, the transmission line 6 can be directly connected to achieve impedance matching.

  As shown in FIG. 6, the antenna device 1 according to the present embodiment includes the conductor member 4, thereby reducing the return value and the input resistance as compared with the conventional antenna device 1. That is, since both the input resistance and the input reactance are reduced, the input impedance is efficiently reduced to take a value around 50Ω.

As described above, according to the antenna device 1 of the present embodiment, since the input impedance is reduced to about 50Ω, it is possible to directly connect the 50Ω transmission line 6 to obtain impedance matching.
Further, since the impedance matching means 3a can be directly attached to each radiation plate 2 to reduce the input impedance, the device itself can be made smaller than an antenna device that is separately provided without directly attaching the impedance matching means to the radiation plate. Therefore, the input impedance can be efficiently reduced.

  In the present embodiment, the antenna device 1 using the two radiation plates 2 as a set has been described. However, the number of the radiation plates 2 is not limited, and as shown in FIG. The present invention can also be applied to an antenna device used as a set. In that case, the four radiation plates 2 are arranged radially with their upper sides directed toward the center of the antenna device, and a conductor member 4 is provided on the upper side of each radiation plate 2. As for the planar view shape of the conductor member 4, the both ends are bent toward the outer side of the antenna apparatus so that adjacent conductor members 4 may not contact. By providing the conductor member 4 as such impedance matching means, the input reactance is reduced in each radiation plate 2, and the input impedance is lowered.

[Second Embodiment]
Next, the configuration of the antenna device 1 according to the second embodiment of the present invention will be described. Note that the antenna device 1 of the present embodiment is different from the first embodiment only in the impedance matching means, and the same components are denoted by the same reference numerals and description thereof is omitted as appropriate.

  As shown in FIGS. 9 and 10, the antenna device 1 includes a radiation plate 2, a power feeding unit, and a transmission line, as in the first embodiment. Conductive impedance matching means 3 b is provided on the upper side of the radiation plate 2. The impedance matching means 3b is provided with the same conductor member 4 as in the first embodiment. A plurality of protrusions 8 having a prismatic shape and conductivity are provided on the opposing surfaces of the conductor member 4 so as to protrude toward the gap. As shown in FIG. 11, the conductor members 4 are arranged so that the protruding portions 8 facing each other are staggered and do not contact each other. In the present embodiment, the projecting portion 8 is a square having an end surface of 0.8 mm × 0.8 mm, a height of 0.3 mm, and is provided in one conductor member 4 in 2 rows × 4 columns. Yes.

  The transmitting / receiving method of the antenna device 1 is the same as that of the first embodiment, and the return value and input impedance at each wavelength were measured. As shown in FIG. 6, in the antenna device 1 of the present embodiment, the impedance matching means 3b is provided with the protrusions 8, thereby increasing the facing area and increasing the capacitance. That is, since the input reactance is further reduced, the return value is further lowered, and the usable frequency is broadened. Further, since the capacitance increases and the input resistance also decreases, the input impedance is efficiently reduced to take a value of about 50Ω.

  As described above, according to the antenna device 1 of the present embodiment, since the input impedance is about 50Ω at 3 to 11 GHz, it is possible to directly connect a 50Ω transmission line.

  In the present embodiment, the protruding portion 8 is provided to increase the facing area of the impedance matching means 3b. However, in order to increase the facing area, the shape of the protruding portion 8 is not particularly limited, and is a weight-like shape. It is good also as providing a thing or forming a recessed part.

[Third embodiment]
Next, the configuration of the antenna device 1 according to the third embodiment of the present invention will be described. The antenna device 1 of this embodiment is different from that of the first embodiment in that the radiation plate 2 is provided on the support substrate, and the same components are denoted by the same reference numerals and description thereof is omitted as appropriate.

  As shown in FIG. 12, the antenna device 1 of this embodiment includes a flat support substrate 9 made of a dielectric material such as Teflon (registered trademark). A radiation plate 2 similar to that of the first embodiment is placed on the upper surface of the support substrate 9, and a power feeding unit 5 and a transmission line 6 are provided on the upper side of the radiation plate 2. An impedance matching means 3c is provided on the upper side of the radiation plate 2. As shown in FIG. 13, as the impedance matching means 3c, a plurality of holes 10 as conductor members whose inner periphery is plated with metal are formed so as to penetrate the support substrate 9 in the vertical direction. . In this embodiment, copper foil is attached as metal plating, and gold plating is applied to the upper surface to prevent rust.

  The transmission / reception method of the antenna device 1 is the same as that of the first embodiment, and the reflected wave of the supplied current is stored in the metal plating portion of the hole 10 and the input resistance and input reactance of the radiation plate 2 are reduced. It is like that.

As described above, according to the antenna device 1 of the present embodiment, since the input resistance and the input reactance are reduced, the input impedance can be efficiently reduced, and the 50Ω transmission line 6 can be directly connected. Is possible.
Furthermore, when the support substrate 9 is used as a circuit board, the hole 10 can also function as a via hole for conduction.

  In the present embodiment, one support substrate 9 is used, but the number of support substrates 9 is not limited. Therefore, as shown in FIG. 14, a plurality of support substrates 9 may be used in an overlapping manner. In the case of such an antenna device 1, the radiation plate 2 may be placed on any support substrate 9, and the hole 10 penetrates the radiation plate 2 and at least the support substrate 9 in contact with the radiation plate 2. What is necessary is just to form. Specifically, as shown in FIG. 14, the hole 10 may be formed so as to penetrate all of the support substrates 9, so as to penetrate the lower two or upper two support substrates 9 in FIG. 14. Alternatively, it may be formed so as to penetrate the middle or bottom one support substrate 9 in FIG. By forming the hole 10 in this way, it is possible to make the support substrates 9 sandwiching the radiation plate 2 conductive.

It is a top view of the antenna device in a first embodiment. It is a perspective view of the antenna device in a first embodiment. It is the side view seen from the gap of the antenna device in a first embodiment. It is a perspective view which shows the modification of the antenna device in 1st embodiment. It is the side view which looked at the modification of the antenna device in 1st embodiment from the clearance gap. It is a graph which shows the measurement result of a return value and input impedance. (A) It is a schematic block diagram of the antenna apparatus in 1st embodiment, (b) It is a circuit diagram of the antenna apparatus in 1st embodiment. It is a top view which shows the modification of the antenna device in 1st embodiment. It is a top view of the antenna apparatus in 2nd embodiment. It is a perspective view of the antenna apparatus in 2nd embodiment. (A) It is the side view which looked at one radiation plate of the antenna device in 2nd embodiment from the gap | interval. (B) It is the side view which looked at the other radiation plate of the antenna apparatus in 2nd embodiment from the gap | interval. It is a top view of the antenna apparatus in 3rd embodiment. It is II sectional drawing of the antenna apparatus in 3rd embodiment. It is sectional drawing which shows the modification of the antenna device in 3rd embodiment. It is a top view of the conventional antenna device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antenna apparatus 2 Radiation plate 3a, 3b, 3c Impedance matching means 4 Conductor member 5 Feeding part 6 Transmission line 8 Protrusion part 9 Supporting substrate 10 Hole part

Claims (5)

An antenna device in which a set of radiation plates is arranged with a predetermined gap, and the radiation plate includes impedance matching means for adjusting an input impedance, and a feeding unit electrically connected to each of the radiation plates. In
The antenna device according to claim 1, wherein the impedance matching means is a conductor member provided in each of the radiation plates.   2. The antenna device according to claim 1, wherein one of the radiation plates is grounded by a grounding means.   3. The antenna device according to claim 1, wherein the impedance matching means is arranged such that the conductor members are flat and are opposed to each other. 4.   The said impedance matching means is provided with the protrusion part in the mutually opposing surface of the said conductor member, The said conductor member is arrange | positioned so that the said protrusion part may become alternate. The antenna apparatus as described in any one. The radiation plate is disposed on a support substrate;
The impedance matching means includes a hole formed as the conductor member on the gap side of the radiation plate, and the hole penetrates the support substrate and is metal-plated on the inner periphery. The antenna device according to claim 1.

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