JP5827167B2 - Array antenna - Google Patents

Description

  The present invention relates to an array antenna that communicates with a plurality of antennas arranged in an array.

  In recent years, wireless devices using adaptive array antennas such as wireless local area networks (LANs), mobile phones, and mobile receivers for digital terrestrial broadcasting tend to be used daily. As a result, the low cost of these wireless devices The need for computerization is increasing. However, an adaptive array antenna, in principle, requires analog circuits such as filters, amplifiers, down converters, A / D converters, etc., as many as the number of antennas. For example, the cost is higher than that of a single-antenna wireless device. There was a problem.

  In order to solve this problem, an adaptive array antenna (C-TDM-AAA: Conventional Time-Division Multiplexing Adaptive Array Antenna) has been proposed in the past, for example, by using time-division multiplexing using switches. (See Non-Patent Document 1). In Non-Patent Document 1, the bandwidth used by the wireless device, the switch switching speed, the filter bandwidth, and the conditions to be satisfied by the sampling speed are examined in detail. When switching and sampling are performed at appropriate timing, each antenna is It is shown that the received signal can be completely reproduced.

A CMA Adaptive Array Antenna System with a Single Receiver Using Time-Division Multiplexing, (IEICE Trans. Commun., Vol. E84-B, no. 6, pp. 1637-1646, June 2001.)

  By the way, in the case of time division multiplexing, a reception signal captured when a certain switch is connected and a signal captured when another switch is connected cause interference. At this time, if the phase difference between these received signals becomes large, the received power of the desired wave is reduced, which leads to a problem that the signal-to-noise ratio is deteriorated. Therefore, there is a need for technology development that can set the antenna directivity to the optimum direction in this type of time-division multiplex array antenna regardless of whether the radio wave to be received is a desired wave or an interference wave.

  In addition, if the amount of calculation increases at the time of calculating the antenna directivity, problems such as a load on the control device and the time required for processing occur. For this reason, there is also a need to reduce the amount of calculation required when setting the antenna directivity.

  An object of the present invention is to provide an array antenna that can appropriately set the directivity of an antenna in a desired direction and can reduce the amount of calculation performed when setting the directivity.

In order to solve the above problems, in the present invention, a switch circuit having a plurality of switches is connected between a plurality of antennas and a common receiving circuit, and the antennas are selectively received by the switches. In a time division multiplexing array antenna that receives radio waves by time division multiplexing by the switch by connecting to the circuit, the phase of each antenna at the time of radio wave reception is calculated, and the switching order of the switches is determined in the direction in which the phase advances. Alternatively, the gist of the present invention is to provide a switch switching order setting means for setting the received power to be the same for any antenna as the switching order No. 1 by setting the fixed one direction of the delaying direction.

  According to the configuration of the present invention, the switching order of switches can be optimized in a time-division multiplexed array antenna, so that the array antenna can be set to a desired directivity. Therefore, it is possible to appropriately set the required directivity, for example, receiving a desired wave with high sensitivity or directing the directivity in the direction of the disturbing wave. In addition, when determining the switch switching order, it is only necessary to obtain one switch switching order, so that it is possible to simplify the calculation performed when setting the antenna directivity.

  The gist of the present invention is that the switch switching order setting means obtains a correlation vector in an order before changing the switch switching order, and sets the switch switching order based on the correlation vector. According to this configuration, the required switch switching order can be accurately set using the correlation vector.

  In the present invention, the switch switching order setting means estimates the arrival direction of the received signal in the order before changing the switch switching order, and sets the switch switching order based on the mode vector calculated from the estimated direction. The gist is to set. According to this configuration, the required switch switching order can be accurately set using the mode vector.

  The gist of the present invention is that the arrangement of the plurality of antennas is point-symmetric. According to this configuration, the received power tends to be uniform in the plane where the antenna is arranged. Therefore, the received power becomes as uniform as possible in all directions.

  The gist of the present invention is that it is an adaptive system for processing a signal by adaptive control. According to this configuration, since the array antenna is an adaptive array antenna, the directivity of the antenna can be accurately set in the direction according to the received radio wave by adaptive control.

The gist of the present invention is that the antenna is arranged in an order in which the received power can be made uniform in all directions by making the antenna array into a circular shape . According to this configuration, radio waves transmitted from any direction can be received with high sensitivity.

  In the present invention, the switch switching order setting means first receives radio waves in a switch switching order in which the received power is uniform in all directions, and based on this received signal, the final switch switching required. The gist is to set the order. According to this configuration, it is possible to more reliably receive radio waves necessary for setting the switch switching order, and thus it is possible to ensure processing reliability.

  According to the present invention, the directivity of the antenna can be appropriately set in a desired direction, and the amount of calculation performed when setting the directivity can be reduced.

The block diagram of the adaptive array antenna of one Embodiment. The time waveform figure of a switch control signal. The time waveform figure of a sampling signal. The graph showing the change by the arrival direction of reception power. FIG. 4 is an exemplary diagram illustrating a specific example of Φ− ¹ . (A), (b) is explanatory drawing which shows the phase relationship of the correlation vector of each antenna. (A) is explanatory drawing which shows switch switching order when antenna # 1 is switching order 1st, (b) is explanatory drawing which shows switch switching order when antenna # 3 is switching order 1st. Explanatory drawing which shows the concept of the switch switching order of this example. The flowchart which shows the setting procedure of a switch switching order. (A), (b) is an array of antennas. The graph showing the change by the arrival direction of reception power. The simulation model figure of the single receiver which uses time division multiplexing. A table showing simulation conditions. The table | surface which shows the selection result of the phase of a correlation vector, and switch switching order. The graph showing the change by the arrival direction of reception power. The graph which shows the directivity formed with the MMSE algorithm. The characteristic figure of SNR-BER in TDM-AAA.

Hereinafter, an embodiment in which the present invention is embodied in an adaptive array antenna will be described with reference to FIGS.
[Overview of Time Division Multiplex Adaptive Array Antenna]
As shown in FIG. 1, the adaptive array antenna 1 includes a plurality of antennas (antenna elements) 2, and the weight of each antenna 2 is adaptively controlled according to the propagation environment, thereby directing in the direction of arrival of a desired desired wave. It can function as an antenna with high communication characteristics by directing the null point in the direction of arrival of unwanted radio waves and removing it. The adaptive array antenna 1 of this example is also of a time division multiplex type in which a plurality of antennas 2 share one receiving circuit 3 and communicate on a single transmission line by dividing received signals in time units.

  In the time-division multiplex type adaptive array antenna 1, if the number of antennas 2 is K (K is an arbitrary odd number), the received signal of the k-th antenna 2 is expressed by the following equation (1).

Here, f _k (t) is a reception baseband signal in the k-th antenna 2. Further, cos (ω _c t) represents a carrier wave, and ω _c represents an angular frequency of the carrier wave.

Each antenna 2 is connected to a first bandpass filter 4 having a passband width W. These first band pass filters 4 filter the received signal f _k (t) cos (ω _c t) received by the antenna 2 with a pass bandwidth W, and pass only the frequency according to W.

The frequency bandwidth W ″ of the received baseband signal f _k (t) is smaller than the pass bandwidth W of the first bandpass filter 4. Therefore, the received signal f _k (t) cos (ω _c t) It passes through the 1 band pass filter 4 as it is.

A switch circuit 5 that selectively switches the connection of the first bandpass filter 4 (antenna 2) is connected between the plurality of first bandpass filters 4 and the receiving circuit 3. The switch circuit 5 is one component of the receiving circuit 3 and includes a plurality of switches 6 for each first bandpass filter 4. These switches 6 are switch-controlled by a switch control signal g _k (t) input from the clock circuit 7.

Here, as shown in FIG. 2, if the k-th switch 6 is switched at the rectangular wave-like ON time τ and period T _S , the switch control signal g _k (t) is expressed by the following equation (2). expressed. In the following formula, r is an arbitrary integer.

Here, when the switch switching frequency is W ′ (W ′ = 1 / T _S ), the switch switching cycle T _S needs to be set appropriately so as to satisfy W ′> W.

The reception signals f _k (t) cos (jω _c t) of each antenna 2 are multiplied by the switch control signal g _k (t) when passing through the switch, and then the signals from the K antennas 2 are combined. This synthesized signal h (t) is expressed as the following equation (3).

The receiving circuit 3 is provided with a second band pass filter 8 having a frequency bandwidth of KW ′. Only one second band pass filter 8 is provided and shared by the plurality of switches 6. The synthesized signal h (t) passes through the second bandpass filter 8 and is output as an output signal h ′ (t). The output signal h ′ (t) is expressed by the following equations (4) and (5).

The receiving circuit 3 includes an amplifier 9 for amplifying the output signal h ′ (t), a converter 10 for downconverting the amplified output signal h ′ (t) to an IF (Intermediate Frequency) frequency, and a signal at the IF frequency. An IF bandpass filter 11 that passes through and a pair of converters 12 and 12 that orthogonally downconvert IF frequencies are provided. Low-pass filters 13 and 13 that filter the outputs from the converters 12 and 12 are connected to the converters 12 and 12, respectively. A / D converters 14 and 14 for A / D converting the filtered signals are connected to the low-pass filters 13 and 13, respectively.

  The baseband signal h ″ (t) output from the low-pass filter 13 is expressed by the following equation (6) if the amplifier amplification and the filter loss are ignored.

The baseband signal h ″ (t) is sampled at a period T _S by the sample output unit 15 in the A / D converter 14. That is, the signal output from the A / D converter 14 is sampled by the sample output unit 15. The signal is branched / output as a signal of each antenna 2. This sampling signal z _i (t) is expressed by the following equation (7).

As shown in FIG. 3, the sampling signal z _i (t) is a signal whose timing is shifted by T _S / K. Actually, the A / D converter 14 performs sampling at z (t) expressed by the following equation (8).

Now, the sample signal x _i (t) obtained by sampling the baseband signal h ″ (t) with the sampling signal z _i (t) is expressed by the following equations (9) and (10).

The sample signal x _i (t) is obtained in a form in which the reception baseband signals f _k (t) of the antennas 2 are mixed, as can be seen from the equation (10). Here, at first glance, if the ON time τ of the switch 6 is τ <(T _S / K), the two switches are not connected at the same time, and the reception baseband signal f _k (t) is mixed. Although there seems to be no, in reality, the waveform rounding when passing through the filter causes mixing of the received baseband signal f _k (t).

  By the way, Non-Patent Document 1 mentioned in the background art has been studied only when the ON time of the switch 6 that connects each antenna system and the shared analog circuit is very short. This is because the reception signals of the antennas are mixed if the ON time of the switch 6 is long. Therefore, Non-Patent Document 1 has a problem that the loss in the switch 6 is very large. In addition, in Non-Patent Document 1, when the amplifier provided in each antenna system is shared for the purpose of further analog circuit reduction, the SNR (Signal-to-Noise Ratio (signal-to-noise ratio) of the reproduced received signal is reduced. Ratio)) is significantly degraded.

  Therefore, the present applicant has developed a technique (M-TDM) that separates the received signal of each antenna 2 from mixing and makes it completely reproducible by devising post processing even if the ON time of the switch 6 is arbitrary -AAA: Modified Time-Division Multiplexing Adaptive Array Antenna (see Japanese Patent Application No. 2011-189760). If this method is adopted, the ON time of the switch 6 can be arbitrarily set. Therefore, the SNR degradation due to time division multiplexing can be reduced by maximizing the ON time of the switch 6.

  However, in this method, if the phase difference of the desired wave in the antenna 2 before and after switching of the switch 6 is increased, there is a problem that the received power P of the desired wave is reduced. Therefore, in this example, the SNR degradation is further reduced by positively using the mixing instead of removing the mixing of the reception signals of the respective antennas 2. That is, the technique of the present example copes with by setting the switching order of the switches 6 which has been in the order of antenna numbers so far to an appropriate order according to the received signal.

  The adaptive array antenna 1 is provided with an adaptive processor 16 that calculates the arrival direction of radio waves by adaptive control and sets the function (operation state) of the array antenna 1. The adaptive processor 16 calculates the arrival direction of a desired wave or an unnecessary radio wave (jamming wave) based on the I-phase signal and the Q-phase signal for each antenna 2 input from the sample output unit 15, and the adaptive array antenna 1. Set the function.

[Changes in received power depending on direction of arrival in receivers using time division multiplexing]
Next, it will be described that the received power P varies depending on the direction of arrival of the received wave in TDM-AAA. A reception signal vector X (t) in the single reception circuit 3 is expressed by the following equations (11) to (19). In the following equation, the integer representing the harmonic component of the switch change frequency 1 / T _S and n, and transpose the ^T.

Now, when the array shape is a linear array of half-wavelength equal intervals, and one incoming wave arrives at an angle θ formed with the boresight direction, the vector F (Δt) having the received baseband signal f _k (t) of each antenna 2 as an element. ) Is expressed by the following equations (20) and (21) using the mode vector a (θ) and the incoming signal f (Δt).

Here, the received power P of the adaptive array antenna 1 is defined as in the following equation (22). In Equation (22), E [•] represents an expected value, and ^H represents a complex conjugate transpose.

When the number of antennas K = 13, the received power P changes as shown in FIG. 4 depending on the arrival direction θ of the incoming wave. That is, as shown in the figure, it can be confirmed that when the arrival direction is close to 0 °, the reception power P is large, and that the reception power P decreases as the arrival direction moves away from 0 °. This is thought to be because the signals received by the respective antennas 2 are all in phase when the angle is 0 °, and are strengthened when signals are mixed. On the other hand, when the arrival direction is away from 0 °, for example, ± 90 °, the reception signals of the antennas adjacent to each other, that is, the antennas immediately before and immediately after the switch switching are all in opposite phases. Since the amount of signal mixing is the largest from the antenna 2 immediately before and after switching, the received power P is considered to decrease as the arrival direction approaches ± 90 °.

  Based on this consideration, when reception signals are mixed, if the switch switching order is set (changed) so that the signal phase difference immediately before and after the switch switching is as much as possible, the reception of the adaptive array antenna 1 is possible. It is expected that the power P can be increased.

FIG. 5 shows the values of the elements of the matrix Φ ⁻¹ when the number of antennas K = 13. Since Φ ⁻¹ is a cyclic matrix, only a part thereof is shown, and the value is represented by one significant digit. Φ ⁻¹ represents how the reception baseband signal F (Δt) of each antenna 2 is mixed, as can be seen from the above equation (11).

As shown in FIG. 5, when the off-diagonal element is “0”, mixing of the received signal does not occur, but in practice it is understood that the mixing is performed little by little. As a characteristic, the absolute value of the element adjacent to the diagonal element among the non-diagonal elements of Φ ⁻¹ is considerably larger than that of the other non-diagonal elements. This means that mixing from the received signal of the antenna 2 immediately before and immediately after the switch switching order accounts for a large proportion. Also from this, it is considered effective to improve the received power P to change the switch switching order so that the received signals of the antenna 2 before and after the switch switching have the same phase as much as possible.

[Mathematical Expression of Received Signal Vector X (t) Considering Switch Switching Order]
From the mathematical point of view, changing the switch switching order is equivalent to replacing the element of the vector F (Δt) in the above equation (1). Now, let p, u ~ _{p be} an integer in the range of -μ to μ, and the vector u≡ [-μ, ..., p, ..., μ] ^T and the rearranged vector u ~ ≡ [u ~ _{− μ, ..., u ~ p,} ..., consider the u ~ μ] ^_T. At this time, assuming that the K-th order square row example representing the replacement from u to u˜ is V, and the elements of the l-th row and m-th column of V are v _{l, m} , v _{l, m} and u˜ It is expressed as equations (23) and (24). Note that the above u ~ is a symbol with ~ added to u.

When the switch switching order is changed, the received signal is expressed by the following equation (25) using the permutation matrix V.

Note that when the switch switching order is the antenna number order as before, V = I (I is a unit matrix).

[How to optimize switch switching order]
As described above, it is considered that the received power P can be improved by optimizing the switch switching order so that the phase change of the received signal becomes as small as possible. Therefore, a method for determining an optimal switch switching order will be described below.

A correlation vector r _xr in an MMSE (Minimum Mean Square Error) adaptive array antenna is expressed by the following equation (26), _assuming that the switch switching order is the antenna number order (V = I). In equation (26), r (t) represents a reference signal, and ^* represents a complex conjugate.

The correlation vector r _xr represents the correlation between the input signal and the reference signal, as can be seen from equation (26). The correlation vector r _xr is expressed by the following equation (27) using the mode vector a (θ) when the desired wave to arrive is one wave. In Equation (27), ξ represents a complex constant.

Since the mode vector a (θ) represents the response of each antenna 2 with respect to the arrival direction θ, it can be confirmed that the reception phase of the desired wave between the antennas 2 can be calculated by _obtaining the correlation vector r _xr . In the case of this example, the correlation vector r _xr is used to optimally set the switching order of the switches 6.

[Specific description related to switch switching order setting]
Here, FIGS. _{6A and} 6B show the phase relationship of the correlation vector r _xr of each antenna 2 when the number of antennas is 13, for example, and the radio wave arrival direction is 70 °. Assuming this, as shown in FIG. 7A, for example, when antenna “# 1” is set to the switch switching order No. 1 and the antennas having the closest phases are selected in order, the switch switching order at this time is received. This is the order in which the power P is maximized.

  On the other hand, as shown in FIG. 7B, when the antenna “# 3” is set to the first switch switching order, the second antenna in the switching order may be “# 1” (however, “# 5”). ), And the third antenna in the switching order becomes “# 5”. Therefore, at this time, the phase difference (phase relationship) between # 1 and # 5 is largely separated, and a loss occurs in the received power P.

  As described above, the received power P of the desired wave to be received changes depending on which of the plurality of antennas 2 is set to the first switch switching order. For this reason, when checking the switch switching order with the highest received power P, for example, if each antenna 2 is set to the switch switching order No. 1 and is checked in its entirety, the optimum switch switching order can be extracted. Become. However, in this case, since the amount of calculation increases, problems such as an increase in calculation load and a long calculation time occur.

Therefore, as shown in FIG. 8, the switch switching order of this example employs a method in which the phase of the correlation vector r _xr is set to a fixed one direction in which the phase advances or is delayed. As a result, the same received power P can be obtained regardless of which antenna 2 has the switch switching order No. 1, so that the calculation for determining the switch order by determining the switch switching order No. 1 is not performed entirely. This reduces the computational load.

As shown in FIG. 1, the adaptive processor 16 is provided with a correlation vector calculation unit 17 that calculates a correlation vector r _xr necessary for setting the switch switching order. In the beginning of setting the switch switching order, the correlation vector calculation unit 17 of this example receives a signal with the switch switching order as the antenna number order, and calculates a correlation vector r _xr . The correlation vector calculation unit 17 constitutes a switch switching order setting unit.

The clock circuit 7 is provided with a switch switching order setting unit 18 that sets the switch switching order based on the correlation vector r _xr obtained by the correlation vector calculation unit 17. In this example, the switch switching order setting unit 18 determines the predetermined antenna as the switch switching order No. 1, and sets the antenna 2 having the smallest phase difference in the direction in which the phase is advanced or delayed from the antenna 2 as the antenna 2 to be switched next. The order along the direction is set as the switch switching order. That is, the above-described restriction is added to the setting of the switch switching order. The switch switching order setting unit 18 constitutes a switch switching order setting unit.

Next, the operation until the switch switching order is determined will be described with reference to the flowchart of FIG.
In step 101, the correlation vector calculation unit 17 receives a signal with the switch switching order as the antenna number order, and calculates a correlation vector r _xr . The correlation vector calculation unit 17 outputs the calculated value of the correlation vector r _xr to the switch switching order setting unit 18.

  In step 102, the switch switching order setting unit 18 selects the antenna 2 with the switching order No. 1. Here, as shown in FIG. 7, for example, it is assumed that antenna # 2 is selected as the antenna having the first switching order.

In step 103, the switch switching order setting unit 18 calculates the phase difference between the selected antenna 2 and the unselected antenna 2.
In step 104, the switch switching order setting unit 18 selects the antenna 2 with the smallest phase difference as the antenna 2 to be switched next. In the example of FIG. 8 of this example, the antenna 2 of # 3 is selected as the antenna 2 to be switched next.

  In step 105, the switch switching order setting unit 18 performs step 103 and step until the switching order of all the antennas 2 is determined under the constraint condition that the switch switching order is set to the first and the antenna 2 is fixed in one direction. Repeat 104. When the switching order of all the antennas 2 is determined, the switching order that minimizes the phase change when a certain antenna 2 is in the switching order 1 is determined. In the example of FIG. 8, the switching order is determined as # 3 → # 5 → # 7 → # 9 → # 11 → # 13 → # 2 → # 4 → # 6 → # 8 → # 10 → # 12 → # 1. When the switch switching order is determined, signals are received again in that order, and adaptive processing is performed.

  Incidentally, the received power P is obtained by the following equations (28) and (29).

Since X is a K-th column vector (K: the number of antennas), the reception power P in each switching order can be obtained by performing calculations using equations (28) and (29). Further, equation _{^{(28), r xr H Φ H V H}} (Φ -1) the same meanings as ^{2 VΦr} _xr.

[Antenna array shape]
The array shape of the antennas 2 may be linear as shown in FIG. 10A, or may be circular as an example of a point-symmetric arrangement as shown in FIG. Incidentally, the order of antenna numbers referred to in this example refers to the order of the arrangement direction shown in these drawings. As shown in FIG. 11, when the antenna 2 is arranged in a circular shape (solid line in the figure), the effect of making the received power P uniform is higher than in the case of a linear shape (dashed line in the figure). Become. This is presumably because radio waves can be received uniformly within the plane where the antenna 2 is disposed.

[simulation]
Subsequently, the technique of this example is evaluated by computer simulation. In the case of this example, in order to reduce the calculation load, the circuit configuration is changed as shown in FIGS. 1 to 12 and a simulation is performed. Here, the converters 10 and 12 for down-conversion are deleted. For this reason, the received signal in each antenna 2 is a baseband signal having a predetermined phase difference depending on the arrival angle of the radio wave. The waveform change at the switch 6 and the band limitation at the filters 4 and 8 are replaced with the multiplication of the matrix ΨSΓ ₋ V. In addition, the waveform change due to aliasing that occurs during sampling in the A / D converter 14 is replaced with multiplication by Γ ₊ . Furthermore, it is assumed that there is no difference in the sample timing of the reception signal of each antenna 2 generated in the time division processing. As for thermal noise, uncorrelated white Gaussian noise is added to each of the amplifier units.

  FIG. 13 shows the simulation specifications. The array antenna 1 is a 13-element linear array with an antenna interval of 0.5 wavelength. Further, the switch switching period is 1 μsec, and the ON time ratio Ψ of the switch 6 is 1/13 (= a state in which one of the antennas 2 is always connected). The incoming waves are two waves, and a desired wave modulated by FSK (Frequency Shift Keying) and an interference wave that is broadband noise arrive. The interference wave power is +30 dB relative to the desired wave. The MMSE algorithm is adopted as the adaptive array algorithm, and the SMI (Sample Matrix Inversion) algorithm is adopted as the optimum weight determination method.

First, in TDM-AAA, it is confirmed that the switch switching order optimization algorithm is operating correctly. FIG. 14 shows the phase of the correlation vector r _xr in a certain trial when SNR = 12 dB and the determined switch switching order. Note that the ideal value represents a value in a state where neither the interference wave nor the thermal noise exists. Also, here, the switch switching order No. 1 is the antenna of “# 1”. As shown in the figure, the difference from the ideal value of the correlation vector phase is 1 ° at the maximum, and it can be seen that the switching order is correctly determined. It can also be seen that the signal phase difference before and after switching, which is about 170 ° when the switching order is antenna number order, decreases to about 20 ° when the switching order is optimized.

  FIG. 15 shows the arrival direction dependence of the received power P of the array antenna 1 in the optimized switching order. As shown in the figure, unlike FIG. 4, it is confirmed in FIG. 15 that the received power P in the −70 ° direction where the desired wave arrives is improved.

  FIG. 16 shows the directivity of the array antenna 1 formed by the MMSE algorithm. As shown in the figure, a beam is formed in the direction of the desired wave and a directional null is formed in the direction of arrival of the disturbing wave, confirming that the MMSE algorithm is operating well.

  FIG. 17 shows the difference in BER (Bit Error Rate) characteristics depending on whether or not the switch switching order is optimized in TDM-AAA. As shown in the figure, compared to “+” when the switch switching order is the antenna number order, it can be confirmed that the characteristics are improved by about 3 dB when the switch switching order is optimized. The effectiveness of the technique of this example is confirmed. This value of 3 dB is almost equal to the difference in the received power P in the −70 ° direction in FIG. 4 and FIG. Further, “x” in FIG. 17 is a characteristic when the switch switching order is fixed to an ideal order. There is no difference between the case where the switch switching order is fixed and the characteristic when the algorithm is optimized by the algorithm, and it is confirmed that the switch switching order optimization algorithm is operating correctly.

According to the configuration of the present embodiment, the following effects can be obtained.
(1) In the time-division multiplex adaptive array antenna 1, the switching order of the switches 6 can be set not in the simple antenna number order but in the order having a specific directivity. For this reason, the time division multiplex adaptive array antenna 1 can be set to a desired directivity. Therefore, the required directivity can be set as appropriate, for example, receiving a desired wave with high sensitivity or directing the directivity in the direction of the interference wave. In addition, a fixed one direction (the direction in which the phase advances or the direction in which the phase advances) from the antenna whose switching order is set to the first is set as the switch switching order. Therefore, since only one switch switching order can be obtained, the calculation of the switch switching order can be simplified.

(2) Since the switch switching order is determined using the correlation vector r _xr , the necessary switch switching order can be accurately set.
(3) If the antenna 2 is arranged in a circular arrangement as shown in FIG. 10B, the received power P is likely to be uniform (isotropic) in the plane where the antenna 2 is arranged. Therefore, the received power P becomes as uniform as possible in all directions, so that radio waves from any direction can be received with high sensitivity.

  (4) Since the array antenna 1 is an adaptive array system, the directivity of the array antenna 1 can be accurately set in the direction according to the received radio wave by adaptive control.

Note that the embodiment is not limited to the configuration described so far, and may be modified as follows.
The switch switching order is not limited to the method using the correlation vector r _xr . For example, the process of step 101 may be replaced with a radio wave arrival direction estimation process, and the switch switching order may be set using the mode vector a (θ) calculated from the estimated direction.

-The antenna with the switch switching order No. 1 can be arbitrarily set.
The equalization of the received power P in all directions is not limited to being realized by making the antenna 2 array circular. For example, even if the arrangement of the antennas 2 is a linear shape, it may be realized by setting the switch switching order in which the received power P in all directions is uniform.

The switch switching order in step 101 is not limited to the antenna number order. For example, signals may be received in a switch switching order in which received power P is as uniform as possible in all directions, and correlation vector r _xr may be calculated based on this received signal.

The process of step 101 may be performed with a preamble signal or may be performed with actual communication data.
The receiving circuit 3 may be a circuit that downconverts the signal by a normal converter instead of the quadrature downconverters 12 and 12.

  The receiving circuit 3 is not limited to the configuration in which the baseband signal is sampled by the A / D converter 14, but for example, the configuration in which the IF signal is sampled or the (Radio Frequency) signal output from the second bandpass filter 8 is sampled. It may be configured.

The plurality of antennas 2 and the receiving circuit 3 are not limited to one-to-one connection by the switch circuit 5, and for example, the plurality of antennas 2 may be simultaneously connected to the receiving circuit 3.
The number K of antenna elements is not limited to an arbitrary odd number, and may be an arbitrary even number.

The ON time τ (ON time ratio Ψ) of the switch 6 is not limited to the example described in the embodiment, and can be appropriately changed to other time widths.
The frequency bandwidth of the second bandpass filter 8 may be a value obtained by multiplying the frequency band of the first bandpass filter 4 by a coefficient K, for example.

  A phase shifter, an attenuator, and an amplifier may be added after the antenna 2. In this case, the degree of directivity is further increased, and the direction of the beam formed by switching can be controlled more flexibly.

  A circuit that combines a plurality of antenna outputs of the antenna 2 to obtain a single or a plurality of outputs may be added after the antenna 2. In this case, the direction of the beam formed by switching the switch can be controlled more flexibly.

The array antenna of this example is not limited to the adaptive array antenna 1 and may be changed to other types such as an array antenna using a fixed antenna.
The setting of the switch switching order may be performed at any time.

The various operations described in the embodiments can be appropriately changed to other arithmetic expressions as long as they are equivalent.
The adaptive array antenna 1 is not limited to being used as a receiver for a vehicle or an electronic key, and can be appropriately applied to other devices and apparatuses.

-The adaptive array antenna 1 of this example is employable for various apparatuses and systems.
Next, technical ideas that can be grasped from the above-described embodiment and other examples will be described below together with their effects.

  (B) A switch circuit having a plurality of switches is connected between a plurality of antennas and a common receiving circuit, and the antenna is selectively connected to the receiving circuit by the switch, thereby In a time switching multiplex array antenna switch switching order setting method for receiving radio waves by time division multiplexing, the phase of each antenna at the time of radio wave reception is calculated, and the switching order of the switches is determined in the direction in which the phase advances or is delayed. An array antenna switch switching order setting method, wherein the switch is set in a fixed direction.

DESCRIPTION OF SYMBOLS 1 ... Array antenna (Time division multiplexing adaptive array antenna), 2 ... Antenna, 3 ... Reception circuit, 5 ... Switch circuit, 6 ... Switch, 17 ... Correlation vector calculation part which comprises switch switching order setting means, 18 ... Switch switching Switch switching order setting unit constituting order setting means, r _xr ... correlation vector, a (θ) ... mode vector, P ... received power.

Claims (7)

A switch circuit having a plurality of switches is connected between a plurality of antennas and a common receiving circuit, and the antenna is selectively connected to the receiving circuit by the switch, whereby time division multiplexing by the switch is performed. In a time division multiplex array antenna that receives radio waves by
By calculating the phase of each antenna at the time of radio wave reception and setting the switching order of the switches to one direction that is fixed in the direction in which the phase advances or lags , the received power can be obtained regardless of which antenna is the first in the switching order. An array antenna comprising similar switch switching order setting means. 2. The array antenna according to claim 1, wherein the switch switching order setting means obtains a correlation vector in an order before changing the switch switching order, and sets the switch switching order based on the correlation vector. . The switch switching order setting means estimates the arrival direction of a received signal in an order before changing the switch switching order, and sets the switch switching order based on a mode vector calculated from the estimated direction. The array antenna according to claim 1, wherein: The array antenna according to any one of claims 1 to 3, wherein the arrangement of the plurality of antennas is point-symmetric. The array antenna according to any one of claims 1 to 4, wherein the array antenna is an adaptive system that processes a signal by adaptive control. The array according to any one of claims 1 to 5, wherein the array shape of the antennas is set in a circular shape so that the received power can be uniform in all directions. antenna. The switch switching order setting means first receives radio waves in a switch switching order in which received power is uniform in all directions, and sets a necessary final switch switching order based on the received signal. The array antenna according to claim 6.