JP5655611B2 - Antenna device and communication device - Google Patents

Description

  The present invention relates to an antenna device and a communication device that are applied to a communication device that uses a relatively high frequency band for wireless transmission, such as a wireless LAN system, and more particularly to portable devices such as tablet PCs, electronic books, mobile communicators, and smartphones. The present invention relates to an antenna device and a communication device that are applied to a small-sized communication device that is used.

  In recent years, various types of wireless transmission systems that use a relatively high frequency band from several hundred MHz to several GHz for wireless transmission have become widespread. For example, as a wireless LAN (Local Area Network) system using 2 GHz band or 5 GHz band, a LTE (Long Term Evolution) or 3G communication system, a mobile phone communication system using a 2 GHz band from 700 MHz band has been developed. Yes. Various antenna devices have been developed and put into practical use as antenna devices included in wireless communication devices using such a band.

  It is widely known in the industry that a diversity effect such as suppressing a fading due to multiple waves can be obtained by arranging a plurality of antenna elements. For example, a proposal has been made for a transmit / receive antenna with radiation diversity having at least a first and second radiating elements connected to a transmission / reception circuit of electromagnetic signals by a network of power supply lines on a substrate ( For example, see Patent Document 1).

  In mobile-use communication devices, it is necessary to reduce SAR (Specific Absorption Ratio). For this reason, proposals have been made for communication devices that reduce transmission power in response to human contact (see, for example, Patent Document 2).

  However, when equipment is used close to the human body, measures such as providing a large clearance area between the antenna and the housing to reduce the transmission power of the circuit or to maintain a contact distance with the human body. If this is taken, there is a concern that the communication characteristics may deteriorate and the size of the equipment may increase.

  In addition, in order to detect the state in which the device is used in contact with the human body, for example, when RSSI (Receiving Signal Strength Indication) is monitored and the sensitivity suddenly decreases, the human body touches The method of judging that. However, the change in RSSI is not limited to the case where the human body is close, and even if a specific human object such as a metal is close to the device, the sensitivity may be lowered. If the transmission power is reduced by misrecognizing it as a human body, a reception error occurs at the receiver, which is inefficient.

  Alternatively, using an acceleration sensor mounted on the device, measure which direction the device is facing with respect to gravitational acceleration, select an antenna that emits radio waves according to the state, and is estimated to be close to the human body Proposals have been made on portable terminal devices that prohibit radiation from antennas (see, for example, Patent Document 3). However, even if the gravitational acceleration is measured to predict the usage state of the device, it cannot be said that the human body is always in close proximity, and there is a possibility that radiation from a good antenna is prohibited.

Special table 2009-514292 JP 2005-208754 A JP 2009-284525 A

  An object of the present invention is to provide an excellent antenna device and communication device that can be suitably applied to small communication devices that are carried and used, such as tablet PCs, electronic books, mobile communicators, and smartphones. is there.

  A further object of the present invention is to provide an excellent antenna device and communication device capable of reducing SAR.

  A further object of the present invention is to provide an excellent antenna device and communication device that can more accurately determine the proximity of a human body and reduce SAR.

The present application has been made in consideration of the above problems, and the invention according to claim 1
A first antenna element;
A second antenna element;
A branch circuit in which the first antenna element is connected via a first transmission line, and the second antenna element is connected via a second transmission line;
A delay line connected on the second transmission line for adjusting the input impedance or phase of the first antenna element and the second antenna element;
A first power reduction unit that reduces power supplied to the first antenna element, connected in parallel to the first antenna element on the first transmission line via a first connection switching unit;
A second power reduction unit that reduces power supplied to the second antenna element, connected in parallel with the second antenna element on the second transmission line via a second connection switching unit;
A determination unit for determining the proximity state of the human body;
When it is determined that the determination unit is not in the proximity state of a human body, the first connection switching unit cuts off the first power reduction unit from the first transmission line, and the second connection switching unit When the second power reduction unit is cut off from the second transmission line and the determination unit determines that the human body is in proximity, the first connection switching unit causes the first power reduction unit to be connected to the first power reduction unit. A control unit that is connected in parallel to the transmission line, and that connects the second power reduction unit in parallel to the second transmission line by the second connection switching unit;
Is an antenna device.

  According to the invention described in claim 2 of the present application, the first power reduction unit of the antenna device according to claim 1 is a first impedance circuit having one end grounded, and the first connection switching unit is , An SPST switch inserted on a line connecting the other end of the first impedance circuit in parallel with the first transmission line. The second power reduction unit is a second impedance circuit having one end grounded, and the second connection switching unit connects the other end of the second impedance circuit in parallel to the second transmission line. SPST switch inserted on the line to be

  According to the invention described in claim 3 of the present application, in the antenna device according to claim 2, the one end of the first impedance circuit is rectified by the first rectifier circuit and the first rectifier circuit. It is grounded through a first power absorption unit that absorbs power. The one end of the second impedance circuit is grounded via a second rectifier circuit and a second power absorber that absorbs the power rectified by the second rectifier circuit.

  According to invention of Claim 4 of this application, the 1st connection interruption | blocking part of the antenna apparatus of Claim 1 is a pair of SPDT switch inserted on the said 1st transmission line, One power reduction unit is a first distribution / combination circuit including a port connected to the pair of SPDT switches and a grounded port. The second connection cutoff unit is a pair of SPDT switches connected to both ends of the delay circuit on the second transmission line, and the second power reduction unit is connected to the pair of SPDT switches. A second distribution / synthesis circuit including a connected port and a grounded port.

  According to the invention described in claim 5 of the present application, the branch circuit of the antenna device described in claim 1 is a hybrid circuit including a plurality of ports connected to the communication circuit.

  According to the invention described in claim 6 of the present application, the first impedance circuit of the antenna device according to any one of claims 1, 3, or 5 is an RC circuit, an LCR equivalent to the first antenna element. It is a series circuit or an LCR parallel circuit. The second impedance circuit is an RC circuit, an LCR series circuit, or an LCR parallel circuit that is equivalent to the second antenna element.

  According to invention of Claim 7 of this application, the determination part of the antenna apparatus of Claim 1 is based on the measurement result of RSSI of the signal received by at least one of the said 1st or 2nd antenna element. It is configured to determine the proximity state of the human body.

  According to invention of Claim 8 of this application, the antenna apparatus of Claim 1 is further provided with the acceleration sensor which measures the gravitational acceleration which acts on an apparatus main body. The determination unit determines the proximity state of the human body by linking the RSSI measurement result of the signal received by at least one of the first or second antenna elements and the gravitational acceleration measured by the acceleration sensor. It is configured.

  According to the invention described in claim 9 of the present application, the determination unit of the antenna device according to claim 8 determines that the object is in the proximity state when the measured value of the RSSI is equal to or less than a specified value, and Based on the gravitational acceleration measured by the acceleration sensor, the presence / absence of the movement of the apparatus body is detected, and when the movement is detected, it is determined that the human body is in the proximity state. Is configured to do.

  According to the invention of claim 10 of the present application, the control unit of the antenna device according to claim 9 is configured such that when the determination unit determines the proximity state of the object based on the measurement result of the RSSI, The first power reduction unit is connected in parallel to the first transmission line by one connection switching unit, and the second power reduction unit is connected in parallel to the second transmission line by the second connection switching unit. When the determination unit determines the proximity state of the human body based on the gravitational acceleration measured by the acceleration sensor, the first power reduction unit is connected in parallel to the first transmission line and the second The power reduction unit continues to be connected in parallel to the second transmission line, but when the proximity state of an object other than a human body is determined, the first connection switching unit causes the first power reduction unit to be connected to the second transmission line. 1 transmission line With blocking, it is configured to block the second power reduction portion from said second transmission line by said second connection switching part.

  According to invention of Claim 11 of this application, the antenna apparatus of Claim 1 is further provided with the temperature sensor which measures the temperature of an apparatus main body. The determination unit is configured to determine the proximity state of the human body by linking the RSSI measurement result of the signal received by at least one of the first or second antenna elements and the temperature measured by the temperature sensor. Has been.

  According to invention of Claim 12 of this application, the antenna apparatus of Claim 1 is further provided with the electrostatic capacitance sensor. Then, the determination unit is configured to link the RSSI measurement result of the signal received by at least one of the first or second antenna elements and the change in the capacitance measured by the capacitance sensor, so that the proximity state of the human body Is configured to determine.

The invention according to claim 13 of the present application is
A first antenna element;
A second antenna element;
A branch circuit in which the first antenna element is connected via a first transmission line, and the second antenna element is connected via a second transmission line;
A communication circuit connected to the first antenna element and the second antenna element via the branch circuit;
A delay line connected on the second transmission line for adjusting the input impedance or phase of the first antenna element and the second antenna element;
A first power reduction unit that reduces power supplied to the first antenna element, connected in parallel to the first antenna element on the first transmission line via a first connection switching unit;
A second power reduction unit that reduces power supplied to the second antenna element, connected in parallel with the second antenna element on the second transmission line via a second connection switching unit;
A determination unit for determining the proximity state of the human body;
When it is determined that the determination unit is not in the proximity state of a human body, the first connection switching unit cuts off the first power reduction unit from the first transmission line, and the second connection switching unit When the second power reduction unit is cut off from the second transmission line and the determination unit determines that the human body is in proximity, the first connection switching unit causes the first power reduction unit to be connected to the first power reduction unit. A control unit that is connected in parallel to the transmission line, and that connects the second power reduction unit in parallel to the second transmission line by the second connection switching unit;
It is a communication apparatus which comprises.

  According to the present invention, an excellent antenna device and communication device that can be applied to small-sized communication devices that are carried and used, such as tablet PCs, electronic books, mobile communicators, and smartphones, and that can reduce SAR are provided. be able to.

  The antenna device according to the present invention can expand the radiation band by forming two coupled antennas during normal communication, while reducing the power supplied to each antenna when determining the proximity of the human body. , SAR can be reduced. However, since the coupling of each antenna is maintained, the radiated power is not halved.

  Further, according to the antenna device according to the present invention, by linking the RSSI measurement and the motion measurement by the acceleration sensor, it is possible to accurately determine the state in which the human body is close to the device, and to reduce the power supplied to each antenna. SAR can be reduced.

  Other objects, features, and advantages of the present invention will become apparent from more detailed description based on embodiments of the present invention described later and the accompanying drawings.

FIG. 1A is a diagram illustrating a configuration example of a communication device 10 including an antenna device. FIG. 1B is a state transition diagram of the communication device 10. FIG. 2 is a diagram exemplifying a design model of an antenna device including the first antenna element 11 and the second antenna element 12. FIG. 3 is a diagram showing a simulation result of the radiation characteristics during normal communication of the antenna device shown in FIG. 1A. FIG. 4 is a diagram showing a simulation model for analyzing the characteristics of the antenna device shown in FIG. 1A and FIG. FIG. 5 is a diagram showing a simulation block when the SPST switches 15b and 16b are turned on in the antenna device shown in FIG. 1A as the human body approaches. FIG. 6A is a Smith chart showing the input impedance (S11) of the antenna when the human body is close. FIG. 6B is a diagram simply showing an equivalent circuit of the antenna elements 11 and 12. FIG. 7 is a diagram showing a simulation result of the SAR distribution when the first antenna element 11 of the antenna device is excited alone. FIG. 8 is a diagram showing a simulation result of the SAR distribution when the second antenna element 12 of the antenna apparatus is excited alone. FIG. 9 is a diagram showing a simulation result of the SAR distribution when both the first antenna element 11 and the second antenna element 12 are excited. FIG. 10 is a diagram illustrating a modification of the communication apparatus illustrated in FIG. 1A. FIG. 11 is a diagram showing another modification of the communication device shown in FIG. 1A. 12 is a diagram showing still another modification of the communication device shown in FIG. 1A. FIG. 13 is a flowchart illustrating a processing procedure for determining a state in which a human body is close to a device in cooperation with RSSI measurement and motion measurement using an acceleration sensor. FIG. 14 is a diagram showing an arrangement example of the first antenna element 11 and the second antenna element 12. FIG. 15 is a diagram illustrating an example of the distribution and synthesis circuit 13. FIG. 16 is a diagram illustrating an example of frequency characteristics of the antenna device illustrated in FIG. 1A. FIG. 17 is a diagram illustrating an example of the hybrid circuit 23 configured as a 90-degree phase shifter.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1A shows a configuration example of a communication device 10 including an antenna device. The antenna device attached to the communication device 10 is a coupled antenna including a first antenna element 11 and a second antenna element 12. Both the first antenna element 11 and the second antenna element 12 are configured as so-called inverted F-type monopole antennas, and the antenna elements 11 and 12 are elements having the same length. Inverted-F antenna is lambda _0/4 monopole antenna tip low profile and antenna by folding the impedance matching between the feeding point of the short-circuit portion provided near the feed point position is taken (although , Λ ₀ is used wavelength).

  The first antenna element 11 is connected to the distribution / synthesis circuit 13 via the transmission line 15. The second antenna element 12 is connected to the distribution / synthesis circuit 13 via the transmission line 16.

  Here, the transmission line 15 is connected to the ground via an impedance circuit 15a and an SPST (Single Pole Single Throw) switch 15b, and the transmission line 16 is connected to the ground via an impedance circuit 16a and an SPST switch 16b. It is connected to the.

  A delay line 16 c is inserted into one of the two transmission lines 15, 16. The delay line 16c has an effect of adjusting input impedances or phases of the first antenna element 11 and the second antenna element. For example, when configured as an 800 MHz band transmitting / receiving antenna, the difference between the length L1 of the transmission line 15 and the length L2 of the transmission line 16 including the delay line 16c is 187 millimeters. However, the values of the lengths L1 and L2 of the transmission lines 15 and 16 are examples.

  FIG. 14 shows an arrangement example of the first antenna element 11 and the second antenna element 12. As shown in the figure, each of the antenna elements 11 and 12 is configured as an inverted F-type monopole antenna, and is arranged on the ground surface 17 so as to be linearly spaced apart from the surface. Yes. The feeding point 11a of the first antenna element 11 is connected to the transmission line 15 and is short-circuited to the ground surface 17 via the connection conductor 11b. The feeding point 12a of the second antenna element 12 is connected to the transmission line 16 and is short-circuited to the ground surface 17 via the connection conductor 12b. The feeding point 11a of the first antenna element 11 and the feeding point 12a of the second antenna element 12 are reversed, and the tip of the first antenna element 11 and the tip of the second antenna element 12 are brought close to each other.

  FIG. 15 shows an example of the distribution / synthesis circuit 13. The illustrated distribution / synthesis circuit 13 is composed of a conductor pattern 14 formed in a T shape on a wiring board, and a first port 13a and a second port 13b are provided at both ends of the T-shaped head. The third port 13c is arranged at the lower end of the T-shaped leg. The first port 13 a is connected to the first antenna element 11 via the transmission line 15, and the second port 13 b is connected to the second antenna element 12 via the transmission line 16. The third port 13c is used as an input port and is connected to a communication circuit.

  The delay line length of the transmission line formed by the conductor pattern 14 between the first port 13a and the third port 13c, and between the second port 13b and the third port 13c is substantially equal, and the two antenna elements The reception signals from 11 and 12 are combined without a phase difference. Further, the radiated power supplied from the third port 13c as the input port is equally distributed to the antenna elements 11 and 12.

  Here, the antenna characteristics of the antenna apparatus shown in FIG. 1A when the communication operation is performed in a normal state where the transmission lines 15 and 16 are not operated with the SPST switches 15b and 16b turned off, that is, not connected to the ground. Let me explain.

  FIG. 16 shows an example of frequency characteristics of the antenna device shown in FIG. 1A. However, the horizontal axis represents frequency [GHz] and the vertical axis represents return loss [dB]. In FIG. 16, a characteristic S1 indicated by a broken line is a frequency characteristic in the case of an antenna apparatus using the first first antenna element 11 alone. On the other hand, a characteristic S2 indicated by a solid line is a frequency characteristic in the case of an antenna device using a combination of the first antenna element 11 and the second antenna element 12. For example, assuming that the frequency range in which a return loss of 6 dB or more is obtained is a range that can be used as an antenna device, in the case of the characteristic S1 of the antenna device that uses the first antenna element 11 alone, the usable bandwidth is Is about 33 MHz. On the other hand, in the case of the characteristic S2 of the antenna device using the first antenna element 11 and the second antenna element 12 in combination, the usable bandwidth is about 120 MHz. Therefore, according to the antenna apparatus shown in FIG. 1A, the antenna characteristics can be very wide.

  This widening of the bandwidth is due to the fact that one of the transmission lines 15 and 16 is configured as a lengthened delay line. That is, by having the delay line, the input impedance or phase of each antenna element 11, 12 is adjusted, and the overall characteristic S 2 can be made wider than the characteristic S 1 of only the first antenna element 11. . For example, as described above, one transmission line 15 and the other transmission line 16 have a phase difference of about 180 ° with respect to a frequency of 800 MHz due to a difference in line length of 187 millimeters. Broadbanding is achieved by combining the signals of the phase difference.

  During normal communication, the communication device 10 does not operate with the SPST switches 15b and 16b of the transmission lines 15 and 16 turned off, that is, without connecting the antennas 11 and 12 to the ground, 12 can be formed, and the radiation band can be expanded.

  On the other hand, at the time of human contact, the communication device 10 can turn on the SPST switches 15b and 16b of the transmission lines 15 and 16 to reduce the power supplied to the antennas 11 and 12, thereby reducing the SAR. However, since the coupling of the antennas 11 and 12 is maintained, the radiated power is not halved.

  FIG. 1B shows a state transition diagram of the communication device 10. For example, the communication device 10 monitors the RSSI and determines that it has touched the human body when a sudden change occurs. Since the sensitivity of the antenna generally changes by about 5 dB when the human body is in contact and when the human body is not in contact, it is determined that the human body is in contact when the sensitivity suddenly decreases, and vice versa. Then, when the communication device 10 determines that it has touched the human body, the SPST switches 15b and 16b may be turned on.

  In addition, it is also possible to determine whether a human body is close or not close by arranging a capacitance sensor in the vicinity of the antennas 11 and 12 and measuring the change in the capacitance. Alternatively, a temperature sensor can be set to monitor and determine the temperature rise due to the proximity of the human body.

  FIG. 2 exemplifies a design model of an antenna device including the first antenna element 11 and the second antenna element 12. For example, the height H of the substrate, the width W, the thickness T, the length L of the first and second antenna elements 11 and 12 having inverted F shapes, the substrate and the antenna element, so that the center of the used frequency band is 800 MHz. A gap G between the antenna elements, a diameter D of the antenna element, a distance L1 between the tips of the first and second antenna elements 11 and 12, a distance L2 from the tip of the antenna element to the feed point, and a distance L3 from the feed point to the short-circuit point. Each parameter may be determined.

FIG. 3 shows a simulation result of the radiation characteristics during normal communication (when the SPST switches 15b and 16b are turned off) of the antenna device shown in FIG. 1A. However, the first antenna element 11 the antenna coupling distance D ₁ of the between the second antenna element 12 and the lambda _0/2, also, the delay line length D ₂ of the delay line 16c to be inserted into one of the transmission line 16 lambda _As 0/2, the antenna elements 11 and 12 are fed and coupled. For reference, the simulation results of the radiation characteristics of the antenna device when only one SPST switch 16b is turned on and the first first antenna element 11 is used alone are shown by broken lines. FIG. 3 shows that the radiation efficiency is improved and the band is expanded as compared with a single antenna.

  FIG. 4 shows a simulation model for analyzing the characteristics of the antenna device shown in FIGS. 1A and 2 when the human body is close to the human body. In the figure, instead of a human body, a combination of two standard models of the head is used. As the standard model of the head, for example, a SAM (Specific Anthropogenic Mannequin) phantom (anthropomorphic mannequin) developed for SAR measurement can be used. As shown in the figure, the antenna device shown in FIGS. 1A and 2 is arranged in the vicinity of the standard model of the head.

  FIG. 5 shows a simulation block when the SPST switches 15b and 16b are turned on in the antenna device shown in FIG. 1A as the human body approaches.

  In FIG. 5, as the impedance circuits 15a and 16a in FIG. 1A, an RC circuit in which a 36Ω resistive element and a 6.2 pF capacitor are connected in series is inserted. Here, a method of determining the impedance circuits 15a and 16a will be described with reference to FIGS. 6A and 6B.

  FIG. 6A shows the input impedance (S11) of the antenna when the human body is close. As described above, the first antenna element 11 and the second antenna element 12 are both configured as inverted F-type monopole antennas. Here, assuming that the radiation resistance of the inverted F antenna is 36Ω (monopole radiation resistance), the equivalent circuit of each antenna element 11 and 12 can be simply expressed from the plot of S11 as shown in FIG. 6B. (Each point on the chart shown in FIG. 6A is R + jX, X = 1 / jωC. At a point corresponding to a center frequency of 800 MHz (0.8 GHz), R = 36 [Ω], ω = 2π × 800 [ [MHz] can be substituted to obtain the capacitance C of the capacitor).

  Therefore, when the SPST switches 15b and 16b are turned on, if the impedance circuits 15a and 16a connected to the transmission lines 15 and 16 are the same as the equivalent circuit shown in FIG. 6B, the antenna elements 11 and 12 and Since the same thing is paralleled, electric power is distributed to two.

  The impedance characteristics vary depending on the characteristics of the antenna and the mounting state of the surrounding ground and parasitic components. Therefore, it is desirable to adjust the configurations and constants of the impedance circuits 15a and 16a as necessary. The impedance circuits 15a and 16a are not only RC, but also LCR series circuits, LCR parallel circuits, or It may be designed in combination with a matching circuit.

  The simulation results in the 800 MHz band using the simulation model shown in FIG. 4 are shown in FIGS. However, FIG. 7 shows the SAR distribution when the first antenna element 11 of the antenna device is excited alone (that is, when the first antenna element 11 is directly fed from the signal source without the distribution / synthesis circuit 13). It is a simulation result. FIG. 8 shows the case where the second antenna element 12 of the antenna apparatus is excited alone (that is, when the second antenna element 12 is directly fed from the signal source without the distribution / synthesis circuit 13 and the delay line 16c). , SAR distribution simulation results. On the other hand, FIG. 9 shows that when both the first antenna element 11 and the second antenna element 12 are excited (the SPST switch 15b and the SPST switch 16b are both turned on, the first antenna element 11 and the second antenna element 11 This is a simulation result of the SAR distribution when power is supplied to the antenna element 12 and power is supplied from a signal source. Comparing FIG. 9 with FIG. 7 and FIG. 8, when a human body approaches, the power supplied to the first antenna element 11 and the second antenna element 12 is distributed to the impedance circuits 15a and 16a, respectively. It is clear that the SAR value can be greatly reduced by the structure.

  In Table 1 below, when the first antenna element 11 is excited alone (see FIG. 7), when the second antenna element 12 is excited alone (see FIG. 8), the first antenna element 11 When the 11 and the second antenna element 12 are combined in a branched structure (see FIG. 9), the SAR values [W / kg] when the human body approaches each frequency band in each case are summarized.

  From Table 1, it can be seen that the value of the SAR can be reduced by combining the first antenna element 11 and the second antenna element 12 in a branched structure in any of 700 to 900 MHz centering on 800 MHz.

  Table 2 below shows that when the first antenna element 11 is excited alone (see FIG. 7), when the second antenna element 12 is excited alone (see FIG. 8), When the antenna element 11 and the second antenna element 12 are combined in a branched structure (see FIG. 9), the radiation efficiency values [dB] when the human body approaches each frequency band in each case are summarized.

  Referring to Table 2, for example, in the 800 MHz band, when the first antenna element 11 and the second antenna element 12 are individually excited, the radiation efficiency is -9.4 dB, whereas the first antenna element 11 and the second antenna element 12 are When the element 11 and the second antenna element 12 are combined in a branched structure, the radiation efficiency is degraded to −12.7 dB. However, referring to Table 1, in the same 800 MHz band, the values of SAR when the first antenna element 11 and the second antenna element 12 are excited independently are the first antenna element 11 and the second antenna element. It is 4.5 times higher than when 12 are combined in a branched structure.

  In other words, when the first antenna element 11 and the second antenna element 12 are excited independently, the SAR value is the same as when the first antenna element 11 and the second antenna element 12 are combined in a branched structure. In this case, the feed power must be reduced by about 6.5 dB. Considering this, the radiation efficiency when the first antenna element 11 and the second antenna element 12 are excited independently is −9.4−6.5 = −15.9 dB. That is, by combining the first antenna element 11 and the second antenna element 12 in a branched structure, even when the SAR level is suppressed to the same level when the human body is approaching, the radiation efficiency of the distant solution is less deteriorated and has a merit. I can say that.

  FIG. 10 shows a modification of the communication device shown in FIG. 1A. The antenna device attached to the communication device 10-2 is a coupled antenna including a first antenna element 11 and a second antenna element 12. For the arrangement example of the antenna elements 11 and 12, the configuration described in FIG. 14 can be applied as it is. The first antenna element 11 is connected to the distribution / synthesis circuit 13 via the transmission line 15. The second antenna element 12 is connected to the distribution / synthesis circuit 13 via the transmission line 16. One transmission line 16 has a delay line 16c inserted therein, and the phase fed to the two transmission lines 15 and 16 is adjusted.

  The transmission line 15 is connected to the ground via the impedance circuit 15a and the SPST switch 15b, and the transmission line 16 is connected to the ground via the impedance circuit 16a and the SPST switch 16b. The main difference from FIG. 1A is that the impedance circuit 16a and the SPST switch 16b are connected to the ground via rectifier circuits 15d and 16d, respectively.

  The communication device 10-2 illustrated in FIG. 10 also basically operates according to the state transition diagram illustrated in FIG. 1B.

  During normal communication, the communication device 10-2 does not operate with the SPST switches 15b and 16b of the transmission lines 15 and 16 turned off, that is, without connecting the antennas 11 and 12 to the ground. 11 and 12 can be formed, and the radiation band can be expanded.

  On the other hand, at the time of human contact, the communication device 10-2 can turn on the SPST switches 15b and 16b of the transmission lines 15 and 16 to reduce the power supplied to the antennas 11 and 12 and reduce the SAR. . However, since the coupling of the antennas 11 and 12 is maintained, the radiated power is not halved. A part of the power flowing to the ground is rectified through the rectifier circuits 15d and 16d, and then recovered as power by the power absorption units 15e and 16e. The collected power can be reused as driving power for the communication device 10-2.

  FIG. 11 shows another modification of the communication apparatus shown in FIG. 1A. The antenna device attached to the communication device 10-3 is a coupled antenna including a first antenna element 11 and a second antenna element 12. For the arrangement example of the antenna elements 11 and 12, the configuration described in FIG. 14 can be applied as it is. The first antenna element 11 is connected to the distribution / synthesis circuit 13 via the transmission line 15. The second antenna element 12 is connected to the distribution / synthesis circuit 13 via the transmission line 16. One transmission line 16 has a delay line 16c inserted therein, and the phase fed to the two transmission lines 15 and 16 is adjusted.

  Here, two SPDT (Single Pole Double Throw) switches 15 f and 15 g are inserted in the transmission line 15. Further, the “2” side terminals of the SPDT switches 15e and 15f are connected to the ground through the distribution / synthesis circuit 15h. When each SPDT switch 15f, 15g is enabled to “1” in the figure, the power distributed by the distribution / combination circuit 13 is directly fed to the first antenna element 11. On the other hand, when each SPDT switch 15f, 15g is enabled with “2” in the figure, the power distributed by the distribution / combination circuit 13 is further divided into two by the distribution / combination circuit 15h to the first antenna element 11 and the ground. Power is supplied.

  Further, two SPDT switches 16e and 16f are inserted into the transmission line 16. Further, the “2” side terminals of the SPDT switches 16gf and 16g are connected to the ground through the distribution / synthesis circuit 16h. When each SPDT switch 16f, 16g is enabled in the figure, the power distributed by the distribution / combination circuit 13 is directly fed to the second antenna element 12. On the other hand, when each SPDT switch 16f, 16g is enabled with “2” in the figure, the power distributed by the distribution / combination circuit 13 is further divided into the second antenna element 12 and the ground by the distribution / combination circuit 16h. Power is supplied.

  The communication device 10-3 illustrated in FIG. 11 also basically operates according to the state transition diagram illustrated in FIG. 1B.

  The communication device 10-3 enables “1” in the drawing for each SPDT switch 15f, 15g and 16f, 16g during normal communication. That is, without connecting the antennas 11 and 12 to the ground, the two coupled antennas 11 and 12 can be formed to expand the radiation band.

  On the other hand, at the time of human contact, the communication device 10-3 enables “2” in the drawing for each SPDT switch 15f, 15g and 16f, 16g. Since the power supplied to the antennas 11 and 12 is reduced, the SAR can be reduced. However, since the coupling of the antennas 11 and 12 is maintained, the radiated power is not halved.

  The communication device 10-3 illustrated in FIG. 11 has a disadvantageous design in consideration of insertion loss because more devices are connected than the communication device 10 illustrated in FIG. 1A. However, since circuit components such as the impedance circuits 15a and 16a are not used, the frequency characteristics of the antenna input impedance are maintained.

  FIG. 12 shows still another modification of the communication device shown in FIG. 1A. The antenna device attached to the communication device 10-4 is a coupled antenna including a first antenna element 11 and a second antenna element 12. For the arrangement example of the antenna elements 11 and 12, the configuration described in FIG. 14 can be applied as it is. The main difference from the communication apparatus shown in FIG. 1A is that a hybrid circuit 23 is connected to each of the antenna elements 11 and 12 instead of the distribution and synthesis circuit 13.

  The first first antenna element 11 is connected to the hybrid circuit 23 via the transmission line 15. The second second antenna element 12 is connected to the hybrid circuit 23 via the transmission line 16. One transmission line 16 has a delay line 16c inserted therein, and the phase fed to the two transmission lines 15 and 16 is adjusted. The transmission line 15 is connected to the ground via the impedance circuit 15a and the SPST switch 15b, and the transmission line 16 is connected to the ground via the impedance circuit 16a and the SPST switch 16b.

  FIG. 17 shows an example of the hybrid circuit 23 configured as a 90-degree phase shifter. The illustrated hybrid circuit 23 includes a conductor pattern 14 on a wiring board, and includes a first port 23a, a second port 23b, a third port 23c, and a fourth port 23d. The first to fourth ports 23a to 23d are connected to adjacent ports by a conductor pattern 14 formed in a square shape. The first port 23 a is connected to the first antenna element 11 via the transmission line 15, and the second port 23 b is connected to the second antenna element 12 via the transmission line 16. In addition, the third port 23c and the fourth port 23d are input ports, respectively, and are connected to different communication circuits. In other words, the antenna device shown in FIG. 12 can increase the number of input ports and perform a diversity operation during communication.

  By preparing the hybrid circuit 23 in which the four ports 23a to 23d are connected with such a conductor pattern 14, a 90 ° phase difference is obtained at a certain frequency with respect to the reception signals from the two antenna elements 11 and 12. To give and synthesize. Further, the combined signal is obtained at the third port 23c and the fourth port 23d with a 90 ° phase difference. Furthermore, by using antenna elements 11 and 12 and hybrid circuit 23 that operate at two frequencies (for example, 800 MHz and 2 GHz), the two frequencies are combined with a 90 ° phase difference. , And 90 ° phase difference.

  The radiation pattern of the signal obtained at the third port 23c and the radiation pattern of the signal obtained at the fourth port 23d are shifted by a predetermined angle. The signal obtained at the third port 23c and the fourth port 23d In other words, the signal obtained has a spatial diversity effect. Further, in the state where the transmission lines 15 and 16 are not operated with the SPST switches 15b and 16b turned off, that is, not connected to the ground, the communication device 10-4 illustrated in FIG. 12 is the communication device 10 illustrated in FIG. 1A. In addition to the effect of expanding the radiation band, the diversity effect can be obtained by increasing the number of input ports.

  The communication device 10-4 illustrated in FIG. 12 also basically operates according to the state transition diagram illustrated in FIG. 1B.

  During normal communication, the communication device 10-4 does not operate with the SPST switches 15b and 16b of the transmission lines 15 and 16 turned off, that is, without connecting the antennas 11 and 12 to the ground. 11 and 12 can be formed, and the radiation band can be expanded.

  On the other hand, at the time of human body contact, the communication device 10-4 can turn on the SPST switches 15b and 16b of the transmission lines 15 and 16 to reduce the power supplied to the antennas 11 and 12 and reduce the SAR. . However, since the coupling of the antennas 11 and 12 is maintained, the radiated power is not halved.

  As described above, the antenna apparatus shown in FIG. 1A and FIGS. 10 to 12 is an antenna apparatus including two antenna elements 11 and 12 in normal communication where a human body is not in proximity. The antenna characteristics are wider than those of a single antenna element, and the broadband characteristics can be obtained with a relatively simple configuration. In addition, the wireless communication characteristics of the communication device including the antenna device can be improved. On the other hand, when the human body is close, the SAR can be reduced as compared with the case where only one conventional antenna element is used alone, and the radiation characteristic at that time is the structure of one conventional antenna element alone. Thus, the deterioration can be reduced as compared with the case where the SAR is reduced by reducing the supply power.

  Next, a method for the communication device to detect the proximity of a human body will be described.

  In order to detect a state in which a device is used in contact with a human body, a method is known in which RSSI is monitored and it is determined that a human body has contacted when the sensitivity suddenly decreases. However, the change in RSSI is not limited to the case where the human body is close, and even if a specific human object such as a metal is close to the device, the sensitivity may be lowered. Also known is a method of predicting the usage state of a device by measuring the gravitational acceleration applied to the device using an acceleration sensor, but it cannot be said that the human body is always close, and a good antenna May ban radiation from

  Therefore, the present inventors propose a method for more accurately determining a state in which a human body is close to a device by linking RSSI measurement and motion measurement by an acceleration sensor.

  Measurement and monitoring of RSSI at the time of wireless communication are also adopted in ordinary wireless devices (such as mobile phones and wireless LAN devices). Here, the RSSI level that can be determined that the human body is not in proximity is defined. In practice, it is realistic to determine in advance by experiment or the like how much the RSSI indicates when the human body actually approaches.

  As a result of the RSSI measurement, if the level is higher than the specified value, the communication device maintains the normal communication state (that is, the SPST switches 15b and 16b are off) and continues the RSSI measurement.

  When the RSSI measurement results in a level equal to or lower than the specified value, the communication apparatus determines that a person or non-human object has approached the antenna apparatus, and sets the communication state in which the SAR is reduced (ie, the SPST switches 15b and 16 The power is switched to the state in which the power supplied to the antenna elements 11 and 12 is reduced.

  In addition, the communication device detects the movement of the device body with an acceleration sensor. When the device body is held by a person, there cannot be a complete stationary state. Therefore, even if the RSSI measurement results in a level equal to or lower than the specified value, if no motion is detected, it is determined that the RSSI measurement value has decreased due to another cause that the human body has not approached. Then, the SPST switches 15b and 16 are turned off to switch to the normal communication state. Another cause mentioned here is that a metal or other non-human body object is close to the communication device, or the radio wave reception state is deteriorated.

  On the other hand, when motion is detected, it is determined that the RSSI measurement value has decreased due to the proximity of the human body, and the communication state with reduced SAR (that is, the SPST switches 15b and 16 are turned on) is held. Continue RSSI measurement.

  After that, if the level of the RSSI measurement is higher than the specified value, it is determined that the state is close to the human body, and the SPST switches 15b and 16 are turned off to switch to the normal communication state.

  FIG. 13 shows a processing procedure in the form of a flowchart for the communication device 10 to determine a state in which a human body is close to a device in cooperation with RSSI measurement and motion measurement by an acceleration sensor. This flowchart starts in a normal communication state in which the SPST switches 15b and 16 are turned off.

  The communication apparatus measures RSSI (step S1301) and compares the measured value with a specified value (step S1302).

  Here, when the measured value of the RSSI becomes a level equal to or lower than the specified value (Yes in step S1302), the communication apparatus determines that an object is close to the antenna apparatus (step S1303), and communication with reduced SAR. The state is switched to a state (that is, a state where the SPST switches 15b and 16 are turned on to reduce the power supplied to the antenna elements 11 and 12) (step S1304). Some kind of object mentioned here includes both human and non-human objects.

  Further, the communication device measures the gravitational acceleration applied to the device main body by the acceleration sensor (step S1305), and determines the presence or absence of the movement of the device main body based on the measurement result (step S1306).

  As a result of the RSSI measurement, even when the measured value becomes a level equal to or lower than the specified value (Yes in step S1302), when it is determined that the device body does not move based on the measurement result of the acceleration sensor (step In step S1306, the communication apparatus determines that the RSSI measurement value has decreased due to another cause other than the proximity of the human body (step S1311), and turns off the SPST switches 15b and 16 to perform normal communication. The state is switched (step S1312). Thereafter, the process returns to step S1301, and RSSI measurement is continuously performed.

  On the other hand, when it is determined that there is movement in the device main body based on the measurement result of the acceleration sensor (Yes in step S1306), the communication device indicates that the human body is close because the RSSI measurement value is low. The communication state in which the SAR is reduced (that is, the state in which the power supplied to the antenna elements 11 and 12 is reduced by turning on the SPST switches 15b and 16) is maintained. After that, RSSI measurement is continued (step S1308), and the measured value is compared with a specified value (step S1309).

  Here, if the RSSI measurement results in a level higher than the specified value (Yes in step S1309), the communication apparatus determines that it has been released from the state of being close to the human body, turns off the SPST switches 15b and 16, and normally Is switched to the communication state (step S1312). Thereafter, the process returns to step S1301, and RSSI measurement is continuously performed.

  As described above, the communication device links the RSSI measurement and the motion measurement by the acceleration sensor, so that the state where the human body is close to the device and the normal communication state where the human body is not close or a non-human body object are close. It is possible to accurately determine the state. The communication apparatus can reduce the SAR by reducing the power supplied to the antenna elements 11 and 12 in the state where the former human body is close to the device as compared with the case where only one antenna element is used. it can. On the other hand, when determining the normal communication state in which the latter human body is not close or the state in which the non-human body object is close, the communication device forms two coupled antennas so that one antenna element alone Therefore, the antenna characteristic is wider than that of the antenna characteristic, and a good antenna apparatus having a broadband characteristic can be obtained with a relatively simple configuration.

  In addition to linking RSSI measurement and motion measurement by an acceleration sensor, it is also possible to accurately determine the proximity state of the human body by linking various sensor information such as electrostatic sensors and temperature sensors with RSSI measurement. Can do. For example, when RSSI measurement and capacitance measurement by an electrostatic sensor are linked, in step S1306 in the flowchart shown in FIG. 13, even if the RSSI measurement value becomes a level equal to or lower than a specified value, When a change in electric capacity is not detected, it can be determined that the RSSI measurement value has decreased due to another cause that the human body does not approach. Further, when the RSSI measurement and the temperature measurement by the temperature sensor are linked, in step S1306 in the flowchart shown in FIG. 13, a temperature rise is detected even when the RSSI measurement value becomes a level equal to or lower than the specified value. If not, it can be determined that the decrease in the RSSI measurement value is another cause that the human body does not approach.

  The present invention has been described in detail above with reference to specific embodiments. However, it is obvious that those skilled in the art can make modifications and substitutions of the embodiment without departing from the gist of the present invention.

  The antenna device according to the present invention can be applied to small communication devices such as a tablet PC, an electronic book, a mobile communicator, a smartphone, and the like, and can reduce SAR, but various other communication devices. Of course, it can also be used.

  The antenna device according to the present invention is a communication device used in various wireless communication systems using a wide band in a relatively high frequency band, such as a wireless LAN system using 2 GHz band or 5 GHz band, LTE or 3G communication system, and the like. Can be applied to.

  In this specification, although the embodiment using the method of determining the proximity state between the human body and the device main body by linking the RSSI measurement and the motion measurement by the acceleration sensor has been described, other than the acceleration sensor such as an electrostatic sensor or a temperature sensor. The human body proximity state can be accurately determined in the same manner by linking various sensor information with RSSI measurement.

  In short, the present invention has been disclosed in the form of exemplification, and the description of the present specification should not be interpreted in a limited manner. In order to determine the gist of the present invention, the claims should be taken into consideration.

DESCRIPTION OF SYMBOLS 10 ... Communication apparatus 11 ... 1st antenna element, 11a ... Feeding point, 11b ... Connection conductor 12 ... 2nd antenna element, 12a ... Feeding point, 12b ... Connection conductor 13 ... Distribution combining circuit 15 ... Transmission line 15a ... Impedance Circuit 15b SPST switch 15d rectifier circuit 15e power absorption unit
15f, 15g ... SPDT switch, 15h ... distribution and synthesis circuit 16 ... transmission line 16a ... impedance circuit, 16b ... SPST switch, 16c ... delay line 16d ... rectifier circuit, 16e ... power absorption part,
16f, 16g ... SPDT switch, 16h ... distribution / synthesis circuit 17 ... ground plane 23 ... hybrid circuit

Claims (13)

A first antenna element;
A second antenna element;
A branch circuit in which the first antenna element is connected via a first transmission line, and the second antenna element is connected via a second transmission line;
Connected only on the second transmission line, make the second transmission line longer than the first transmission line, and adjust the input impedance or phase of the first antenna element and the second antenna element Delay line to
A first power reduction unit that reduces power supplied to the first antenna element, connected in parallel to the first antenna element on the first transmission line via a first connection switching unit;
A second power reduction unit that reduces power supplied to the second antenna element, connected in parallel with the second antenna element on the second transmission line via a second connection switching unit;
A determination unit for determining the proximity state of the human body;
When it is determined that the determination unit is not in the proximity state of a human body, the first connection switching unit cuts off the first power reduction unit from the first transmission line, and the second connection switching unit When the second power reduction unit is cut off from the second transmission line and the determination unit determines that the human body is in proximity, the first connection switching unit causes the first power reduction unit to be connected to the first power reduction unit. A control unit that is connected in parallel to the transmission line, and that connects the second power reduction unit in parallel to the second transmission line by the second connection switching unit;
An antenna device comprising: The first power reduction unit is a first impedance circuit having one end grounded,
The first connection switching unit is an SPST switch inserted on a line connecting the other end of the first impedance circuit in parallel with the first transmission line,
The second power reduction unit is a second impedance circuit having one end grounded,
The second connection switching unit is an SPST switch inserted on a line connecting the other end of the second impedance circuit in parallel with the second transmission line.
The antenna device according to claim 1. The one end of the first impedance circuit is grounded via a first rectifier circuit and a first power absorber that absorbs the power rectified by the first rectifier circuit,
The one end of the second impedance circuit is grounded via a second rectifier circuit and a second power absorber that absorbs the power rectified by the second rectifier circuit.
The antenna device according to claim 2. The first connection blocking unit is a pair of SPDT switches inserted on the first transmission line;
The first power reduction unit is a first distribution / combination circuit including a port connected to the pair of SPDT switches and a grounded port.
The second connection blocking unit is a pair of SPDT switches connected to both ends of the delay circuit on the second transmission line;
The second power reduction unit is a second distribution / synthesis circuit including a port connected to the pair of SPDT switches and a grounded port.
The antenna device according to claim 1. The branch circuit is a hybrid circuit having a plurality of ports connected to a communication circuit.
The antenna device according to claim 1. The first impedance circuit is an RC circuit equivalent to the first antenna element, an LCR series circuit, or an LCR parallel circuit,
The second impedance circuit is an RC circuit equivalent to the second antenna element, an LCR series circuit, or an LCR parallel circuit.
The antenna device according to claim 2. The determination unit determines a proximity state of a human body based on a measurement result of RSSI (Received Signal Strength Indicator) of a signal received by at least one of the first or second antenna elements.
The antenna device according to claim 1. An acceleration sensor for measuring gravitational acceleration acting on the device body;
The determination unit determines the proximity state of the human body by linking the RSSI measurement result of the signal received by at least one of the first or second antenna elements and the gravitational acceleration measured by the acceleration sensor.
The antenna device according to claim 1. The determination unit
When the measured value of the RSSI is equal to or less than a specified value, it is determined that the object is in proximity,
Based on the gravitational acceleration measured by the acceleration sensor, the presence or absence of movement of the apparatus main body is detected, and when the movement is detected, it is determined that the human body is in the proximity state. judge,
The antenna device according to claim 8. The controller is
When the determination unit determines the proximity state of the object based on the measurement result of the RSSI, the first power switching unit is connected in parallel to the first transmission line by the first connection switching unit, and The second power reduction unit is connected in parallel to the second transmission line by the second connection switching unit,
When the determination unit determines the proximity state of the human body based on the gravitational acceleration measured by the acceleration sensor, the first power reduction unit is connected in parallel to the first transmission line and the second power reduction unit The parallel connection to the second transmission line is continued, but when the proximity state of an object other than a human body is determined, the first power switching unit is connected to the first transmission line by the first connection switching unit. And from the second transmission line by the second connection switching unit, the second power reduction unit is cut off from the second transmission line,
The antenna device according to claim 9. A temperature sensor for measuring the temperature of the device body;
The determination unit determines the proximity state of the human body by linking the RSSI measurement result of the signal received by at least one of the first or second antenna elements and the temperature measured by the temperature sensor.
The antenna device according to claim 1. A capacitance sensor,
The determination unit associates the RSSI measurement result of the signal received by at least one of the first or second antenna elements with the change in capacitance measured by the capacitance sensor, thereby determining the proximity state of the human body. judge,
The antenna device according to claim 1. A first antenna element;
A second antenna element;
A branch circuit in which the first antenna element is connected via a first transmission line, and the second antenna element is connected via a second transmission line;
A communication circuit connected to the first antenna element and the second antenna element via the branch circuit;
Connected only on the second transmission line, make the second transmission line longer than the first transmission line, and adjust the input impedance or phase of the first antenna element and the second antenna element Delay line to
A first power reduction unit that reduces power supplied to the first antenna element, connected in parallel to the first antenna element on the first transmission line via a first connection switching unit;
A second power reduction unit that reduces power supplied to the second antenna element, connected in parallel with the second antenna element on the second transmission line via a second connection switching unit;
A determination unit for determining the proximity state of the human body;
When it is determined that the determination unit is not in the proximity state of a human body, the first connection switching unit cuts off the first power reduction unit from the first transmission line, and the second connection switching unit When the second power reduction unit is cut off from the second transmission line and the determination unit determines that the human body is in proximity, the first connection switching unit causes the first power reduction unit to be connected to the first power reduction unit. A control unit that is connected in parallel to the transmission line, and that connects the second power reduction unit in parallel to the second transmission line by the second connection switching unit;
A communication apparatus comprising: