Patent Grant
8200301
The present invention relates to an antenna unit for a wireless communication apparatus, the antenna unit being controlled so as to realize high speed communication by increasing channel capacity while maintaining high communication quality in mobile communication using a mobile telephone or the like, and more particularly to a wireless communication apparatus equipped with a MIMO antenna and/or an adaptive array antenna.
As an antenna device employing MIMO (Multi-Input Multi-Output) technique for transmitting and receiving wireless signals of a plurality of channels simultaneously by using a plurality of antennas, a MIMO antenna device is disclosed in Patent Document 1, for example.
The conventional MIMO antenna device disclosed in Patent Document 1 includes four groups of antenna elements, the respective groups being arranged at even intervals, and a main body. Each group of antenna elements includes four antenna elements having polarization directions different from each other. Meanwhile, the main body includes a switch section connected to the antenna elements, a signal reception section receiving a reception signal via the switch section, an antenna control section generating a control signal for the switch section, an antenna selection section generating a combination of the antenna elements to inform the antenna control section of information of the selected elements, and an antenna determination section determining, based on the reception signal received by the antenna elements generated by the antenna selection section, a specific combination of the antenna elements to inform the antenna control section of information of the determined elements.
The conventional MIMO antenna device with the above-described configuration is intended to reduce correlation between antenna elements and ensure sufficient transmission capacity by determining a combination of the antenna elements in a manner that one antenna element is selected from each group of antenna elements.
That is, in the conventional MIMO antenna device, a plurality of antenna elements operate simultaneously and then each of the antenna elements obtains largest possible received power, thereby increasing total transmission rate of a plurality of signal sequences after MIMO demodulation. The MIMO antenna device described in Patent Document 1 achieves this by including more antenna elements in number than channels for concurrent communication and by selecting the antenna elements, each having larger received signal strength therefrom.
Such selection of the antenna elements is especially effective in mobile communication in the case where signal intensities of main polarization and cross polarization temporally vary or an arriving angle thereof varies, in accordance with a movement of a mobile station (user) and/or time-dependent change of an ambient environment. Further, a change in the polarization direction can be dealt with by using the antenna elements having different polarization characteristics from each other, and the time-dependent change can be overcome by controlling the antenna elements to be switched.
As described above, the MIMO antenna device described in Patent Document 1 including the plurality of groups of antenna elements, each group having the plurality of antenna elements, and can reduce correlation between the antenna elements or increase transmission capacity by causing the switch section to select a combination of the antenna elements having the weakest correlation therebetween or a combination of the antenna elements having the largest transmission capacity.
Further, with reference to Patent Documents 2 and 3, an example of a mobile wireless communication apparatus utilizing a portion thereof as an antenna will be described.
In a mobile wireless communication apparatus described in Patent Document 2, a part of a conductive housing of the mobile communication apparatus operates as a part of an antenna so as to aim at reduction of production costs, thinning and downsizing by reduction of the number of parts without employing dedicated parts for an antenna. Further, it is possible to configure a larger antenna by causing the housing itself to operate as the antenna, whereby higher sensitivity of the antenna can be expected. According to the mobile wireless communication apparatus described in Patent Document 2, high quality wireless communication can be expected, as to the portable telephone desired to be downsized, by causing the conductive housing to operate as a part of the antenna.
A mobile telephone described in Patent Document 3 is aimed at reduction of gain variation depending on a condition of a user's hand, and configuration of a lip-type mobile telephone 1 is disclosed, where a shield box 14 in the upper housing 3 and an output terminal of a transmission circuit 15 within the lower housing 4 are connected by a flexible cable 9, and the shield box 14 is used as an antenna (FIG. 3 of Patent Document 3). With such configuration where the shield box 14 is used as the antenna, the gain variation depending on the condition of the user's hand can be diminished.
However, the conventional MIMO antenna device described in Patent Document 1 has the following problems.
The conventional MIMO antenna device includes, as described above, more antenna elements in number than the channels for the MIMO concurrent communication in order to obtain the largest possible received power, and performs MIMO demodulation by selecting antenna elements having stronger received signal strength from among the included antenna elements. However, a small device such as a mobile telephone in a one-wavelength size or less has a problem. That is, in the case where a plurality of antennas are mounted, a distance between adjacent antennas becomes small, so that radiation efficiency is decreased owing to mutual coupling between antenna elements and to the MIMO communication performed with an antenna array composed of antennas having the same polarization.
On the other hand, a conventional mobile wireless communication apparatus as described in Patent Document 2 has the following problems.
According to the conventional mobile wireless communication apparatus proposes a construction downsized by using a part of the conductive housing as an antenna, and a construction suitable for a single antenna or switching diversity with a slot antenna. However, the mutual coupling between antenna elements is not a problem since a single antenna operates even in the case of the switching diversity, and thus configuration of an antenna to reduce the mutual coupling is not taken into consideration. That is, the mobile wireless communication apparatus disclosed in Patent Document 2 cannot be used as a MIMO antenna in a MIMO antenna or an adaptive array antenna where a plurality of antennas operate concurrently.
Further, according to the conventional antenna included in a mobile telephone disclosed in Patent Document 3, only an operation of a single antenna is considered, and configuration of a MIMO antenna or an adaptive array antenna where a plurality of antennas concurrently operate is not considered.
Accordingly, an object of the present invention is to provide a wireless communication apparatus for a mobile object, the apparatus having lower mutual coupling between antennas in order to allow a plurality of feed antenna elements to concurrently maintain good reception conditions even if the apparatus is small-sized.
The present invention is directed to a mobile wireless communication apparatus including a plurality of antenna elements. In order to achieve the above-described object, one embodiment of the present invention includes a rectangular-shaped first conductor section; a second conductor section having the same shape as the first conductor section, arranged in parallel with and spaced from the first conductor section so as to have a predetermined distance therebetween; three short-circuit conductor sections electrically connecting any three edges of the first conductor section with face-to-face three edges of the second conductor section; a ground conductor section spaced by a predetermined distance from the first conductor section; and a wireless communication circuit, wherein a first feeding point on the first conductor section is connected to the wireless communication circuit via a first power supply section arranged between the first conductor section and the ground conductor section, so that the first conductor section and the ground conductor section are allowed to operate as a first antenna element; and a second feeding point on the second conductor section is connected to the wireless communication circuit via a second power supply section arranged between the first conductor section and the second conductor section, so that the first conductor section, the second conductor section and the short-circuit conductor sections are allowed to operate as a second antenna element.
When the length of one edge, to which the three short-circuit conductor sections are not connected, is set at a half wavelength of a communication signal, the second antenna element can operate as a half-wavelength slot antenna. Only adjacent two short-circuit conductor sections may be connected to the first and the second conductor sections, and the total length of the adjacent two short-circuit conductor sections may be set at one-half of the communication signal wavelength. Further, a part of a housing of the mobile wireless communication apparatus, the housing being formed of a conductive material, may be used as the first conductor section. Still further, the wireless communication circuit may be mounted on the first conductor section.
When one second antenna element is caused to operate at a different frequency, either one of the short-circuit conductor sections may be controlled to be switched in accordance with the frequency. In this case, as the one of the short-circuit conductor sections, a parallel resonant circuit including an inductor and capacitor, a switch circuit controlled by the control section and the like can be employed.
Here, the mobile wireless communication apparatus of the present invention can be caused to operate as an adaptive antenna when the mobile wireless communication apparatus further includes an adaptive control circuit executing adaptive control processing on a wireless signal received by each of the First and the second antenna elements to synthesize the adaptively controlled wireless signals; a demodulation circuit demodulating the synthesized wireless signal as well as a wireless signal individually received by each of the first antenna element and the second antenna element; and an apparatus control circuit controlling the adaptive control circuit so as to compare signal integrity obtained from demodulation of the synthesized wireless signal, and signal integrity obtained from demodulation of the wireless signals received by the First and the second antenna elements with each other, and causing the adaptive control circuit to receive a wireless signal having optimum signal integrity determined by the comparison.
Further, the mobile wireless communication apparatus of the present invention can be caused to operate as a selection diversity antenna when a mobile wireless communication apparatus further includes a first processing circuit executing adaptive control processing on the wireless signals received by the first and the second antenna elements; a second processing circuit executing selection diversity processing on the wireless signals received by the First and the second antenna elements; and a selection circuit comparing signal integrity of a wireless signal outputted from the first processing circuit, with signal integrity of a wireless signal outputted from the second processing circuit, and selectively outputting a signal having desirable signal integrity.
Furthermore, the mobile wireless communication apparatus of the present invention can be caused to operate as a combined diversity antenna when a mobile wireless communication apparatus further includes an adaptive control circuit executing adaptive control processing on a wireless signal received by each of the first and the second antenna elements, and synthesizing the adaptively controlled wireless signals; and an apparatus control circuit detecting phase and amplitude of a wireless signal received by each of the first and the second antenna elements, and controlling the adaptive control circuit so as to perform maximum ratio combining on the wireless signals.
Still further, when a mobile wireless communication apparatus further includes a MIMO demodulation circuit executing a MIMO demodulation processing on a wireless signal received by each of the first and the second antenna elements to output one demodulated signal, the mobile wireless communication apparatus of the present invention can be caused to operate as a MIMO antenna.
According to the above-described present invention, an array antenna can be realized in a small terminal without significantly increasing the number of parts of the antenna. Additionally, the antenna can be enlarged to a large extent by using the housing itself as an antenna. Further, mutual coupling between antennas can be reduced by arranging the short-cut side of the slot antenna so as to face the power supply section for the housing antenna. Still further, a correlation coefficient between antennas can be lowered by arranging antennas so as to have different radiation directivity from each other. Therefore, increase in performance as an array antenna can be expected, and an improved operation of a MIMO antenna and/or an adaptive array antenna can be provided.
Embodiments of the present invention will be described in detail with reference to the drawings. Note that with respect to figures for describing the embodiments of the present invention, components having similar functions are denoted by the same reference numerals and repeated description thereof will be omitted.
(First Embodiment)
The mobile wireless communication apparatus according to the first embodiment includes, as an antenna array, a housing antenna which is obtained by using a part or a conductive housing as an antenna, and a half-wavelength slot antenna which is obtained by using a part of the conductive housing as a ground plane. The first power supply section 2 is a power supply section for supplying power to the housing antenna via the first feedline 6. The second power supply section 3 is a power supply section for supplying power to the half-wavelength slot antenna via the second feedline 5. The first and second power supply sections 2 and 3 are connected to the wireless communication circuit 4 and allow wireless communication. The wireless communication circuit 4 includes high-frequency circuits such as a filter, an amplifier and a frequency conversion mixer, and a baseband circuit such as a modulator and a demodulator.
First, an operation of a housing antenna 20 will be described with reference to
Note that, although the open top box shaped half-wavelength slot antenna 30 is described in the first embodiment, the short-circuit conductor section 11 or the short-circuit conductor section 12 can be omitted. That is, when the total length of two edges (line a and line b), to which the short-circuit conductor sections 10 and 12 are not connected, of the first conductor section 7 is a half of the wavelength of the communication signal, the short-circuit conductor section 11 is unnecessary. Further, when the total length of two edges (line a and line c), to which the short-circuit conductor sections 10 and 11 are not connected, of the conductor section 7 is a half of the wavelength of the communication signal, the short-circuit conductor section 12 is unnecessary.
Next, examples of prototypes of the housing antenna 20 and the half-wavelength slot antenna 30 will be described with reference to
As described above, the housing antenna 20 and the half-wavelength slot antenna 30 have different radiation directivities from each other, so that it is assumed that correlation coefficient between the antennas is low. Accordingly, desirable array performance can be expected as a MIMO antenna, an adaptive array antenna, and an array antenna of maximum ratio combining or the like.
Next, an antenna array formed by combining the housing antenna 20 and the half-wavelength slot antenna 30 will be described.
From
Accordingly, each antenna can be designed independently, which provides an effect of easing designing of each antenna. Further, according to
As described above, the mobile wireless communication apparatus according to the first embodiment of the present invention can realize an antenna which has small mutual coupling between antennas and different directivities to obtain desirable array characteristics, and the mobile wireless communication apparatus according to the First embodiment of the present invention is most suitable for a compact mobile wireless communication apparatus.
The example where the wireless communication circuit 4 is mounted on the ground conductor section 9 is described in the First embodiment. However, as shown in
Additionally, although, in the first embodiment, the flip-type mobile wireless communication apparatus as shown in
Further, when a part of the housing of the mobile wireless communication apparatus is formed of a conductive material, the part can be used as the first conductor section 7.
(Second Embodiment)
A mobile wireless communication apparatus according to a second embodiment of the present invention allows the half-wavelength slot antenna 30 to resonate at different frequencies by switching the short-circuit conductor section 12 (or the short-circuit conductor section 11, hereinafter referred to similarly) of the mobile wireless communication apparatus according to the first embodiment.
In order to achieve resonances at two frequencies, the short-circuit conductor section 12 of the half-wavelength slot antenna 30 is caused to be an open circuit in the case of resonance at a first frequency, and is caused to be a short circuit in the case of resonance at a second frequency. As a result, two orthogonal resonant modes can be realized.
On the other hand, the short-circuit conductor section 12 may be replaced with a switch 43 shown in
As described above, the mobile wireless communication apparatus according to the second embodiment of the invention uses, for the short-circuit conductor section 12, a circuit where impedance is changed in accordance with a frequency, whereby resonance at two frequencies can be achieved in one apparatus.
(Third Embodiment)
In
The adaptive control circuit 102 includes four variable amplifiers 104a-d, four variable phase-shifters 105a-d and a signal synthesizer 106. The amount of variable amplification of the variable amplifiers 104a-d and the amount of phase shift of the variable phase-shifters 105a-d are controlled by the controller 103. A wireless signal received by the antenna element 100a is outputted via the variable amplifier 104a and the variable phase-shifter 105a, a wireless signal received by the antenna element 100b is outputted via the variable amplifier 104b and the variable phase-shifter 105b, a wireless signal received by the antenna element 100c is outputted via the variable amplifier 104c and the variable phase-shifter 105c, and a wireless signal received by the antenna element 100d is outputted via the variable amplifier 104d and the variable phase-shifter 105d, to the signal synthesizer 106, respectively. The signal synthesizer 106 synthesizes (adds) the inputted four wireless signals so as to output the result to the demodulator 107.
The demodulator 107 demodulates the synthesized wireless signals inputted from the signal synthesizer 106, by using a predetermined digital demodulation method, to a baseband signal that is the demodulated signal, and outputs the demodulated result to the output terminal 108 and the determinator 109. The determinator 109 determines an error rate based on a reference pattern, which is included in the inputted baseband signal and is within a predetermined reference pattern period, and outputs the error rate to the controller 103. The controller 103 uses an adaptive control method, which will be described in detail, to control the adaptive control circuit 102 such that a wireless signal having the optimum signal integrity is received and demodulated.
Note that, in
First, an adaptive control method in the adaptive antenna device will be described below. The adaptive antenna device uses an adaptive control technique to maximize a radiation pattern of an antenna toward a direction of arrival of a desired radio wave (i.e., to substantially direct the main beam in the radiation pattern toward the direction of the desired wave), and to direct NULL in the radiation pattern toward a direction of an interference wave which causes interference (i.e., to substantially direct NULL in the radiation pattern toward the direction of the interference wave), thereby achieving a stable wireless communication. Generally, the adaptive antenna device performs controlling to obtain the maximum desired signal power and the minimum interference signal power, by providing a wireless signal received by each of the antenna elements 100a-d, (or an intermediate-frequency signal frequency converted from the wireless signal) with an amplitude difference and a phase difference.
Each of the antenna elements 100a-d generally receives a thermal noise component together with a desired wave. Further, a co-channel interference wave having a common frequency radiated from a neighboring base station, or a delay wave which is temporally delayed because of having been arrived via a detour route, though it is a desired wave, may be received. The delay wave deteriorates, as a ghost, for example, appearing on a television receiver, quality of a screen display in an analog wireless communication system such as television broadcasting or radio broadcasting. On the other hand, a thermal noise component, the co-channel interference wave and the delay wave affect a digital wireless communication system as a bit error rate, and directly deteriorate signal integrity. Here, assuming that a desired wave power is C, a thermal noise power is N, and power of an interference wave including a co-channel interference wave and the delay wave is 1, the adaptive antenna device performs adaptive control to favorably maximize C/(N+1) in order to improve signal integrity.
Next, a specific operation of the adaptive control apparatus will be described.
A wireless signal received by each of the antenna elements 100a-d is converted in the A/D converter circuit 101 to a digital signal x(t) (a signal vector having four parameters in the case of the present embodiment) to be inputted to the controller 103. The controller 103 determines amplitude amounts and shift amounts of the variable amplifiers 104a-d and the variable phase-shifters 105a-d in the adaptive control circuit 102, respectively, and the amplitude amounts and the shift amounts allow a wireless signal y(t), outputted from the adaptive control circuit 162, to have the optimum signal integrity.
A method for calculating a weighting coefficient including the amplitude amount and shift amount will be described. Note that, the weighting coefficient Wi is defined by the following formula (1) based on an amplitude amount Ai and a shift amount φi.
Wi−Ai×exp(j×φi) (1)
Here, j represents an imaginary unit. Additionally, i takes values 1 through 4, corresponding to systems for processing wireless signals received by the antenna elements 100a-d, respectively. A method for calculating the weighting coefficient Wi will be shown by defining weighting coefficient vector W that has the weighting coefficient Wi as a component thereof.
Although there are several methods for calculating the weighting coefficient Wi, an example using Least Means Squares (LMS) will be described. In the method, the adaptive antenna device preliminarily stores a reference signal r(t) that is a signal sequence included in a known desired wave, and performs control such that the signal sequence included in the received wireless signal become close to the reference signal r(t). Here, an example where the reference signal r(t) is preliminarily stored in the controller 103 will be shown. Specifically, the controller 103 controls the adaptive control circuit 102 so as to multiply a wireless digital signal x(t) by the weighting coefficient w(t) including components of an amplitude amount and a phase shift amount. A residual error e(t) between a multiplication result obtained by multiplying the weighting coefficient w(t) by the wireless digital signal x(t) and the reference signal r(t) is calculated from the following formula (2).
e(t)=r(t)−W(t)×x(t) (2)
Here, the residual error e(t) takes a positive or negative value. Accordingly, a minimum square value of the residual error e(t), calculated by the above-described formula (2), is calculated by repeating the calculation recursively. That is, the weighting coefficient w(t, m+1), obtained by repeating a calculation multiple times (m+1 limes), can be obtained by the following formula (3) based on the m-th weighting coefficient w(t, m).
W(t,m+1)=W(t,m)+u×x(t)×e(t,m) (3)
Here, u is referred to as step size, and the repetition count of calculation, which allows the weighting coefficient w to converge to minimum value, is advantageously reduced when the step size u is large, but has a disadvantage that the weighting coefficient w fluctuates near the minimum when the step size u is too large. Accordingly, special attention should be paid depending on the system for selection of the step size U. On the contrary, the weighting coefficient w stably converges to the minimum when the step size u is small. However, the repetition count of calculation increases. When the repetition count increases, it takes a long time to obtain the weighting coefficient. In the case where calculation time of the weighting coefficient w takes longer than time (a few milliseconds) during which surrounding environment changes, improvement in signal integrity by the weighting coefficient w cannot be achieved. Consequently, it is necessary to select highest possible speed and more stable convergence condition when the step size u is determined. Further, the residual error e (t, m) is defined by the following formula (4).
e(t,m)=r(t)−W(t,m)×x(t) (4)
The formula (3) is updated in a recurring manner by using the value in the formula (4). Note that the maximum number of repetition of calculation for obtaining the weighting coefficient w is set such that time to calculate the weighting coefficient is not longer than switching time of a wireless system.
Here, a method for an adaptive control of the wireless communication system based on the Least Means Squares method is described as an example, but the present invention is not limited to this method, and RLS (Recursive Least Squares) method, or SMI (Sample Matrix Inversion) method, for example, which allow faster determination, for example, can be employed. Although determination can be performed faster by the methods, calculation in the determinator 109 becomes complicated. Further, in the case where the modulating method of a signal sequence is a constant envelope modulation, like a digital phase modulation, having a constant envelope, CMA (Constant Modulus Algorithm) can be employed.
In
In the case where the error rate is determined to be greater than or equal to 10−5 in step S5, the controller 103 obtains again, from the A/D converter circuit 101, the received data received by each of the antenna elements 100a-d (step S1). On the other hand, in the case where the error rate is determined to be less than 10−5 in step S5, the controller 103 controls the adaptive control circuit 102 to obtain an error rate of each of the antenna elements 100a-d in the individual operation (step S6).
Here, the antenna elements 100a-d in the individual operation means a state where only one of the antenna elements 100a-d operates. For example, the antenna element 100a in the individual operation means that only the antenna element 100a operates and the antenna elements 100b-d are not in operation. In this case, specifically, an amplification amount of a variable amplifier 104a is set at “1” and phase shift amount of a variable phase-shifter 115a at “0”, and an amplification amount of a variable amplifier 104a at “0”.
Finally, the controller 103 compares an error rate at the time when the adaptive control synthesis is outputted, with an error rate of the signal received by each of the antenna elements 100a-d in the individual operation, and selects the optimum error rate to control the adaptive control circuit 102 so as to receive a received signal having the selected optimum error rate (step S7).
Note that, in
As described above, in the adaptive antenna device according to the third embodiment of the present invention, error rates are checked while adaptive control is performed by using four antenna elements 100a-d. The error rate of each of the antenna elements 100a-d in the individual operation is measured when the error rate is under a predetermined threshold value, and the adaptive control circuit 102 is controlled so as to receive a received signal having the optimum error rate. Such switching control between the adaptive control and the individual operation of each of the antenna elements makes it possible to constantly select the received signal having the optimum signal integrity.
(Fourth Embodiment)
First, a wireless signal received by each of the antenna elements 201 and 202 is inputted to both of the processing circuits 203 and 204. The processing circuit 203 performs adaptive control processing on the inputted wireless signals to output the results to the wave detector 205 and the signal integrity monitoring circuit 207. Here, the processing circuit 203 maintains desirable signal integrity by suppressing interference waves in the received wireless signals. That is, the processing circuit 203 is significantly effective when a delay wave and/or a co-channel interference wave arrive from a neighboring base station. Additionally, the processing circuit 204 performs selection diversity processing on the inputted wireless signal to output the result to the wave detector 206 and the signal integrity monitoring circuit 207. Here, the processing circuits 204 maintains the desirable signal integrity by selecting a wireless signal having greater received power from among the received wireless signals received by the antenna elements 201 and 202, respectively. That is, the processing circuit 204 produces a great effect when a change in the received power is great like in the case of fading.
Here, the signal integrity monitoring circuit 207 determines signal integrity of a baseband signal which is a wireless signal adaptively controlled and modulated by the processing circuit 203, and signal integrity of a wireless signal on which selection diversity processing is performed by the processing circuit 204. Next, the selection circuit 208 selects, based on the determination result of the signal monitoring circuit 207, a baseband signal from a wave detector 205 or 206 corresponding to a signal having more desirable signal integrity and outputs the selected baseband signal to the output terminal 209.
As described above, the selection diversity antenna device according to the fourth embodiment of the present invention can solve both of two main factors, that is, interference waves and fading, for deterioration in signal integrity of the received signal in a mobile communication system.
(Fifth Embodiment)
In
As described above, the combined diversity antenna device according to the fifth embodiment of the present invention makes it possible to obtain the stable received power.
(Sixth Embodiment)
The three feed antenna elements 501a-c are provided to respectively receive three different wireless signals transmitted from base station equipment (not shown) on the MIMO transmission side using a predetermined MIMO demodulation method. Each of the feed antenna elements 501a-c inputs the received wireless signal to the A/D converter circuit 502. The A/D converter circuit 502 includes three A/D converters corresponding to the inputted wireless signals, respectively, and the A/D converters individually perform A/D conversion processing on the respective wireless signals and outputs the processed signals (hereinafter referred to as received signals) to both of the MIMO demodulation circuit 503 and the signal level comparison circuit 504.
The MIMO demodulation circuit 503 performs MIMO demodulation processing on the three received signals to output one demodulated signal. The signal level comparison circuit 504 compares signal levels of the three received signals to output result data of the comparison to the controller 505. The controller 505 may change, depending on the result of the MIMO adaptive control processing, a MIMO communication method used in the base station equipment on the MIMO transmission side and used in the MIMO demodulation circuit 503. That is, the controller 505 transmits a control signal, by using the wireless transmission circuit 506 and the antenna element 507, to request the base station equipment on the MIMO transmission side to change MIMO demodulation method used in the base station equipment on the MIMO transmission side, and additionally cause the MIMO demodulation circuit 503 to change the MIMO demodulation method used therein.
It is desirable that the MIMO antenna device according to the sixth embodiment includes, in the first stage of the A/D conversion circuit 502, a high-frequency filter for separating a signal, having a predetermined frequency, from each of the wireless signals received by the feed antenna elements 501a-c, and a high-frequency amplifier for amplifying a signal when necessary. Further, it is desirable that the MIMO antenna device according to the sixth embodiment includes, in the first stage of the MIMO demodulation circuit 503, a high frequency circuit such as a mixer for converting a frequency of each of the received signals outputted from the A/D converter circuit 502, an inter-mediate frequency circuit, the processing circuits, and the like when necessary. Note that the above-described components are omitted in the present specification and drawings for simplicity.
The present invention is applicable to a wireless communication apparatus, for example, equipped with a MIMO antenna and/or an adaptive array antenna, and especially suitable, for the case of controlling mobile communication using a mobile telephone and the like so as to maintain desirable communication quality while realizing high-speed communication by increasing communication capacity.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-258655 | Oct 2007 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2008/002753 | 9/30/2008 | WO | 00 | 7/14/2009 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2009/044541 | 4/9/2009 | WO | A |
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| 6999793 | Jinushi | Feb 2006 | B2 |
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| Number | Date | Country | |
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| 20100056234 A1 | Mar 2010 | US |
