JP6178292B2 - Antenna device - Google Patents

Description

  The present invention relates to an antenna device, and more particularly to an antenna device that operates at a plurality of frequencies.

  Today's portable wireless devices often support multiple wireless communication standards, and antennas also need to support multiple frequency bands. In general, an antenna tends to increase in size in order to cope with a plurality of frequencies. On the other hand, miniaturization of today's portable wireless devices is remarkable, and miniaturization of antennas is also desired. Therefore, by realizing an antenna that operates at a plurality of frequencies without increasing the antenna size, it is possible to support a plurality of frequency bands without increasing the size of the portable wireless device.

  FIG. 11 shows a configuration example of an existing antenna. This figure is a diagram showing a basic form of an antenna (SRR antenna) having a split ring resonator.

  FIG. 11 includes a split ring resonator 1, a power feeding unit 2, and a GND plate 3, and the split resonator 1 is disposed so as to be in contact with the outer periphery of the GND plate 3.

  FIG. 12 is an enlarged view of the split ring resonator 1 of the basic form of the SRR antenna shown in FIG. The split ring resonator 1 has an opening 11 disposed so as to be in contact with the outer periphery of the GND plate 3, a power supply conductor 12 is connected to the power supply unit 2, and AC power is supplied from the power supply unit 2. The first conductor 13 is disposed so as to be connected to the opening edge and the power supply conductor 12, and the second conductor 14 is disposed so as to be connected to the opening edge. In addition, a split portion 15 is formed in the portion where the first conductor 13 and the second conductor 14 are closest to each other and the conductors extending from the first conductor 13 and the second conductor 14 are opposed to each other.

  FIG. 13 schematically shows the flow of current at the operating frequency of the SRR antenna shown in FIGS. 11 and 12, and the current is indicated by the dotted arrow. The operating frequency of the SRR antenna is fed from the feeder 2, feeder 12, part of the first conductor 13, second conductor 14, second conductor 14, and opening 11. The coil portion equivalently formed on the outer periphery of the opening 11 connecting up to the portion 2 and the capacitor portion equivalently constituted in the split portion 15 constitute a series resonance circuit, so that the resonance frequency of the series resonance circuit Determined by.

  FIG. 14 shows the impedance characteristics of the SRR antenna shown in FIGS. This is a diagram showing the locus of impedance with respect to frequency using a Smith chart. The point at which the locus of impedance is closest to the center of the Smith chart is the operating frequency of the antenna.

  On the other hand, FIG. 15 shows the return loss characteristics of the SRR antenna shown in FIGS. The return loss is the same measurement as the impedance characteristic shown in FIG. 14, and the chart (diagram) is merely different. A chart made so that the closer the impedance is to 50Ω, the smaller the value is. FIG. 5 shows that at frequency 1, the impedance is close to 50Ω and the antenna characteristics are improved. This valley portion is called antenna resonance. That is, the valley portion indicates the frequency at which the antenna is operating. In order for the antenna to operate satisfactorily, it is generally desirable that the return loss be -5 dB or less at the frequency at which the antenna operates. From FIG. 15, it can be seen that only the frequency 1 is the valley where the return loss is -5 dB or less. That is, this antenna is an antenna that operates only at frequency 1 within the frequency range shown in FIG.

WO2014 / 073703

  Today's portable wireless devices often support multiple wireless communication standards, and antennas also need to support multiple frequency bands, but it is difficult to support multiple frequency bands with the basic form of the above SRR antenna It is.

  In order to solve the above problem, an SRR antenna as shown in Patent Document 1 has been proposed. However, this SRR antenna has a plurality of split ring resonators arranged side by side on one conductor plane in order to correspond to a plurality of frequency bands. Therefore, there is a problem that the antenna becomes large.

  An object of the present invention is to provide a small antenna device that supports a plurality of frequency bands.

  The present invention relates to an antenna device that operates at a frequency determined by the split ring resonator by disposing a split ring resonator on a GND plate, and the conductor constituting the antenna device is connected to the first in the opening of the antenna device. The additional conductor portion is connected to the antenna device.

  According to the present invention, it is possible to provide a small antenna device that supports a plurality of frequency bands.

It is a top view which shows the antenna of the 1st Embodiment of this invention. It is the top view to which the SRR part of the antenna of FIG. 1 was expanded. It is a figure which shows the impedance characteristic of the antenna of FIG. It is a figure which shows the return loss characteristic of the antenna of FIG. FIGS. 5A, 5B, and 5C are diagrams schematically showing the flow of current on the SRR at frequency 1, frequency 2, and frequency 3 of the antenna of FIGS. It is a top view which shows the antenna of the 2nd Embodiment of this invention. (A), (b), (c) is a figure which shows typically the flow of the electric current on SRR in the frequency 1, frequency 2, and frequency 3 of the antenna of FIG. 6, respectively. It is a top view which shows the antenna of the 3rd Embodiment of this invention. It is a figure which shows the impedance characteristic of the antenna of FIG. It is a figure which shows the return loss characteristic of the antenna of FIG. It is a top view which shows the basic form of the antenna which has SRR of the background art of this invention. It is the top view to which the SRR part of the antenna of FIG. 11 was expanded. It is a figure which shows typically the flow of the electric current in the operating frequency of the antenna of FIG. It is a figure which shows the impedance characteristic of the antenna of FIG. It is a figure which shows the return loss characteristic of the antenna of FIG.

(First embodiment)
(Description of configuration)
FIG. 1 is a plan view showing the antenna of the first embodiment. The antenna has a split ring resonator 1, a power feeding unit 2, and a GND plate 3, and the split resonator 1 is disposed so as to be in contact with the outer periphery of the GND plate 3. The difference from the antenna of FIG. 11 is that a first additional conductor portion 4 and a second additional conductor portion 5 are added in the opening 11 of the split ring resonator 1.
(Description of operation)
FIG. 2 is an enlarged view of the split ring resonator 1 of the SRR antenna of FIG. The first additional conductor 41 is disposed so as to be connected to the tip of the second conductor 14 on the split portion 15 side, and is connected to the opening edge of the opening portion 11 so that the other end faces the first additional conductor 41. A second additional conductor 42 is disposed. The conductors respectively extending from the first additional conductor 41 and the second additional conductor 42 constitute a first additional split portion 43.

  Further, the third additional conductor 51 is arranged so as to be connected to the tip of the second additional conductor 42 on the first additional split portion 43 side, and the other end is connected to the opening edge of the opening 11 and the third additional conductor 42 is connected to the third additional conductor 42. A fourth additional conductor 52 is arranged so as to face the conductor 51. Conductors extending from the third additional conductor 51 and the fourth additional conductor 52 constitute a second additional split portion 53, respectively.

  FIG. 3 shows the impedance characteristics of the antenna of this embodiment. From FIG. 3, it can be seen that at frequency 1, frequency 2, and frequency 3, the impedance locus intersects the horizontal line that is closest to or passes through the center of the Smith chart.

  FIG. 4 shows the return loss characteristics of the antenna of this embodiment. From this figure, since it is a valley portion with a return loss of -5 dB or less at frequency 1, frequency 2 and frequency 3 shown in the impedance characteristics of FIG. I understand that 3 shows the same frequency range as FIG. 15 showing the return loss characteristic of the SRR antenna of FIG. 11 (background art), and therefore operates at a higher frequency than the SRR antenna of FIG. .

  5A, 5B, and 5C schematically show current flows on the split ring resonator at the above-described frequency 1, frequency 2, and frequency 3, respectively. From these figures, it can be seen that the current path at each frequency is different. The inductance of the coil that is equivalently changed due to a different current path changes, and the capacitance of the capacitor that is equivalently changed changes depending on the number of split parts that pass therethrough. As a result, three types of resonance frequencies are generated in the split ring resonator. Therefore, the antenna shown in this embodiment operates at three different frequencies.

  The resonance frequency 2 is generated by the addition of the SRR resonator composed of the first additional conductor 41 and the second additional conductor 42. The resonance frequency 3 is generated by the addition of the SRR resonator constituted by the third additional conductor 51 and the fourth additional conductor 52.

Further, by changing the length of the first additional split section 43 and the second additional split section 53 and the split interval in FIG. Frequency 2 and frequency 3 can be changed.
(effect)
As explained above, by adding the first additional conductor 4 and the second additional conductor 5 in the opening of the SRR antenna, the operating frequency of the antenna can be increased without increasing the antenna size. Can do.
(Second Embodiment)
FIG. 6 shows a second embodiment. FIG. 6 is an enlarged view of the split ring resonator portion of the SRR antenna in this embodiment. The difference from the first embodiment (FIG. 1) is that the first additional conductor 41 is connected to the middle portion of the second conductor 14 instead of the tip, and the second additional conductor 41 is opposed to the first additional conductor 41. The point is that the position of the conductor 42 is moved. Further, the third additional conductor 51 is connected not to the tip of the second additional conductor 42 but to the intermediate portion, and the position of the fourth additional conductor 52 is moved so as to face the third additional conductor 51. It is. With such a configuration, the same effect as in the first embodiment can be obtained. FIGS. 7A, 7B, and 7C schematically show current flows of frequencies 1, 2, and 3 in the present embodiment, respectively.
(Third embodiment)
In the first embodiment, the first additional conductor 41 is connected to the tip of the split portion 13, and the third additional conductor 42 is also connected to the tip of the first additional split portion 43. In the second embodiment, the first additional conductor 41 is connected in the middle of the second conductor 14, and the third additional conductor 51 is connected in the middle of the second additional conductor 42.

The third embodiment is a compromise between the two. That is, the first additional conductor 41 is connected to the tip of the split portion 13, and the third additional conductor 51 is connected in the middle of the second additional conductor. The same effect can be obtained with such a configuration.
(Fourth embodiment)
In the first to third embodiments, the case where the first and second additional conductor portions are provided has been described. However, only the first additional conductor portion 4 may be added. An example is shown in FIG. The power feeding unit 2, the power feeding conductor 12, the first conductor 13, and the second conductor 14 are the same as those in the first and second embodiments. In the present embodiment, only the first additional conductor 41 and the second additional conductor 42 are added thereto, and the third and fourth additional conductors 51 and 52 are not added.

In FIG. 8, the current flow of frequency 2 is also indicated by a thick arrow. FIG. 9 shows the impedance characteristics of the antenna of this embodiment. In addition to the original frequency 1, a frequency 2 is added. FIG. 10 shows the return loss characteristic, and it can be seen from FIG. 10 that frequency 2 is added.
(Fifth embodiment)
In the first to fourth embodiments, the split portion includes the tips of the first and second conductors, the tips of the first additional conductor and the second additional conductor, and the third additional conductor and the fourth addition. The tip of the conductor was bent and faced. However, it is not always necessary to bend the tip, and the operating frequency can be increased by adding a conductor in which a split portion is formed.
(Sixth embodiment)
In the first to fifth embodiments, the substrate layer is a single layer. However, the present invention can also be applied to a multilayer substrate. Specifically, an antenna is configured by forming split rings having the same shape on upper and lower conductor layers sandwiching a dielectric substrate and connecting the layers with conductor vias.

1 Split ring resonator
2 Power supply unit
3 GND plate
4 First additional conductor
5 Second additional conductor
11 opening
12 Feeding conductor
13 First conductor
14 Second conductor
15 Split section
41 First additional conductor
42 Second additional conductor
43 First additional split section
51 Third additional conductor
52 4th additional conductor
53 Second additional split section

Claims (7)

An antenna device in which a split ring resonator including a first conductor and a second conductor facing each other with a first split portion interposed therebetween is disposed so as to be in contact with the outer periphery of a GND plate,
A first additional conductor is connected to the first or second conductor within an opening of the split ring resonator surrounded by the first split portion, the first or second conductor, and the GND plate. The second additional conductor facing the first additional conductor across the second split portion is connected to the outer periphery of the GND plate to form a first additional split ring resonator. Antenna device.   A third additional conductor is connected to the second additional conductor in the opening of the first additional split ring resonator surrounded by the second split portion and the first or second additional conductor; 2. The second additional split ring resonator according to claim 1, wherein a fourth additional conductor facing the third additional conductor across the third split portion is connected to an outer periphery of the GND plate to form a second additional split ring resonator. Antenna device.   The antenna device according to claim 1, wherein a power feeding unit is provided on the first conductor or the second conductor. The operating frequency can be adjusted by changing at least one of the length of the split portion of the first additional conductor and the second additional conductor or the length of the split portion of the third additional conductor and the fourth additional conductor. The antenna device according to claim 2 . The operating frequency is changed by changing at least one of an interval between the split portions of the first additional conductor and the second additional conductor or an interval between the split portions of the third additional conductor and the fourth additional conductor. The antenna device according to claim 2, wherein the antenna device is adjustable.   The antenna device according to any one of claims 1 to 5, wherein the first conductor and the second conductor constitute the first split portion by bending a tip to face each other.   The antenna device according to claim 6, wherein the first additional conductor is connected to the facing portion of the first conductor or the second conductor.

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