JP2015185910A - Communication device and antenna device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication device and an antenna device that are capable of handling a plurality of bands and obtaining a sufficient antenna characteristic with the same size as a single SRR antenna unit.SOLUTION: A communication device includes: a split ring resonator antenna that includes a split ring unit, an impedance control unit and a power supply unit, and has a first resonant frequency; and an antenna element connected with the split ring resonator antenna via an LC parallel circuit or a first inductor. A second resonant frequency formed by the power supply unit, the LC parallel circuit or the first inductor, and the antenna element is different from the first resonant frequency.

Description

  The present invention relates to a communication device and an antenna device that operate in a plurality of frequency bands.

  Miniaturization and cost reduction are desired for wireless communication devices, and miniaturization and cost reduction are also required for antennas. Further, with respect to the arrangement of the antenna, the characteristics are improved by moving away from the surrounding electronic components and the ground, that is, expanding the antenna area. However, in a high-functional electronic device typified by a smartphone, there are many parts to be mounted in addition to the antenna, and the antenna may not be disposed at a position where a sufficient antenna area can be secured.

  In view of this, it has been proposed to apply a split ring resonator (SRR) antenna that functions as an antenna wherever it is small and has an outer periphery on a multilayer printed circuit board. Since the SRR antenna is formed by a wiring pattern on the substrate, no additional cost is required. An SRR antenna is disclosed in Patent Document 1, for example.

  On the other hand, in recent years, the mounting of wireless communication functions in electronic devices such as digital cameras and printers has increased. In addition, the Internet of Things (IoT) is called “Internet of Things”, and efforts to connect all electronic devices to the Internet are also progressing. As means for connecting an electronic device to the Internet, there are a wireless LAN (Local Area Network) and a Wi-Fi (Wireless Fidelity) (registered trademark). Since the wireless LAN can be used in the 2.4 GHz band and the 5 GHz band, an antenna corresponding to both bands is desired.

WO2013 / 027824

  However, the related technology has the following problems. That is, when the SRR antenna is mounted in the corner of the board, the antenna performance cannot be secured and the antenna performance deteriorates. This deterioration increases as the frequency decreases. The performance degradation caused by mounting the SRR antenna at the corner of the substrate can be mitigated by increasing the antenna size. However, increasing the antenna size may lead to a change in wiring pattern or component position, or a change in product design or an increase in size.

  The objective of this invention is providing the communication apparatus and antenna apparatus which solve the above-mentioned subject.

  The communication device of the present invention includes a split ring resonator, an impedance control unit, and a power feeding unit, and split ring resonance via a split ring resonator antenna having a first resonance frequency and an LC parallel circuit or a first inductor. A second resonance frequency formed by the power supply unit, the LC parallel circuit or the first inductor, and the antenna element is different from the first resonance frequency. Features.

  The antenna device according to the present invention includes a split ring resonator, an impedance control unit, and a power feeding unit, and a split ring resonator antenna having a first resonance frequency and split ring resonance via an LC parallel circuit or a first inductor. A second resonance frequency formed by the power supply unit, the LC parallel circuit or the first inductor, and the antenna element is different from the first resonance frequency. Features.

  According to the present invention, it is possible to provide a communication device and an antenna device that can handle a plurality of bands and can obtain sufficient antenna characteristics with the same size as a single SRR antenna.

It is a top view which shows the structure of the antenna apparatus 1000 concerning 1st Embodiment. It is a top view which shows the structure of the antenna apparatus 1000 concerning 1st Embodiment. It is a figure which shows the return loss characteristic of the antenna apparatus 1000 concerning 1st Embodiment. It is a figure which shows the radiation characteristic of the antenna apparatus 1000 concerning 1st Embodiment. It is a figure which shows the return loss characteristic at the time of arrange | positioning a SRR antenna in the center of a board | substrate. It is a figure which shows the radiation characteristic at the time of arrange | positioning a SRR antenna in the center of a board | substrate. It is a figure which shows the return loss characteristic at the time of arrange | positioning a SRR antenna in the corner of a board | substrate. It is a figure which shows the radiation characteristic at the time of arrange | positioning a SRR antenna in the corner of a board | substrate. It is a top view which shows the structure of the antenna apparatus 2000 concerning 2nd Embodiment. It is a figure which shows the return loss characteristic of the antenna device 2000 concerning 2nd Embodiment.

[First Embodiment]
The antenna device according to the embodiment of the present invention can be used in a portable router that supports, for example, IEEE 802.11a / b / g / n.

  1A and 1B are plan views showing a configuration of an antenna apparatus 1000 according to the first embodiment. In the present embodiment, an example in which the antenna device 1000 is mounted on a corner of the substrate is shown.

  In the following description, the corner of the substrate refers to a region that occupies a corner portion where one side of the substrate intersects with the other side that touches the substrate, and the end portion of the substrate refers to a region that occupies the terminal portion in the corner region. To do.

  The antenna device 1000 includes a split ring resonator antenna 110 having a first resonance frequency and an antenna element 120 having a second resonance frequency different from the first resonance frequency.

  A split ring resonator (SRR) antenna 110 surrounded by a long broken line in FIG. 1A includes a split ring unit 111, an impedance control unit 113, and a power feeding unit 112.

  The split ring unit 111, the impedance control unit 113, and the power feeding unit 112 are drawn and printed on a printed circuit board (substrate) 100 with a copper foil. In FIG. 1A, a copper foil is provided in a portion shown in gray, and a copper foil is not provided in a portion shown in white. The portion shown in white is filled with the substrate dielectric material 101 by removing the substrate.

  The split ring portion 111 surrounded by a broken line in FIG. 1A has a split portion (opening) at a part of the periphery thereof. In the opening, the copper foil patterns face each other across the gap. The opening has a function of a capacitor and is provided to increase the capacitance of the SRR antenna 110.

  The impedance control unit 113 surrounded by a one-dot chain line in FIG. 1A has a function of controlling impedance matching with an RF circuit (not shown) and controlling the radiation resistance of the antenna device 1000.

  A transmission line that transmits radio waves to the antenna device 1000 without loss, such as a coaxial cable or a microstrip line, is connected to the power feeding unit 112.

  The antenna element 120 is a general monopole antenna.

  The SRR antenna 110 and the antenna element 120 are connected via an LC parallel circuit (filter) or an inductor (first inductor) L1. 1A and 1B show an example in which the SRR antenna 110 and the antenna element 120 are connected via a filter 121. FIG.

  The filter 121 is adjusted to have a cutoff frequency that sufficiently attenuates the resonance frequency of the SRR antenna 110.

  The antenna region is a region in which a substrate ground is formed in order to pattern the antenna, and indicates a broken line region shown in FIG. 1B.

The length [m] of a general monopole antenna can be obtained by the following formula 1. c represents the speed of light [m], and f represents the frequency [MHz].
Length = (c / f) / 4 (Formula 1)
Further, the resonance frequency in the LC series resonance circuit, which is an equivalent circuit of the monopole antenna, is obtained by the following equation 2. π (pi) represents the circular ratio.
f = 1 / (2π√ (LC)) (Formula 2)
From Expression 1 and Expression 2, it can be seen that the inductor L or the inductor L1 constituting the filter 121 contributes to shortening of the antenna element 120 which is a monopole antenna.

  The length of the monopole antenna is approximately 3.125 [cm] at 2.4 GHz.

  Next, the operation of the antenna device 1000 will be described.

  An SRR antenna to which an RF signal having a frequency f is input has an LC series resonance composed of an inductance L generated by a current flowing in a ring shape along the opening edge of each opening and a capacitance C generated in the opening. As a circuit, the input RF signal is made to resonate based on the above-described Expression 2.

  As a premise, it is assumed that the resonance frequency of the SR resonator antenna 110 is set to f1, and the resonance frequency of the antenna element 120 is set to f2. Here, f2 is a frequency different from f1, and an example in which f1 is a higher band than f2 will be described below. Further, it is assumed that the RF circuit (not shown) outputs an RF signal having a frequency f1 and an RF signal having an frequency f2 for each period.

  When the RF circuit outputs the RF signal having the frequency f1 to the power feeding unit 112, the power feeding unit 112 propagates the RF signal input from the RF circuit without reflection, and outputs the RF power to the SRR antenna 110. The SRR antenna 110 to which the RF signal is input forms an LC series resonance circuit as described above, and resonates the input RF signal. Based on this phenomenon, an electromagnetic wave signal having a frequency f1 is radiated in the air. The RF signal having the frequency f1 is attenuated by the filter 121 and does not flow to the antenna element 120.

  As described above, the antenna device 1000 functions as an antenna that radiates electromagnetic waves having the frequency f1 in the air.

  On the other hand, when the RF signal having the frequency f2 is input to the power feeding unit 112, the power feeding unit 112, the filter 121, and the antenna element 120 resonate the input RF signals. Based on this phenomenon, an electromagnetic wave signal having a frequency f2 is radiated in the air.

  As described above, the antenna device 1000 also functions as an antenna device that radiates electromagnetic waves having the frequency f2 in a hollow state.

  Next, characteristics of the antenna device 1000 will be described. FIG. 2 shows the return loss characteristic of the antenna device 1000, and FIG. 3 shows the radiation characteristic.

  The return loss characteristic is one of the indexes for improving the performance of the antenna device, and is measured by connecting a network analyzer to the power feeding unit 112. The return loss characteristic indicates that the smaller the value is, the better the performance of the antenna device is. If the return loss is less than −5 dB, it functions as an antenna.

  Similarly, the radiation characteristic (radiation efficiency) is one of the indexes for improving the performance of the antenna device, and is determined by the ratio of the power output from the antenna device as a radio wave in the air to the power input to the antenna device. The larger the value of the radiation efficiency, the better the performance of the antenna device.

  2 that the return loss of the antenna device 1000 at 2.4 GHz and 5.15 GHz is −5 dB or less. That is, it can be seen that it functions as an antenna. 3 that the radiation efficiency of the antenna device 1000 is −3.0 dB at 2.4 GHz and −3.0 dB at 5.15 GHz.

  Here, for comparison, the return loss characteristic (FIG. 4) and the radiation characteristic (FIG. 5) when the SRR antenna is mounted at the center of the substrate edge, and the return loss characteristic when the SRR antenna is mounted at the corner of the substrate (FIG. 5) FIG. 6) and radiation characteristics (FIG. 7) are shown. Note that the antenna region of the SRR antenna used for comparison is the same as the antenna region of the antenna device shown in FIG.

  4 and 6, it can be seen that the return loss at 2.4 GHz is -5 dB or less. That is, it can be seen that the SRR antenna functions as an antenna even when mounted at the center of the substrate edge and when mounted at the corner of the substrate.

  FIG. 5 shows that the radiation characteristic at 2.4 GHz when the SRR antenna is mounted at the center of the substrate end is −2.5 dB. Further, FIG. 7 shows that the radiation efficiency at 2.4 GHz when the SRR antenna is mounted at the corner of the substrate is −5.6 dB. Comparing FIG. 5 and FIG. 7, it can be seen that the performance of the antenna is deteriorated by mounting the SRR antenna at the corner of the substrate.

  Also, comparing FIG. 3 and FIG. 5, it can be seen that even the antenna device 1000 according to the present embodiment can ensure the same performance as when the SRR antenna is mounted at the center of the substrate end. That is, it can be seen that the antenna device 1000 exhibits sufficient performance even when mounted on a corner of the substrate.

  The antenna device 1000 according to the present embodiment includes an SRR antenna 110 and an antenna element 120 connected to the SRR antenna 110 via a filter or an inductor. As a result, for the frequency band in which the antenna characteristics can be ensured even if the SRR antenna is mounted on the corner of the substrate (in the above description, the high frequency band), the SRR antenna is used and the frequency band where the antenna characteristics cannot be secured With respect to the low frequency band in the above description, sufficient antenna characteristics can be ensured by the SRR antenna, the resonance circuit, and the antenna element. As a result, it is possible to realize an antenna device that can deal with a plurality of bands and can obtain sufficient antenna characteristics with the same size as that of a single SRR antenna.

  Here, the antenna device formed with an array of antenna elements and SRR antennas from the edge of the substrate has been described, but the resonance frequency is assigned to the SRR antenna so that it is a lower band regardless of the array. If you can. That is, it can also be formed in an array that becomes an SRR antenna and an antenna element from the end of the substrate.

  Note that the mounting area can be reduced by forming the antenna device from the end portion of the substrate in an array to be an antenna element and an SRR antenna as compared to the case of forming an array to be an antenna element and an SRR antenna.

  When the SRR antenna and antenna element are arranged from the edge of the substrate, it is necessary to form a substrate ground on the substrate opposite to the SRR antenna arrangement side, and as a result, it is necessary to widen the antenna area. Arise.

  In addition, since the characteristics of the SRR antenna are improved as the distance from the end of the substrate is increased, the antenna is formed from the end of the substrate to the array that becomes the antenna element and the SRR antenna in order to secure the distance. This makes it possible to improve the characteristics.

  In the above embodiment, the radiation resistance of the antenna device 100 is adjusted by the impedance control unit 113 of the SRR antenna 110. However, changing the loop diameter of the impedance control unit 113 affects the characteristics of the SRR antenna 110. Therefore, when the antenna device is used in multibands of frequencies f1 and f2, by providing an inductor (second inductor) L2 that connects the impedance control unit 113 and the substrate (ground) 100, the inductor L2 is controlled. It is preferable to adjust the radiation resistance of the antenna device 100.

  In the above description of the operation, it has been described that the RF circuit outputs the RF signals of the frequencies f1 and f2 separately for each period. In addition, RF signals of frequencies f1 and f2 may be superimposed and output simultaneously.

  Moreover, the case where the antenna apparatus 1000 is an antenna apparatus that radiates electromagnetic waves on the wireless signal transmission side has been described. In addition, the antenna device 1000 can receive an electromagnetic wave as a radio signal receiving side. In other words, the antenna device 1000 can receive an electromagnetic wave having the frequency f1 or f2 propagating through the hollow from the outside, and can output the received RF signal to an RF circuit (receiving circuit). The operation procedure in this case is the reverse of the above-described operation when radiating.

  By providing at least one antenna device 1000 described above in a wireless communication device having a communication function, the entire wireless communication device can be downsized.

[Second Embodiment]
FIG. 8 is a plan view showing the configuration of the antenna device 2000 according to the second embodiment. The antenna device 2000 has a configuration in which the power feeding unit is provided between the split ring unit and the impedance control unit in the antenna device 1000 according to the first embodiment. Further, the SRR antenna 210 and the antenna element 220 are connected via an element adjusting inductor (first inductor) L1 instead of the filter 121. Furthermore, the connection position of the antenna element 220 with respect to the SRR antenna 210 is also changed.

  FIG. 9 is a diagram illustrating the return loss characteristics of the antenna device 2000. FIG. 9 shows that the frequency is −5 dB or less at 2.4 GHz and 5 CHz, and functions as an antenna.

  Also in the antenna device 2000 according to the present embodiment, it is possible to realize an antenna device that can deal with a plurality of bands and can obtain sufficient antenna characteristics with the same size as that of a single SRR antenna.

  In the antenna device 2000, the connection position A between the power feeding unit 212 and the split ring unit 211 is moved along the arm B of the SRR antenna 210, so that the power feeding unit 212 and the SRR antenna are not inserted without inserting an impedance matching circuit. It is possible to match the impedance with 210.

[Other Embodiments]
In the embodiment described above, the example in which the SRR antenna and the antenna element are provided on the same substrate and the split ring portion, the impedance control unit, and the power feeding portion of the SRR antenna are provided on the same substrate has been described. In addition, a plurality of printed circuit boards may be provided in layers, and the respective configurations may be provided in separate layers. In this case, each layer is electrically connected using a conductor via. Alternatively, the conductor pattern constituting the SRR antenna may be formed in a plurality of upper and lower layers of the printed board at the same shape and at the same position, and the layers may be connected by conductor vias.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, Of course, unless it deviates from the meaning of this invention, another modification and an application example are included. .

1000, 2000 Antenna device 101 Substrate dielectric material 100 Substrate (ground)
DESCRIPTION OF SYMBOLS 110 Split ring resonator antenna 111 Split ring part 112 Feed part 113 Impedance control part 120 Antenna element 121 LC parallel circuit (filter) or inductor (first inductor) L1
L2 inductor (second inductor)

Claims (7)

A split ring resonator antenna having a split ring portion, an impedance control portion, and a power feeding portion and having a first resonance frequency;
An antenna element connected to the split ring resonator antenna via an LC parallel circuit or a first inductor;
A communication apparatus, wherein a second resonance frequency formed by the power feeding unit, the LC parallel circuit or the first inductor, and the antenna element is different from the first resonance frequency.   The communication device according to claim 1, wherein a radiation resistance of the antenna element is adjusted by controlling the impedance control unit. A second inductor connecting the impedance control unit and the ground of the split ring resonator;
The communication device according to claim 1, wherein a radiation resistance of the antenna element is adjusted by controlling the second inductor.   The communication device according to any one of claims 1 to 3, wherein the power feeding unit is provided between the split ring unit and the impedance control unit.   The communication device according to any one of claims 1 to 4, wherein the split ring resonator antenna and the antenna element are provided on the same substrate.   The communication device according to any one of claims 1 to 5, wherein the antenna element is provided at a corner position from the split ring resonator antenna. A split ring resonator antenna having a split ring portion, an impedance control portion, and a power feeding portion and having a first resonance frequency;
An antenna element connected to the split ring resonator antenna via an LC parallel circuit or a first inductor;
An antenna device, wherein a second resonance frequency formed by the power feeding unit, the LC parallel circuit or the first inductor, and the antenna element is different from the first resonance frequency.

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