JP4337671B2 - Wireless communication device - Google Patents

Description

  The present invention relates to a wireless communication device, and more particularly, to a wireless communication device that performs wireless communication simultaneously using a plurality of antennas, a wireless communication system, a control method therefor, and a computer (for example, a microcomputer, a CPU, a signal processing LSI, etc.) Relates to a program to be executed.

  In recent years, wireless communication functions include not only information processing devices such as personal computers and communication terminal devices such as mobile phones and PDAs (Personal Digital Assistance), but also various consumer electronic devices such as audio products, video devices, camera devices, and printers. Or it is also installed in entertainment robots. Further, this wireless communication function is not limited to electronic devices, for example, access points for wireless LAN (Local Area Network), PCMCIA specification (Personal Computer Memory Card International Association) cards, CompactFlash (registered trademark) cards, mini PCI ( It is also mounted on so-called small accessory cards such as Peripheral Component Interconnection cards. As a result, a wireless card module having a storage function and a wireless communication function is configured.

  Currently, the systems mainly used in home wireless LANs are IEEE802.11a using a 5.2 GHz band as a carrier frequency and IEEE802.11b / g using a 2.4 GHz band. These IEEE802.11a and IEEE802.11g have a data transmission speed of 54 Mbps, but recently, with the increase in the amount of data information handled in the world, research on wireless systems for realizing higher transmission speeds.・ Development is thriving.

  One of the methods that are attracting attention as a method that enables such high-speed transmission is MIMO (Multi Input Multi Output). MIMO is a scheme in which communication is performed using a plurality of spatial propagation channels using a plurality of antennas. Currently, IEEE802.11a and IEEE802.11g used in wireless LANs in the world use OFDM (Orthogonal Frequency Division Multiplexing) as a modulation method. By adopting this OFDM, transmission on each subcarrier can be regarded as almost flat fading. Therefore, even in a relatively wideband communication scheme such as IEEE802.11a or IEEE802.11g, the MIMO propagation path can be expressed by a somewhat simple model, and realization with an actual wireless device has become possible. . In this MIMO, in principle, the transmission rate increases linearly with respect to the number of antennas. However, in reality, the radio wave propagation environment of each signal transmitted and received in a plurality of propagation channels is a multipath environment in which reflection, scattering, diffraction, and shielding are mixed, and the spatial correlation characteristics associated with this are information transmission of MIMO. A big impact on ability.

In the case where both transmitting and receiving stations are in the same scatterer area or in the case of a mobile station in mobile communication, the spatial correlation is zero order because the path direction is uniform in the horizontal plane or the angular spread is sufficiently large. It is known that it is expressed by a Bessel function. The correlation coefficient decreases as the distance between the antennas increases, but the decrease becomes moderate from around the half wavelength. Therefore, it is customary to treat fluctuations due to multipath fading as uncorrelated by securing a distance between antennas of about a half wavelength or more (see, for example, Non-Patent Document 1).
Yoshio Karasawa “MIMO propagation channel modeling”, IEICE Transactions B, Vol. J86-B, P.I. 1707, September 2003

  However, in the direction of technological development in which wireless devices are mounted on home or personal devices, it is difficult to ensure the distance between antennas uniformly over half a wavelength. For example, the half-wavelength of the 2.4 GHz band, which is a frequency band used in IEEE802.11b / g, is about 63 mm, and designing a device in which a plurality of antennas are arranged at such a distance is From the standpoint of miniaturization, the progress is significantly hindered.

  Therefore, an object of the present invention is to reduce the distance between antennas by controlling the independence of each antenna in MIMO.

  The present invention has been made to solve the above-described problems, and a first aspect thereof includes a plurality of transmission circuits that perform transmission by MIMO and a plurality of first circuits that are connected to each of the plurality of transmission circuits. An antenna; a second antenna disposed in the vicinity of the plurality of first antennas; and a characteristic control circuit connected to the second antenna to control a radiation direction of the plurality of first antennas. It is the transmitter characterized by doing. Thereby, the radiation direction of the first antenna used for transmission is appropriately controlled, and MIMO transmission suitable for the usage environment is realized.

  Here, the characteristic control circuit causes the second antenna to function as a reflector, or causes the second antenna to function as a director. That is, the radiation direction of the first antenna is appropriately controlled by causing the second antenna to function as a reflector or a director under the control of the characteristic control circuit.

  In addition, the plurality of first antennas and the second antenna may be arranged in a substantially linear shape or may be arranged in a polygonal shape. These arrangements also affect the radiation direction of the first antenna.

  Further, the plurality of first antennas and the second antenna may have the same single-unit characteristics, or may have different single-unit characteristics. The radiation direction of the first antenna is also affected by the combination of these single characteristics.

  In addition, a second aspect of the present invention provides a plurality of receiving circuits that perform MIMO reception, a plurality of first antennas connected to each of the plurality of receiving circuits, and the vicinity of the plurality of first antennas. A receiving apparatus comprising: a second antenna disposed; and a characteristic control circuit connected to the second antenna to control a radiation direction of the plurality of first antennas. Thereby, the radiation direction of the first antenna used for reception is appropriately controlled, and MIMO transmission suitable for the usage environment is realized.

  Here, the characteristic control circuit causes the second antenna to function as a reflector, or causes the second antenna to function as a director. That is, the radiation direction of the first antenna is appropriately controlled by causing the second antenna to function as a reflector or a director under the control of the characteristic control circuit.

  In addition, the plurality of first antennas and the second antenna may be arranged in a substantially linear shape or may be arranged in a polygonal shape. These arrangements also affect the radiation direction of the first antenna.

  Further, the plurality of first antennas and the second antenna may have the same single-unit characteristics, or may have different single-unit characteristics. The radiation direction of the first antenna is also affected by the combination of these single characteristics.

  The receiving apparatus is provided between a second receiving circuit that performs reception, the second antenna, and the characteristic control circuit, and the connection destination of the second antenna is the characteristic control circuit or the second This is realized by further including a switch for switching to any one of the receiving circuits. By switching this switch to the second receiving circuit, it is possible to cope with diversity reception.

  The third aspect of the present invention provides N (N is an integer of 2 or more) first antennas, N reception circuits that perform MIMO reception, and N transmission circuits that perform MIMO transmission. N switches for switching each connection destination of the first antenna to either the reception circuit or the transmission circuit, a second antenna disposed in the vicinity of the first antenna, A wireless communication apparatus comprising: a characteristic control circuit connected to a second antenna to control a radiation direction of the first antenna. Thereby, the radiation direction of the first antenna used for communication is appropriately controlled, and MIMO transmission suitable for the usage environment is realized.

  Here, the characteristic control circuit causes the second antenna to function as a reflector, or causes the second antenna to function as a director. That is, the radiation direction of the first antenna is appropriately controlled by causing the second antenna to function as a reflector or a director under the control of the characteristic control circuit.

  The receiving apparatus is provided between a second receiving circuit that performs reception, the second antenna, and the characteristic control circuit, and the connection destination of the second antenna is the characteristic control circuit or the second And a second switch that switches to any one of the receiving circuits. By switching the second switch to the second receiving circuit, diversity reception can be supported.

  According to a fourth aspect of the present invention, there is provided a control method in a wireless communication apparatus that performs communication using MIMO, wherein one communication state is selected from the plurality of communication states with respect to a plurality of communication states in the wireless communication apparatus. The procedure for setting, the procedure for detecting the communication quality in the set communication state, and the procedure for maintaining the communication state as the optimum state if the detected communication quality is optimal are sequentially repeated, and the optimum A control method comprising a procedure for performing communication according to a communication state held as a state. Thereby, MIMO transmission suitable for the use environment is realized by using the communication state when the optimum communication quality is detected.

  According to the present invention, an excellent effect of controlling the independence of each antenna in MIMO and shortening the distance between the antennas can be obtained.

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

  FIG. 1 is a diagram showing a basic configuration of signal propagation by MIMO. Here, it is assumed that the receiving terminal 20 receives the signal transmitted from the transmitting terminal 10 via the radio wave propagation channel 30. The transmitting terminal 10 performs spatial multiplexing encoding, and the receiving terminal 20 performs spatial multiplexing decoding. The transmission terminal 10 is provided with n (n is an integer) antennas 11, and a spatially multiplexed signal is transmitted from these antennas 11. On the other hand, the receiving terminal 20 is provided with m (m is an integer) antennas 21, and a signal transmitted from the antenna 11 of the transmitting terminal 10 is received by these antennas 21.

  The radio wave propagation channel 30 is a multipath environment having a plurality of propagation channels. For example, a propagation path that reaches the receiving terminal 20 after the radio wave transmitted from the transmitting terminal 10 hits the reflecting object twice, and a receiving path 20 after the radio wave transmitted from the transmitting terminal 10 hits the reflecting object five times. Since the frequency characteristics of the transfer function are different from the reaching propagation path, these propagation paths can be treated as separate ones. The technique of simultaneously transmitting and receiving using such propagation paths having different transfer functions is called MIMO (Multi Input Multi Output).

  As a demodulation method in MIMO, channel information is unknown on the transmission side and linear calculation only on the reception side, such as zero forcing and V-BLAST (Vertical Bell Labs Layered Space-Time). Demodulation method, MLD (Maximum Likelihood Detection) method to demodulate by non-linear operation, STBC (Space Time Block Coding) method to give orthogonality to two transmission signals, and transmission side However, various schemes such as eigen-mode MIMO for transmitting / receiving channel information in advance and performing transmission / reception by performing appropriate power distribution and phase vector synthesis according to the channel information have been proposed.

  FIG. 2 is a diagram illustrating a configuration example of the wireless communication device 100 according to the embodiment of the present invention. In this wireless communication apparatus 100, as an example, three antennas 111 to 113, three switches 121 to 123, three reception RF (Radio Frequency) circuits 131 to 133, two transmission RF circuits 142, and 143, a characteristic control circuit 150, and a communication control circuit 160.

  Antennas 111 to 113 are antennas used for transmitting and receiving high-frequency signals, and are connected to switches 121 to 123, respectively. Various types of antennas can be used in addition to a single-resonance type dipole antenna. Moreover, a thing corresponding to a multi-frequency band, a wideband antenna, a multi-resonance antenna, etc. can be used.

  The switches 121 to 123 are for switching the connection of the antennas 111 to 113. The switch 121 connects either the reception RF circuit 131 or the characteristic control circuit 150 to the antenna 111. The switch 122 connects either the reception RF circuit 132 or the transmission RF circuit 142 to the antenna 112. The switch 123 connects either the reception RF circuit 133 or the transmission RF circuit 143 to the antenna 113.

  As these switches 121 to 123, a normal semiconductor switch can be used as a matter of course. For example, a micromachine switch formed by a film forming technique such as a MEMS (Micro Electro Mechanical System) switch is used. It may be used.

  The reception RF circuits 131 to 133 convert the received high-frequency signal into an intermediate frequency, demodulate it, and generate a baseband signal. This baseband signal is supplied to the communication control circuit 160. On the other hand, the transmission RF circuits 142 and 143 modulate the baseband signal supplied from the communication control circuit 160, convert the intermediate frequency to a high frequency signal, and transmit the modulated signal.

  The communication control circuit 160 generates a baseband signal from the data signal supplied from the data interface 169 and supplies the baseband signal to the transmission RF circuits 151 and 152 or data from the baseband signal supplied from the reception RF circuits 141 and 142. A signal is generated and supplied to the data interface 169. Further, the communication control circuit 160 detects the communication quality, and controls the power feeding method in the power feeding circuits 121 and 122 and the subcarrier modulation method in the communication control circuit 160 based on this.

  The characteristic control circuit 150 is a circuit that controls the characteristics of the antenna 111 via the switch 121. Details of the characteristic control circuit 150 will be described below.

  FIG. 3 is a diagram illustrating a configuration example of the characteristic control circuit 150 according to the embodiment of the present invention. The characteristic control circuit 150 includes a switch 151, a resistor 152, a capacitor 153, and a coil 154.

  The switch 151 performs switching so that the output signal line 129 and one end of the resistor 152 or one end of the capacitor 153 are connected. One output signal line 129 of the switch 121 is connected to the input terminal of the switch 151. One end of the switch 151 is connected to the other end of the resistor 152 having one end grounded 155. The other end of the output terminal of the switch 151 is connected to the other end of the LC series circuit (capacitor 153 and coil 154) having one end grounded 155.

  The resistor 152 is a variable resistor. The characteristics of the antenna 111 can be controlled by switching the switch 151 to the resistor 152 side and adjusting the resistance value of the resistor 152. For example, when the resistance value of the resistor 152 is 0Ω (that is, a short circuit), the apparent element length is increased by the image current of the ground 155, and the antenna 111 has a property as a reflector. On the other hand, for example, when the resistance value of the resistor 152 is ∞Ω (that is, open), the element length does not become long. If the physical length of the antenna 111 is formed shorter than that of other antennas in advance, the wave is guided in this state. It has properties as a vessel. Then, by setting the resistance 152 to any value between the above, the degree of the effect as a reflector or a director can be controlled. Of course, this characteristic is affected in various ways by the environment in which the antenna is used, that is, the arrangement interval of the antenna itself, the material of the surrounding casing, the positional relationship with the surrounding casing, and the frequency characteristics of the variable resistance. Although it is difficult to express it quantitatively in general, by adjusting the resistance 152 to a predetermined resistance value, the antenna 111 can exhibit properties as a director or a reflector.

  As described above, when the switch 151 is switched to the resistor 152 side and the resistor 152 is short-circuited, the apparent element length as a resonator is increased by the image current of the ground 155, thereby causing the antenna 111 to reflect. It has properties as a vessel.

  The capacitor 153 and the coil 154 constitute an LC series circuit. The capacitor 153 is a variable capacitor, and realizes a variable reactance by an LC series circuit. The characteristics of the antenna 111 can be controlled by adjusting the capacitance of the capacitor 153 after switching the switch 151 to the LC series circuit side. Here, assuming that the coil 154 is fixed at 1.5 nH and the capacitance of the variable capacitance diode in the capacitor 153 is changed from about 1.5 pF to 5 pF, when the capacitance is 1.5 pF, the impedance viewed from the switch 151 is about − j15.8Ω (@ 2.4 GHz), which is capacitive. Further, when the capacitance is 5 pF, the impedance is about + j14Ω (@ 2.4 GHz), which is inductive. Since it acts as a shortening capacitor when it is capacitive, the resonator length of the antenna 111 is shortened, and it has properties as a waveguide. On the other hand, when it is inductive, it acts as a loading coil, so that the resonator length of the antenna 111 is long, and it has a property as a reflector. Of course, this characteristic has various effects depending on the usage environment of the antenna, that is, the arrangement interval of the antenna itself, the material of the surrounding casing, the arrangement relationship with the surrounding casing, the frequency characteristics of the variable capacitance diode and the coil, etc. Therefore, it is difficult to express it quantitatively in general, but by adjusting the capacitor 153 to a predetermined capacity, the antenna 111 can exhibit the properties as a director or a reflector.

  As described above, when the switch 151 is switched to the LC series circuit side and the capacitance of the capacitor 153 is set to a predetermined value, the resonator length of the element becomes long, and thus the antenna 111 has a property as a reflector. Have. The same effect can be expected even if the capacitor 153 is short-circuited and only the coil 154 is connected.

  FIG. 4 is a diagram showing another configuration example of the characteristic control circuit 150 according to the embodiment of the present invention. In the configuration example of FIG. 3, either the resistor circuit or the LC series circuit is selected by the switch 151, but in FIG. 4, the resistor circuit and the LC series circuit are connected in series or in parallel.

  In FIG. 4A, a resistor 152, a capacitor 153, and a coil 154 are connected in series, and one end thereof is grounded 155. On the other hand, in FIG. 4B, the resistor 152 and the LC series circuit (the capacitor 153 and the coil 154) are connected in parallel, and one end thereof is grounded 155.

  Also in this example, the characteristics of the antenna 111 can be controlled by adjusting the resistance value of the resistor 152 and the capacitance of the capacitor 153. This characteristic varies depending on the usage environment of the antenna, that is, the arrangement interval of the antenna itself, the material of the surrounding casing, the arrangement relationship with the surrounding casing, the variable capacitance diode, the variable resistance, the frequency characteristics of the coil, etc. However, it is difficult to express quantitatively in general. However, by adjusting the resistance 152 to a predetermined resistance value or adjusting the capacitor 153 to a predetermined capacity, the antenna 111 can be a waveguide or It can exhibit properties as a reflector.

  Here, the example in which the resistor circuit and the LC series circuit are connected in series or in parallel has been described. However, in order to simplify the configuration, the antenna may be provided with only one of the resistor circuit and the LC series circuit. 111 may exhibit properties as a director or a reflector.

  FIG. 5 is a diagram showing an example of the state of the antenna at the time of transmission in the embodiment of the present invention. FIG. 5A shows a connection state when the switch 121 in FIG. 2 is switched to the characteristic control circuit 150 side, the switch 122 is switched to the transmission RF circuit 142 side, and the switch 123 is switched to the transmission RF circuit 143 side. That is, the characteristic control circuit 150 is connected to the antenna 111, the transmission RF circuit 142 is connected to the antenna 112, and the transmission RF circuit 143 is connected to the antenna 113.

  In this connection state, by adjusting the resistance value of the resistor 152 and the capacitance of the capacitor 153 in the characteristic control circuit 150, the antenna 111 has a property as a reflector, and the antenna as shown in the radiation state of FIG. Interference between 112 and 113 can be suppressed. This makes it possible to set the distance between the antennas 112 and 113 that is conventionally required to be about a half wavelength away to a shorter distance.

  FIG. 6 is a diagram showing an example of the state of the antenna at the time of reception in the embodiment of the present invention. FIG. 6A shows a connection state when the switch 121 in FIG. 2 is switched to the characteristic control circuit 150 side, the switch 122 is switched to the reception RF circuit 132 side, and the switch 123 is switched to the reception RF circuit 133 side. That is, the characteristic control circuit 150 is connected to the antenna 111, the reception RF circuit 132 is connected to the antenna 112, and the reception RF circuit 133 is connected to the antenna 113.

  According to the connection state of FIG. 6A, a radiation state similar to that in the case of FIG. 5B can be exhibited, and interference between the antennas 112 and 113 can be suppressed. Similarly, the distance between the conventional antennas 112 and 113 that had to be separated by about half a wavelength can be set to a shorter distance here.

  6B shows the connection state when the switch 121 in FIG. 2 is switched to the reception RF circuit 131 side, the switch 122 is switched to the reception RF circuit 132 side, and the switch 123 is switched to the reception RF circuit 133 side. Show. That is, the reception RF circuit 131 is connected to the antenna 111, the reception RF circuit 132 is connected to the antenna 112, and the reception RF circuit 133 is connected to the antenna 113.

  The connection state in FIG. 6B represents diversity reception by three antennas. As shown in FIG. 1, when the number of antennas on the transmission side is n and the number of antennas on the reception side is m, the diversity order that means the effect of diversity is represented by “mn + 1”. Therefore, if the number of antennas is the same on the transmission side and the reception side, the effect of diversity cannot be obtained. Here, for example, the effective number of antennas on the transmitting side is “n = 2” as shown in FIG. 5A, and the effective number of antennas on the receiving side is “m = 3” as shown in FIG. 6B. Then, the effect of diversity can be obtained. In the linear operation such as “V-BLAST” described above, it is considered that the quality of communication can be improved by increasing the number of reception antennas as compared with the number of transmission antennas. Such a form may be used. In that case, since only two antennas are used at the time of transmission, the remaining one is a useless element that does not function. In the present invention, as described above, proposals have been made to effectively use the remaining elements that are wasted during transmission in order to improve transmission quality. However, since the propagation environment actually used can take various states depending on the use conditions of the user, transmission quality may be improved if the diversity effect according to the conventional method is used in a straightforward manner. In view of this, the embodiment of the present invention is configured such that a reception signal from the antenna 111 can be processed by the reception RF circuit 131 on a case-by-case basis, and diversity reception can be selected in accordance with a radio wave propagation state.

  Next, the relationship between the antenna arrangement and the radiation pattern in the embodiment of the present invention will be described with reference to the drawings.

  FIG. 7 is a diagram showing a first example of antenna arrangement in the embodiment of the present invention. In this first example, as shown in FIG. 7A, the three antennas 111 to 113 are arranged in a substantially straight line. By making the antenna 111 function as a reflector in this arrangement example, radiation patterns 312 and 313 directed in different directions from the antennas 112 and 113 can be obtained as shown in FIG. 7B.

  FIG. 8 is a diagram illustrating a second example of the antenna arrangement according to the embodiment of the present invention. In the second example, as shown in FIG. 8A, three antennas 111 to 113 are arranged in a triangular shape. By causing the antenna 111 to function as a reflector in this arrangement example, radiation patterns 312 and 313 directed in directions different from the antenna 111 can be obtained from the antennas 112 and 113, respectively, as shown in FIG. 8B.

  In addition, although the example arrange | positioned at triangle shape was demonstrated here, it cannot be overemphasized that it can arrange in polygonal shape according to the number of antennas.

  FIG. 9 is a diagram illustrating a third example of the antenna arrangement according to the embodiment of the present invention. In this third example, as shown in FIG. 9A, five antennas 111 to 115 are arranged in a substantially straight line. In this arrangement example, it is assumed that the antenna 111 functions as a reflector and the antennas 114 and 115 function as waveguides. In the above description, it has been explained that the antenna functions as a reflector by adjusting the resonator length of the element to be longer, but in the same manner, the antenna is adjusted by adjusting the resonator length of the element to be shorter. It is possible to function as a director.

  By arranging the antennas 111 to 115 as shown in FIG. 9A, the radiation pattern 312 having a higher directivity is directed from the antennas 112 and 113 in different directions as shown in FIG. 9B. And 313 can be obtained.

  FIG. 10 is a diagram illustrating a fourth example of the antenna arrangement according to the embodiment of the present invention. In the fourth example, as shown in FIG. 10A, three antennas 111, 113, and 116 are arranged in a triangular shape. In this arrangement example, it is assumed that the antenna 111 functions as a reflector and the directional antenna 116 is used. That is, in the first to third examples described above, it is assumed that the individual characteristics of each antenna, that is, polarization, directivity, gain, and frequency band are the same. In this fourth example, the antenna The antenna 116 having different directivities is used as a single characteristic of the. Thus, the single characteristics of the antenna may be different from each other.

  By arranging the antennas 111, 113, and 116 as shown in FIG. 10 (a), the radiation patterns 313 and the antennas 113 and 116 directed in directions different from the antenna 111, respectively, as shown in FIG. 10 (b). 316, and a radiation pattern with higher directivity can be obtained for the radiation pattern 316.

  Next, communication state feedback control in the embodiment of the present invention will be described with reference to the drawings.

  FIG. 11 is a diagram showing a functional configuration example for communication state control in the embodiment of the present invention. Here, a quality detection unit 161, a communication state switching unit 162, an optimum state holding unit 163, a communication state holding unit 164, and a subcarrier modulation unit 165 are provided for communication state control. By assuming these configurations, feedback control related to the communication state is performed according to the state of the received signal.

  The quality detection unit 161 monitors the received signal and detects the quality of the received signal. Here, as an indicator of the quality of the received signal, for example, a transmission rate can be used. In addition, the signal power to interference power ratio (SIR), the power density to noise power density ratio (Eb / No), the received signal strength indication (RSSI), etc. The reception quality may be determined.

  The communication state switching unit 162 switches the communication state according to the reception quality determined by the quality detection unit 161. For example, in the characteristic control circuit 150 of FIG. 3, the resistance value of the resistor 152 is switched in a state where the switch 151 is connected to the resistor 152 side, or the capacitance of the capacitor 153 is changed in a state where the switch 151 is connected to the capacitor 153 side. The characteristics of the antenna 111 are changed by switching. Further, for example, in the communication control circuit 160 of FIG. 2, the modulation state is changed by switching the modulation scheme of the subcarrier.

  The communication state holding unit 164 holds the current communication state. For example, in the characteristic control circuit 150 of FIG. 3, which output the switch 151 is connected to, the resistance value of the resistor 152 and the capacitance of the capacitor 153, what is the modulation scheme of the subcarrier, etc. That state is maintained.

  The optimum state holding unit 163 holds the communication state that is determined to be optimum by the quality detection unit 161 among the communication states that have been held in the communication state holding unit 164 as the communication state. As a result of switching the communication state by the communication state switching unit 162, if the quality detection unit 161 determines that the reception quality is improved, the content of the optimum state holding unit 163 is updated with the content of the communication state holding unit 164. On the other hand, if the quality detection unit 161 determines that the reception quality has deteriorated, the contents of the optimum state holding unit 163 are maintained. Finally, the contents of the communication state holding unit 164 are updated with the contents of the optimum state holding unit 163.

  The subcarrier modulation unit 165 modulates the subcarrier in the transmission signal, and which modulation method is used is determined according to the communication state held in the communication state holding unit 164.

  FIG. 12 is a diagram showing an example of parameters for communication state control in the embodiment of the present invention. For example, as an antenna characteristic, an index variable I (1 to N, I and N are integers of 1 or more) is assumed as shown in FIG. 12A, and an antenna characteristic is assigned to each index variable I. Can do. In FIG. 12A, the resistance value of the resistor 152 is assigned as an example of the antenna characteristic, but the capacitance of the capacitor 153 or the like may be assigned.

  Further, for example, as a subcarrier modulation scheme, an index variable J (1 to M, J and M are integers of 1 or more) is assumed as shown in FIG. A carrier modulation scheme can be assigned. As this modulation method, 64QAM (64-position quadrature amplitude modulation), 16QAM (16-value quadrature amplitude modulation), 8PSK (Octuple Phase Shift Keying), QPSK (Quadrature Phase Shift) are used here. Keying: 4-phase modulation) is switched as appropriate.

  FIG. 13 is a flowchart showing an example of a control procedure regarding a communication state in the embodiment of the present invention. First, “1” is set as an initial value in the index variable J related to the subcarrier modulation scheme and the index variable I related to antenna characteristics described with reference to FIG. 12 (steps S910 and S911). These communication states (subcarrier modulation scheme and antenna characteristics) are set in the communication state holding unit 164 by the communication state switching unit 162, and communication is performed under the settings. Thereby, for example, the transmission rate is measured as the reception quality in the quality detection unit 161 (step S912).

  As a result of the transmission rate measurement, if the transmission rate is the maximum among the measurement results so far (step S913), the communication state held in the communication state holding unit 164 is held in the optimum state holding unit 163 ( Step S914). However, if the transmission rate is measured for the first time, the value is always maximized, and the initial communication state is held in the optimum state holding unit 163 as it is.

  Then, “1” is added to the index variable I related to the antenna characteristics (step S915). As a result, if the index variable I does not exceed the maximum value N (step S916), the antenna corresponding to the new index variable I is obtained. The characteristic is set in the communication state holding unit 164 by the communication state switching unit 162, and communication is performed under the setting. Thereby, the transmission rate is measured again in the quality detection unit 161 (step S912), and the transmission rate determination process is repeated (steps S913 and S914).

  On the other hand, if the index variable I exceeds the maximum value N in step S916, “1” is added to the index variable J related to the subcarrier modulation scheme (step S917). As a result, if the index variable J does not exceed the maximum value M (step S918), “1” is again set as the initial value for the index variable I related to antenna characteristics (step S911), and the above-described processing is repeated.

  On the other hand, if the index variable J exceeds the maximum value M in step S918, the communication state held in the optimum state holding unit 163 is held in the communication state holding unit 164, and the communication state is set. Then, the subsequent communication is performed (step S919).

  Here, it is assumed that the set values of the resistor 152 and the capacitor 153 are changed as the characteristics of the antenna. However, when satisfactory performance cannot be obtained by adjusting these values, FIG. The switch 121 may be switched to perform the diversity reception described in the above.

  In addition, here, an example of performing communication state control in a predetermined frequency band has been described. However, when a multi-frequency band antenna or the like is assumed, communication state control corresponding to the frequency band is performed for each frequency band to be used. Done.

  As described above, according to the embodiment of the present invention, the communication state switching unit 162 determines the circuit constant in the characteristic control circuit 150 and the subcarrier modulation in the communication control circuit 160 according to the determination result of the communication quality in the quality detection unit 161. By switching the method, the radiation state required for MIMO can be formed while shortening the distance between the antennas.

  The embodiment of the present invention is an example for embodying the present invention and has a corresponding relationship with the invention-specific matters in the claims as shown below, but is not limited thereto. However, various modifications can be made without departing from the scope of the present invention.

That is , in claim 1 , the first antenna corresponds to the antennas 112 and 113, for example. The first receiving circuit corresponds to the receiving RF circuits 132 and 133, for example. The transmission circuit corresponds to the transmission RF circuits 142 and 143, for example. The switches correspond to the switches 122 and 123, for example. The second antenna corresponds to the antenna 111, for example. The characteristic control circuit corresponds to the characteristic control circuit 150, for example. The second receiving circuit corresponds to the receiving RF circuit 131, for example. The second switch corresponds to the switch 121, for example.

  The processing procedure described in the embodiment of the present invention may be regarded as a method having a series of these procedures, and these series of procedures are executed by a computer (for example, a microcomputer, a CPU, a signal processing LSI, etc.). It may be considered as a program for recording the program or a recording medium for storing the program.

  As an application example of the present invention, for example, the present invention can be applied when designing a miniaturization of a wireless communication apparatus that performs communication by MIMO.

It is a figure which shows the basic composition of the signal propagation by MIMO. It is a figure which shows the example of 1 structure of the radio | wireless communication apparatus 100 in embodiment of this invention. It is a figure which shows the example of 1 structure of the characteristic control circuit 150 in embodiment of this invention. It is a figure which shows the other structural example of the characteristic control circuit 150 in embodiment of this invention. It is a figure which shows an example of the state of the antenna at the time of transmission in embodiment of this invention. It is a figure which shows an example of the state of the antenna at the time of reception in embodiment of this invention. It is a figure which shows the 1st example of the antenna arrangement | positioning in embodiment of this invention. It is a figure which shows the 2nd example of the antenna arrangement | positioning in embodiment of this invention. It is a figure which shows the 3rd example of the antenna arrangement | positioning in embodiment of this invention. It is a figure which shows the 4th example of the antenna arrangement | positioning in embodiment of this invention. It is a figure which shows the function structural example for the communication state control in embodiment of this invention. It is a figure which shows the parameter example for the communication state control in embodiment of this invention. It is a flowchart which shows an example of the control procedure regarding the communication state in embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Transmission terminal 20 Reception terminal 11, 21 Antenna 30 Radio wave propagation channel 100 Wireless communication apparatus 111-116 Antenna 121-123 Switch 131-133 Reception RF circuit 142, 143 Transmission RF circuit 150 Characteristic control circuit 151 Switch 152 Resistance 153 Capacitor 154 Coil 155 Grounding 160 Communication control circuit 161 Quality detection unit 162 Communication state switching unit 163 Optimal state holding unit 164 Communication state holding unit 165 Subcarrier modulation unit

Claims (8)

N first antennas (N is an integer greater than or equal to 2);
N first receiving circuits that perform MIMO reception;
N transmission circuits that perform MIMO transmission;
N switches for switching each connection destination of the first antenna to either the first reception circuit or the transmission circuit;
A second antenna disposed in the vicinity of the first antenna;
A characteristic control circuit for controlling the characteristics of the first antenna connected to said second antenna,
A second receiving circuit for receiving;
Switches the connection destination of the second antenna to the characteristic control circuit at the time of transmission, at the time of reception comprise a <br/> a second switch for switching the connection of the second antenna to the second receiving circuit radio Communication device.   The wireless communication apparatus according to claim 1, wherein the characteristic of the first antenna is a radiation direction of the first antenna. The characteristic control circuit, said second wireless communication apparatus 請 Motomeko 1, wherein the antenna Ru to function as a reflector. The characteristic control circuit, said second antenna radio communication apparatus 請 Motomeko 1, wherein Ru is made to function as a waveguide. Wherein the plurality of first antennas and the second antennas, the wireless communication apparatus 請 Motomeko 1, wherein that will be disposed substantially linearly. Wherein the plurality of first antennas and the second antennas, the wireless communication apparatus 請 Motomeko 1, wherein that will be disposed in a polygonal shape. Wherein the plurality of first antennas and the second antennas, the wireless communication apparatus 請 Motomeko 1 wherein independent characteristics each other Ru same der. Wherein the plurality of first antennas and the second antennas, the wireless communication apparatus 請 Motomeko 1 wherein alone characteristics that differ from each other.

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