JP2007139521A - Array antenna device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an array antenna device capable of estimating the incoming direction of a radio wave highly accurately without using a high-speed switch. <P>SOLUTION: A reference signal from a reference antenna element 101 is sampled successively by the first reception part 121, and each signal from a plurality of other antenna elements 102-10n other than the reference antenna element input successively by switching of a switch 11 is sampled by the second reception part 122. Each phase difference of the signals from the plurality of other antenna elements 102-10n inputted and sampled by the second reception part 122 is corrected by a digital processing part 18, based on a phase difference generated in the reference signal when sampled successively by the first reception part 121. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an array antenna device, and more particularly to an array antenna device that performs direction-of-arrival estimation by digital processing.

  2. Description of the Related Art Conventionally, there is an array antenna apparatus that includes an array antenna such as an adaptive array antenna including a plurality of antenna elements that receive radio waves, and estimates the arrival direction of radio waves based on the phase difference of each signal from the plurality of antenna elements of the array antenna. In such an array antenna apparatus, when the direction of arrival of radio waves is estimated, the received signal from each antenna element is AD converted and the direction of arrival of radio waves is estimated by digital processing. FIG. 10 is a block diagram of such a conventional array antenna apparatus.

  In FIG. 10, received signals from the amplifier 34, the filter 35, and the antenna elements 301 to 30n and the signal from the local transmitter 33 are mixed and down-converted to each of the n antenna elements 301 to 30n of ch1 to chn. A mixer 36 is connected.

  The received signals from the antenna elements 301 to 30n are down-converted by the mixer 36, and a beat signal having a frequency lower than that of the received signal obtained by the down-conversion is converted into digital data by the AD conversion unit 37. Thereafter, the beat signal is sent to the digital processing unit 38, which estimates the direction of arrival of radio waves by processing the amplitude and phase of the sampled signal with a predetermined algorithm. Hereinafter, the amplifier 34, the filter 35, the mixer 36, and the AD conversion unit 37 are collectively referred to as a receiver.

  By the way, in the configuration of the array antenna apparatus shown in FIG. 10, the receivers 321 to 32n are connected to the antenna elements 301 to 30n. In such a configuration, the number of components increases as the number of antenna elements increases. Therefore, there is a problem of increasing the size and cost. In addition, from the viewpoint of arrival direction estimation accuracy, the influence of variations in the characteristics of each component also increases due to an increase in the number of components.

  Further, in order to accurately obtain the phase relationship of each antenna element 301 to 30n, the signal path length in the receiver and the signal path length from the local transmitter 33 to the mixer 36 of each receiver 321 to 32n, It is necessary to adjust precisely. For example, if the path length of the high-frequency circuit is shifted by 1 mm with respect to an input signal of 2.5 GHz, an error of about 3 ° occurs in the phase of the received signal, which greatly affects the arrival direction estimation. Thus, the basic array antenna configuration is very disadvantageous in terms of cost, size, and accuracy.

  Therefore, as a means for solving such a problem, there is one in which only one receiver is provided for a plurality of antenna elements, and each antenna element is sequentially switched by a changeover switch to be connected to the receiver. . In such an array antenna apparatus, received signals from the antenna elements that are sequentially switched and connected to the receiver are acquired after time-division with a switch switching period (for example, see Patent Document 1). .)

  FIG. 11 is a block diagram of such a conventional array antenna apparatus. This array antenna apparatus includes antenna elements 301 to 30n, a changeover switch 31 for sequentially switching the antenna elements 301 to 30n, a receiver 321, a digital processing unit 38, and a switching signal transmitter 39. . With such a configuration, the receiver 321 can be integrated into one, and the array antenna apparatus is greatly simplified.

  In such an array antenna apparatus, the selector switch 31 and the AD converter 37 are controlled by the same clock signal generated by the selector signal generator 39, and AD conversion is performed at the timing when the selector switch 31 is switched. Here, the frequency fsw of the clock signal for switching the changeover switch 31 is set larger than the frequency fb of the beat signal input to the AD conversion unit 37.

  For example, fsw / fb >> 100 to 1000 is set. For this reason, the beat signal is sampled by time-dividing one cycle from 100 to 1000 times.

  FIG. 12 is a diagram illustrating how the beat signal is sampled. In FIG. 12, the number of antenna elements is four (ch1 to ch4), and fsw is set to a small value for convenience of illustration. Also, the four continuous waveforms in FIG. 12 show beat signals when the received signals of the four antenna elements are always down-converted, and the signals of ch1 to ch4 have different phases and amplitudes. It is displayed as a thing.

  The part that is boldly displayed on this signal is the part that is AD-converted, and the four beat signals are sequentially AD-converted by the channel switching by the switch 31. As described above, for convenience of display, fsw is displayed using a small value. However, in practice, by setting as fsw >> fb, the beat signal is further subdivided on the time axis. And sampled.

JP-A-11-160423

  However, in such a conventional array antenna apparatus, the frequency fsw of the clock signal is set to be high speed so as to satisfy fsw >> fb with respect to the frequency fb of the beat signal. A switch that can do this is necessary.

  When high-speed switching of switches is performed in this way, noise such as harmonics is generated, which affects the received signal and ultimately reduces the accuracy of radio wave arrival direction estimation. In addition, when the switching timing of the selector switch 31 is not stable or when it takes time to switch, there is a possibility that the phase of each measured signal is not captured at the scheduled timing and includes an error.

  Furthermore, assuming that the switching clock is constant, if the number of antenna elements is increased, the sampling interval of each channel (antenna element) becomes longer, and only large-spaced data can be obtained. Reliability is inferior. If the switching clock frequency is increased in order to increase the reliability of the sampling result, it is necessary to use a faster switch, and the problem of harmonic noise becomes more serious. Furthermore, a switch that can be switched at high speed is expensive and disadvantageous in terms of cost.

  Therefore, the present invention has been made in view of such a situation, and an object thereof is to provide an array antenna apparatus capable of estimating the arrival direction of radio waves with high accuracy without using a high-speed switch. To do.

  The present invention provides an array antenna apparatus that includes an array antenna including a plurality of antenna elements, and estimates an arrival direction of a radio wave based on a phase difference of each signal from the plurality of antenna elements. A reference antenna element, a first receiver for sequentially sampling a reference signal from the reference antenna element, and signals from a plurality of antenna elements other than the reference antenna element among the plurality of antenna elements A second receiving unit for sampling, and the second receiving unit provided between the plurality of other antenna elements and the second receiving unit, and sequentially receiving signals from the other antenna elements A switch to be input to the switch, a switching control unit that controls switching of the switch, a digital processing unit that stores signals of the plurality of antenna elements, The is characterized in that it comprises.

  As in the present invention, based on the phase difference generated in the reference signal when sequentially sampled by the first receiver, the signals from other antenna elements sampled by being input to the second receiver are sampled. Correct the phase difference. As a result, the switch switching time interval can be greatly delayed, and as a result, the arrival direction of radio waves can be estimated with high accuracy without using a high-speed switch.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a block configuration diagram of the array antenna apparatus according to the first embodiment of the present invention. Here, this array antenna apparatus is a digital beam forming (DBF) array antenna apparatus that AD-converts received signals from each antenna element and estimates the arrival direction of radio waves by digital processing. In this array antenna apparatus, the direction of arrival is estimated using the phase and amplitude of the received signal with a predetermined algorithm. In this array antenna apparatus, a beamformer method, a MUSIC method, an ESPRIT method, or the like is used as an arrival direction estimation algorithm.

  The array antenna apparatus shown in FIG. 1 switches n antenna elements 101 to 10n, a switch 11, an amplifier 14, a filter 15, a local oscillator 13, a mixer 16, an AD conversion unit 17, a digital processing unit 18, and a switch 11. A switching control unit 19 is provided.

  In FIG. 1, reference numerals 121 and 122 denote a reference receiver and a switching receiver each including an amplifier 14, a filter 15, a mixer 16, and an AD conversion unit 17. The mixer 16 of the reference receiver 121 and the switching receiver 122 receives a signal from the local transmitter 13 that is used in common.

  The signals received by the plurality of antenna elements 101 to 10n first pass through the reference receiver 121 that is the first receiver and the amplifier 14 and the filter 15 of the switching receiver 122 that is the second receiver. At this time, the amplitude and frequency are adjusted, and then mixed with the signal of the local oscillator 13 by the mixer 16 to become a beat signal having a frequency lower than that of the received signal. Next, the beat signal is sampled by the AD conversion unit 17, and then the sampling signal is sent to the digital processing unit 18.

  By the way, in the present embodiment, the switch 11 includes n−1 input terminals 1 to n−1 and one output terminal Ex. Of the n antenna elements 101 to 10n, for example, the first antenna element (ch1) 101 is connected to the reference receiver 121 as a reference antenna element. The signal from the first antenna element (ch1) is sequentially sampled by the reference receiver 121 as a reference signal, and then taken into the digital processing unit 18.

  Further, the other n−1 antenna elements 102 to 10 n are sequentially connected to the switching receiver 122 via the switch 11 that is electrically switched by a signal from the switching control unit 19. As a result, the signal connected to the switch 11 among ch2 to chn is sampled by the switching receiver 122, and then taken into the digital processing unit 18 from the switching receiver 122.

  Next, the switching timing of the switch 11 will be described.

  The switch 11 is connected to the antenna elements 102 to 10 n in a predetermined order by a switching signal from the switching control unit 19. Hereinafter, the time during which the switch 11 is connected to a certain antenna element and the signal from the antenna element is sampled is referred to as a sampling time. Here, when the time required for switching the switch 11 is not considered, the time interval for switching the switch 11 is equal to the sampling time.

  In the present embodiment, the sampling time is set to be longer than the time when characteristics such as the amplitude and phase of the beat signal to be sampled can be discriminated, and the switch 11 is always switched at a fixed sampling time. Here, it is desirable that the time during which the characteristics can be discriminated in this way is a signal of one cycle or more of the beat signal within the sampling time, as will be described later.

  However, even if a signal having a half cycle of the beat signal is acquired, or in some cases, the maximum amplitude and the phase change are found even in a shorter cycle, one cycle is obtained from the acquired signal even at such a time. Can be virtually restored.

  Therefore, the shortest sampling time may be about ½ period, and the switching control unit 19 may transmit the switching signal of the switch 11 intermittently at the time interval. In the present embodiment, as shown in FIG. 2 to be described later, the switch 11 is switched at a sampling time of two cycles of the beat signal.

  By setting the sampling time (switch switching time interval) to such a time, the switch speed can be significantly reduced as compared with the case where the beat signal is finely time-divided to obtain the signal of each channel. That is, the switch switching time interval can be greatly delayed. As a result, it is possible to reduce noise and errors such as harmonics caused by switching.

  By the way, when the signal of each channel is sampled by switching the switch 11 at a time interval of at least 1/2 cycle of the beat signal as described above, the time when each signal is acquired is different. The phase difference cannot be determined. Therefore, the acquired signal cannot be used for estimating the arrival direction of radio waves.

  Therefore, in this embodiment, a signal from a reference channel (antenna element) that continuously acquires signals without switching is used as a reference signal, and the phase relationship of each channel can be determined based on this reference signal. ing. Note that this reference channel is ch1 in this embodiment, and the signal from this ch1 is always connected to the reference receiver 121 without switching as described above, and is always used as a reference signal. It is sampled.

  In other words, in this embodiment, the reference receiver 121 for connecting the reference antenna element 101 (reference channel ch1) and the switched reception for connecting a plurality of antenna elements ch2 to chn that are sequentially switched by the switch 11. Machine 122 is required.

  Next, a method for discriminating the phase difference of signals sampled at different times by switching the switch 11 using the reference signal will be described with reference to FIGS.

  Here, FIG. 2 shows the relationship between the switching of the switch 11 and the sampled signal, where the horizontal direction indicates the passage of time and the vertical direction indicates each channel. Further, t1, t2, t3,..., Tn−1 indicate sampling times when switches are set for the antenna elements ch2 to chn, respectively.

  In this embodiment, the sampling time is fixed to the time of two cycles of the beat signal (frequency fb), and t1 = t2 = t3... = Tn-1 = 2 / fb. The channel notation of ch1 to chn corresponds to the antenna element of FIG. 1, and ch1 is a reference channel that is always sampled without being switched by the switch 11 as described above.

  A portion indicated by a thick line in the signal waveform shown in FIG. 2 is a portion that is sampled and stored (stored) in the memory of the digital processing unit 18, and the switch 11 is connected to the other dotted line signals. The part which is not sampled is shown.

  The part that is not sampled is a part that is virtually shown for the sake of explanation, and since the switch 11 is not actually connected, there is no signal as shown in the figure. In this embodiment, since the ch1 reception signal is always sampled as a reference signal, the ch1 signal is always represented by a thick line, and all portions of the signal are sampled.

  On the other hand, the other channels ch2 to chn are sampled in order as the switch 11 is switched. In the present embodiment, ch2 to chn are sampled in order, and ch2 to chn are in the order of sampling times t1, t2, t3. It is sampled at.

  Further, at the same time, two signals are sampled: the beat signal of ch1 and the beat signal of one of the channels ch2 to chn connected by the switch. That is, since ch2 to chn are sampled while being switched by the switch 11, the received signals of ch2 to chn cannot be measured at the same time. Therefore, the phase difference information of each channel is unknown from the data that has only been sampled.

  Therefore, in this embodiment, as described above, sampling is always performed using ch1 as a reference signal. Here, if each channel is sampled in a time range in which the received signal does not change, the signal of each channel shows the same waveform periodically, so the phase of the signal sampled at different times is adjusted to When combined, the same signal is obtained.

  Since the reference signal is always sampled, a signal sampled virtually at the same time can be obtained by adjusting the phase of the reference signal sampled at different times. Since each sampling of ch2 to chn is sampled at the same time as the reference signal, if the phases of the reference signal sampled at different times and the signal of each channel are arranged so that the phase of the reference signal is the same, The phase difference can be discriminated.

  Next, a method for organizing signal phases will be described.

  This signal rearrangement can be performed by digital processing in the digital processing unit 18. The signal sampled at each sampling time is stored in the memory of the digital processing unit 18 in time series as a set of channel reference signals and channel signals connected by switches.

  Referring to FIG. 2 as an example, at the sampling time t1, the ch1 signal as the reference signal and the ch2 signal connected to the switch 11 are stored as combined data. When data is stored in the digital processing unit 18, the signal is input to the switching control unit 19 and the switch 11 is switched, and the reference signal (ch1) and the ch3 signal are stored in combination at the next sampling time t3. . This operation is continued until the switching of all the channels ch2 to chn is completed.

  Next, the phase difference between the reference signals sampled at different sampling times is obtained. FIG. 3 is an enlarged view of data sampled at the sampling times t1 and t2 in FIG.

  As shown in FIG. 3, the phase shift of the reference signal at the sampling times t1 and t2 is φt1-t2. Since sampling is performed on the premise that the reference signal does not change during sampling of all channels ch2 to chn, the reference signal at the times t1 and t2 is the same signal.

  Therefore, if the phase of the reference signal of t2 is shifted by φt1-t2, it overlaps with the reference signal of t1, and can be made a signal virtually sampled at the same time. Similarly, by shifting the phase of the ch3 signal sampled at the sampling time t2 by φt1-t2, a signal sampled at the same time as the sampling time t1 can be obtained. In the operation of shifting the phase, it is preferable to shift the data array.

  As described above, the phase difference between the signals of ch1, ch2, and ch3 sampled at different times can be measured by an operation including the following steps.

(1) Step of switching and sampling each channel ch2 to chn with the switch 11, and storing the reference signal and the signal of each channel ch2 to chn together (2) Step of obtaining a phase difference between the reference signals of different sampling times (3) ) Step of correcting the sampled signal based on the phase difference of the reference signal In the following, for signals measured at other sampling times, the phase difference of the reference signal is obtained in the same manner, and the phase of the sampled signal simultaneously measured By shifting only the phase difference, a signal obtained by virtually sampling all channels at the same time can be obtained. FIG. 4 shows an example in which the phases of all sampling signals are gathered at the sampling time t1.

  When the sampling time is one cycle or more of the beat signal, the phase may be shifted by looping the leading and trailing ends of the signal within the sampling time based on the periodicity of the signal. In FIG. 4, by performing such processing, the signal after phase alignment is also continuous data within the sampling time. Even when the sampling time is one cycle or less, the same processing can be performed by virtually converting the sampled signal into a signal of one cycle. However, it is desirable to set a sampling time of one period or more from the viewpoint of accuracy and for the purpose of slowing down the switching speed of the switch.

  In the present embodiment, the ch1 signal as the reference signal is measured n-1 times during one round of switching of each channel of ch2 to chn, but the measurement result n-1 times by digital processing. May be averaged to obtain the final ch1 signal. Alternatively, a representative signal may be selected as the final ch1 signal.

  Further, according to the present invention, the phase difference of each channel can be accurately obtained even when the switch switching time as shown in FIG. 2 occurs. Ideally, the switch switching time is 0. For example, when the switch is switched every two cycles of ch1, the end of the sampling time before switch switching ends with the phase angle of ch1, and the sampling time after switch switching. The phase angle is also zero at the beginning.

  However, in actuality, it takes time to switch the switch. As shown in FIG. 2, there is a time during which the signal cannot be acquired when the switch is switched. When the switches are switched so that the signals are finely time-divided and the signals are sequentially sampled, the switch switching time is affected, and the phases between the channels cannot be compared.

  However, if ch1 is used as a reference signal as in the present invention and the phase is arranged by the digital processing unit 18 at the subsequent stage, information on the phase difference can be obtained without being affected by the switch switching time. Since the reference signal is always sampled, sampling is performed during the switch switching time, but the data at this time may be discarded.

  In FIG. 2, the switch switching interval is the time of two cycles of the beat signal. However, if a signal with a clear amplitude and phase can be acquired, it may be shortened to about a half cycle as described above. Conversely, sampling may be performed over a period of two cycles or more. Desirably, sampling should be performed with a sampling time of one cycle or more so that the shape of the signal can be sufficiently determined. However, if the time for sampling one channel is made too long, it takes a long time to acquire the signals of all the channels, and it becomes easy to be affected by the fluctuation of the signal, so it is set not to be too long.

  Further, in the present embodiment, a precondition is necessary that there is no change in the received signal while sampling is performed by switching all channels ch2 to chn. This is because if a change occurs in the received signal before the switching of all channels ch2 to chn is completed, the phase difference between the channels ch2 to chn cannot be obtained for the signal before and after the change of the received signal. It is.

  Therefore, it is not preferable that the sampling time is too long, and it is necessary to select a sampling time suitable for the measurement environment and measurement conditions. Specifically, it is necessary to set a switch switching time so that the signals can be acquired at least once for each of ch2 to chn within a time during which no significant change occurs in the received signal.

  The maximum value that can be set for the sampling time varies depending on the moving speed of the measurement target (radio wave transmission source) and the measurement environment (time change of the surrounding radio wave environment and the distance to the measurement target). For example, the radio wave arrival direction changes when the radio wave source moves greatly during the time from when the switch 11 is switched to all the channels ch2 to chn switched by the switch 11 until sampling is completed, and the received signal of each antenna element also changes. Change.

  For this reason, the time of (sampling time) × (number of antenna elements−1) needs to be sufficiently shorter than the time for the radio wave source to move. In addition, (the number of antenna elements-1) is a number obtained by subtracting the number of reference antenna elements for obtaining a reference signal from the number of antenna elements of the array antenna.

  However, as described above, since it is desirable that the sampling time has at least about one cycle, the sampling time in the present invention is about one cycle or more of the beat signal, (sampling time) × (number of antenna elements) -1) is set to be less than or equal to the time not affected by the measurement environment.

  In this way, based on the phase difference generated in the reference signal when sequentially sampled by the reference receiver 121, the phase difference of the signals from the other antenna elements input to the switching receiver 122 and sampled is corrected. To do. As a result, the switch switching time interval can be greatly delayed. As a result, the arrival direction can be estimated with high accuracy without using a high-speed switch. In addition, it is possible to provide an array antenna apparatus that can acquire signals from a plurality of antenna elements without requiring a high-speed switch while having a simple configuration.

  By the way, in this embodiment, the array antenna apparatus is configured by one reference receiver 121, one switching receiver 122, and one switch 11. However, for example, when there are a large number of antenna elements and it takes time to connect switches to connect all channels, it is affected by the environment as described above. The above switching receiver and switch may be used.

  FIG. 5 is a block diagram of an array antenna apparatus according to the second embodiment of the present invention in which the number of switches and receivers is increased. In FIG. 5, the same reference numerals as those in FIG. 1 denote the same or corresponding parts.

  In FIG. 5, 122 and 123 are first and second switching receivers 1210 and 111 that constitute a second receiving unit, and are first and second switches. In the present embodiment, ch2 to chm are connected to the first switch 110 and the first switching receiver 122, and chm + 1 to chn are connected to the second switch 111 and the second switching receiver 123.

  Thus, by using two (or two or more) switching receivers 122 and 123 and switches 110 and 111 in accordance with the number of antenna elements, the time for acquiring data of all channels can be shortened. Therefore, the influence of the environment can be reduced.

  In the present embodiment, a reference signal (ch1), ch2 to chm, and chm + 1 to chn are sampled and stored as a set at a certain sampling time t. Similarly to the first embodiment, the digital processing unit 18 obtains the signal of the array antenna by obtaining the phase difference of the reference signal and performing phase adjustment for the signals having different sampling times.

  By the way, the configuration in which the reference signal is fixed to ch1 and sampled has been described so far, but an antenna element that acquires the reference signal may be selected and used according to the reception state.

  Next, a third embodiment of the present invention will be described.

  FIG. 6 is a block diagram of the array antenna apparatus according to the present embodiment. In FIG. 6, the same reference numerals as those in FIG. 1 denote the same or corresponding parts.

  In the present embodiment, the switch 11 is also connected to the reference receiver 121 as shown in FIG. With this configuration, in this embodiment, first, the switch 11 is switched and connected to all the antenna elements 101 to 10n to acquire signals, and the reception state of each antenna element 101 to 10n is investigated. can do.

  As a method for investigating the reception state of each of the antenna elements 101 to 10n, for example, the signals after AD conversion are respectively compared, and the reception state is the best in consideration of reception strength, SN ratio, and signal stability. Identify the antenna element.

  As a result of such investigation, the antenna element with the best reception state is selected as the antenna element for the reference signal, and the switch 11 is switched and connected to the reference receiver 121. For example, when the reception states of all the antenna elements 101 to 10n are investigated and the reception state of the second antenna element (ch2) 102 is the best, the second antenna element 102 is set as the reference antenna element as shown in FIG. And connected to the reference receiver 121.

  Note that the switch 11 connected to the second antenna element 102 is fixed as it is. Accordingly, the reference receiver 121 sequentially acquires the reference signals from the second antenna element 102 and performs sampling. The remaining antenna elements are switched by the switch 11 and sampled by the switching receiver 122 as in the first embodiment.

  In the above description, the sampling time is fixed at a fixed time. However, the switch may be switched after the signal during the sampling time is evaluated. Signal evaluation may be performed by the digital processing unit 18 after sampling, or may be performed by analog processing before AD conversion.

  For example, there are cases where noise is generated in the received signal and the signal is not stable. In this case, the switch 11 is not switched until a stable signal is obtained in the digital processing unit 18 or an analog circuit for signal evaluation (not shown) provided between the second receiving unit 122 and the digital processing unit 18. Sampling is performed. When it is determined that a highly accurate signal is obtained, the digital processing unit 18 or the analog circuit for signal evaluation notifies the switching control unit 19 that the sampling is completed, and the switching control unit 19 switches the switch 11. Do.

  With such a configuration, when the waveform is disturbed due to the influence of sudden noise or the like, the switch 11 is not immediately switched and sampling can be continued. Can be reduced.

  In such a configuration, the length of the sampling time of each channel is different, but in the present invention, there is no particular problem even if the length of the sampling time of each channel is different. However, when the influence of noise is strong, if a signal of one channel is measured over a long period of time, it takes a long time to acquire signals of all the channels, and it is easily affected by environmental fluctuations.

  For this reason, when a maximum value is set for the time until switch switching and signal acquisition is performed up to the maximum value, even if a sufficient signal cannot be acquired, the switch is switched and signal acquisition for the next channel is started. It is desirable.

  In addition, the evaluation of the signal may be performed independently to determine whether the signal acquired at that time contains a lot of noise, or it differs greatly from the signal when the reference signal has been measured simultaneously with another channel. In this case, it may be determined that the signal is not stable. These evaluations need to be performed in real time for signal acquisition.

  By the way, the signals of the respective channels obtained at different times so far are arranged by the digital processing unit so that the phase difference can be calculated. However, the sampling start timing may be matched.

  Next, the fourth embodiment of the present invention will be described.

  FIG. 7 is a block configuration diagram of the array antenna apparatus according to the present embodiment. In the present embodiment, as shown in FIG. 7, the switch 11 is also notified from the switching control unit 19 to the AD conversion unit 17 of the reference receiver 121. The AD converter 17 of the reference receiver 121 starts AD conversion at a constant trigger timing such as an edge trigger at the same time.

  With this configuration, every time the switch 11 is switched, sampling of the reference signal is started at the same timing. Further, by notifying the AD converter 17 of the switching receiver 122 of the timing at which the AD converter 17 of the reference receiver 121 starts sampling as a trigger signal, the switching receiver 122 also has the same timing as the reference receiver 121. Sampling is started.

  FIG. 8 is a diagram showing a state of sampling according to the present embodiment. 8, t1, t2, t3,..., Tn-1 are sampling times for sampling the received signals of the antenna elements ch2 to chn, and ch1 is sampled as a reference signal.

  In the example of FIG. 8, every time the switch is switched, the rising edge of ch1 is used as a trigger timing, and sampling is performed with a sampling time of two periods of the beat signal. By using the rising edge of ch1 as a trigger, the phase of ch1 is the same in all sampling results. Therefore, even if the phase is not arranged in the digital processing unit, the values stored in the memory are compared as they are. Can be used for

  That is, simultaneously with the switching signal, the trigger signal is transmitted to the reference receiver 121, and sampling is started with a specific timing of the reference signal to be sampled as a trigger. Further, by starting the sampling of the switching receiver 122 using the sampling start of the reference receiver 121 as a trigger, the values sampled and stored in the memory can be directly compared with each other without arranging the phase in the digital processing unit. Can be used.

The block block diagram of the array antenna apparatus which concerns on the 1st Embodiment of this invention. The figure which shows the switching of the switch of the said array antenna apparatus, and the relationship of the sampled signal. The figure which expands and displays the signal acquired by sampling time t1 and t2 of FIG. 2, and demonstrates the phase difference of a reference signal. The figure which arranged the sampling result in FIG. 2 based on the phase of the reference signal. The block block diagram of the array antenna apparatus which concerns on the 2nd Embodiment of this invention. The block block diagram of the array antenna apparatus which concerns on the 3rd Embodiment of this invention. The block block diagram of the array antenna apparatus which concerns on the 4th Embodiment of this invention. The figure which shows the switch switching of the array antenna apparatus which concerns on the said 4th Embodiment, and the relationship of the sampled signal. It is the figure which put together the sampling result in FIG. 8 on the same axis | shaft. The block block diagram of the conventional array antenna apparatus. The block block diagram of the other conventional array antenna apparatus. The figure which shows the mode of the sampling of the other conventional array antenna apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Switch 13 Local transmitter 14 Amplifier 15 Filter 16 Mixer 17 AD conversion part 18 Digital processing part 19 Switching control part 101-10n Antenna element 110, 111 Switch 121 Reference receiver 122, 123 Switching receiver

Claims (7)

In an array antenna apparatus comprising an array antenna composed of a plurality of antenna elements, and estimating the arrival direction of radio waves from the phase difference of each signal from the plurality of antenna elements,
A predetermined reference antenna element of the plurality of antenna elements;
A first receiver for sequentially sampling a reference signal from the reference antenna element;
A second receiver for sampling signals from a plurality of antenna elements other than the reference antenna element among the plurality of antenna elements;
A switch provided between the other plurality of antenna elements and the second receiving unit, and sequentially inputting signals from the other plurality of antenna elements to the second receiving unit;
A switching control unit for controlling switching of the switch;
A digital processing unit for storing the signals of the plurality of antenna elements,
An array antenna apparatus characterized by that.   The digital processing unit is sequentially input to the second receiving unit by switching the switch by the switching control unit based on a phase difference generated in the reference signal when sequentially sampled by the first receiving unit. The array antenna apparatus according to claim 1, wherein a phase difference of signals from the plurality of other antenna elements sampled by the correction is corrected. Storing the reference signal and the signals of the plurality of other antenna elements each time the switch is switched, obtaining a phase difference between the reference signals generated at different sampling times due to the switch switching, and the storing Correcting the phase difference of the signals from the plurality of other antenna elements by correcting the phase of the signal of the second receiving unit being performed based on the phase difference between the reference signals,
The array antenna apparatus according to claim 2. Investigate all reception states of the plurality of antenna elements in advance, and set the antenna element with the best reception state as the reference antenna element.
The array antenna apparatus according to claim 1, wherein the array antenna apparatus is any one of claims 1 to 3. A determination means for determining characteristics of signals from the plurality of other antenna elements to be sampled;
The switching control unit transmits the switching signal to the switch at an interval longer than the time required for the characteristic determination of the sampling signal by the determination unit;
The array antenna apparatus according to claim 1, wherein the array antenna apparatus is any one of claims 1 to 4. Determining means for determining characteristics of signals from the plurality of other antenna elements to be sampled;
The sampling time per antenna element of the other plurality of antenna elements is variable, and the switching control unit transmits a switching signal to the switch at the time when the characteristic determination of the sampling signal by the determination unit is completed.
The array antenna apparatus according to claim 1, wherein the array antenna apparatus is any one of claims 1 to 4. At the same time as the switching signal, the switching control unit causes the first receiving unit to start sampling using a specific timing of the reference signal to be sampled as a trigger, and to start sampling of the first receiving unit as a trigger. Transmitting a trigger signal for starting sampling of the second receiving unit;
The array antenna apparatus according to claim 1, wherein the array antenna apparatus is any one of claims 1 to 4.

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