Antenna device and communication device

An antenna device and a communication device capable of changing over polarization characteristics of an antenna to improve transmission capacity in various kinds of polarization environments and used configuration by preventing reduction of the communication capacity for a reception signal degrading or varying depending on momentarily changing polarization conditions between a base station and a terminal. The antenna device (110) includes a plurality of first antenna elements (111,112) for a first polarizing direction, a second antenna element (121) provided in the direction orthogonal to the first polarizing direction, a plurality of switches (131,132) for switching connection between the plurality of first antenna elements (111,112) and the second antenna element (121), and power supply parts (141,142) respectively provided on the plurality of first antenna elements (111,112).

TECHNICAL FIELD

The present invention relates to an antenna apparatus and communication apparatus such as a mobile telephone device. In particular, the present invention relates to an antenna apparatus and communication apparatus using a plurality of antenna elements for performing diversity operations, MIMO (Multiple-Input Multiple-Output) communication or adaptive array antenna operations.

BACKGROUND ART

An antenna apparatus is provided in various communication devices to transmit and receive radio waves of a predetermined frequency band. The popularity and the range of application of portable radio devices represented by mobile telephones have grown, and therefore there is a growing demand for wideband capability of portable radio device antennas. Also, with the rapid spread of portable radio devices, the number of channels in one wireless communication system is likely to be insufficient. Consequently, studies are underway to use one system together with other wireless communication systems using different frequency bands to secure a necessary number of channels. With significant advances in techniques for reducing size and weight, as a terminal, a single portable radio device that can use two kinds of wireless communication systems have been developed. Moreover, a bandwidth of several hundreds MHz is considered to be necessary in the UHF band for, for example, reception of terrestrial digital broadcast. Furthermore, to reduce the size of a radio apparatus by supporting a plurality of WLAN (Wireless Local Area Network) standards using different frequency bands by means of a single antenna, for example, an antenna covering the 2.4 GHz and 5.2 GHz bands is required.

In communication between a mobile station and base station in a mobile communication system, fading often occurs in which the received signal level fluctuates depending on various radio wave propagation environments. Effective measures to take against fading include providing antenna selective diversity and combined diversity. With antenna selective diversity, a plurality of antennas are generally installed, and communication is performed by selecting an antenna with good conditions when the receiving state degrades due to fading. For example, there are antenna selective diversity apparatuses with a TDMA (Time Division Multiple Access) communication scheme in which the same frequency is shared by a plurality of users by means of time division.

Also, in recent wireless communication systems, MIMO communication has attracted attention as a technique to improve the efficiency of transmission. In MIMO communication, a transmitting apparatus having a plurality of transmitting antennas simultaneously transmit streams comprised of a plurality of bits from these transmitting antennas, and a receiving apparatus having a plurality of receiving antennas demultiplex and demodulate those streams from the transmitting apparatus. Therefore, when mutually different streams are simultaneously transmitted from all of the transmitting antennas of the transmitting apparatus, compared to the case of one transmitting antenna, theoretically, it is possible to increase the efficiency of transmission to the multiples of the number of transmitting antennas.

In communication providing a plurality of antenna elements and adopting diversity operations, MIMO communication or adaptive array antenna operations, the directivity of a single antenna alone is not sufficient to cope with the fluctuation of polarization conditions which change every minute between a base station and a terminal. In particular, the directivity of a single antenna alone is not sufficient to cope with the fluctuation of polarization characteristics of received signals. To secure the communication capacity, an antenna system is necessary which flexibly responds to the fluctuation of polarization characteristics.

As measures to take against the above, Patent Documents 1 to 4 disclose techniques to improve communication capacity utilizing polarization.

Patent Document 1 discloses a communication apparatus and method using adaptive array antennas by which a base station switches polarization characteristics and in which the terminal side performs reception with a polarization matching a polarization characteristic from the base station. With the apparatus disclosed in Patent Document 1, if the base station outputs a vertically polarized wave, the terminal receives this with vertical polarization. By this means, antenna polarization matches between the terminal and the base station, so that it is possible to improve communication capacity. Further, by performing communication using polarizations which change between terminals, it is possible to suppress the interference for communication paths between the terminals and the base station.

Patent Document 2 discloses a radio wave transmitting and receiving apparatus for improving communication capacity by providing a plurality of antenna elements of different polarizations in a base station, implementing selective diversity and performing MIMO operations using this antenna group.

Patent Document 3 discloses an antenna apparatus that performs directivity synthesis using a plurality of antenna elements from a large number of antenna elements and then performs MIMO communication.

Patent Document 4 discloses a MIMO wireless communication system for providing a plurality of antenna elements of different polarizations both in a base station and in a terminal, and performing MIMO. By this means, the directivity and polarization change between antenna elements for transmission and reception in MIMO propagation paths, and the separation level between propagation paths improves, so that it is possible to improve communication capacity.Patent Document 1: Japanese Patent Application Laid-Open Number 2004-80353Patent Document 2: Japanese Patent Application Laid-Open Number 2004-312381Patent Document 3: Japanese Patent Application Laid-Open Number 2005-86518Patent Document 4: Japanese Patent Application Laid-Open Number 2004-517549

DISCLOSURE OF INVENTION

Problems to be Solved by the Invention

However, such a conventional portable radio device having a plurality of antenna elements has the following problems.

(1) In the apparatus disclosed in Patent Document 1, a base station communicates with terminals by switching polarization characteristics per antenna and the apparatus switches polarization from the base station per terminal, thereby improving separation between communication paths. However, with this technique, polarization from a base station changes depending on the propagation environment, and, consequently, it is difficult to secure the separation level between paths in terminals. Also, polarization of terminals is not fixed in mobile telephones, and therefore it is difficult to separate paths.

(2) The apparatus disclosed in Patent Document 2 selects the best antenna element from an antenna group having a plurality of antenna elements of different polarizations and implement diversity or perform MIMO using that antenna element. However, with this technique, although the transmission capacity in MIMO is increased by switching polarization per antenna, the gradient of terminals is not taken into account, and therefore the transmission capacity may be degraded depending on the condition of gradient.

(3) The apparatus disclosed in Patent Document 3 performs directivity synthesis using a plurality of antenna elements from a large number of antenna elements and then performs MIMO communication. That is, by performing directivity synthesis after adjusting the amplitude and phase using a plurality of antenna elements, it is possible to provide directivity suitable to various propagation characteristics and polarization characteristics. However, this technique does not disclose that the terminal side acquires an antenna of an optimal polarization characteristic not depending on the operating states of a base station, propagation environment and terminal. Further, this technique does not disclose an antenna apparatus that provides various polarization patterns in accordance with polarization characteristics, where these polarization characteristics provide extremely low power loss and change depending on place and time.

(4) The apparatus disclosed in Patent Document 4 provides a plurality of antenna elements of different polarizations both in a base station and in a terminal, and performs MIMO. The polarizations of antennas are not switched depending on changes in the propagation environment, and the same directivities and polarization characteristics are always used. Similar to the apparatus disclosed in Patent Document 3, this technique does not disclose that the terminal side acquires an antenna of an optimal polarization characteristic not depending on the operating states of a base station, propagation environment and terminal. Further, this technique does not disclose an antenna apparatus that provides various polarization patterns in accordance with polarization characteristics, where these polarization characteristics provide extremely low power loss and change depending on place and time

Therefore, with an antenna apparatus and communication apparatus using a plurality of conventional antenna elements, when a base station and terminal perform communication, it is necessary to provide a larger communication capacity more reliably by responding to changes in polarization by antennas. Here, changes in polarization occur depending on: polarizations of base station antennas; changes in polarization characteristics due to radio propagation characteristics between the base station and the terminal; the method of using the terminal by the user; and various conditions such as the gradient of the terminal.

In view of the above, it is an object of the present invention to provide an antenna apparatus and communication apparatus that can switch antenna polarization characteristics, prevent the decrease in communication capacity for received signals that attenuate or fluctuate depending on the conditions of polarization that changes every minute between a base station and a terminal.

Means for Solving the Problem

The antenna apparatus of the present invention employs a configuration having: at least two first antenna elements for a first polarization direction; a second antenna element that is set in a direction orthogonal to the first polarization direction; a switch that switches connections between the first antenna elements and the second antenna element; and a feeding section that is set in each of the first antenna elements.

The communication apparatus of the present invention employs a configuration having the above antenna apparatus used for MIMO (Multiple Input Multiple Output) or diversity.

Advantageous Effect Of The Invention

According to the present invention, by switching the antenna polarization characteristics, it is possible to provide optimal antenna performance for received signals that attenuate or fluctuate depending on the conditions of polarization that changes every minute between a base station and a terminal. Further, it is equally possible to provide an advantage of preventing the decrease in communication capacity in communication using a plurality of antenna elements for performing diversity operations, MIMO communication or adaptive array antenna operations. By this means, for example, it is possible to flexibly cope with changes in polarization that occur depending on: polarization characteristics of base station antennas; radio propagation characteristics between the base station and a terminal; the method of using the terminal by the user; and various conditions such as the gradient of the terminal. Therefore, it is possible to provide the best signal level, prevent the decrease in communication capacity and improve transmission capacity in various polarization environments and usage types.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be explained below in detail with reference to the accompanying drawings.

FIG. 1shows an outline configuration of a portable radio device mounting an antenna apparatus using a plurality of antenna elements according to Embodiment 1 of the present invention. An example case will be described where the present embodiment is applied to a portable radio device mounting a terminal antenna apparatus used in MIMO communication or diversity communication.

InFIG. 1, portable radio device100has, inside the housing, antenna apparatus110using a plurality of antenna elements used in MIMO communication or diversity communication.

Portable radio device100only needs to represent a portable radio device mounting antenna apparatus110using a plurality of antenna elements used in MIMO communication or diversity communication, such as a mobile telephone device and PHS (Personal Handy-phone System). Also, portable information terminals such as PDA's (Personal Digital Assistants) and information processing apparatuses such as a laptop computer are applicable.

The housing of portable radio device100is formed with a molded insulating resin such as a non-conductive ABS resin. Also, as measures to take against degradation in antenna efficiency upon close antenna elements, for example, the housing uses metamaterials to prevent degradation in antenna efficiency. Also, as is not shown in the figure, portable radio device100is provided with an LCD display section, a subscreen display section, a speaker that outputs, for example, a ringtone, a camera section that photographs an image, a connector that connects with external devices, and so on.

Antenna apparatus110is provided with first antenna elements111and112for the first polarization direction, second antenna element121that is set in the direction orthogonal to the first polarization direction, switches131and132that switch connection between first antenna elements111and112and second antenna element121, and feeding sections141and142that are provided in first antenna elements111and112, respectively.

As shown inFIG. 1, antenna apparatus110employs a configuration in which three antenna elements (i.e. first antenna elements111and112and second antenna element121) are arranged in the shape of the letter “U,” two switches (i.e. switches131and132) are arranged between these antenna elements, and two feeding sections (i.e. feeding sections141and142) are arranged in one end of first antenna elements111and112.

Assume that first antenna elements111and112and second antenna element121are formed with metal frames and have a length of approximately λ/4 (where λ is the wavelength) in the longitudinal direction. Regarding the antenna element parallel to the housing, when this antenna element is set as far as possible from this housing, the antenna efficiency improves and is therefore advantageous. The materials naturally carries radio waves, and examples include copper, iron and magnesium alloy providing a high conduction level with low loss at used frequencies and having high hardness with lightweight.

Switches131and132switch the connections between second antenna element121and first antenna element111and/or first antenna element112, according to a control signal from a control section (not shown). Also, the control section (not shown) outputs a control signal to switches131and132for switching the connections according to the polarization direction.

Switches131and132use switches providing minimum loss at used frequencies in the case where switches131and132are turned on, and use switches providing as much isolation as possible in the case where switches131and132are turned off. Further, switches131and132need to withstand the large power of transmission waves upon transmission. For example, it is preferable to use MEMS (Micro-Electro-Mechanical System) switches with low loss. Also, specific examples of combinations of switching in switches131and132will be described later.

Feeding sections141and142are formed with conductive metals and connected with first antenna elements111and112for feeding these antenna elements.

If switch131is turned off and first antenna element111and second antenna element121are separated from each other, first antenna element111and feeding section141operate as a monopole antenna. Similarly, if switch132is turned off and first antenna element112and second antenna element121are separated from each other, first antenna element112and feeding section142operate as an monopole antenna. Also, second antenna element121is arranged orthogonal to first antenna elements111and112such that second antenna element121links these two monopole feeding sections.

Here, antenna apparatus110incorporated in portable radio device100may be mounted transversely to the housing of portable radio device100.

FIG. 2shows an outline configuration of portable radio device100having above antenna apparatus110. The same components as inFIG. 1will be assigned the same reference numerals.

As shown inFIG. 2, three antenna elements are arranged in the shape of the letter “U” such that antenna apparatus110is transversely arranged to the housing of portable radio device100. If antenna apparatus110is transversely arranged, the performance is the same as inFIG. 1. By arranging antenna apparatus110transversely, it is possible to improve the degree of freedom of arrangement of parts in the housing.

The operations of antenna apparatus110configured as above will be explained.

An example case will be described where MIMO communication that switches polarization characteristics depending on the condition is performed to cope with various polarizations.

FIGS. 3A to 3Cillustrate switching of polarization characteristics of antenna apparatus110, whereFIG. 3Ashows vertical polarization in MIMO,FIG. 3Bshows diagonal polarization (MIMO+) andFIG. 3Cshows diagonal polarization (MIMO−). Also,FIG. 4shows a table illustrating switching of polarization characteristics inFIGS. 3A to 3C. InFIGS. 3A to 3CandFIG. 4, diagonal polarization is inclined at +45 degrees or −45 degrees from vertical polarization. The direction of polarization is shown by the arrow points in the figure. SW1and SW2represent switches131and132, and Rx1and Rx2represent the receiving ends of portable radio device100with which antenna apparatus110is connected. Also, V represents vertical polarization. Also, if this antenna apparatus110is applied to the base station side that performs MIMO communication, Rx1and Rx2need to be read as Tx1and Tx2.

As shown inFIG. 3AandFIG. 4, switch131(SW1) and switch132(SW2) are turned off. Then, second antenna element121is separated from first antenna elements111and112, and only first antenna elements111and112in the first polarization direction perform monopole antenna operations. Therefore, antenna apparatus110has antenna characteristics of (90 degrees-90 degrees) polarization.

As shown inFIG. 3BandFIG. 4, switch131(SW1) is turned on and switch132(SW2) is turned off. Then, first antenna element111and second antenna element121are connected, and second antenna element121and first antenna element112are separated. Second antenna element121is arranged in the direction orthogonal to first antenna element111, and, consequently, when first antenna element111and second antenna element121are connected, the antenna element formed with first antenna element111and second antenna element121provides diagonal polarization inclined at +45 degrees from vertical polarization. First antenna element112in the first polarization direction performs monopole antenna operations. Therefore, antenna apparatus110has antenna characteristics of (+45 degrees-90 degrees) polarization.

As shown inFIG. 3CandFIG. 4, switch131(SW1) is turned off and switch132(SW2) is turned on. Then, first antenna element112and second antenna element121are connected, and second antenna element121and first antenna element111are separated. Similar to first antenna element111, second antenna element121is arranged in the direction orthogonal to first antenna element112, and, consequently, when first antenna element112and second antenna element121are connected, the antenna element formed with first antenna element112and second antenna element121provides diagonal polarization inclined at −45 degrees from vertical polarization. First antenna element111in the first polarization direction performs monopole antenna operations. Therefore, antenna apparatus110has antenna characteristics of (90 degrees-(−45) degrees) polarization.

As shown in the table ofFIG. 4, by switching switch131(SW1) and switch132(SW2), antenna apparatus110can provide three types of antenna characteristics of (90 degrees-90 degrees) polarization, (45 degrees-90 degrees) polarization and (90 degrees-(−45) degrees) polarization. By this means, even in the case where mismatch of polarization occurs in a receiving antenna due to the antenna configuration of the base station, the rotation of propagating polarization and the gradient of the terminal (e.g. portable radio device100), it is possible to improve the receiving level by three variations of antenna polarizations. In particular, these antenna polarizations are effective to improve the received signal level in MIMO and diversity communication.

As described above, according to the present embodiment, antenna apparatus110is provided with first antenna elements111and112for the first polarization direction, second antenna element121set in the direction orthogonal to the first polarization direction, switches131and132that switch the connections between first antenna elements111and112and second antenna element121, and feeding sections141and142provided in first antenna elements111and112, respectively. By switching switches131and132and changing operating antenna elements, it is possible to switch the polarization characteristics of antenna apparatus110, so that it is possible to provide antenna performance to cope with the condition of polarization that changes every minute between a base station and a terminal. By this means, it is possible to improve transmission capacity in various polarization environments and usage types. For example, in the case of portable radio device100mounting antenna apparatus110shown inFIG. 1, in MIMO communication or diversity communication, even if polarization of a base station fluctuates, propagating polarization fluctuates or polarization fluctuates due to various causes such as polarization changes caused by the gradient of the terminal, it is possible to perform MIMO communication or diversity communication with high transmission capacity by controlling switches131and132mounted on antenna apparatus110and providing the antenna directivity of optimal polarization characteristics according to the operation state.

Also, with the present embodiment, by using MEMS switches of low loss as switches131and132, it is possible to alleviate the power loss due to switching and prevent the decrease in communication capacity.

FIG. 5shows an outline configuration of a portable radio device mounting an antenna apparatus using a plurality of antenna elements according to Embodiment 2 of the present invention. In the explanation of the present embodiment, the same components as inFIG. 1will be assigned the same reference numerals and overlapping explanation will be omitted.

InFIG. 5, portable radio device200has built-in antenna apparatus210using a plurality of antenna elements used in MIMO communication or diversity communication.

Antenna apparatus210is provided with first antenna elements111and112for the first polarization direction, second antenna element121set in the direction orthogonal to the first polarization direction, switches131and132that are set at one end of first antenna elements111and112and that switch the connections between first antenna elements111and112and second antenna element121, and feeding sections141and142that are set in the other end of first antenna elements111and112, respectively.

Antenna apparatus210differs fromFIG. 1only in arranging second antenna element121and switches131and132on the side opposite to the side of feeding sections141and142of antenna elements111and112. Therefore, similar to antenna apparatus110inFIG. 1, antenna apparatus210employs a configuration where three antenna elements (i.e. first antenna elements111and112and second antenna element121) are arranged in the shape of the letter “U,”, two switches (i.e. switches131and132) are arranged between these antenna elements, and two feeding sections (i.e. feeding sections141and142) are arranged in one end of first antenna elements111and112.

Here, as is not shown in the figure, antenna apparatus210incorporated in portable radio device100may be provided transversely to the housing of portable radio device200.

The operations of antenna apparatus210configured as above will be explained below.

The basic operations are the same as in Embodiment 1. An example case will be described where MIMO communication that switches polarization characteristics depending on the condition is performed.

FIGS. 6A to 6Cillustrate switching of polarization characteristics of antenna apparatus210, whereFIG. 6Ashows vertical polarization in MIMO,FIG. 6Bshows diagonal polarization (MIMO−) andFIG. 6Cshows diagonal polarization (MIMO+). Also,FIG. 7shows a table illustrating switching of polarization characteristics inFIGS. 6A to 6C. InFIGS. 6A to 6CandFIG. 7, diagonal polarization is inclined at +45 degrees or −45 degrees from vertical polarization. SW1and SW2represent switches131and132, and Rx1and Rx2represent the receiving ends of portable radio device200with which antenna apparatus210is connected. Also, V represents vertical polarization. Also, if this antenna apparatus210is applied to the base station side that performs MIMO communication, Rx1and Rx2need to be read as Tx1and Tx2.

As shown inFIG. 6AandFIG. 7, switch131(SW1) and switch132(SW2) are turned off. Then, second antenna element121is separated from first antenna elements111and112, and only first antenna elements111and112in the first polarization direction perform monopole antenna operations. Therefore, antenna apparatus210has antenna characteristics of (90 degrees-90 degrees) polarization.

As shown inFIG. 6BandFIG. 7, switch131(SW1) is turned on and switch132(SW2) is turned off. Then, first antenna element111and second antenna element121are connected, and second antenna element121and first antenna element112are separated. Second antenna element121is arranged in the direction orthogonal to first antenna element111, and, consequently, when first antenna element111and second antenna element121are connected, the antenna element formed with first antenna element111and second antenna element121provides diagonal polarization inclined at +45 degrees from vertical polarization. First antenna element112in the first polarization direction performs monopole antenna operations. Therefore, antenna apparatus210has antenna characteristics of (−45 degrees-90 degrees) polarization.

As shown inFIG. 6CandFIG. 7, switch131(SW1) is turned off and switch132(SW2) is turned on. Then, first antenna element112and second antenna element121are connected, and second antenna element121and first antenna element111are separated. Similar to first antenna element111, second antenna element121is arranged in the direction orthogonal to first antenna element112, and, consequently, when first antenna element112and second antenna element121are connected, the antenna element formed with first antenna element112and second antenna element121provides diagonal polarization inclined at −45 degrees from vertical polarization. First antenna element111in the first polarization direction performs monopole antenna operations. Therefore, antenna apparatus210has antenna characteristics of (90 degrees-45 degrees) polarization.

As shown in the table ofFIG. 7, by switching switch131(SW1) and switch132(SW2), antenna apparatus210can provide three types of antenna characteristics of (90 degrees-90 degrees) polarization, (−45 degrees-90 degrees) polarization and (90 degrees-45 degrees) polarization. By this means, even in the case where mismatch of polarization occurs in a receiving antenna due to the antenna configuration of the base station, the rotation of propagating polarization and the gradient of the terminal (e.g. portable radio device200), it is possible to improve the receiving level by three variations of antenna polarizations. In particular, these antenna polarizations are effective to improve the received signal level in MIMO and diversity communication. By switching switches131and132and changing operating antenna elements, it is possible to switch the polarization characteristics of antenna apparatus210, so that it is possible to provide antenna performance to cope with the condition of polarization that changes every minute between a base station and a terminal. By this means, it is possible to improve transmission capacity in various polarization environments and usage types.

Cases have been described with Embodiments 1 and 2 where an antenna apparatus uses a plurality of antenna elements used in 2×2 MIMO communication or diversity communication. A case will be explained with Embodiment 3 where an antenna apparatus uses a plurality of antenna elements used in 3×3 MIMO communication or diversity communication.

FIG. 8shows an outline configuration of a portable radio device mounting an antenna apparatus using a plurality of antenna elements according to Embodiment 3 of the present invention. In the explanation of the present embodiment, the same components as inFIG. 1will be assigned the same reference numerals and overlapping explanation will be omitted.

InFIG. 8, portable radio device300has built-in antenna apparatus310using a plurality of antenna elements used in MIMO communication or diversity communication.

Antenna apparatus310is provided with first antenna elements111,112and113for the first polarization direction, second antenna elements121and122set in the direction orthogonal to the first polarization direction, switches131,132,133and134that switch the connections between first antenna elements111,112and113and second antenna elements121and122, and feeding sections141,142and143that are set in first antenna elements111,112and113.

The present embodiment shows a configuration example of an antenna apparatus in 3×3 MIMO communication. The number of antenna elements, the number of switches and the number of feeding points in the antenna apparatus are generally shown as follows.

In the case of N×N MIMO (where N is an arbitrary natural number), the number of feeding points is N, the number of elements is N+(N−1) and the number of switches is (N−1)×2.

Here, as is not shown in the figure, antenna apparatus310incorporated in portable radio device300may be provided transversely to the housing of portable radio device300.

Also, although an example case has been described withFIG. 8where antenna apparatus310is incorporated in the housing of portable radio device300, it is equally possible to set antenna apparatus310in any positions such as the outside of portable radio device300.

FIGS. 9A and 9Bshow a perspective view of an outline configuration of a portable radio device mounting above antenna apparatus310. As shown inFIG. 9A, it is possible to arrange antenna apparatus310in the upper part of portable radio device300A, or cover antenna apparatus310with cover320as shown inFIG. 9B.

The operations of antenna apparatus31configured as above will be explained.

The basic operations are the same as in Embodiment 1. An example case will be described where 3×3 MIMO communication that switches polarization characteristics depending on the condition is performed.

FIGS. 10A to 10Iillustrate switching of polarization characteristics of antenna apparatus310, whereFIGS. 10A and 10Bshow vertical polarization in MIMO andFIGS. 10C to 10Ishow at least one diagonal polarization in the receiving end of portable radio device300. Also,FIGS. 11 to 13show a table illustrating switching of polarization characteristics inFIGS. 10A to 10I. InFIGS. 10A to 10IandFIGS. 11 to 13, diagonal polarization is inclined at +45 degrees or −45 degrees from vertical polarization. SW1, SW2and SW3represent switches131,132and133, and Rx1, Rx2and Rx3represent the receiving end of portable radio device310with which antenna apparatus300is connected. Also, if this antenna apparatus310is applied to the base station side that performs MIMO communication, Rx1, Rx2and Rx3need to be read as Tx1, Tx2and Tx3.

As shown inFIG. 10AandFIG. 11, switch131(SW1) to switch134(SW4) are turned off. Then, second antenna elements121and122are separated from first antenna elements111,112and113, and only first antenna elements111,112and113in the first polarization direction perform monopole antenna operations. Therefore, antenna apparatus310has antenna characteristics of (90 degrees-90 degrees-90 degrees) polarization.

As shown inFIG. 10BandFIG. 11, switches131(SW1) and134(SW4) are turned off and switches132(SW2) and133(SW3) are turned on. Then, first antenna element112and second antenna elements121and122are connected, second antenna element121and first antenna element111are separated, and second antenna element122and first antenna element113are separated. Although second antenna elements121and122are arranged in the direction orthogonal to first antenna elements111,112and113, second antenna elements121and122are connected equally on the sides of first antenna element112, and therefore the antenna element formed with first antenna element112and second antenna elements121and122provide vertical polarization. First antenna elements111,112and113in the first polarization direction perform monopole antenna operations. Therefore, antenna apparatus310has antenna characteristics of (90 degrees-90 degrees-90 degrees) polarization.

As shown inFIG. 10CandFIG. 11, switch131(SW1) is turned on, switch132(SW2) is turned off, switch133(SW3) is turned off and switch134(SW4) is turned on. Then, first antenna element111and second antenna elements121are connected, first antenna element113and second antenna element122are connected, and first antenna element112and second antenna elements121and122are separated. Second antenna elements121and122are arranged in the direction orthogonal to first antenna elements111,112and113, and, consequently, when first antenna element111and second antenna element121are connected, the antenna element formed with first antenna element111and second antenna element121provides diagonal polarization inclined at +45 degrees from vertical polarization. Similarly, when first antenna element113and second antenna element122are connected, the antenna element formed with first antenna element113and second antenna element122provides diagonal polarization inclined at −45 degrees from vertical polarization. First antenna element112in the first polarization direction performs monopole antenna operations. Therefore, antenna apparatus310has antenna characteristics of (45 degrees-90 degrees-(−45) degrees) polarization.

As shown inFIG. 10DandFIG. 12, switch131(SW1) is turned off, switch132(SW2) is turned off, switch133(SW3) is turned on and switch134(SW4) is turned off. Then, first antenna element112and second antenna elements122are connected, second antenna element121and first antenna element111are separated, and second antenna element122and first antenna elements113are separated. Second antenna elements122is arranged in the direction orthogonal to first antenna elements111,112and113, and, consequently, when first antenna element112and second antenna element122are connected, the antenna element formed with first antenna element112and second antenna element122provides diagonal polarization inclined at +45 degrees from vertical polarization. First antenna elements112and113in the first polarization direction perform monopole antenna operations. Therefore, antenna apparatus310has antenna characteristics of (90 degrees-45 degrees-90 degrees) polarization.

As shown inFIG. 10EandFIG. 12, switch131(SW1) is turned off, switch132(SW2) is turned off, switch133(SW3) is turned off and switch134(SW4) is turned on. Then, first antenna element113and second antenna element122are connected, second antenna element121and first antenna element111are separated, and second antenna element122and first antenna element112are separated. Second antenna elements122is arranged in the direction orthogonal to first antenna elements111,112and113, and, consequently, when first antenna element113and second antenna element122are connected, the antenna element formed with first antenna element113and second antenna element122provides diagonal polarization inclined at −45 degrees from vertical polarization. First antenna elements111and112in the first polarization direction perform monopole antenna operations. Therefore, antenna apparatus310has antenna characteristics of (90 degrees-90 degrees-(−45) degrees) polarization.

As shown inFIG. 10FandFIG. 12, switch131(SW1) is turned off, switch132(SW2) is turned on, switch133(SW3) is turned off and switch134(SW4) is turned on. Then, first antenna element112and second antenna element121are connected, first antenna element113and second antenna element122are separated, second antenna element121and first antenna element111are separated, and second antenna element122and first antenna element112are separated. Second antenna elements121and122are arranged in the direction orthogonal to first antenna elements111,112and113, and, consequently, when first antenna element112and second antenna element121are connected, the antenna element formed with first antenna element112and second antenna element121provides diagonal polarization inclined at −45 degrees from vertical polarization. Similarly, when first antenna element113and second antenna element122are connected, the antenna element formed with first antenna element113and second antenna element122also provides diagonal polarization inclined at −45 degrees from vertical polarization. First antenna element111in the first polarization direction performs monopole antenna operations. Therefore, antenna apparatus310has antenna characteristics of (90 degrees-(−45) degrees-(−45) degrees) polarization.

As shown inFIG. 10GandFIG. 13, switch131(SW1) is turned off, switch132(SW2) is turned on, switch133(SW3) is turned off and switch134(SW4) is turned off. Then, first antenna element112and second antenna element121are connected, second antenna element122and first antenna elements112and113are separated. Second antenna elements121is arranged in the direction orthogonal to first antenna elements111,112and113, and, consequently, when first antenna element112and second antenna element121are connected, the antenna element formed with first antenna element112and second antenna element121provides diagonal polarization inclined at −45 degrees from vertical polarization. First antenna elements111and113in the first polarization direction perform monopole antenna operations. Therefore, antenna apparatus310has antenna characteristics of (90 degrees-(−45) degrees-90 degrees) polarization.

As shown inFIG. 10HandFIG. 13, switch131(SW1) is turned on, switch132(SW2) is turned off, switch133(SW3) is turned off and switch134(SW4) is turned off. Then, first antenna element111and second antenna elements121are connected, second antenna element122and first antenna elements112and113are separated. Second antenna elements121is arranged in the direction orthogonal to first antenna elements111,112and113, and, consequently, when first antenna element111and second antenna element121are connected, the antenna element formed with first antenna element111and second antenna element121provides diagonal polarization inclined at +45 degrees from vertical polarization. First antenna elements112and113in the first polarization direction perform monopole antenna operations. Therefore, antenna apparatus310has antenna characteristics of (45 degrees-90 degrees-90 degrees) polarization.

As shown inFIG. 10IandFIG. 13, switch131(SW1) is turned on, switch132(SW2) is turned off, switch133(SW3) is turned on and switch134(SW4) is turned off. Then, first antenna element111and second antenna element121are connected, first antenna element112and second antenna element122are connected, and second antenna element122and first antenna element113are separated. Second antenna elements121and122are arranged in the direction orthogonal to first antenna elements111,112and113, and, consequently, when first antenna element111and second antenna element121are connected and first antenna element112and second antenna element122are connected, the antenna element formed with first antenna element111and second antenna element121and the antenna element formed with first antenna element112and second antenna element122provide diagonal polarization inclined at +45 degrees from vertical polarization. First antenna element113in the first polarization direction performs monopole antenna operations. Therefore, antenna apparatus310has antenna characteristics of (45 degrees-45 degrees-90 degrees) polarization.

Thus, by switching switches131to134(SW1to SW4), antenna apparatus310can provide antenna characteristics of combinations of polarizations in the tables shown inFIG. 12andFIG. 13. By this means, even in the case where mismatch of polarization occurs in a receiving antenna due to the antenna configuration of the base station, the rotation of propagating polarization and the gradient of the terminal (e.g. portable radio device300), it is possible to improve the receiving level by various variations of antenna polarizations. In particular, these antenna polarizations are effective to improve the received signal level in MIMO and diversity communication. That is, by switching between switches131to134(SW1to SW4) and changing operating antenna elements, it is possible to switch polarization characteristics with more variations than in Embodiments 1 and 2, so that it is possible to provide antenna performance to cope with the condition of polarization that changes every minute between a base station and a terminal. As a result, it is possible to improve transmission capacity in various polarization environments and usage types.

Here, it is possible to use above antenna apparatus310of the same configuration between the receiving side and the transmitting side. A supplemental case will be explained where feeding points of antenna apparatus310are connected directly.

FIG. 14illustrates a method of directly connecting feeding points of antenna apparatus310.

In the case of using antenna apparatus310on the receiving side, there is no problem if feeding points of antenna apparatus310are directly connected. However, in the case of using antenna apparatus310in, for example, a base station on the transmitting side, it is not possible to directly connect feeding points of antenna apparatus310. For example, in the case of using antenna apparatus310on the transmitting side, it is not possible to implement a combination of switch operations in which switch131(SW1) and switch132(SW2) are turned on or switch133(SW3) and switch134(SW4) are turned on inFIG. 14.

FIG. 15shows a perspective view of an outline configuration of a portable radio device mounting an antenna apparatus using a plurality of antenna elements, according to Embodiment 4 of the present invention. In the explanation of the present embodiment, the same components as inFIG. 1andFIG. 8will be assigned the same reference numerals and overlapping explanation will be omitted.

InFIGS. 15A and 15B, antenna apparatus410using a plurality of antenna elements used in MIMO communication or diversity communication, is placed on the upper part of portable radio device400A.

Antenna apparatus410is provided with first antenna elements111,112and113for the first polarization direction, second antenna elements121and122that are set in the direction orthogonal to the first polarization direction, switches131,132,133and134(not shown inFIG. 15A) that are set in one end of first antenna elements111,112and113and that switch the connections between first antenna elements111,112and113and second antenna elements121and122, and feeding sections141,142and143(not shown inFIG. 15A) that are provided in first antenna elements111,112and113, respectively.

Antenna apparatus410differs fromFIG. 8only in arranging second antenna elements121and122and switches131,132and133on the side opposite to the side of feeding sections141,142and143of antenna elements111,112and113.

Also, as shown inFIG. 9B, it is possible to arrange antenna apparatus410in the upper part of portable radio device400A and further cover antenna apparatus410with cover420.

The operations of antenna apparatus410configured as above are the same as in Embodiment 1 and explanation will be omitted.

Thus, according to the present embodiment, similar to Embodiment 3, by switching between switches131to134(SW1to SW4), it is possible to acquire the antenna characteristics of various combinations. By this means, even in the case where mismatch of polarization occurs in a receiving antenna due to the antenna configuration of the base station, the rotation of propagating polarization and the gradient of the terminal (e.g. portable radio device400), it is possible to improve the receiving level by various variations of antenna polarizations. In particular, these antenna polarizations are effective to improve the received signal level in MIMO and diversity communication. Also, with the present embodiment, similar to Embodiment 3, by switching between switches131to134(SW1to SW4) and changing operating antenna elements, it is possible to switch polarization characteristics with more variations than in Embodiments 1 and 2, so that it is possible to provide antenna performance to cope with the condition of polarization that changes every minute between a base station and a terminal. As a result, it is possible to improve transmission capacity in various polarization environments and usage types.

FIG. 16shows a perspective view of an outline configuration of a portable radio device mounting an antenna apparatus using a plurality of antenna elements, according to Embodiment 5 of the present invention. In the explanation of the present embodiment, the same components as inFIG. 1andFIG. 9Awill be assigned the same reference numerals and overlapping explanation will be omitted.

InFIG. 16, antenna apparatus310using a plurality of antenna elements used in MIMO communication or diversity communication, is placed on the upper part of portable radio device500A.

Also, switch controller501that controls switching between switches131,132,133and134(not shown) of antenna apparatus310, switch controller command section502that controls switch controller501and communication capacity calculating section503that calculates the communication capacity, are provided in portable radio device500A.

Above switch controller command section502and communication capacity calculating section503may be comprised of, for example, microprocessors or electronic circuits such as a logical circuit and timer. Here, in the case of forming these sections with microprocessors, it is equally possible to use resources such as a CPU provided as a main unit function in portable radio device500A.

The operations of portable radio device500A having antenna apparatus310configured as above will be explained. The operations of antenna apparatus310are the same as in Embodiment 1 and explanation will be omitted, and the specific operations of the present embodiment will be described.

Switch controller command section502sequentially switches between switches131,132,133and134via switch controller501, according to predetermined operation modes. For example, switch controller command section502commands switch controller501to switch between switches131,132,133and134in a switching configuration to implement Mode 1, Mode 2 to Mode 3 in order, as shown inFIGS. 10Ato10C andFIG. 11. By this means, switches131,132,133and134are switched in a switching configuration to implement above Mode 1, Mode 2 to Mode 3 in order.

Communication capacity calculating section503detects the communication capacities upon switching a switching configuration to implement Mode 1, Mode 2 to Mode 3 in order. Further, communication capacity calculating section503compares the communication capacities of those modes, and outputs a signal to report the mode in which the highest communication capacity is found, to switch controller command section502. Switch controller command section502gives a command to switch the switch configuration to the switch configuration corresponding to the mode in which the highest communication capacity is found. By this means, portable radio device500A is operated so as to perform communication in the mode in which the highest communication capacity is found.

The above operation flow is implemented at arbitrary timings. Also, it is equally possible to implement the operation flow at regular time intervals.

Thus, according to the present embodiment, by switching between switches131to134(SW1to SW4) to perform communication in a mode in which the highest communication capacity is found, even in the case where mismatch of polarization occurs in a receiving antenna due to the antenna configuration of the base station, the rotation of propagating polarization and the gradient of the terminal (e.g. portable radio device300), portable radio device500A can switch the polarization characteristics with the best reception signal level and provide antenna performance to cope with the condition of polarization that changes every minute between the base station and a terminal. As a result, it is possible to further improve transmission capacity in various polarization environments and usage types.

Also, by forming switch controller command section502and communication capacity calculating section503using resources such as a CPU provided as a main unit function in portable radio device500A, it is possible to provide an advantage of requiring no additional components and realizing the configuration in an easy manner. Also, there is an advantage of making it possible to set and change a specification in an easy manner.

Also, it is natural that the present embodiment can be combined with above Embodiments 1 to 4.

The above explanation is an example of the best mode for carrying out the present invention, and the scope of the present invention is not limited to this.

The present invention is applicable to any apparatuses as long as these apparatuses are equivalent to a communication apparatus having an antenna apparatus using a plurality of antenna elements for performing diversity operations, MIMO communication or adaptive array antenna operations. For example, the present invention is applicable to a mobile telephone device and PHS (Personal Handy-phone System) as well as portable information terminals such as PDA (Personal Digital Assistant) and information processing apparatuses such as a laptop computer.

Also, in the above embodiments, a used frequency band is not limited to the DTV band, and any bands are applicable. As a portable radio device supporting a plurality of frequency bands, in Japan, portable radio devices are commercialized which use both PDC (Personal Digital Cellular) using a 900 MHz band and CDMA (Code Division Multiple Access) using a 2 GHz band. Even in foreign countries, portable radio devices are commercialized which use GSM (Global System for Mobile communications) using a 900 MHz band, DCS (Digital Communication System) using a 1.8 GHz band, PCS (Personal Communication Services) using 1.9 GHz and UMTS (Universal Mobile Telecommunication System) using a 2 GHz band. For example, a case is possible where the first frequency band is a 2 GHz single band and a second frequency band is comprised of three bands of 900 MHz band, 1.8 GHz band and 1.9 GHz band.

Also, although the name “portable radio device” is used for ease of explanation in the above embodiments, for example, “portable telephone device” and “wireless communication apparatus” are equally applicable. Also, a communication apparatus having an antenna apparatus may be a base station apparatus on the transmitting side, for example.

Also, the type, the number and the method of connecting circuits forming the above portable radio device are not limited to the above embodiments.

Industrial Applicability

With the antenna apparatus and communication apparatus of the present invention, it is possible to provide a communication apparatus having an antenna apparatus using a plurality of antenna elements for performing diversity operations, MIMO communication or adaptive array antenna operations. Further, it is possible to provide optimal antenna performance for received signals that attenuate or fluctuate due to the condition of polarization that changes every minute between a base station and a terminal. Especially, the present invention is useful for techniques having an advantage of preventing the decrease in communication capacity in communication using a plurality of antenna elements for performing diversity operations, MIMO communication or adaptive array antenna operations.