JP2018044872A - Angle measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an angle measuring device capable of removing an initial phase from IQ data obtained from SDR units by using the two low-cost SDR units.SOLUTION: A DPDT switch is provided between an array antenna and two SDR units to which clock synchronization is applied. A radio wave incident angle calculation unit switches the state of the DPDT switch if it detects a frame header pattern included in a received radio wave. Then, it applies frame synchronization to first IQ data and second IQ data, subtracts the difference between phase angles right before and right after the state of the DPDT switch is switched from the phase angles, and thereby finds phase difference φ derived from an incident angle of the radio wave.SELECTED DRAWING: Figure 1

Description

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

In recent years, small digital TV tuners connected to a USB host such as a personal computer in a form called a USB dongle have been distributed on the market at a low price. The price starts at 3,000 yen, and some of them are overseas specifications, but some are priced below 1,000 yen.
The contents of these digital TV tuners include an RF front-end unit called a tuner chip, a coded orthogonal frequency-division multiplexing (COFDM) demodulating unit that demodulates a digital TV signal, and a USB interface.
The RF front end includes an RF amplifier, a phase locked loop (hereinafter abbreviated as “PLL”), and an intermediate frequency filter (hereinafter abbreviated as “IF filter”). Specific examples include R820T from Rafael Micro of Taiwan and E4000 from Elonics of British Scotland.
The COFDM demodulation unit includes an orthogonal modulation circuit, an A / D converter, and an FFT. The COFDM demodulator and the USB interface are made into one chip, specifically, for example, RTL2832u of Taiwan Realtek.
In particular, the RTL2832u directly extracts IQ data composed of I data and Q data, which is output data obtained by performing A / D conversion on the I signal and Q signal obtained by quadrature modulation with an A / D converter, from the USB interface. It has a function that can. For this reason, the RTL2832u can easily convert the digital TV tuner to an FM radio, an aerial radio receiver, or the like by devising software on the personal computer side which is a USB host. In other words, software defined radio (SDR), which was expensive before, can be obtained at a low price.
Hereinafter, this digital TV tuner is referred to as an SDR unit for convenience.

  Japanese Patent Application Laid-Open No. 2004-151561 discloses technical contents for improving the detection accuracy of a target orientation in a phase monopulse radar apparatus.

JP 2013-217669 A

The inventors studied to realize a phase monopulse type angle measuring device using this low-cost SDR unit.
FIG. 8 is a schematic diagram of an angle measuring device 801 according to the prior art, which was originally assumed by the inventors.
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 reflected by the DUT 107 from the radio wave transmitted from the radar wave transmitter 106. For example, the radar wave transmitter 106 transmits a radar wave that has been ASK modulated (Amplitude-shift Keying) with the subcarrier frequency set to 1 MHz. In the radio wave transmitted by the radar wave transmitter 106, a predetermined data string is ASK-modulated for each frame having a frame header pattern at the head. Therefore, the radio wave transmitted by the radar wave transmitter 106 is modulated by repeating the frame header pattern at predetermined time intervals.

The first antenna 102a and the second antenna 102b constituting the array antenna 102 are fixed to a predetermined fixing member 102c, so that their relative positional relationship is fixed.
A first SDR unit 103 is connected to the first antenna 102a, and a second SDR unit 104 is connected to the second antenna 102b. The first SDR unit 103 and the second SDR unit 104 are connected to a coaxial cable L108 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 a radio wave incident angle calculation unit 805 that includes an arithmetic processing unit such as a personal computer.

The radio wave incident angle calculation unit 805 obtains the direction of the radio wave reflected by the DUT 107 by the data processing by software based on the phase difference between the signals received from the first antenna 102a and the second antenna 102b constituting 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 radio wave angle θ, the antenna interval d, and the radio wave carrier wavelength λ.
φ = 2πdsin 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. The first mixer 1002 receives a local oscillation signal having a frequency slightly lower than the frequency of the radio wave output from the PLL 1004 which is a local oscillator. The second mixer 1003 is inputted with a signal whose local signal is shifted by 90 ° by a 90 ° phase shifter 1005.

The first mixer 1002 integrates the high-frequency signal from the RF amplifier 1001 and the local oscillation signal from the PLL 1004, and adds a frequency obtained by adding and subtracting the frequency of the high-frequency signal and the local oscillation frequency to the first low-pass filter ( (Hereinafter “LPF”) 1006. The first LPF 1006 outputs an I signal obtained by subtracting the frequency of the radio wave received by the first antenna 102a, that is, the frequency of the local 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 generated by shifting the phase of the local oscillation signal by 90 ° by the 90 ° phase shifter 1005 so that the frequency of the high-frequency signal and the local oscillation signal are 90. A signal obtained by adding and subtracting the frequency of the phase-shifted signal is supplied to the second LPF 1007. Then, the second LPF 1007 outputs a radio wave received by the first antenna 102a, that is, a Q signal obtained by subtracting the frequency of a signal obtained by shifting the local oscillation signal by 90 ° from 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 constitute a well-known quadrature detection circuit (quadrature 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 a USB.

The PLL 1004, the first A / D converter 1008, the second A / D converter 1009, and the like receive a clock derived from the reference clock oscillator 1011 configured with a crystal oscillator or the like.
On the other hand, the second SDR unit 104 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 system, the first SDR unit 103 and the second SDR unit 104 connected to the first antenna 102a and the second antenna 102b constituting the array antenna 102 are synchronized with each other in the reference clock. And the start timing of the operation must be completely coincident. 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 a coaxial cable L108, and connect the first SDR unit 103 and the second SDR unit 104 to each other. On the other hand, forced reference clock synchronization was realized.
However, in the SDR unit on the market, the COFDM demodulation unit is packaged as a single IC together with the USB interface 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 provided in the first SDR unit 103 and the second SDR unit 104, respectively. It is virtually impossible to match the timing perfectly. Therefore, when the angle measurement processing as the radio wave incident angle calculation unit 805 is executed on the personal computer with the prototype of the angle measuring device 801 shown in FIGS. 8 to 10, the first SDR unit 103 and the second SDR unit 104. In addition to the phase difference φ between the first antenna 102a and the second antenna 102b to be originally measured, the signal obtained from the initial phase difference φ1 derived from the first SDR unit 103 and the signal derived from the second SDR unit 104 A signal to which the initial phase difference φ2 is added is observed.

Furthermore, 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 simultaneously 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 in a waiting state when one IQ data is transferred. Become. That is, a large time difference occurs when IQ data is transferred.
Due to the above factors, the angle measuring device 801 using the SDR unit cannot be realized simply by adopting the prior art as it is.

  An object of the present invention is to solve such a problem and to provide an angle measuring device capable of removing an initial phase from IQ data obtained from each SDR unit by using two low-cost SDR units. .

In order to solve the above problems, the angle measuring device of the present invention includes a first antenna, a second antenna disposed at a predetermined distance from the first antenna, and a carrier wavelength of λ. The first software receiver that receives the radio wave, converts the frequency of the radio wave signal and outputs the digitized first IQ data, the first software receiver and the reference clock are synchronized, and the carrier wavelength is λ And a second software receiver that outputs a second IQ data obtained by frequency-converting and digitizing the radio signal. Further, 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. In the second control state, the first antenna is opposite to the first control state. And a second antenna are connected to the first software receiver and the second software receiver, 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. Furthermore, a pattern detection unit that detects a pattern indicating the start position of the frame 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 for detecting a time difference between the first IQ data and the second IQ data stored in the second frame buffer, and based on the time difference obtained from the frame synchronization detection unit, A delay unit that adjusts a time difference with respect to IQ data, a first phase angle calculation unit that calculates a phase angle of a sample extracted from the first IQ data and outputs a first phase angle, and a second IQ data A second phase angle calculation unit that calculates a phase angle of the sample to be extracted and outputs a second phase angle.
The phase difference calculation unit obtains a first phase angle and a second phase angle in a 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 the DPDT switch After obtaining the first phase angle and the second phase angle at the stage after switching, obtaining the second phase difference value obtained by subtracting the second phase angle from the first phase angle, By subtracting the phase difference value, the phase difference between the radio waves entering the first antenna and the second antenna is calculated.
It comprises.

According to the present invention, it is possible to provide an array antenna receiving apparatus that can remove an initial phase from IQ data obtained from a mutual SDR unit using two low-cost SDR units.
Problems, configurations, and effects other than those described above will become apparent from the description of the embodiments described below.

It is the schematic which shows the whole structure of the angle measuring apparatus which concerns on embodiment of this invention. It is a functional block diagram of the angle measuring device which concerns on embodiment of this 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 which shows the experimental installation of an angle measuring device. It is a graph which shows the experimental result of an experimental installation. 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 with the experiment equipment. It is the schematic of the angle measuring device according to a prior art which the inventors assumed initially. 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 the angle measuring device according to the 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 calculation unit 105, a DPDT. It consists of a switch (Double Pole Double Throw) 109.

  In the angle measuring device 101 using the phase monopulse method, a radio wave transmitted from the radar wave transmitter 106 is received by the array antenna 102 as a reflected wave reflected by the DUT 107. As an example, the radar wave transmitter 106 transmits an ASK-modulated radar wave with a subcarrier frequency of 1 MHz. In the radio wave transmitted by the radar wave transmitter 106, a predetermined data string is ASK-modulated for each frame having a frame header pattern at the head. Therefore, the radio wave transmitted by the radar wave transmitter 106 is modulated by repeating the frame header pattern at predetermined time intervals.

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

  As described with reference to FIG. 10, the first SDR unit 103 and the second SDR unit 104 include a PLL 1004 (local oscillator), a first mixer 1002, a 90 ° phase shifter 1005, a second mixer 1003, a first LPF 1006, and a first LPF 1006. Two LPFs 1007 are included. These constitute a known quadrature detection circuit (quadrature mixer). 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 from the first SDR unit 103 and the second IQ data output from the second SDR unit 104 are sent to a radio wave incident angle calculation unit 105 made up of an arithmetic processing unit such as a personal computer.
The angle measuring device 101 shown in FIG. 1 is different from the angle measuring device 801 shown in FIG. 8 in the prior art in that there is a radio wave between the array antenna 102, the first SDR unit 103, and the second SDR unit 104. 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 change-over switches and switches the connection between the first SDR unit 103 and the second SDR unit 104 of the first antenna 102a and the second antenna 102b to each other. A signal for controlling the 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 illustrating a 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, and an operation unit such as a keyboard and a mouse. 306 is connected to the bus 307.
Further, a serial port 308 such as a USB interface to which the first SDR unit 103 and the second SDR unit 104 are connected is connected to the bus 307. The nonvolatile 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 illustrating software functions of the radio wave incident angle calculation unit 105.
The first IQ data output from the first SDR unit 103 is stored in the first frame buffer 401 constituting the ring buffer.
Similarly, the second IQ data output from the second SDR unit 104 is stored in the second frame buffer 402 constituting 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, the pattern detection unit 403 outputs a switching control signal to the DPDT switch 109.

The frame synchronization detection unit 404 corrects a deviation 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 time difference information.
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 transmitted to the radio wave incident angle calculation unit 105 at the same time. Either one is always transmitted to the radio wave incident angle calculation unit 105 first, and the other is kept waiting. This waiting time becomes a delay.

The first IQ data and the second IQ data do not include absolute time information or the like as a clue to align the time axis. Therefore, in order to eliminate the delay caused by the data transfer in the serial interface, the frame synchronization detection unit 404 includes 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 correlation calculation is, for example, multiplication. The multiplication is repeated while shifting the stored IQ data samples of the first frame buffer 401 and the second frame buffer 402 on the time axis, and the values are observed. If the time axes of the first IQ data and the second IQ data match each other, the multiplication value is maximized. Therefore, the frame synchronization detection unit 404 obtains the shifted sample number obtained at that time, 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 arithmetic processing for 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, with I data of the first IQ data being I ₁ and Q data being Q ₁ .
φ _n1 = tan ⁻¹ (Q ₁ / I ₁ ) (2)
Similarly, the second phase angle calculator 407 calculates the phase angle for each sample via the delay unit 405 for the second IQ data stored in the second frame buffer 402. The phase angle φ _n2 in the second IQ data is obtained as follows, where I data of the second IQ data is I ₂ and Q data is Q ₂ .
φ _n2 = tan ⁻¹ (Q ₂ / I ₂ ) (3)

In response to the pattern detector 403 detecting the frame header pattern from the first IQ data or the second IQ data and switching the DPDT switch 109 three times, the phase difference calculator 408 detects the first phase angle. 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 and the first phase angle calculation unit 406 and the second phase angle between the time when the pattern detection unit 403 switches the DPDT switch 109 for the first time to the second time. Phase angle data is acquired from each of the angle calculation units 407.
The first phase angle data acquired from the first phase angle calculation unit 406 is set to φ ₁ between the time when the DPDT switch 109 is switched for the first time and the second time, and the second phase angle calculation unit 407 is used. the second phase angle data obtained from the phi _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 is φ _x , the phase difference derived from the first SDR unit 103 is φ _o1 , and the phase difference derived from the second SDR unit 104 is _Is φ _o2 , and the phase difference between the first antenna 102 a and the second antenna 102 b is φ, and the following relationship is 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 includes a first phase angle calculation unit 406 and a second phase angle calculation unit 407 between the time when the pattern detection unit 403 switches the DPDT switch 109 for the second time to the third time. Respectively, phase angle data is acquired.
This, until switching to third from the time of switching the DPDT switch 109 a second time, a third phase angle data obtained from the first phase angle calculating section 406 and phi _3, the second phase angle calculating section 407 Let the fourth phase angle data acquired from ( ₄₎ be φ4.
The third phase angle data φ ₃ and the fourth phase angle data φ ₄ include the phase angle of the received radio wave as φ _y , the phase difference derived from the first SDR unit 103 as φ _o1 , and the phase difference derived from the second SDR unit 104. _Is φ _o2 , and the phase difference between the first antenna 102 a and the second antenna 102 b is φ, and the following relationship is 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)
Note that the above equation shows that the phase difference φ between the first SDR unit 103 and the second SDR unit 104 becomes the third phase angle data φ obtained from the first SDR unit 103 by switching the DPDT switch 109. ₃ included.

Therefore, the phase difference φ between the first antenna 102a and the second antenna 102b can be easily derived by the following equation (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) A 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) for 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) By subtracting the difference between the phase angles immediately before and after the DPDT switch 109 is switched (phase difference calculation unit 408),
A phase difference φ derived from the incident angle of the radio wave can be obtained.

[Results of simulation experiment]
FIG. 5 is a block diagram of the experimental facility 501 for verifying the angle measuring device according to the embodiment of the present invention.
In the experimental facility 501, instead of emitting radio waves and receiving reflected waves with an array antenna, all components are connected from an oscillator 502 by wire. The high frequency signal output from the oscillator 502 is divided by the frequency divider 503 and then supplied to the phase shifter 504.
The phase shifter 504 that mimics the phase difference of the array antenna delays the phase semi-fixedly to 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 in the simulation of the prior art, and switches the DPDT switch 109 in the simulation of the embodiment of the present invention, so that the arithmetic processing in the phase difference calculation unit 408 is performed. I do.

FIG. 6 is a graph showing an 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 the range enclosed by the ellipse G601 is an estimation result using the DPDT switch 109. On the other hand, data outside the range of the ellipse G601 is an estimation result without using the DPDT switch 109.
Although the estimation result without using the DPDT switch 109 shows a large variation, all the estimation results using the DPDT switch 109 agree with the phase difference set by the phase shifter 504.

  FIG. 7 is a graph showing the phase angle of IQ data output from the first SDR unit 103 and the second SDR unit 104, 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 ) includes the phase difference φ _o1 derived from the first SDR unit 103, and the second IQ data (φ ₂ ) includes the second A phase difference φ _o2 derived from the two SDR units 104 and a phase difference φ between the first antenna 102a and the second antenna 102b are observed.

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

  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 by the DPDT switch 109, the positions of the first antenna 102a and the second antenna 102b are changed. The phase difference moves from the first SDR unit 103 to the second SDR unit 104 or vice versa.

In the embodiment of the present invention, an angle measuring device using two inexpensive SDR units has been disclosed.
A DPDT switch 109 is provided between the array antenna and two SDR units that are clock-synchronized, and a radio wave incident angle calculation unit 105 made of an electronic computer is connected to the DPDT switch 109. 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. The first IQ data stored in the first frame buffer 401 and the second IQ data stored in the second frame buffer 402 are subjected to frame synchronization and immediately before switching the DPDT switch 109. By subtracting the phase angle differences immediately after, the phase difference φ derived from the incident angle of the radio wave is obtained.
By using an angle measuring device that previously required expensive parts and complicated design, an inexpensive DPDT switch 109 is added, and calculation processing is performed while controlling the DPDT switch 109 with software, thereby significantly reducing the price. realizable.

As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, Other modifications are included unless it deviates from the summary of this invention described in the claim.
For example, the above-described embodiment is a detailed and specific description of the configuration of the apparatus 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 the configuration of another embodiment can be added to the configuration of one embodiment. In addition, a part of the configuration of the embodiment can be added to, deleted from, or replaced with another configuration.

Each of the above-described configurations, functions, processing units, and the like may be realized by hardware by designing a part or all of them with, for example, an integrated circuit. Further, each of the above-described configurations, functions, and the like may be realized by software for interpreting and executing a program that realizes each function by the processor. Information such as programs, tables, and files that realize each function must be held in a volatile or non-volatile storage such as a memory, hard disk, or SSD (Solid State Drive), or a recording medium such as an IC card or an optical disk. Can do.
In addition, the control lines and information lines are those that are considered necessary for the explanation, and not all the control lines and information lines on the product are necessarily shown. Actually, it may be considered that almost all the components are connected to each other.

  DESCRIPTION OF SYMBOLS 101 ... Angle measuring device, 102 ... Array antenna, 102a ... 1st antenna, 102b ... 2nd antenna, 102c ... Fixed member, 103 ... 1st SDR unit, 104 ... 2nd SDR unit, 105 ... Radio wave incident angle calculation part, DESCRIPTION OF SYMBOLS 106 ... Radar wave transmitter, 107 ... DUT, 109 ... DPDT switch, 301 ... CPU, 302 ... ROM, 303 ... RAM, 304 ... Nonvolatile storage, 305 ... Display part, 306 ... Operation part, 307 ... Bus, 308 ... Serial port 401 ... First frame buffer 402 ... Second frame buffer 403 ... Pattern detection unit 404 ... Frame synchronization detection unit 405 ... Delay unit 406 ... First phase angle calculation unit 407 ... Second Phase angle calculation unit, 408 ... phase difference calculation unit, 501 ... experimental equipment, 502 ... oscillator, 503 ... frequency divider, 504 ... Phaser 505 ... Software signal processing unit 801 ... Angle measuring device 805 ... Radio wave incident angle calculation unit 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 disposed at a position away from the first antenna by a predetermined distance;
A first software receiver that receives a radio wave having a carrier wavelength of λ, outputs a first IQ data obtained by frequency-converting and digitizing the radio wave signal;
The first software receiver and the reference clock are synchronized, receive a radio wave having a carrier wavelength of λ, and output a second IQ data obtained by frequency-converting and digitizing the radio signal. A software receiver;
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 One of the second antennas is connected to the first software receiver and the other is connected to the second software receiver. 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 for detecting a pattern indicating a start position of a frame from the first frame buffer or the second frame buffer and outputting a switching signal for switching a control state to the DPDT switch;
A frame synchronization detector for detecting 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 for adjusting the 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 a phase angle of a sample extracted from the first IQ data and outputs a first phase angle;
A second phase angle calculator that calculates a phase angle of a sample extracted from the second IQ data and outputs a second phase angle;
The first phase angle and the second phase angle in 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 a first phase angle and a second phase angle in a later stage and obtaining a second phase difference value obtained by subtracting the second phase angle from the first phase angle, the first phase difference value An angle measuring device, comprising: a phase difference calculation unit that subtracts a second phase difference value to calculate a phase difference of the radio wave that has entered the first antenna and the second antenna. The first software receiver and the second software receiver have the same function,
The first software receiver is:
A local oscillator that outputs a local oscillation signal using a reference clock derived from the reference clock;
A 90 ° phase shifter that gives a phase difference of 90 ° to the local oscillation signal and outputs a phase shift local oscillation signal;
A first mixer that multiplies an input radio wave signal by the local oscillation signal and outputs an I signal;
A second mixer that multiplies the input radio wave signal and the phase-shifted local oscillation signal to output 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.

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