Wireless device and method for transmitting common signal

Abstract

An array antenna (10) has a plurality of antenna elements (20), and forms directivity corresponding to complex amplitudes given to each of at least one antenna element (20). A common signal generation unit (40) uses the array antenna (10) to generate a common signal that is repeatedly transmitted toward terminals with unspecified presence positions. When transmitting the common signal, a directional antenna control unit (50) sets a set of complex amplitudes given to each of the at least one antenna element (20). The directional antenna control unit (50) has a plurality of sets of complex amplitudes, in each of which the directivity formed by the array antenna (10) is different from the others, and changes the set of complex amplitudes given to each of the at least one antenna element (20) every time the common signal is transmitted at least once.

Description

Wireless device and method for transmitting a common signal

[0001] The present disclosure relates to a wireless device that uses a directional antenna to perform wireless communication with a terminal, and a method for transmitting a common signal from a wireless device having a directional antenna to a terminal whose location is unspecified.

[0002] In cellular wireless communication systems and wireless local area networks (LANs), terminals such as smartphones or laptop PCs (personal computers), or communication modules attached to various sensors and industrial equipment, connect to wireless base stations or access points according to predetermined standards and communicate with other terminals and computers via these. In the following description, wireless base stations in cellular wireless communication systems and access points in wireless LANs are collectively referred to as "access points." Smartphones, laptop PCs, and communication modules are collectively referred to as "terminals."

[0003] An access point periodically transmits information to each terminal to allow it to connect to that access point. The terminal then transmits a connection request signal to the access point according to the received information, and performs connection procedures such as authentication with the access point that received the connection request signal. This connects the access point and terminal, allowing them to exchange data with each other.

[0004] In data exchange after the connection procedure is completed, if the terminal's location and the direction of the terminal from the access point are identified, the access point can use a directional antenna to transmit data to the terminal, thereby increasing the signal-to-noise ratio (S / N) and enabling high-speed, low-error-rate data communication. At the same time, the directional antenna weakens radio wave strength in directions other than the direction of the terminal, thereby reducing interference with communications between other access points and terminals using the same radio frequency. As a result, this can also contribute to improving the communication quality of those other access points and terminals.

[0005] Furthermore, by using a directional antenna when an access point receives a signal from a terminal, the S / N ratio of the received signal can be increased and interference from communications conducted by other access points and terminals can be reduced.

[0006] In this way, for signals exchanged between an access point and a specific terminal (hereinafter also referred to as "individual signals"), a directional antenna can be used to increase the S / N ratio and reduce interference with other access points and terminals.

[0007] On the other hand, for example, in order to inform each terminal of information necessary for the terminal to issue a connection request to the access point, an access point transmits a signal (hereinafter also referred to as a "common signal") to unspecified terminals, and the direction in which the terminals receiving the signal are located is not determined. Therefore, the access point needs to transmit the common signal using an antenna with no directionality (omnidirectional antenna), or to transmit the common signal using various directivities so that all directions are covered.

[0008] In particular, in cellular wireless communication systems and wireless LANs that utilize millimeter waves, which represent radio waves with frequencies between 10 and 100 GHz, sub-terahertz waves exceeding 100 GHz, and terahertz waves ranging from 1 to 10 THz, directional antennas with a large number of elements and high directional gain are used to compensate for large propagation losses (see, for example, Non-Patent Document 1). Since a directional antenna with high directional gain generates a sharper directivity, when transmitting a common signal using such an antenna, more directivity is used to cover all directions. According to the standard specifications of New Radio (NR), a wireless communication method for fifth-generation mobile communication systems (5G), an access point is configured to transmit a common signal with up to 64 different directivities. The access point transmits the common signal by sequentially switching the directivity at a predetermined transmission interval.

[0009] Takeda et al., "NR Physical Layer Specifications for 5G," NTT DoCoMo Technical Journal, Vol. 26, No. 3

[0010] However, in a configuration in which a common signal is transmitted by sequentially switching more directivities, the frequency with which the common signal is transmitted in a specific direction decreases unless the transmission interval of the common signal is shortened. If a terminal does not know when a common signal will be transmitted in its own direction, the terminal must continue detecting the common signal until the common signal is detected. On average, the time from when a terminal starts detecting the common signal to when the common signal is transmitted in its own direction is half the transmission interval of the common signal, but in the worst case, it can be almost the same as the transmission interval of the common signal.

[0011] In contrast, when a common signal is transmitted using an omnidirectional antenna or a directional antenna with a weak directivity, the radio wave strength is weakened by the lack of directional gain. Therefore, it is necessary to transmit the common signal with a higher transmission power or to transmit the common signal multiple times. In this way, the terminal can detect the common signal once the common signal has been transmitted with a high transmission power or the number of common signals required for detection has been transmitted.

[0012] However, equipping an omnidirectional antenna or a directional antenna with a weak directivity in addition to an array antenna consisting of a large number of antenna elements to transmit a common signal will complicate the configuration of the access point, which may result in increased design and equipment costs for the access point.

[0013] The present disclosure has been made to solve such problems, and the purpose of the present disclosure is to provide a technology for transmitting a common signal from an access point to unspecified terminals without complicating the device configuration.

[0014] A wireless device according to one aspect of the present disclosure includes an array antenna, a common signal generation unit, a directional antenna control unit, a baseband signal generation unit, and a radio unit. The array antenna has multiple antenna elements and is configured to form directivity according to a complex amplitude assigned to at least one antenna element. The common signal generation unit uses the array antenna to generate a common signal that is repeatedly transmitted to terminals whose locations are unspecified. The directional antenna control unit sets a set of complex amplitudes to be assigned to at least one antenna element when transmitting the common signal. The baseband signal generation unit uses the set of complex amplitudes to generate a baseband signal from the common signal to be supplied to at least one antenna element. The radio unit is provided for at least one antenna element and converts the corresponding baseband signal into a radio signal and supplies it to the array antenna. The directional antenna control unit has multiple sets of complex amplitudes that differ from each other in the directivities formed by the array antenna, and changes the set of complex amplitudes to be assigned to at least one antenna element each time the common signal is transmitted at least once.

[0015] According to the present disclosure, in a cellular wireless communication system and a wireless LAN, an access point can form a pseudo-omnidirectional antenna from a directional antenna used to transmit individual signals and transmit a common signal to unspecified terminals. This allows the terminals to quickly detect the common signal. Furthermore, since the access point does not need to be equipped with an omnidirectional antenna for transmitting the common signal, this can contribute to reducing design and manufacturing costs.

[0016] FIG. 1 is a block diagram showing a functional configuration of a radio apparatus according to a first embodiment. FIG. 2 is a diagram schematically showing an example configuration of an array antenna. FIG. 3 is a diagram showing a result of a simulation of directivity generated when a complex amplitude having a random phase is applied to each antenna element of an equally-spaced planar array antenna. FIG. 4 is a diagram showing an example of a data sequence generated by a common signal generating unit. FIG. 5 is a diagram showing an example configuration of a data sequence generator. FIG. 6 is a diagram schematically showing a time waveform of a baseband signal. FIG. 7 is a diagram for explaining processing in a directional antenna control unit. FIG. 8 is a diagram showing an example configuration of a radio unit. FIG. 9 is a diagram showing a result of a simulation of directivity generated in an array antenna when a common signal is transmitted. FIG. 10 is a diagram showing the directional gain of an array antenna versus the number of repetitions of a common signal. FIG. 11 is a diagram schematically showing an example configuration of an array antenna provided in a radio apparatus according to a second embodiment. FIG. 12 is a diagram showing an example configuration of an antenna group. FIG. 13 is a diagram schematically showing directivity generated in an antenna group. FIG. 14 is a diagram showing a result of a simulation of directivity generated when a complex amplitude having a random phase is applied to each antenna group of an array antenna. FIG. 15 is a diagram for explaining processing in a directional antenna control unit.

[0017] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0018] 1 is a block diagram showing a functional configuration of a wireless device according to a first embodiment of the present disclosure. Wireless device 100 according to the first embodiment can be applied to an access point in a cellular wireless communication system and a wireless LAN.

[0019] (Array Antenna 10) As shown in Fig. 1, the wireless device 100 includes an array antenna 10. The array antenna 10 has N ＡＮＴ The antenna element 20 is configured to include N ＡＮＴ is an integer of 2 or more. ＡＮＴ The antenna elements 20 are arranged at equal intervals.

[0020] The directional gain of the array antenna 10 is N ＡＮＴThis can be achieved by arranging antenna elements 20. For example, if two antenna elements 20 are arranged side by side and fed equally, or if the received signals of both are equally combined, a directional gain of 3 dB (double) can be obtained in the direction perpendicular to the arrangement direction of the two antenna elements 20. The directional gain in other directions is determined by the angle formed by the line on which the two antenna elements 20 are arranged and the distance between the two antenna elements 20. This directional gain can have a maximum value of 3 dB (double) and a minimum value of 0. A directional gain of 0 means that no radio waves are emitted in that direction and no radio waves are received from that direction.

[0021] The number of antenna elements 20 is N ＡＮＴ , the maximum value of the directional gain is 10 log １０ N ＡＮＴ dB (N ＡＮＴ times), and the minimum value is 0. ＡＮＴ The antenna elements 20 are not limited to being arranged in a straight line, but may be arranged in various shapes such as a circle, a plane, or a three-dimensional shape. FIG. 2 is a diagram schematically showing an example of the configuration of the array antenna 10.

[0022] As shown in FIG. 2, the array antenna 10 has N ＡＮＴ a uniform linear array (ULA) in which N antenna elements 20 are arranged at equal intervals on a straight line; ＡＮＴ a uniform circular array (UCA) in which antenna elements 20 are arranged at equal intervals on a circle; and ＡＮＴ The antenna elements 20 may be arranged in a grid pattern on a plane, such as a uniform planar array (UPA).

[0023] Here, consider an equally spaced linear array antenna in which the n-th antenna element 20 is arranged on a line at a position given by equation (1), where n is 1 or more and N ＡＮＴ The following integers:

[0024]

[0025] The directional gain obtained by this equally spaced linear array antenna is given by equation (2).

[0026]

[0027] where d is the spacing between the antenna elements 20 in the uniform linear array, a(n) is the complex amplitude given when feeding power to the n-th antenna element 20, or the complex amplitude given when combining the received signals of the n-th antenna element 20 during reception. λ is the wavelength of the radio wave, and N ＡＮＴ is the number of antenna elements 20, and θ is the direction of radio wave emission or reception, which is the angle between the straight line on which the antenna elements 20 are arranged and a plane perpendicular to the straight line.

[0028] When the complex amplitudes given to all the antenna elements 20 are equal, directivity occurs in the direction of θ=0, that is, in the direction perpendicular to the line on which the antenna elements are arranged. Also, when the complex amplitudes according to equation (3) are given to all the antenna elements 20, θ=θ ０ This creates directionality in the direction of the beam.

[0029]

[0030] Equation (2) is the sum of complex amplitudes that take into account the phase difference due to the path difference that occurs from each antenna element 20 in the direction of θ, and the directional gain of array antennas of other shapes can also be calculated in a similar manner.

[0031] In the first embodiment, the array antenna 10 has N ＡＮＴ pieces (=N ＡＮＴｘ ×N ＡＮＴｙ ) antenna elements 20 are arranged on the xy plane. ＡＮＴｘ is the number of antenna elements 20 arranged in the x-axis direction, and N ＡＮＴｙ is the number of antenna elements 20 arranged in the y-axis direction. The position (x, y) of the nth antenna element 20 on the xy plane is given by equations (4) and (5).

[0032]

[0033]

[0034] The directional gain generated in the direction of an azimuth angle θ and an elevation angle ψ with respect to the x-axis on the xy plane on which the array antenna 10 is arranged is given by equation (6).

[0035]

[0036] where a(n ｘ , n ｙ ) is the xy plane (x, y) = (n ｘ d, n ｙ d) is the complex amplitude given to the antenna element 20 located at the position of the antenna element 20. This complex amplitude a(n ｘ , n ｙ ) is expressed as equation (7), the azimuth angle θ ０ and elevation angle ψ ０ The maximum directivity occurs in the direction of

[0037]

[0038] When the number of antenna elements 20 is increased to obtain a higher directional gain, the directivity generated by the array antenna 10 becomes sharper. As a result, radio waves are emitted more concentratedly in a specific direction. In addition, radio waves in a specific direction are more selectively received.

[0039] Radio device 100 according to the first embodiment transmits a common signal to terminals located in unspecified positions using array antenna 10 having such a high directional gain. To achieve this, when radio device 100 transmits the common signal, it is possible to make array antenna 10 a pseudo-omnidirectional antenna by providing a complex amplitude with a random phase to each antenna element 20 of array antenna 10.

[0040] FIG. 3 shows the results of a simulation of the directivity generated when a complex amplitude with a random phase is applied to each antenna element 20 of an equally spaced planar array antenna.

[0041] As shown in Figure 3, the pseudo-omnidirectional pattern generated by the uniformly spaced planar array antenna is not completely omnidirectional, and the strength of the radio wave radiation varies depending on the direction. This raises the concern that if a terminal is located in a direction where the radio wave radiation is weak, the terminal may not be able to detect the common signal.

[0042] To address such concerns, radio apparatus 100 according to the first embodiment is configured to repeatedly transmit a common signal using array antenna 10. Furthermore, in this configuration, the complex amplitude provided to each antenna element 20 of array antenna 10 is changed every time the common signal is transmitted at least once.

[0043] In contrast to embodiment 1, in a configuration in which a common signal is repeatedly transmitted with a fixed complex amplitude given to each antenna element 20, the imperfect omnidirectional pattern shown in Figure 3 is continuously generated in the array antenna 10.

[0044] In contrast, in the first embodiment, by repeatedly transmitting a common signal while changing the complex amplitude given to each antenna element 20, it is possible to prevent the array antenna 10 from continuously generating the same pseudo-omnidirectional pattern when the common signal is repeatedly transmitted. As a result, imperfections in the pseudo-omnidirectional pattern are eliminated, and the common signal can be received by terminals in any direction.

[0045] 1 shows processing blocks involved in transmitting common signals included in wireless device 100. Note that processing blocks involved in transmitting wireless signals other than common signals, processing blocks involved in receiving wireless signals, and processing blocks for exchanging data to be transmitted and received with the outside of the device (or with upper layers of the device) are not directly necessary for explaining this embodiment, and are therefore not shown in the figure. The processing blocks involved in transmitting common signals will be described in detail below.

[0046] As shown in FIG. 1, the wireless device 100 includes a wireless protocol control unit 30, a common signal generation unit 40, a directional antenna control unit 50, a baseband signal generation unit 60, and N ＡＮＴand radio units 70. These processing blocks are realized by hardware such as a CPU (Central Processing Unit) and memory, and software that performs the arithmetic processing described below.

[0047] (Radio Protocol Control Unit 30) The radio protocol control unit 30 is configured to instruct the common signal generation unit 40 and the directional antenna control unit 50 on the timing to transmit the common signal when it has decided to transmit the common signal.

[0048] Specifically, the radio protocol control unit 30 transmits a sequence of data symbols (hereinafter also referred to as a "data sequence") A to the common signal generation unit 40. ｋ In response to this instruction, the wireless protocol control unit 30 generates the data sequence A. ｋ The parameter determining the number of times the common signal is to be transmitted and / or the number of times the common signal is to be transmitted may be specified.

[0049] (Common Signal Generator 40) The common signal generator 40 generates a data sequence A defined as a common signal at a timing instructed by the wireless protocol controller 30. ｋ and the generated data sequence A ｋ to the baseband signal generating unit 60.

[0050] FIG. 4 shows the data sequence A generated by the common signal generator 40. ｋ As shown in FIG. 4, a data sequence A ｋ is a Zadoff-Chu sequence Z of length La. ｋ N ＲＥＰ It can be a sequence that repeats N times. ＲＥＰ corresponds to the number of repetitions of transmission of the common signal. The Zadoff-Chu sequence of length La is given by equation (8). R is a parameter that determines the Zadoff-Chu sequence. k is an integer between 0 and La-1.

[0051]

[0052] The wireless protocol control unit 30 receives the data sequence A ｋ When specifying the timing to generate La, N ＲＥＰ , R to the common signal generating unit 40. If there is no instruction from the radio protocol control unit 30, the common signal generating unit 40 can set these values ​​to default values ​​that it has in advance.

[0053] Data Sequence A ｋ can also be generated by a data sequence generator shown in Fig. 5. As shown in Fig. 5, the data sequence generator includes a shift register in which a plurality of (for example, seven) flip-flops 42 are connected in multiple stages.

[0054] The common signal generator 40 generates a data sequence A ｋ When an instruction to generate a sequence of 1's and 0's is issued, an initial value is set in each flip-flop 42. Then, by shifting the data in order for each symbol clock, a sequence of predetermined 1's and 0's is generated. In the example of FIG. 5, the data sequence generator is a data sequence generator that generates an M sequence in accordance with the generating polynomial g(x) shown in equation (9), and has a period of 127 (=2 ７ −1).

[0055]

[0056] Shift register 127×N ＲＥＰ By shifting the M sequence of length 127, ＲＥＰ Data sequence A repeated times ｋ It should be noted that by changing the number of flip-flops constituting the shift register and the number and positions of adders, it is possible to generate different M sequences corresponding to different generating polynomials. ｋ When instructing the timing for generating the data sequence generator, the generator polynomial to be used by the data sequence generator and its initial value can be specified.

[0057] (Baseband Signal Generator 60) The baseband signal generator 60 generates the data sequence A sent from the common signal generator 40. ｋ , and generates a continuous baseband signal representing the amplitude and phase of the radio signal transmitted from each antenna element 20 of the array antenna 10.

[0058] The data sequence sent from the common signal generating unit 40 is denoted by A. ｋ (k=1,...,N ＲＥＰ ×La), the baseband signal generator 60 generates a baseband signal S corresponding to the radio signal to be transmitted from the n-th antenna element 20 using equation (10). ｎ (t) is generated.

[0059]

[0060] a ｋ (n) is the data sequence A ｋ is the complex amplitude given to the n-th antenna element 20 when transmitting the k-th symbol. n is 1 or more and N ＡＮＴ h(t) is an integer that is the sum of the data sequence A ｋ h(t) is a time-continuous signal waveform for transmitting one symbol in t. For h(t), a raised cosine waveform given by equation (11) can be used.

[0061]

[0062] T Ｓ is the data sequence A ｋ is the duration of one symbol of the symbol α. α is a number called a roll-off factor, and is usually chosen to be a value between 0.2 and 0.5 depending on the allowable bandwidth of the wireless signal.

[0063] FIG. 6 shows the baseband signal S ｎ 1 is a diagram showing a time waveform of a baseband signal S ｎ (t) is a waveform that is continuous in time, but in an actual device, the value of equation (10) is calculated for one symbol time T Ｓis sampled at time intervals divided into 4 to 16, the sampled values ​​are converted from digital to analog, and a waveform is output that has been smoothed by a low-pass filter.

[0064] (Directional antenna control unit 50) The directional antenna control unit 50 is configured to set the complex amplitude to be given to each antenna element 20 of the array antenna 10 when transmitting a common signal, and to supply the set complex amplitude to the baseband signal generation unit 60.

[0065] In the wireless device 100 according to the first embodiment, the complex amplitude given to each antenna element 20 is a random complex number whose magnitude is 1 and whose phase angle is uniformly distributed in the range of 0 to 2π, so as to prevent directivity from being formed in only a specific direction.

[0066] 7 is a diagram for explaining the processing in the directional antenna control unit 50. As shown in FIG. 7, the directional antenna control unit 50 controls the number N of antenna elements 20 constituting the array antenna 10. ＡＮＴ A set of complex numbers equal in number to the above is taken as one set, and multiple sets of these complex numbers are prepared.

[0067] A set of complex numbers is a random set of N with magnitude 1 and phase angles uniformly distributed in the range 0 to 2π. ＡＮＴ In the example of FIG. 7, this set of complex numbers is divided into N complex numbers, which are the repetition times of the common signal. ＲＥＰ Prepare a number equal to the number of

[0068] The directional antenna control unit 50 calculates N ＲＥＰ One set of complex numbers is selected from the sets of complex numbers, and the selected set of complex numbers is used as a complex amplitude a ｋ The signal is supplied to the baseband signal generator 60 as (n).

[0069] In the example of FIG. 7, when the number of repetitions is 1, the first set of complex numbers is selected, and the complex amplitude a ｋ (n) is given to the baseband signal generator 60. Therefore, the data sequence A ｋ The first to Lath symbols A １ ~A Ｌａ and N included in the first set of complex numbersＡＮＴ and complex numbers, the baseband signal S ｎ (t) is generated.

[0070] At the second iteration, a second set of complex numbers is selected to produce a complex amplitude a ｋ (n) is given to the baseband signal generator 60. Therefore, the data sequence A ｋ The La+1th to 2×Lath symbols A Ｌａ＋１ ~A ２×Ｌａ and N in the second set of complex numbers ＡＮＴ and complex numbers, the baseband signal S ｎ (t) is generated.

[0071] The number of repetitions is N ＲＥＰ When the time is Nth ＲＥＰ A set of complex numbers is selected to obtain the complex amplitude a ｋ (n) is given to the baseband signal generator 60. According to this, the data sequence A ｋ Of which (N ＲＥＰ −1) × La + 1st to Nth ＲＥＰ ×Lath symbol A （ＮＲＥＰ－１）×Ｌａ＋１ ~A ＮＲＥＰ×Ｌａ and the Nth ＲＥＰ N included in the set of complex numbers ＡＮＴ and complex numbers, the baseband signal S ｎ (t) is generated.

[0072] In this way, the number of repetitions of the common signal is N ＲＥＰ By preparing the same number of complex number sets as N, it is possible to set complex amplitudes using different complex number sets for repetition of the common signal. ＲＥＰ When transmitting repeatedly, the array antenna 10 ＲＥＰ Therefore, the imperfection of the omnidirectionality of the pseudo-omnidirectional antenna is eliminated, and it is possible to prevent the formation of directivity in only a specific direction.

[0073] However, if there is a limit to the number of sets of complex numbers that the directional antenna control unit 50 can prepare, the number of repetitions of the common signal N ＲＥＰIn one aspect, one set of complex numbers is selected from the X sets of complex numbers every X times, and the complex amplitude a ｋ (n) to the baseband signal generator 60. However, X is 2 or more and N ＲＥＰ In this case, it is sufficient for the directional antenna control unit 50 to prepare at least X sets of complex numbers.

[0074] (Radio unit 70) N ＡＮＴ The radio units 70 are N ＡＮＴ The radio section 70 is provided corresponding to each of the antenna elements 20 and is configured to handle radio signals transmitted by the corresponding antenna elements 20. Fig. 8 is a diagram showing an example configuration of the radio section 70. As shown in Fig. 8, the radio section 70 is configured to include a quadrature modulator 72, a frequency converter 74, and an amplifier 76.

[0075] The quadrature modulator 72 receives the baseband signal S ｎ The quadrature modulator 72 quadrature-modulates (t) and supplies it to a frequency converter 74. The frequency converter 74 converts the modulated signal supplied from the quadrature modulator 72 into a high-frequency signal. The amplifier 76 amplifies the high-frequency signal to a level required for transmission and outputs it to the corresponding antenna element 20. The antenna element 20 radiates the amplified high-frequency signal into space as a radio wave.

[0076] <Effect> As described above, the radio device 100 according to embodiment 1 is configured to change the complex amplitude given to each antenna element 20 of the array antenna 10 at least once each time the common signal is transmitted repeatedly.

[0077] 9 is a diagram showing the results of a simulation of the directivity generated by the array antenna 10 when a common signal is transmitted. In the simulation, a complex amplitude set of different complex amplitudes was used to set the complex amplitudes to be applied to each antenna element 20 for the repetition of the common signal. As described above, one complex amplitude set is a set of random N complex amplitudes with a magnitude of 1 and a phase angle uniformly distributed in the range of 0 to 2π. ＡＮＴ It contains complex numbers.

[0078] 9 shows the directivity when the number of repetitions is 1, the directivity when the number of repetitions is 2, and the directivity when the number of repetitions is 3. It can be seen that by changing the complex amplitude given to each antenna element 20 for each repetition of the common signal, the directivity generated by the array antenna 10 also changes for each repetition.

[0079] FIG. 10 shows the number of repetitions of the common signal, N ＲＥＰ 10 is a diagram showing the directional gain of the array antenna 10 with respect to the number of repetitions of the common signal N. ＲＥＰ When = 1, N ＲＥＰ = 10, and N ＲＥＰ 10 shows the average value of the directional gain of the array antenna 10 when .times. ...

[0080] As shown in FIG. ＲＥＰ When N = 1, the directivity gain varies in both the azimuth and elevation directions. ＲＥＰ As the number of repetitions N increases, the variation in the directivity gain decreases in both the azimuth and elevation directions. ＲＥＰ When .DELTA.=100, the directional gain is nearly uniform in the azimuth and elevation directions, and as a result, the radiation pattern of radio waves from array antenna 10 is nearly a perfect circle. This makes it possible for terminals in any direction to receive the common signal.

[0081] Therefore, wireless device 100 can transmit a common signal to terminals whose locations are unspecified using array antenna 10. This eliminates the need for wireless device 100 to be equipped with an omnidirectional antenna for transmitting the common signal, which contributes to reducing design and manufacturing costs. Furthermore, terminals can quickly detect the common signal transmitted from wireless device 100.

[0082] [Embodiment 2] In the first embodiment, N ＡＮＴｘ ×N ＡＮＴｙ A configuration has been described in which omnidirectionality is formed over the range of all azimuth angles and all elevation angles by giving each of the antenna elements 20 a complex amplitude consisting of complex numbers with a magnitude of 1 and a random phase angle.

[0083] In the second embodiment, a configuration will be described in which a uniformly spaced planar array antenna configured to have directivity in a specific range is used to transmit a common signal to unspecified terminals present within that range. Note that the configuration of radio device 100 according to the second embodiment is the same as the configuration of radio device 100 according to the first embodiment shown in FIG. 1, except for the configuration of array antenna 10.

[0084] 11 is a diagram schematically illustrating an example of the configuration of array antenna 10 included in radio device 100 according to the second embodiment. As shown in FIG. 11, array antenna 10 has N ＡＮＴｘ ×N ＡＮＴｙ It is an equally spaced planar array antenna in which N antenna elements 20 are arranged on the xy plane. ＡＮＴｘ ×N ＡＮＴｙ The antenna elements 20 are grouped into a plurality of antenna groups 12, with 2×2 antenna elements 20 forming one antenna group 12. The total number of antenna groups 12 included in the array antenna 10 is N ＡＮＴｘ / 2 x N ＡＮＴｙ / 2.

[0085] Fig. 12 is a diagram showing an example of the configuration of the antenna group 12. As shown in Fig. 12, the antenna group 12 includes four antenna elements 20_1 to 20_4, two phase shifters 14 and 16, and a feed terminal 18. The feed terminal 18 is provided in common to the four antenna elements 20_1 to 20_4. The feed terminal 18 receives a radio signal transmitted from the n-th antenna group from the corresponding radio unit 70.

[0086] The phase shifter 14 is provided between the feed terminal 18 and the second antenna element 20_2, and provides a phase difference of −90° between the radio signal provided to the first antenna element 20_1 and the radio signal provided to the second antenna element 20_2.

[0087] The phase shifter 16 is provided between the power supply terminal 18 and the fourth antenna element 20_4, and provides a phase difference of +90° between the radio signal provided to the third antenna element 20_3 and the radio signal provided to the fourth antenna element 20_4.

[0088] The four antenna elements 20_1 to 20_4 constituting the antenna group 12 are configured to radiate signals into space having phase differences of 0°, −90°, 0°, and 90° with respect to the fed radio signal.

[0089] Fig. 13 is a diagram schematically illustrating the directivity generated by the antenna group 12 shown in Fig. 12. As shown in Fig. 13, the antenna group 12 has a wide directivity centered on a direction of an azimuth angle of 45° and an elevation angle of 45°, and covering a range of an azimuth angle of 0 to 90° and an elevation angle of 0 to 90°.

[0090] The wireless device 100 according to the second embodiment is ＡＮＴｘ / 2 x N ＡＮＴｙ / 2 antenna groups 12, respectively. ＡＮＴｘ / 2 x N ＡＮＴｙ / 2 baseband signal generating units 60, and N ＡＮＴｘ / 2 x N ＡＮＴｙ / 2 radio units 70 and N ＡＮＴｘ / 2 x N ＡＮＴｙ and two radio units 70.

[0091] In the wireless device 100 according to the second embodiment, the directional antenna control unit 50 ＡＮＴｘ / 2 x N ＡＮＴｙ A complex amplitude with a magnitude of 1 and a random phase is applied to each of the two antenna groups 12. Fig. 14 shows the results of simulating the directivity generated when a complex amplitude with a random phase is applied to each antenna group 12 of the array antenna 10. As shown in Fig. 14, the array antenna 10 generates a pseudo-omnidirectional pattern within the range of the directivity shown in Fig. 13. However, it is not completely omnidirectional, and the strength of the radio wave radiation varies depending on the direction.

[0092] Therefore, when the common signal is repeatedly transmitted, the directional antenna control unit 50 is configured to change the complex amplitude provided to each antenna group 12 at least once for each transmission of the common signal. As a result, the directivity generated by the array antenna 10 changes in response to the repetition of the common signal, thereby eliminating the imperfection of the omnidirectionality in the pseudo-omnidirectional antenna. As a result, omnidirectionality can be achieved within the range of directivity shown in FIG. 13.

[0093] In order to install array antenna 10 shown in FIG. 11 on a wall or ceiling to cover all directions in a half space, four wireless devices 100 according to the second embodiment may be provided.

[0094] In addition, in embodiment 2, a configuration has been described in which a common signal is repeatedly transmitted using an array antenna 10 in which 2 x 2 antenna elements 20 are grouped into one antenna group 12. However, by appropriately changing the number of antenna elements 20 that make up one antenna group 12 and the phase difference given to each antenna element 20, omnidirectionality within a range of various directivities can be easily achieved.

[0095] [Embodiment 3] In embodiment 2, N ＡＮＴｘ ×N ＡＮＴｙ The antenna elements 20 are grouped into 2×2 groups on the hardware. ＡＮＴｘ / 2 x N ＡＮＴｙThe wireless device 100 has been described as being configured to form omnidirectionality within a specific range using an equally spaced planar array antenna having two feed terminals 18 .

[0096] In the third embodiment, a radio device will be described that uses an equally-spaced planar array antenna made up of antenna elements 20 that are not grouped in terms of hardware, and that can perform operations similar to those of radio device 100 according to the second embodiment. Note that the configuration of radio device 100 according to the third embodiment is the same as the configuration of radio device 100 according to the first embodiment shown in FIG. 1, except for the configuration of directional antenna control unit 50.

[0097] In radio apparatus 100 according to the third embodiment, array antenna 10 has N ＡＮＴｘ ×N ＡＮＴｙ The antenna elements 20 are grouped into 2×2 equal-spaced planar array antennas. ＡＮＴｘ ×N ＡＮＴｙ The array antenna 10 according to the second embodiment differs from the array antenna 10 according to the second embodiment in that it has feeding terminals.

[0098] The baseband signal generator 60 generates a baseband signal S transmitted from the i-th antenna element 20 of the n-th group of the array antenna 10. ｎｉ (t) to generate the baseband signal S ｎｉ (t) is given by equation (12).

[0099]

[0100] a included in the right side of equation (12) ｋ (n ｉ ) is generated by the directional antenna control unit 50. FIG. 15 is a diagram for explaining the processing in the directional antenna control unit 50. As shown in FIG. 15, the directional antenna control unit 50 generates the number N of groups included in the array antenna 10. ＡＮＴｘ / 2 x N ＡＮＴｙ A set of complex numbers equal in number to 1 / 2 is prepared, and multiple sets of such complex numbers are prepared.

[0101] A set of complex numbers is a random set of N with magnitude 1 and phase angles uniformly distributed in the range 0 to 2π. ＡＮＴｘ / 2 x NＡＮＴｙ In the example of FIG. 15, this set of complex numbers is divided into N complex numbers, which are the number of repetitions of the common signal. ＲＥＰ Prepare a number equal to the number of

[0102] The directional antenna control unit 50 calculates N ＡＮＴｘ / 2 x N ＡＮＴｙ By selecting one set of complex numbers from the set of two complex numbers, the complex amplitude a given to the nth group is ｋ (n) is set. Note that the complex amplitude a ｋ (n) is the data sequence A ｋ is a random complex amplitude for each group at the k-th symbol of

[0103] Next, the directional antenna control unit 50 calculates the complex amplitude a ｋ (n), the complex amplitude a given to each of the 2×2 antenna elements 20 constituting the n-th group is ｋ (n ｉ ) to set the

[0104] Specifically, the complex amplitude given to the first antenna element 20 in the nth group is a ｋ (n １ ), and the complex amplitude given to the second antenna element 20 is a ｋ (n ２ ), and the complex amplitude given to the third antenna element 20 is a ｋ (n ３ ), and the complex amplitude given to the fourth antenna element 20 is a ｋ (n ４ ) As shown in FIG. 15, the directional antenna control unit 50 calculates the complex amplitude a ｋ (n) is expressed as a complex amplitude a ｋ (n １ ), a ｋ (n ３ ) Furthermore, the directional antenna control unit 50 sets the complex amplitude a ｋ The complex amplitude a is the number obtained by multiplying (n) by the complex number "-j". ｋ (n ２ ) and the complex amplitude a ｋ The complex amplitude a is the number obtained by multiplying (n) by the complex number "+j". ｋ (n４ ) Using the complex amplitude multiplied by this complex number "-j" is equivalent to shifting the phase of the radio signal by -90°. Using the complex amplitude multiplied by the complex number "+j" is equivalent to shifting the phase of the radio signal by +90°.

[0105] That is, generating baseband signals multiplied by complex numbers "-j" and "+j" in baseband signal generating unit 60 is substantially equivalent to performing phase shifts of -90° and 90° when feeding power to antenna elements 20 in antenna group 12 shown in Fig. 12. Therefore, similar to radio apparatus 100 according to the second embodiment, radio apparatus 100 according to the third embodiment can also achieve omnidirectionality within various directivity ranges by grouping antenna elements 20 and changing the complex number by which the complex amplitude given to each antenna element 20 in a group is multiplied.

[0106] Furthermore, compared to the radio device 100 according to the second embodiment in which each antenna group 12 has a hardware phase shifter 14, 16, the radio device 100 according to the third embodiment can group and phase control the antenna elements 20 by arithmetic processing in the baseband signal generating unit 60 and the directional antenna control unit 50, and therefore can more easily form various directivities.

[0107] The present disclosure allows for the combination of the embodiments, as well as the appropriate modification or omission of the embodiments, within the scope of the invention. In addition, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriate combinations of the disclosed constituent elements.

[0108] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The technical scope of the present disclosure is defined by the claims, not by the description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims.

[0109] 10 Array antenna, 12 Antenna group, 14, 16 Phase shifter, 18 Power supply terminal, 20 Antenna element, 30 Radio protocol control unit, 40 Common signal generation unit, 50 Directional antenna control unit, 60 Baseband signal generation unit, 70 Radio unit, 72 Quadrature modulator, 74 Frequency converter, 76 Amplifier, 100 Radio device.

Claims

1. An array antenna having a plurality of antenna elements and configured to form a directivity according to a complex amplitude given for each at least one antenna element, a common signal generation unit that generates a common signal repeatedly transmitted toward a terminal whose existence position is unspecified using the array antenna, a directivity antenna control unit that sets a set of complex amplitudes given for each at least one antenna element when transmitting the common signal, a baseband signal generation unit that generates a baseband signal supplied to each at least one antenna element from the common signal using the set of set complex amplitudes, and a radio unit provided for each at least one antenna element that converts a corresponding baseband signal into a radio signal and supplies it to the array antenna, wherein the directivity antenna control unit has a plurality of sets of the complex amplitudes whose directivities formed by the array antenna are different from each other, and changes the set of complex amplitudes given for each at least one antenna element every time the common signal is transmitted at least once, a wireless device.

2. The wireless device according to claim 1, wherein each of the plurality of complex amplitudes constituting the set of complex amplitudes is a complex number having a magnitude of 1 and a phase following a uniform distribution.

3. Each of the at least one antenna element constitutes a group having two or more antenna elements, the group having at least one phase shifter configured to give a phase difference between radio signals given to each of the two or more antenna elements, wherein the directivity antenna control unit changes the set of complex amplitudes given for each group every time the common signal is transmitted at least once, the wireless device according to claim 1 or 2.

4. Each of the at least one antenna element constitutes a group having two or more antenna elements, the directivity antenna control unit changes the set of complex amplitudes given for each group every time the common signal is transmitted at least once, and sets the complex amplitudes given to each of the two or more antenna elements by multiplying the complex amplitudes given for each group by a complex number, the wireless device according to claim 1 or 2.

5. A method for transmitting a common signal toward a terminal with an unspecified location using an array antenna, wherein the array antenna has a plurality of antenna elements and is configured to form a directivity according to a complex amplitude given for each at least one antenna element, the method comprising: generating a common signal repeatedly transmitted toward the unspecified terminal; setting a set of complex amplitudes to be given for each at least one antenna element when transmitting the common signal; generating a baseband signal to be supplied for each at least one antenna element from the common signal based on the set of set complex amplitudes; and converting the corresponding baseband signal for each at least one antenna element into a radio signal and supplying the radio signal to the array antenna, wherein the step of setting the set of complex amplitudes includes a step of changing the set of complex amplitudes to be given for each at least one antenna element each time the common signal is transmitted at least once, the set of complex amplitudes having a plurality of sets with different directivities formed by the array antenna. A method for transmitting a common signal.

6. The method for transmitting a common signal according to claim 5, wherein each of the plurality of complex amplitudes constituting the set of complex amplitudes is a complex number having a magnitude of 1 and a phase following a uniform distribution.

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