JP6718342B2 - Angle measuring device - Google Patents

Description

The present invention relates to an angle measuring device using a phase monopulse system.

In recent years, a small-sized digital TV tuner, which is called a USB dongle and is used by connecting to a USB host such as a personal computer, is available on the market at a low price. The price starts from 3,000 yen, but some of them are priced below 1,000 yen although they are overseas specifications.
The contents of these digital TV tuners are composed of an RF front end section called a tuner chip, a COFDM (coded orthogonal frequency-division multiplexing) demodulation section for demodulating a digital TV signal, and a USB interface.
The RF front end unit includes an RF amplifier, a phase locked loop (hereinafter abbreviated as “PLL”), and an intermediate frequency filter (hereinafter abbreviated as “IF filter”). Specific examples thereof include R820T manufactured by Rafael Micro of Taiwan and E4000 manufactured by Elonics of British Scotland.
The COFDM demodulation unit includes a quadrature modulation circuit, an A/D converter, and an FFT. The COFDM demodulator and the USB interface are integrated into one chip, and specifically, for example, RTL2832u manufactured by Realtek Co., Ltd. of Taiwan.
In particular, the RTL2832u extracts IQ data consisting of I data and Q data, which is output data obtained by A/D converting the I signal and Q signal obtained by quadrature modulation, directly from the USB interface. It has the ability to For this reason, the RTL2832u can easily realize the conversion of the digital TV tuner to the FM radio, the aviation radio receiver, or the like by devising the software on the personal computer side that is the USB host. In other words, it is possible to obtain software-defined radio (SDR) that was expensive until now at a low price.
Hereinafter, this digital TV tuner will be referred to as an SDR unit for convenience.

Patent Document 1 discloses a technical content for improving the detection accuracy of a target direction in a phase monopulse radar device.

JP 2013-217669 JP

The inventors have studied to realize a phase monopulse type angle measuring device by using this low-priced SDR unit.
FIG. 8 is a schematic diagram of an angle measuring device 801 according to the prior art that the inventors initially assumed.
FIG. 9 is a functional block diagram of the angle measuring device 801.

The angle measuring device 801 includes an array antenna 102, a first SDR unit 103, a second SDR unit 104, and a radio wave incident angle calculation unit 805.
In the angle measuring device 801 using the phase monopulse method, the array antenna 102 receives the reflected wave of the radio wave transmitted from the radar wave transmitter 106, which is reflected by the DUT 107. As an example, the radar wave transmitter 106 transmits a radar wave that is ASK-modulated (Amplitude-shift Keying) with the subcarrier frequency set to 1 MHz. The radio wave transmitted by the radar wave transmitter 106 has a predetermined data string ASK-modulated in frame units having a frame header pattern at the beginning. Therefore, in the radio wave transmitted by the radar wave transmitter 106, the frame header pattern is repeatedly modulated at predetermined time intervals.

The first antenna 102a and the second antenna 102b that form the array antenna 102 are fixed to a predetermined fixing member 102c, so that their relative positional relationship is fixed.
The first SDR unit 103 is connected to the first antenna 102a, and the second SDR unit 104 is connected to the second antenna 102b. A coaxial cable L108 is connected to the first SDR unit 103 and the second SDR unit 104 in order to synchronize the reference clock.
The IQ data output from the first SDR unit 103 and the second SDR unit 104 is sent to the radio wave incident angle calculation unit 805, which includes an arithmetic processing device such as a personal computer.

The radio wave incident angle calculation unit 805 uses data processing by software to determine the direction of the radio wave reflected by the DUT 107 based on the phase difference between the signals received from the first antenna 102a and the second antenna 102b forming the array antenna 102. Ask.
The phase difference φ between the first antenna 102a and the second antenna 102b is obtained by the following equation as the angle θ of the radio wave, the antenna distance d, and the wavelength λ of the carrier wave of the radio wave.
φ=2πd sin θ/λ (1)
That is, if the phase difference φ can be obtained from the received data, the angle θ of the radio wave, that is, the direction of the DUT 107 viewed from the array antenna 102 can be calculated backward from the above equation.

FIG. 10 is a block diagram showing the internal configuration of the first SDR unit 103 and the second SDR unit 104.
First, the internal configuration of the first SDR unit 103 will be described.
The RF amplifier 1001 amplifies the radio wave received from the first antenna 102a. The high frequency signal amplified by the RF amplifier 1001 is input to the first mixer 1002 and the second mixer 1003. A local oscillator signal having a frequency slightly lower than the frequency of the radio wave, which is output from the PLL 1004 which is a local oscillator, is input to the first mixer 1002. To the second mixer 1003, a signal generated by shifting the phase of the local oscillation signal by 90° by the 90° phase shifter 1005 is input.

The first mixer 1002 integrates the high-frequency signal from the RF amplifier 1001 and the local oscillator signal from the PLL 1004, and adds a signal having a frequency obtained by adding the frequency of the high-frequency signal and the frequency of the local oscillator signal and a signal having the subtracted frequency to the first low-pass filter ( Hereinafter, "LPF") 1006. Then, the first LPF 1006 outputs an electric signal received by the first antenna 102a, that is, an I signal obtained by subtracting the frequency of the local oscillation signal transmitted by the PLL 1004 from the frequency of the high frequency signal.
Similarly, the second mixer 1003 integrates the high frequency signal from the RF amplifier 1001 and the signal obtained by shifting the phase of the local oscillation signal by 90° by the 90° phase shifter 1005, and calculates the frequency of the high frequency signal and the local oscillation signal by 90°. A signal having a frequency obtained by adding the frequency of the phase-shifted signal and a signal obtained by subtracting the frequency of the phase-shifted signal are supplied to the second LPF 1007. Then, the second LPF 1007 outputs a Q signal obtained by subtracting the frequency of the signal obtained by phase-shifting the local oscillation signal by 90° from the frequency of the radio wave received by the first antenna 102a, that is, the frequency of the high frequency signal.
That is, the PLL 1004, the first mixer 1002, the 90° phase shifter 1005, the second mixer 1003, the first LPF 1006 and the second LPF 1007 form a well-known quadrature detection circuit (quadracha mixer).

The analog I signal is converted into digital I data by the first A/D converter 1008. Similarly, the analog Q signal is converted into digital Q data by the second A/D converter 1009. The I data and Q data are sent to the radio wave incident angle calculation unit 805 through the serial interface 1010. The serial interface 1010 is typically USB.

A clock derived from a reference clock oscillator 1011 composed of a crystal oscillator or the like is input to the PLL 1004, the first A/D converter 1008, the second A/D converter 1009, and the like.
On the other hand, the second SDR unit 104 also has the same configuration as the first SDR unit 103.
The coaxial cable L108 is connected to the reference clock oscillator 1011 of the first SDR unit 103 and the reference clock oscillator 1021 of the second SDR unit 104, thereby forcibly synchronizing the reference clocks with each other.

In the angle measuring device 801 using the phase monopulse method, the first SDR unit 103 and the second SDR unit 104, which are respectively connected to the first antenna 102a and the second antenna 102b that form the array antenna 102, have their reference clocks synchronized with each other. And the start timings of the operations must be exactly the same. For this purpose, the inventors connect the reference clock oscillator 1011 of the first SDR unit 103 and the reference clock oscillator 1021 of the second SDR unit 104 with the coaxial cable L108 to connect the first SDR unit 103 and the second SDR unit 104. On the other hand, forcible reference clock synchronization was realized.
However, in the SDR unit distributed in the market, the COFDM demodulation unit is packaged together with the USB interface as one IC in order to realize a low price. That is, even if the reference clocks of the first SDR unit 103 and the second SDR unit 104 can be synchronized, the operation of the internal functions of the ICs installed in the first SDR unit 103 and the second SDR unit 104, respectively. It is virtually impossible to match the timing perfectly. Therefore, in the prototype of the angle measuring device 801 shown in FIG. 8 to FIG. 10, when the angle measuring calculation process as the radio wave incident angle calculating unit 805 is executed on the personal computer, the first SDR unit 103 and the second SDR unit 104 are executed. In addition to the phase difference φ between the first antenna 102a and the second antenna 102b which is originally desired to be measured, the initial phase difference φ1 derived from the first SDR unit 103 and the second SDR unit 104 are derived from the signal obtained from The signal to which the initial phase difference φ2 is added is observed.

Further, IQ data transferred from the first SDR unit 103 and the second SDR unit 104 to the personal computer as the radio wave incident angle calculation unit 805 through the USB interface can be obtained completely at the same time because the USB is the serial interface 1010. is not. That is, the IQ data transferred from the first SDR unit 103 and the second SDR unit 104 to the radio wave incident angle calculation unit 805 through the serial interface 1010 is such that when one IQ data is transferred, the other IQ data is in a waiting state. Become. That is, when IQ data is transferred, a large time difference occurs.
Due to the above factors, the angle measuring device 801 using the SDR unit cannot be realized only by directly adopting the conventional technique.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problem and to provide an angle measuring device capable of removing an initial phase from IQ data obtained from mutual SDR units by using two low cost SDR units. ..

In order to solve the above problems, the angle measuring device of the present invention has a first antenna, a second antenna arranged at a position separated from the first antenna by a predetermined distance, and a carrier wave wavelength is λ. The first software receiver that receives a radio wave, frequency-converts the radio wave signal, and outputs first digitized IQ data, the first software receiver and the reference clock are synchronized, and the carrier wave wavelength is λ. And a second software receiver that receives the radio wave, converts the frequency of the radio wave signal, and outputs the second IQ data digitized. Furthermore, it is provided between the first antenna, the second antenna, the first software receiver, and the second software receiver, and in the first control state, the first antenna and the second antenna One of the antennas is connected to the first software receiver and the other is connected to the second software receiver, and in the second control state, the first antenna is opposite to the first control state. And a second antenna for connecting the first software receiver and the second software receiver to each other, a DPDT switch, a first frame buffer for storing the first IQ data, and a second IQ data. And a second frame buffer for storing. Further, a pattern detection unit that detects a pattern indicating a frame start position from the first frame buffer or the second frame buffer and outputs a switching signal for switching the control state to the DPDT switch, and stores the pattern detection unit in the first frame buffer. A frame synchronization detection unit that detects a time difference between the first IQ data that is stored and the second IQ data that is stored in the second frame buffer, and the second time based on the time difference obtained from the frame synchronization detection unit. For IQ data, a delay unit for adjusting the time difference, a first phase angle calculation unit for calculating the phase angle of the sample extracted from the first IQ data and outputting the first phase angle, and a second IQ data And a second phase angle calculator that calculates the phase angle of the sample to be extracted and outputs the second phase angle.
The phase difference calculation unit obtains the first phase angle and the second phase angle at the stage before switching the DPDT switch, obtains a first phase difference value obtained by subtracting the second phase angle from the first phase angle, and then obtains the DPDT switch. After obtaining the first phase angle and the second phase angle in the stage after switching, after obtaining the second phase difference value obtained by subtracting the second phase angle from the first phase angle, the second from the first phase difference value The phase difference value is subtracted to calculate the phase difference between the radio waves entering the first antenna and the second antenna.
It is equipped with.

According to the present invention, it is possible to provide an array antenna receiving apparatus capable of removing an initial phase from IQ data obtained from mutual SDR units by using two low cost SDR units.
Problems, configurations, and effects other than those described above will be clarified by the description of the embodiments below.

It is a schematic diagram showing the whole composition of the angle measuring device concerning the embodiment of the present invention. It is a functional block diagram of the angle measuring device concerning the embodiment of the present invention. It is a block diagram which shows the hardware constitutions of a radio wave incident angle calculation part. It is a block diagram which shows the software function of a radio wave incident angle calculation part. It is a block diagram showing the experimental equipment of the angle measuring device. It is a graph which shows the experimental result of experimental equipment. The vertical axis represents the physical phase difference, and the horizontal axis represents the estimated phase difference. It is a graph which shows the phase of the received data measured by the experimental equipment. It is a schematic diagram of the angle measuring device according to the prior art which the inventors initially assumed. It is a functional block diagram of an angle measuring device. It is a block diagram which shows the internal structure of the SDR unit which comprises an angle measuring device.

[Overall configuration of angle measuring device]
FIG. 1 is a schematic block diagram showing the overall configuration of an angle measuring device according to an embodiment of the present invention.
FIG. 2 is a functional block diagram of the angle measuring device according to the embodiment of the present invention.
The angle measuring device 101 includes an array antenna 102, a first SDR unit 103 (first software receiver), a second SDR unit 104 (second software receiver), a radio wave incident angle calculator 105, and a DPDT. It is composed of a switch (Double Pole Double Throw: double pole double throw) 109.

In the angle measuring device 101 using the phase monopulse method, the array antenna 102 receives the reflected wave of the radio wave transmitted from the radar wave transmitter 106, which is reflected by the DUT 107. The radar wave transmitter 106 transmits the ASK-modulated radar wave with the subcarrier frequency of 1 MHz, for example. The radio wave transmitted by the radar wave transmitter 106 has a predetermined data string ASK-modulated in frame units having a frame header pattern at the beginning. Therefore, in the radio wave transmitted by the radar wave transmitter 106, the frame header pattern is repeatedly modulated at predetermined time intervals.

The first antenna 102a and the second antenna 102b that form the array antenna 102 are fixed to a predetermined fixing member 102c, so that their relative positional relationship is fixed.
The first SDR unit 103 and the second SDR unit 104 are connected to the first antenna 102a and the second antenna 102b via the DPDT switch 109. A coaxial cable L108 is connected to the first SDR unit 103 and the second SDR unit 104 in order to synchronize the reference clock.

As described in FIG. 10, the first SDR unit 103 and the second SDR unit 104 include the PLL 1004 (local oscillator), the first mixer 1002, the 90° phase shifter 1005, the second mixer 1003, the first LPF 1006, and the first LPF 1006. Two LPF 1007 are included. And these constitute a well-known quadrature detection circuit (quadracha mixer). Then, the I signal output from the first LPF 1006 is converted into I data by the first A/D converter 1008, and the Q signal output from the second LPF 1007 is converted into Q data by the second A/D converter 1009. ..

The first IQ data output by the first SDR unit 103 and the second IQ data output by the second SDR unit 104 are sent to a radio wave incident angle calculation unit 105 including an arithmetic processing device such as a personal computer.
The difference between the angle measuring device 101 shown in FIG. 1 and the angle measuring device 801 shown in FIG. 8 in the prior art is that an electromagnetic wave is transmitted between the array antenna 102 and the first SDR unit 103 and the second SDR unit 104. That is, the DPDT switch 109 controlled by the incident angle calculation unit 105 is interposed.

As shown in FIG. 2, the DPDT switch 109 constitutes two changeover switches, and switches the connection of the first antenna 102a and the second antenna 102b between the first SDR unit 103 and the second SDR unit 104 to each other. A signal for controlling switching is output from the radio wave incident angle calculation unit 105.

[Radio wave incident angle calculation unit 105]
FIG. 3 is a block diagram showing the hardware configuration of the radio wave incident angle calculation unit 105.
A radio wave incident angle calculation unit 105 configured by a general personal computer or the like includes a CPU 301, a ROM 302, a RAM 303, a nonvolatile storage 304 such as a hard disk device or a flash memory, a display unit 305 such as a liquid crystal display, an operation unit such as a keyboard or a mouse. 306 is connected to the bus 307.
A serial port 308 such as a USB interface, which connects the first SDR unit 103 and the second SDR unit 104, is further connected to the bus 307. The non-volatile storage 304 stores a program for operating a personal computer or the like as the radio wave incident angle calculation unit 105.

FIG. 4 is a block diagram showing the software function of the radio wave incident angle calculation unit 105.
The first IQ data output by the first SDR unit 103 is stored in the first frame buffer 401 forming the ring buffer.
Similarly, the second IQ data output by the second SDR unit 104 is stored in the second frame buffer 402 forming the ring buffer.
The pattern detection unit 403 detects the frame header pattern included in the radio wave transmitted by the radar wave transmitter 106 from the first frame buffer 401 and the second frame buffer 402. When the pattern detection unit 403 detects a frame header pattern from both the first frame buffer 401 and the second frame buffer 402, it outputs a switching control signal to the DPDT switch 109.

The frame synchronization detection unit 404 corrects a shift on the time axis between the first IQ data stored in the first frame buffer 401 and the second IQ data stored in the second frame buffer 402. Output the time difference information for.
The first SDR unit 103, the second SDR unit 104, and the radio wave incident angle calculation unit 105 are connected by a serial interface. That is, the first IQ data and the second IQ data are not simultaneously transmitted to the radio wave incident angle calculation unit 105. One of them is always transmitted to the radio wave incident angle calculation unit 105 first, and the other is kept waiting during that time. This waiting time becomes a delay.

The first IQ data and the second IQ data do not include absolute time information or the like that is a clue to align the time axes. Therefore, in order to eliminate the delay caused by the data transfer in the serial interface, the frame synchronization detection unit 404 uses the first IQ data in the first frame buffer 401 and the second IQ data in the second frame buffer 402. Calculate the correlation with. The calculation of the correlation is, for example, multiplication. The stored mutual IQ data samples of the first frame buffer 401 and the second frame buffer 402 are repeatedly multiplied while shifting them on the time axis, and the values are viewed. If the mutual time axes of the first IQ data and the second IQ data match, the multiplication value becomes the maximum, so the frame synchronization detection unit 404 obtains the shifted sample number, that is, Information on the time difference is given to the delay unit 405.
When the pattern detection unit 403 acquires the address of the frame header pattern detected by the first frame buffer 401 and the second frame buffer 402, a rough time difference between the first frame buffer 401 and the second frame buffer 402 can be obtained. Therefore, it is possible to reduce the calculation processing for the frame synchronization detection in the frame synchronization detection unit 404.

The first phase angle calculation unit 406 calculates the phase angle for each sample for the first IQ data stored in the first frame buffer 401. The phase angle φ _n1 in the first IQ data is obtained as follows, where I ₁ is I data and Q ₁ is Q data in the first IQ data.
φ _n1 =tan ⁻¹ (Q ₁ /I ₁ ) (2)
Similarly, the second phase angle calculation unit 407 calculates the phase angle of the second IQ data stored in the second frame buffer 402 for each sample via the delay unit 405. The phase angle φ _n2 in the second IQ data is determined as follows, where I ₂ is I data and Q ₂ is Q data in the second IQ data.
φ _n2 =tan ⁻¹ (Q ₂ /I ₂ ) (3)

The phase difference calculation unit 408 detects that the pattern detection unit 403 has detected the frame header pattern from the first IQ data or the second IQ data and switched the DPDT switch 109 three times. Phase angle data is acquired from the calculation unit 406 and the second phase angle calculation unit 407.
Specifically, first, the phase difference calculation unit 408 causes the pattern detection unit 403 to switch the DPDT switch 109 from the first time to the second time by the first phase angle calculation unit 406 and the second phase. Phase angle data is acquired from each of the angle calculation units 407.
During the period from the first switching of the DPDT switch 109 to the second switching, the first phase angle data acquired from the first phase angle calculating unit 406 is set to φ _1, and the second phase angle calculating unit 407. The second phase angle data obtained from the above is set to φ ₂ .
The first phase angle data φ ₁ and the second phase angle data φ ₂ are the phase angle of the received radio wave φ _x , the phase difference derived from the first SDR unit 103 φ _o1 , and the phase difference derived from the second SDR unit 104. _Is φ _o2 and the phase difference between the first antenna 102a and the second antenna 102b is φ, the following relationships are established.
φ ₁ =φ _x +φ _o1 (4)
φ ₂ =φ _x +φ _o2 +φ (5)
φ ₂ −φ ₁ =φ _o2 +φ−φ _o1 (6)

Next, the phase difference calculation unit 408 switches the first phase angle calculation unit 406 and the second phase angle calculation unit 407 between the time when the pattern detection unit 403 switches the DPDT switch 109 the second time and the time when it switches the DPDT switch 109 the third time. To obtain the phase angle data respectively.
During the period from the second switching of the DPDT switch 109 to the third switching, the third phase angle data acquired from the first phase angle calculating unit 406 is set to φ _3, and the second phase angle calculating unit 407 is set. The fourth phase angle data acquired from is set to φ ₄ .
The third phase angle data φ ₃ and the fourth phase angle data φ ₄ are the phase angle of the received radio wave φ _y , the phase difference derived from the first SDR unit 103 φ _o1 , and the phase difference derived from the second SDR unit 104. _Is φ _o2 and the phase difference between the first antenna 102a and the second antenna 102b is φ, the following relationships are established.
φ ₃ =φ _y +φ _o1 +φ (7)
φ ₄ =φ _y +φ _o2 (8)
φ ₄ −φ ₃ =φ _o2 −φ _o1 −φ (9)
In the above equation, the phase difference φ between the first SDR unit 103 and the second SDR unit 104 is obtained by switching the DPDT switch 109 so that the third phase angle data φ obtained from the first SDR unit 103 is obtained. Included in ₃ .

Therefore, the phase difference φ between the first antenna 102a and the second antenna 102b can be easily derived by the following formula (10).
(Φ ₂ −φ ₁ )−(φ ₄ −φ ₃ )
=(φ _o2 +φ−φ _o1 )−(φ _o2 −φ _o1 −φ)=2φ (10)

That is, in order to realize an angle measuring device using two SDR units,
(A) The DPDT switch 109 is provided between the array antenna and the SDR unit,
In the radio wave incident angle calculation unit 105,
(B) a function (pattern detection unit 403) of switching the DPDT switch 109 when a frame header pattern is detected,
(C) After performing frame synchronization on the first IQ data stored in the first frame buffer 401 and the second IQ data stored in the second frame buffer 402 (frame synchronization detection unit 404) ,
(D) If the difference between the phase angles immediately before and immediately after switching the DPDT switch 109 is subtracted (phase difference calculation unit 408),
The phase difference φ derived from the incident angle of the radio wave can be obtained.

[Simulation experiment results]
FIG. 5 is a block diagram of experimental equipment 501 for verifying the angle measuring device according to the embodiment of the present invention.
In the experimental facility 501, instead of emitting an electric wave and receiving a reflected wave with an array antenna, all components are connected from an oscillator 502 by wire. The high frequency signal output from the oscillator 502 is frequency-divided by the frequency divider 503 and then supplied to the phase shifter 504.
The phase shifter 504 which imitates the phase difference of the array antenna delays the phase semi-fixedly at 0°, 30°, 60° and 90°.
The output signal of the frequency divider 503 and the output signal of the phase shifter 504 are supplied to the first SDR unit 103 and the second SDR unit 104 via the DPDT switch 109.
The software signal processing unit 505 does not switch the DPDT switch 109 during the simulation of the conventional technique, switches the DPDT switch 109 during the simulation of the embodiment of the present invention, and performs the arithmetic processing in the phase difference calculation unit 408 described above. I do.

FIG. 6 is a graph showing the estimation result in the experimental facility 501. The horizontal axis represents the phase difference physically set by the phase shifter 504, and the vertical axis represents the phase difference estimated by the software signal processing unit 505.
In FIG. 6, data within a range surrounded by an ellipse G601 is an estimation result using the DPDT switch 109. On the other hand, the data outside the range of the ellipse G601 is the estimation result without using the DPDT switch 109.
The estimation result without using the DPDT switch 109 shows a large variation, but all the estimation results using the DPDT switch 109 match the phase difference set by the phase shifter 504.

FIG. 7 is a graph showing the phase angle of IQ data output by the first SDR unit 103 and the second SDR unit 104, which is measured by the experimental facility 501 of FIG. The horizontal axis is the number of samples, that is, the time axis, and the vertical axis is the phase angle (radian).

Immediately before switching the DPDT switch 109 at time t1, the first IQ data (φ ₁ ) has the phase difference φ _o1 derived from the first SDR unit 103, and the second IQ data (φ ₂ ) has the phase difference φ _o1 . The phase difference φ _o2 derived from the second SDR unit 104 and the phase difference φ between the first antenna 102a and the second antenna 102b are respectively observed.

Immediately after the DPDT switch 109 is switched at the time t1, the first IQ data (φ ₃ ) includes the phase difference φ _o1 derived from the first SDR unit 103 and the position of the first antenna 102a and the second antenna 102b. Regarding the phase difference φ, the second IQ data (φ ₄ ) shows the phase difference φ _o2 derived from the second SDR unit 104, respectively.

That is, when the connection relationship between the first antenna 102a and the second antenna 102b and the first SDR unit 103 and the second SDR unit 104 is reversed in the DPDT switch 109, the position of the first antenna 102a and the second antenna 102b is changed. The phase difference moves from the first SDR unit 103 to the second SDR unit 104 and vice versa.

In the embodiment of the present invention, the angle measuring device using two inexpensive SDR units is disclosed.
A DPDT switch 109 is provided between the array antenna and the two SDR units that are clock-synchronized, and the DPDT switch 109 is connected to a radio wave incident angle calculation unit 105 composed of an electronic computer. The radio wave incident angle calculation unit 105 switches the DPDT switch 109 when detecting the frame header pattern included in the received radio wave. Then, after performing frame synchronization on the first IQ data stored in the first frame buffer 401 and the second IQ data stored in the second frame buffer 402, immediately before switching the DPDT switch 109. By subtracting the difference in the phase angles immediately after, the phase difference φ derived from the incident angle of the radio wave is obtained.
By adding an inexpensive DPDT switch 109 to the angle measuring device, which required expensive parts and complicated design up to now, and performing arithmetic processing while controlling the DPDT switch 109 by software, a significant cost reduction is achieved. realizable.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and includes other modifications without departing from the gist of the present invention described in the claims.
For example, the above-described embodiment is a detailed and specific description of the configuration of the device and the system in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to one having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and further, the configuration of one embodiment can be added to the configuration of another embodiment. Further, a part of the configuration of the embodiment can be added/deleted/replaced with another configuration.

Further, the above-described respective configurations, functions, processing units, and the like may be realized by hardware by partially or entirely designing them with an integrated circuit, for example. Further, the above-described respective configurations, functions and the like may be realized by software for the processor to interpret and execute programs for realizing the respective functions. Information such as programs, tables, and files that realize each function should be retained in a volatile or non-volatile storage such as a memory, a hard disk, an SSD (Solid State Drive), or a recording medium such as an IC card or an optical disk. You can
In addition, the control lines and information lines shown are those that are considered to be necessary for explanation, and not all the control lines and information lines on the product are necessarily shown. In practice, it may be considered that almost all configurations are connected to each other.

101... Angle measuring device, 102... Array antenna, 102a... First antenna, 102b... Second antenna, 102c... Fixing member, 103... First SDR unit, 104... Second SDR unit, 105... Radio wave incident angle calculation unit, 106... Radar wave transmitter, 107... DUT, 109... DPDT switch, 301... CPU, 302... ROM, 303... RAM, 304... Nonvolatile storage, 305... Display section, 306... Operation section, 307... Bus, 308... Serial port, 401... First frame buffer, 402... Second frame buffer, 403... Pattern detecting section, 404... Frame synchronization detecting section, 405... Delay section, 406... First phase angle calculating section, 407... Second Phase angle calculation unit, 408... Phase difference calculation unit, 501... Experimental equipment, 502... Oscillator, 503... Divider, 504... Phase shifter, 505... Software signal processing unit, 801,... Angle measuring device, 805... Radio wave incidence Angle calculator, 1001... RF amplifier, 1002... First mixer, 1003... Second mixer, 1004... PLL, 1005... Phase shifter, 1006... First LPF, 1007... Second LPF, 1008... First A/D Converter, 1009... Second A/D converter, 1010... Serial interface, 1011... Reference clock oscillator, 1021... Reference clock oscillator, L108... Coaxial cable

Claims (2)

The first antenna,
A second antenna arranged at a position separated from the first antenna by a predetermined distance,
A first software receiver for receiving a radio wave having a carrier wave wavelength of λ, frequency-converting the radio wave signal, and outputting first digitized IQ data;
A second clock that is synchronized with the first software receiver and has a reference clock, receives a radio wave having a carrier wavelength of λ, converts the frequency of the radio wave signal, and outputs second digitized IQ data. Software receiver,
Provided between the first antenna, the second antenna, the first software receiver, and the second software receiver, in the first control state, the first antenna and One of the second antenna is connected to the first software receiver and the other is connected to the second software receiver, and in the second control state, the first control state is Conversely, a DPDT switch that connects the first antenna and the second antenna to the first software receiver and the second software receiver;
A first frame buffer for storing the first IQ data;
A second frame buffer for storing the second IQ data;
A pattern detection unit that detects a pattern indicating a start position of a frame from the first frame buffer or the second frame buffer and outputs a switching signal for switching a control state to the DPDT switch;
A frame synchronization detector that detects a time difference between the first IQ data stored in the first frame buffer and the second IQ data stored in the second frame buffer;
A delay unit that adjusts a time difference with respect to the second IQ data based on the time difference obtained from the frame synchronization detection unit;
A first phase angle calculator that calculates the phase angle of the sample extracted from the first IQ data and outputs the first phase angle;
A second phase angle calculator that calculates the phase angle of the sample extracted from the second IQ data and outputs the second phase angle;
The first phase angle and the second phase angle at the stage before switching the DPDT switch are obtained, the first phase difference value obtained by subtracting the second phase angle from the first phase angle is obtained, and the DPDT switch is switched. After obtaining the first phase angle and the second phase angle in the subsequent stage, after obtaining the second phase difference value obtained by subtracting the second phase angle from the first phase angle, the first phase difference value from the An angle measuring device comprising: a phase difference calculation unit that subtracts a second phase difference value to calculate a phase difference between the radio waves entering the first antenna and the second antenna. The first software receiver,
A PLL that outputs a local oscillation signal using a reference clock derived from the reference clock;
A 90° phase shifter for giving a phase difference of 90° to the local oscillation signal and outputting a phase shift local oscillation signal;
A first mixer for multiplying an input radio wave signal by the local oscillation signal and outputting an I signal;
A second mixer for multiplying an input radio wave signal by the phase shift local oscillation signal and outputting a Q signal;
A first A/D converter for A/D converting the I signal;
A second A/D converter for A/D converting the Q signal,
The first IQ data is output data of the first A/D converter and the second A/D converter,
The angle measuring device according to claim 1.

Images