CN111103583A - Three-dimensional radio frequency imaging system and method with real-time calibration - Google Patents
Three-dimensional radio frequency imaging system and method with real-time calibration Download PDFInfo
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- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
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Abstract
The invention discloses a three-dimensional radio frequency imaging system with real-time calibration, which comprises a plurality of MIMO radio frequency imaging transceiving array pairs. One transceiving array pair has two opposite transceiving arrays, and the receiving array in each transceiving array is provided with a reference signal by a transmitting source in the other opposite transceiving array to complete phase alignment between array units. When the radio frequency imaging system works, the phase of an irradiation signal is taken out to be used as a reference to realize real-time phase calibration by utilizing the gap of a target when the target moves according to the difference of irradiation and reflection amplitudes when the target receives, so that the imaging precision of the radio frequency imaging system is improved, and the bandwidth of the use frequency is reduced.
Description
Technical Field
The invention relates to application of a radio frequency phased array or a Multiple Input Multiple Output (MIMO) array, such as a radio frequency imaging technology, and mainly focuses on millimeter wave anti-terrorism human body security inspection imaging. The radar system can also be regarded as an imaging system, so that the invention has application in radar detection systems as well. Other applications of radio frequency imaging can be robot vision imaging systems in any application occasions requiring array receiving and transmitting, satellite microwave/millimeter wave remote sensing imaging and the like.
Here, the radio frequency means a radio frequency including ultra high frequency/microwave/millimeter wave/terahertz.
Background
The complete analog radio frequency phased array can only form a single beam, so that the receiver has low speed on searching and scanning, low signal-to-noise ratio and short detection distance. The analog radio frequency phased array single-beam technology is used for two-dimensional imaging, and has the defects of low sensitivity, long imaging time and the like.
The digital multi-beam radio frequency phased array receiver overcomes the limitation of an analog radio frequency phased array, can simultaneously generate two-dimensional signals, and is a theoretically ideal phased array receiving system. However, in practical situations, the implementation can be only performed in a narrow-band system, because in the case of a wide band, a high-speed analog-to-digital converter (ADC) satisfying the nyquist sampling theorem is required, and it is difficult to achieve a small size and low power consumption, and thus it is difficult to install the ADC in a narrow space together with a receiving channel in a radio frequency phased array receiver. In addition, since no spatial filtering is performed before the ADC, a larger dynamic range and a larger number of quantization levels are required in order not to be affected by an interference signal, thereby greatly increasing the requirements for ADC design. A larger dynamic range of the ADC and a larger number of quantization levels means a larger power consumption. The large power consumption brings larger current pulses, causing higher interference pulse voltages, making the design of the ADC more difficult.
The large power consumption of the digital multi-beam radio frequency phased array receiver causes heat dissipation problems, and the device may be damaged when the device is overheated. The larger dynamic range and the larger number of quantization levels require more independent power supply networks, which means more package pins and larger chip package, and also pose a huge challenge to the design and integration of the system.
The most troublesome problem of digital multibeam rf phased array receivers is the wiring of the large number of digital transmissions and the resulting electromagnetic interference. There must be two ADCs per receive channel, and an array of M rows and N columns requires 2MN ADCs and high speed interfaces. When the number of elements in the array is large, it is difficult to connect these high-speed signal lines directly to the central processing unit, especially at millimeter wave or higher frequencies. This is because in the implementation method of the phased array, the distance between the antennas is half a wavelength, and all components and high-speed digital lines need to be placed in the narrow area, which causes a great challenge. The resulting electromagnetic interference noise, coupled into the antennas of the array, directly reduces the sensitivity of the array.
In addition to this, another problem is a large amount of image information identification and processing problem. If in anti-terrorism human safety inspection radio frequency imaging system, people's clothing is the transparence, can't hide the body, invades people's privacy, and in addition, a large amount of image information cause artifical monitoring visual fatigue.
The existing human body security check radio frequency imaging system generally uses linear frequency modulation to realize imaging, a large radio frequency bandwidth is required to be occupied to detect the distance from a target to the imaging system, the detection precision of the distance has a direct relation with the radio frequency bandwidth, and the method is unrealistic in practical application.
Disclosure of Invention
The invention aims at the technical problem, and provides a real-time calibration radio frequency imaging system which comprises at least one MIMO radio frequency imaging transceiving array pair; each MIMO radio frequency imaging transceiving array pair comprises two opposite MIMO radio frequency transceiving arrays, a parallel two-dimensional digital signal processing imaging system and a digital signal processing imaging unit 700; the receiving array in each MIMO radio frequency transceiving array is provided with a reference signal by a transmitting source in the other opposite transceiving array, and phase calibration among receiving array units is completed; the MIMO radio frequency transceiving array also comprises a receiving antenna array, a receiving channel array corresponding to the receiving antenna array and a receiving processing unit; each receiving unit in the receiving channel array comprises: the system comprises a radio frequency low noise amplifier, at least one down converter, a radio frequency and baseband filter, an analog baseband multi-beam forming circuit, a local receiving clock generating circuit, a receiving beam controller and a receiving data interface circuit; the transmitting array in the transceiving array comprises a plurality of transmitting units with orthogonal frequencies, and a phased array or a virtual array is formed by adopting a frequency division multiplexing MIMO structure; the parallel two-dimensional digital signal processing imaging system comprises the following circuit units: the system comprises a one-dimensional multi-column beam acquisition array ADC401, a two-dimensional spatial-domain beam forming weighting array 402, a two-dimensional time domain FFT403, an amplitude absolute value processing unit 404, a phase processing unit 405, an orthogonal emission baseband signal generating unit 412, a two-dimensional signal decomposition and image generating unit 406, a two-dimensional high-resolution image restoring unit 408, a depth image generating unit 407 and a control unit 450.
In the real-time calibrated rf imaging system as described above, the quadrature transmit baseband signal generating unit 412 in the transmitter in one transmit-receive array generates a plurality of frequency quadrature transmit baseband signals 413, which are FFT-converted into amplitude and phase patterns, and the phases of the amplitude and phase patterns serve as the transmit reference phases 410 of the local plurality of quadrature transmit baseband signals 413; a plurality of orthogonal transmitting baseband signals 413 modulate the distributed transmitter in the transmitting array, send out radio frequency signals to the front of the array, reflect back when touching a target, and are received by the receiving array; the receiving array amplifies the received reflection signal, down-converts the signal to a baseband signal, forms a first-dimension analog baseband multi-beam signal output after passing through a radio frequency and baseband filter and an analog baseband multi-beam forming circuit, converts the signal into a one-dimension digital multi-column beam signal 421 through a parallel analog-to-digital converter, generates a two-dimension multi-column beam signal 422 through a two-dimension space-domain beam forming weighting array 402, and converts the signal into a frequency domain signal through a two-dimension time domain FFT unit 403; the frequency domain signal generates a two-dimensional frequency domain amplitude signal 424 through the absolute value unit 404, generates a two-dimensional parallel image 427 through the two-dimensional signal decomposition and image generation unit 406, and restores the two-dimensional parallel image 427 into a two-dimensional high-resolution image 429 through the two-dimensional high-resolution image restoration unit 408. The implementation of the receive beam controller may be centralized or distributed.
In the real-time calibrated radio frequency imaging system, the generated two-dimensional multi-column beam signal 422 is transformed into a frequency domain signal 423 by the two-dimensional time domain FFT unit 403, and the frequency domain signal generates a two-dimensional frequency domain phase signal 425 by the phase processing unit 405; the depth image generating unit 407 recovers the absolute phase from the transmission source to the target to be detected returning to the receiving array at each frequency point according to the two-dimensional frequency domain phase signals 425 at a plurality of different frequency points and the phase difference caused by the different frequencies, subtracts the transmission reference phase 410 from the absolute phase, divides the absolute phase by 4 pi, multiplies the absolute phase by the wavelength to obtain the radial distance, calculates the radial distance from the target to be detected to the receiving array, and completes the depth detection.
In the real-time calibration rf imaging system, when no target passes through or is blocked by the receiving unit of the receiving array in the MIMO rf imaging transceiving array pair, the receiving unit directly receives the calibration signal transmitted from the opposite reference signal transmitting source 203; the control unit 450 of the real-time calibrated rf imaging system calibrates the receive phases and amplitudes of the receive elements based on the position of each receive element in the array and the actual physical distance from the reference signal transmission source 203 to improve the coherence and consistency of the receive array.
In the real-time calibration radio frequency imaging system, in the real-time monitoring, a signal emitted by the reference signal emission source 203 generates a smaller two-dimensional frequency domain amplitude signal 424 with a single frequency point when a target is shielded in a receiving unit of a receiving array, so that the phase calibration operation is not started; when no target is shielded, the amplitude signal 424 of the signal of the reference signal emission source 203 in the two-dimensional frequency domain at the frequency point is larger, and the system starts the real-time phase calibration operation by coordinating by the control unit 450 at the moment.
In the real-time calibration radio frequency imaging system, the phase calibration operation is performed on all the receiving units, and the phase difference value between the receiving units is eliminated.
In the real-time calibrated rf imaging system, the two-dimensional frequency domain amplitude signal 424 is transformed into the corresponding sub-image signal by IFFT the amplitude value at each frequency point.
In the real-time calibrated rf imaging system, the two-dimensional frequency domain amplitude signal 424 is transformed into a plurality of corresponding sub-image signals by IFFT according to the amplitude values of a plurality of frequency points; and the sub-images are subjected to image fusion to generate a main image with a large size.
In the real-time calibrated rf imaging system, the large-size main image is processed to recover the high-resolution large-size main image.
In the real-time calibrated radio frequency imaging system as described above, with the digital signal processing imaging unit 700, the two-dimensional high resolution large size image 429 and the depth image 430 are further fused to obtain a 3D digital image.
In the real-time calibrated rf imaging system, the artificial intelligence processing unit 702 is provided to perform image recognition on the 3D digital image, detect the patterns of the metal dangerous goods and various dangerous goods through a great amount of deep learning, and identify the goods in the main image with large size and high resolution restored.
In the real-time calibrated rf imaging system, the artificial intelligence processing unit 702 is provided to directly perform image recognition on the main image with large size, detect the patterns of the dangerous metal and various dangerous goods through a great amount of deep learning, and identify the dangerous metal and various dangerous goods in the main image with large size and high resolution.
In the real-time calibrated rf imaging system, the artificial intelligence processing unit 702 is provided to directly perform image recognition on a plurality of sub-image signals, detect the patterns of metal dangerous goods and various dangerous goods through a large amount of deep learning, and identify the metal dangerous goods and various dangerous goods in the main image with large size and high resolution.
In the real-time calibrated radio frequency imaging system as described above, the phase calibration signal is generated by using the two-dimensional frequency domain amplitude signal variation when there is a target occlusion and when there is no target occlusion. In the real-time calibration radio frequency imaging system, when a receiving unit of a receiving array is shielded by a target, a two-dimensional frequency domain amplitude signal is small, and the phase calibration operation is not started; and when no target is shielded, the amplitude signal of the two-dimensional frequency domain is larger, and phase calibration operation is started. To eliminate the phase difference between the receiving units, a phase calibration operation needs to be performed for all receiving units.
Another technical problem to be solved by the present invention is image recognition and target detection, which is characterized in that an artificial intelligence visual neural network is adopted to perform image recognition and filtering on a two-dimensional baseband multi-beam image, and detect the image of a sensitive object. For example, in an anti-terrorism human body security check radio frequency imaging system, due to perspective detection, the application of the radio frequency imaging system is limited when the privacy of a human body is invaded. The artificial intelligence visual neural network is adopted, the machine vision is used for replacing the human eye vision monitoring, the personal privacy can not be invaded, the detection speed can be faster, and the visual fatigue can not occur. Massive image information in the satellite remote sensing imaging system can also be used for carrying out image recognition and filtering on the two-dimensional baseband multi-beam image through an artificial intelligent visual neural network, so that a target is quickly found, and the image of an interested sensitive object is detected. The same is true for the application in object detection of flying objects.
Drawings
FIG. 1 shows one example of an application of the real-time calibration radio frequency imaging system: human body security check instrument
FIG. 2 shows transmit and receive arrays (a) and (b) of a real-time calibrated RF imaging system
FIG. 3 receive array module and digital dimensional beamforming
FIG. 4 is a process for image generation and phase calibration signal generation for a real-time calibrated RF imaging system
FIG. 5 is a schematic diagram of generating a phase calibration signal using changes in an amplitude signal with and without target occlusion
FIG. 6 block diagram of a real-time calibrated RF imaging system receiver
FIG. 7 block diagram of a digital signal processing two-dimensional imaging unit
Detailed Description
A schematic diagram of a human body security check instrument as an example of an application of the real-time calibration rf imaging system is shown in fig. 1. The four transceiving arrays 101, 102, 103, 104 are arranged oppositely in pairs as shown in the figure, and the detected person passes through the detection channel in turn. Each transmit/receive array 101, 102, 103, 104 has its own set of transmit frequencies, e.g., F1, F2, F3, F4, each set of frequencies contains multiple frequencies, or frequency points, which are not repeated, so as to achieve the purpose of frequency division multiplexing.
Each transmit-receive array in the real-time calibrated radio frequency imaging system is composed of a receiving array 201, a transmitting array 202 and a reference signal transmitting source 203, as shown in fig. 2 (a); one transceiver array pair has two opposite transceiver arrays, and the receiving array in each transceiver array is provided with a reference signal by a transmitting source in the other opposite transceiver array to complete phase calibration between array elements, see fig. 2(b), and the delay caused by the wave front of the reference signal transmitting source 203 is considered in the calibration process.
A reference signal emission source 203a in one transceiving array 101 emits at the frequency of f1, and the other transceiving array 102 opposite to the reference signal emission source receives 101 emitted signal f1 as a calibration signal; meanwhile, the reference signal emitting source 203b in the other transceiving array 102 emits at the frequency f2, and the transceiving array 101 opposite to the reference signal emitting source receives the signal f2 emitted by 102 as a calibration signal; here F1 belongs to F1 and F2 belongs to F2.
The transmit and receive arrays 103 and 104 perform the same transmit and receive processes and use different frequencies. In the installation process of the real-time calibration radio frequency imaging system, different frequency sets are reasonably planned, so that a plurality of radio frequency imaging systems can multiplex the frequency sets without causing mutual interference. In a normal operation mode, the transmitting channel of the transceiving array 101 uses the frequency set of F1 as the transmitting frequency, and uses a frequency orthogonal method to transmit a plurality of signals with different frequencies, while the receiving channel of the transceiving array 101 receives all the frequencies.
The real-time calibration radio frequency imaging system comprises three parts, namely a receiving channel array module 300, an analog-digital conversion Array (ADC)305 and a digital dimension beam forming unit 306, which are shown in figure 3. The receive channel array has NxM receive elements, i.e., N groups of elements in a first dimension and M groups of elements in a second dimension, where the groups may be rows or columns. In other words, the array may be positioned horizontally or vertically. The real-time calibration radio frequency imaging system performs analog coherent superposition on all receiving units in the array in a first dimension, performs spatial filtering in space, and then generates M groups of analog multi-beam signals in the direction of the first dimension. The number of beams is set to K.
The parallel analog-to-digital converter array 305 in the real-time calibrated radio frequency imaging system is used for converting analog signals of M groups of K beams into digital multi-beam signals of M groups of K beams; the parallel digital dimensional beam forming unit 306 is configured to convert two-dimensional digital beam signals of M groups of K beams into two-dimensional digital image signals, and achieve scanning coverage by time-sharing scanning, thereby completing synthesis of the whole image.
The real-time calibration radio frequency imaging system receiving channel array can be decomposed into a plurality of receiving sub-array modules (301, 302, 303, 304) from the aspect of engineering realization, so that the development and manufacturing cost can be reduced. Decomposable multiple receive sub-arrays also means modularity, structuring, and building blocks. The implementation of the receive beam controller may be centralized or distributed.
The real-time calibrated RF imaging system receiving channel array can be decomposed into parallel one-dimensional analog receiving channel arrays. The one-dimensional array of analog receive channels and receive units can be decomposed into physically realizable rf integrated circuit chip structures 310. In a radio frequency chip, a plurality of receiving units may be integrated, each receiving unit including: the device comprises an antenna, an antenna input circuit, a low noise amplifier, a band-pass filter, a one-stage or two-stage down converter, a multi-path complex weighting factor unit, a local clock generator and a corresponding control unit. In the radio frequency receiving channel structure of the primary down converter, the down converter is a quadrature balance down converter and can be realized by an active or passive mixer. In the rf receive channel configuration of the two-stage down-converter, the second down-converter is a quadrature balanced down-converter, which may also be implemented as an active or passive mixer.
The multi-path complex weighting factor unit is realized by parallel complex weighting factor units, and each complex weighting factor unit completes:
Y(m,n,b)＝A(m,n,b)Xe-φ(m,n,b)
where m, and n are the location coordinates of the receiving element in the array and b is the index of the b-th beam. Y and X are the output and input of the cell, respectively, and φ (m, n, b) is the angle of the kth beam to be rotated by the complex weight factor cell. Delta thetabAnd
the phase difference values of two adjacent receiving units in the first dimension and the second dimension are respectively. A (m, n, b) is a weighting factor, phi0(m, n) are intrinsic correction values for compensating the system phase error. The complex weighting factor unit is realized by analog linear circuit units, such as wide-band operational amplifiers and vector unit amplifiers.
The processing method for generating images and generating phase calibration signals of a real-time calibration radio frequency imaging system is shown in fig. 4 and comprises the following parts: the system comprises an orthogonal transmitting baseband signal generating unit 412, a one-dimensional multi-column beam collecting array ADC401, a two-dimensional space-domain beam forming weighting array 402, a two-dimensional time-domain fast Fourier transform unit FFT403, an amplitude absolute value processing unit 404, a phase processing unit 405, a two-dimensional signal decomposition and image generating unit 406, a two-dimensional high-resolution image restoring unit 408, a depth image generating unit 407 and a control unit 450.
The quadrature transmit baseband signal generating unit 412 generates baseband signals 413 with different frequencies, which are modulated and transmitted to the transmit array 202, and then radiated by the transmit antenna. A fast fourier transform unit FFT 409 performs fast fourier transformation on the baseband signal 413 and converts it to polar representation, i.e. amplitude and phase format, resulting in the transmitted reference phase 410.
The plurality of radio frequency signals with orthogonal frequencies radiated by the transmitting antenna are transmitted to the forward airspace and generate radio frequency reflection signals on the detected target, and the radio frequency reflection signals are received by the antenna array of the receiving array 201. The MxN receive channels in the receive array 201 amplify, downconvert, and generate analog baseband multi-beam signal outputs 420 that generate M columns of K beams, the rf reflected signals. The analog baseband multi-beam signal output 420 is converted into a digital baseband multi-beam signal output 421 of K beams of M columns by a one-dimensional multi-column beam acquisition array ADC401 consisting of 2KM ADCs. The digital baseband multi-beam signal output 421 passes through the two-dimensional space-domain beam forming weighting array 402, and performs phase-related weighting in the second dimension to generate a two-dimensional time-division space-domain beam signal. Note that the two-dimensional time-space-domain beam signals here are due to beam time-sharing formation in the first dimension. By time-sharing the sampling in the first dimension and buffering the results, a two-dimensional spatial-domain beam signal 422 is generated.
For example, K is 8, the number Kn of time-sharing processes is 32, and finally, K · Kn is 256 beams in the first dimension. In order to achieve the effect of video imaging, for example, the acquisition of one image is completed within 1/50 seconds, the time length of the time sharing process can be 1/32/50 seconds.
The two-dimensional space-domain beam signal 422 is output to the two-dimensional time-domain fast fourier transform unit FFT403 in parallel, and then is subjected to parallel fast fourier transform on a time axis, and then is converted into a polar format through the amplitude absolute value processing unit 404 and the phase processing unit 405, and is output, that is, an amplitude output signal 424 and a phase output signal 425.
The amplitude output signal 424 is a combination of multiple orthogonal signals in frequency, and since the signals are orthogonal in frequency, the signals of different frequency points can be decomposed according to different frequencies through the two-dimensional signal decomposition and image generation unit 406, and then a plurality of sub-images related to specific frequency points are obtained through inverse fast fourier transform IFFT. These lower resolution sub-images may be passed through a two-dimensional high resolution image restoration unit 408 and corresponding image processing algorithms to produce a high resolution large size image 429.
In the distance detection, other distance detection means, such as ultrasonic, infrared or optical techniques, may also be adopted as an auxiliary method, and more accurate distance information is comprehensively processed and recovered on the basis of the depth image generating unit 407.
The transmitting array in the transceiving array comprises a plurality of transmitting units with orthogonal frequencies, and a phased array or a virtual array can be formed by adopting a frequency division multiplexing MIMO structure.
In the real-time calibrated rf imaging system, an orthogonal transmitting baseband signal generating unit 412 in a transceiver array transmitter generates orthogonal transmitting baseband signals 413 with different frequencies, which are converted into amplitude and phase modes through FFT, and the phases of the orthogonal transmitting baseband signals are used as reference phases of a plurality of local orthogonal transmitting baseband signals 412; a plurality of orthogonal transmit baseband signals 412 that modulate a distributed transmitter in a transmit array, send out radio frequency signals to the front of the array, reflect back when touching a target, and are received by a receive array; the receiving array amplifies the received reflection signal, down-converts the signal to a baseband signal, forms a first-dimension analog baseband multi-beam signal output after passing through a radio frequency and baseband filter and an analog baseband multi-beam forming circuit, converts the signal into a one-dimension digital multi-column beam signal 421 through a parallel analog-to-digital converter, generates a two-dimension multi-column beam signal 422 through a two-dimension space-domain beam forming weighting array 402, and converts the signal into a frequency domain signal through a two-dimension time domain FFT unit 403; the frequency domain signal generates a two-dimensional frequency domain amplitude signal 424 through the absolute value unit 404, generates a two-dimensional parallel image 427 through the two-dimensional signal decomposition and image generation unit 406, and restores the two-dimensional parallel image 427 into a two-dimensional high-resolution image 429 through the two-dimensional high-resolution image restoration unit 408.
FIG. 5 is a schematic diagram of the generation of a phase calibration signal using the variation of an amplitude signal with and without target occlusion. In the real-time calibration radio frequency imaging system, when a target is shielded, a two-dimensional frequency domain amplitude signal 424 of a receiving unit of a receiving array is smaller and does not exceed an amplitude threshold 510, so that phase calibration operation is not started; when the two-dimensional frequency domain amplitude signal 424 is larger without target occlusion and exceeds the amplitude threshold 510, a phase calibration operation is initiated. To eliminate the phase difference between the receiving units, the phase calibration operation needs to be performed on all receiving units in time-sharing mode one by one, i.e. the phi is updated in real time0The value of (m, n).
Fig. 6 is a block diagram of a receiver architecture for a real-time calibrated rf imaging system. The analog baseband multi-beam forming complex weight matrix unit of each receiving unit 602 in the receiving array 201 is coupled to the input of a parallel multi-path complex weight unit based on the output of the baseband low pass filter. The multi-path complex weighting factor unit weights a plurality of signals with specific incidence angles according to a plurality of specific complex weighting factor matrixes in a first dimension direction, enables a plurality of received signals from different incidence angles to achieve signal phase synchronization in the corresponding directions of a plurality of different incidence angles in the first dimension, and carries out in-phase superposition on output joints thereof to form parallel analog baseband multi-beam signals to be output. The controller generates a plurality of complex weighting control signals specific to the desired phase shift angle, and also controls both static and dynamic settings for brightness, viewing angle width, power intensity of the emitting illumination source, and various parameters of the system in operation.
The next processing is performed by two methods, the first method is to output the analog baseband multi-beam signals in parallel with the first dimension in the receiving array, convert the analog baseband multi-beam signals into parallel digital baseband multi-beam signals with the first dimension through the parallel analog-to-digital converter array 604, and then form the second-dimension two-dimensional digital beam signals on the output of the parallel digital baseband multi-beam signals with the first dimension.
The second method is to perform amplitude detection or power detection on the output signal of the analog baseband multi-beam signal parallel to the first dimension to obtain a narrow-band signal, and then convert the narrow-band signal into a parallel digital baseband multi-beam signal parallel to the first dimension by the analog-to-digital converter array 604. And performing second-dimension digital beam forming on the output of the narrow-band parallel digital baseband multi-beam signal of the first dimension. The benefit of the second approach is that the slew rate requirements of the analog-to-digital converter array 604 are reduced, but the imaging is less effective than the first direct analog-to-digital conversion because amplitude detection or power detection can corrupt the signal coherence.
The real-time calibrated radio frequency imaging system is further characterized by amplitude detection and two-dimensional baseband multi-beam image signal formation in the second dimension by a digital signal processor or other hardware.
Referring to fig. 7, the parallel digital signal processing two-dimensional imaging unit 700 includes: two-dimensional high-resolution image 429, depth image 430, digital image fusion 701, artificial intelligent visual neural network or image recognition and processing unit 702, and wireless or wired transmission interface 703 of display interface.
The real-time calibration radio frequency imaging system adopts an artificial intelligent visual neural network to carry out image feature identification and filtration on a two-dimensional baseband multi-beam image and detect the graph of a sensitive object. For example, the method is significant in human body safety detection, because human outer clothing is transparent under microwave, and human body contour is exposed. In such applications, it is unacceptable to the test person. With the artificial intelligence visual neural network, the machine vision is used for completing the target filtering, hiding sensitive human body parts and only detecting dangerous goods and weapons. When suspicious objects and items are found, the panoramic image may be displayed. The panoramic image comprises a video image generated by an optical camera, a two-dimensional image generated by a radio frequency multi-beam intelligent imaging system and a superposed image of the two images. Meanwhile, the artificial intelligence visual neural network improves the detection speed.
The real-time calibration radio frequency imaging system adopts artificial intelligence and deep learning, and can directly detect dangerous goods from a plurality of sub-images with low resolution ratio through a large amount of sample analysis. Although the human eye cannot identify the hazardous material from these multiple low-resolution sub-images, artificial intelligence and deep learning can do so directly. And detecting the graphs of the metal dangerous goods and various dangerous goods through a large amount of deep learning, and identifying the goods in the large-size main image with the recovered high resolution.
In the real-time calibrated radio frequency imaging system as described above, the two-dimensional high resolution large-size image 429 and the depth image 430 may be further fused by the digital signal processing imaging unit 700 to obtain a 3D three-dimensional digital image. In the application example shown in fig. 1, the images obtained by the arrays 101, 102, 103, 104 can be further synthesized into a 3D digital image, or 4 image projection/reflection surfaces with 4 independent detections can be formed, and if one of them detects dangerous goods, an alarm is given immediately.
In the real-time calibrated rf imaging system, the detected target carries a directional reflector, such as a kitchen knife, which may reflect very little on one detection surface but will reflect more on other surfaces. The artificial intelligence processing unit 702 can directly integrate various information and determine the existence of dangerous goods by using information of various time and space in a short time.
The real-time calibration radio frequency imaging system greatly improves the detection speed and the detection quality due to the adoption of the multi-beam two-dimensional time-sharing imaging, the real-time calibration and the MIMO technology. By using the multi-frequency point phase detection method, the bandwidth of the system is greatly reduced, and the requirement on wireless resources is reduced.
The technology proposed by the invention can be applied to occasions such as radar detection, robot vision, satellite remote measurement, remote sensing and the like. Because radar technology and communication technology have many commonalities, the technology can also find application scenarios in the field of communications.
Claims (13)
1. A real-time calibrated radio frequency imaging system is characterized by comprising at least one MIMO radio frequency imaging transceiving array pair; each MIMO radio frequency imaging transceiving array pair comprises two opposite MIMO radio frequency transceiving arrays, a parallel two-dimensional digital signal processing imaging system and a digital signal processing imaging unit 700; the receiving array in each MIMO radio frequency transceiving array is provided with a reference signal by a transmitting source in the other opposite transceiving array, and phase calibration among receiving array units is completed; the MIMO radio frequency transceiving array also comprises a receiving antenna array, a receiving channel array corresponding to the receiving antenna array and a receiving processing unit; each receiving unit in the receiving channel array comprises: the system comprises a radio frequency low noise amplifier, at least one down converter, a radio frequency and baseband filter, an analog baseband multi-beam forming circuit, a local receiving clock generating circuit, a receiving beam controller and a receiving data interface circuit; the transmitting array in the transceiving array comprises a plurality of transmitting units with orthogonal frequencies, and a phased array or a virtual array is formed by adopting a frequency division multiplexing MIMO structure; the parallel two-dimensional digital signal processing imaging system comprises the following circuit units: the system comprises a one-dimensional multi-column beam acquisition array ADC401, a two-dimensional spatial-domain beam forming weighting array 402, a two-dimensional time domain FFT403, an amplitude absolute value processing unit 404, a phase processing unit 405, an orthogonal emission baseband signal generating unit 412, a two-dimensional signal decomposition and image generating unit 406, a two-dimensional high-resolution image restoring unit 408, a depth image generating unit 407 and a control unit 450.
2. The real-time calibrated radio frequency imaging system of claim 1, wherein the quadrature transmit baseband signal generating unit 412 in the transmitter of a transmit/receive array generates the quadrature transmit baseband signal generating unit 412 to generate a plurality of quadrature transmit baseband signals 413 with different frequencies, which are FFT-converted into amplitude and phase patterns, and the phases of the quadrature transmit baseband signals 413 are used as the transmit reference phases 410 of the plurality of local quadrature transmit baseband signals 413; a plurality of orthogonal transmitting baseband signals 413 modulate the distributed transmitter in the transmitting array, send out radio frequency signals to the front of the array, reflect back when touching a target, and are received by the receiving array; the receiving array amplifies the received reflection signal, down-converts the signal to a baseband signal, forms a first-dimension analog baseband multi-beam signal output after passing through a radio frequency and baseband filter and an analog baseband multi-beam forming circuit, converts the signal into a one-dimension digital multi-column beam signal 421 through a parallel analog-to-digital converter, generates a two-dimension multi-column beam signal 422 through a two-dimension space-domain beam forming weighting array 402, and converts the signal into a frequency domain signal through a two-dimension time domain FFT unit 403; the frequency domain signal generates a two-dimensional frequency domain amplitude signal 424 through the absolute value unit 404, generates a two-dimensional parallel image 427 through the two-dimensional signal decomposition and image generation unit 406, and restores the two-dimensional parallel image 427 into a two-dimensional high-resolution image 429 through the two-dimensional high-resolution image restoration unit 408.
3. The real-time calibrated radio frequency imaging system of claim 1, wherein two-dimensional multi-column beam signals 422 are generated, and then transformed into frequency domain signals 423 by the two-dimensional time domain FFT unit 403, and the frequency domain signals are processed by the phase processing unit 405 to generate two-dimensional frequency domain phase signals 425; the depth image generating unit 407 recovers the absolute phase from the transmission source to the target to be detected returning to the receiving array at each frequency point according to the two-dimensional frequency domain phase signals 425 at a plurality of different frequency points and the phase difference caused by the different frequencies, subtracts the transmission reference phase 410 from the absolute phase, divides the absolute phase by 4 pi, multiplies the absolute phase by the wavelength to obtain the radial distance, calculates the radial distance from the target to be detected to the receiving array, and completes the depth detection.
4. The real-time calibration RF imaging system according to claim 1, wherein the receiving unit of the receiving array in the MIMO RF imaging transmit-receive array pair directly receives the calibration signal transmitted from the opposite reference signal transmitting source 203 when no target passes or blocks; the control unit 450 of the real-time calibrated rf imaging system calibrates the receive phases and amplitudes of the receive elements based on the position of each receive element in the array and the actual physical distance from the reference signal transmission source 203 to improve the coherence and consistency of the receive array.
5. The real-time calibration radio frequency imaging system according to claim 1, wherein in real-time monitoring, the two-dimensional frequency domain amplitude signal 424 of a single frequency point generated by the signal emitted by the reference signal emission source 203 when a target is shielded in the receiving unit of the receiving array is smaller, so that the phase calibration operation is not started; when no target is shielded, the amplitude signal 424 of the signal at the frequency point in the two-dimensional frequency domain, which is sent by the reference signal emission source 203, is larger, and the system uses the moment and is coordinated by the control unit 450 to start the real-time phase calibration operation.
6. The real-time calibrated radio frequency imaging system according to claim 1, wherein the phase calibration operation is performed on all receiving units to eliminate the phase difference between the receiving units.
7. The real-time calibrated radio frequency imaging system according to claim 1, wherein the two-dimensional frequency domain amplitude signal 424 is transformed into the corresponding sub-image signal by IFFT for the amplitude value at each frequency point.
8. The real-time calibrated radio frequency imaging system according to claim 1, wherein the two-dimensional frequency domain amplitude signal 424 is transformed into a plurality of sub-image signals corresponding to the amplitude values at a plurality of frequency points by IFFT; and the sub-images are subjected to image fusion to generate a main image with a large size.
9. The real-time calibrated radio frequency imaging system according to claim 1, wherein the large-size primary image is processed to recover a high-resolution large-size primary image.
10. The real-time calibrated radio frequency imaging system according to claim 1, characterized by having a digital signal processing imaging unit 700 for further fusing the two-dimensional high resolution large-size image 429 and the depth image 430 to obtain a 3D digital image.
11. The real-time calibrated radio frequency imaging system according to claim 1, characterized by having an artificial intelligence processing unit 702, performing image recognition on the 3D digital image, detecting the patterns of the metal dangerous goods and various dangerous goods through a large amount of deep learning, and identifying the goods in the main image with large size and restored high resolution.
12. The real-time calibrated radio frequency imaging system according to claim 1, characterized by having the artificial intelligence processing unit 702, directly performing image recognition on the main image with large size, detecting the patterns of the metal dangerous goods and various dangerous goods through a large amount of deep learning, and identifying the goods in the main image with large size restored with high resolution.
13. The real-time calibrated radio frequency imaging system according to claim 1, wherein the artificial intelligence processing unit 702 is provided to directly perform image recognition on the plurality of sub-image signals, detect the patterns of the metal dangerous goods and various dangerous goods through a large amount of deep learning, and identify the goods in the main image with large size and high resolution restored.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111694073A (en) * | 2020-06-19 | 2020-09-22 | 北京遥测技术研究所 | Circumferential scanning imaging security check calibrating device |
| CN113341351A (en) * | 2021-06-08 | 2021-09-03 | 广东技术师范大学 | Omnidirectional magnetic induction intensity testing instrument calibration and time-frequency testing method and device |
| CN113933834A (en) * | 2021-10-13 | 2022-01-14 | 苏州威陌电子信息科技有限公司 | Cylindrical scanning microwave imaging method |
| WO2022219833A1 (en) * | 2021-04-15 | 2022-10-20 | パナソニックＩｐマネジメント株式会社 | Imaging device |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102135610A (en) * | 2010-12-28 | 2011-07-27 | 中国航天科工集团第二研究院二○三所 | Near-field real-time calibration method for human body millimeter wave imaging safety inspection system |
| CN102438111A (en) * | 2011-09-20 | 2012-05-02 | 天津大学 | Three-dimensional measurement chip and system based on double-array image sensor |
| CN102495396A (en) * | 2011-11-15 | 2012-06-13 | 北京无线电计量测试研究所 | Amplitude and phase consistency calibration method of multiple channels of human body security inspection system |
| CN102890271A (en) * | 2012-10-25 | 2013-01-23 | 北京理工大学 | Correction method for amplitude and phase consistency of external radiation source radar array antenna |
| CN104954083A (en) * | 2015-06-16 | 2015-09-30 | 上海华为技术有限公司 | Antenna array calibration method, device and system |
| CN105425221A (en) * | 2015-11-09 | 2016-03-23 | 四川九洲电器集团有限责任公司 | Radio frequency channel real-time calibration method and secondary radar |
| CN105824021A (en) * | 2016-04-22 | 2016-08-03 | 慕丰浩 | Analog and digital hybrid two-dimensional phased array radio frequency multiple-beam intelligent imaging system |
-
2019
- 2019-07-04 CN CN201910597592.2A patent/CN111103583B/en active Active
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102135610A (en) * | 2010-12-28 | 2011-07-27 | 中国航天科工集团第二研究院二○三所 | Near-field real-time calibration method for human body millimeter wave imaging safety inspection system |
| CN102438111A (en) * | 2011-09-20 | 2012-05-02 | 天津大学 | Three-dimensional measurement chip and system based on double-array image sensor |
| CN102495396A (en) * | 2011-11-15 | 2012-06-13 | 北京无线电计量测试研究所 | Amplitude and phase consistency calibration method of multiple channels of human body security inspection system |
| CN102890271A (en) * | 2012-10-25 | 2013-01-23 | 北京理工大学 | Correction method for amplitude and phase consistency of external radiation source radar array antenna |
| CN104954083A (en) * | 2015-06-16 | 2015-09-30 | 上海华为技术有限公司 | Antenna array calibration method, device and system |
| CN105425221A (en) * | 2015-11-09 | 2016-03-23 | 四川九洲电器集团有限责任公司 | Radio frequency channel real-time calibration method and secondary radar |
| CN105824021A (en) * | 2016-04-22 | 2016-08-03 | 慕丰浩 | Analog and digital hybrid two-dimensional phased array radio frequency multiple-beam intelligent imaging system |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111694073A (en) * | 2020-06-19 | 2020-09-22 | 北京遥测技术研究所 | Circumferential scanning imaging security check calibrating device |
| CN111694073B (en) * | 2020-06-19 | 2022-12-13 | 北京遥测技术研究所 | Circumferential scanning imaging security check calibrating device |
| WO2022219833A1 (en) * | 2021-04-15 | 2022-10-20 | パナソニックＩｐマネジメント株式会社 | Imaging device |
| CN113341351A (en) * | 2021-06-08 | 2021-09-03 | 广东技术师范大学 | Omnidirectional magnetic induction intensity testing instrument calibration and time-frequency testing method and device |
| CN113933834A (en) * | 2021-10-13 | 2022-01-14 | 苏州威陌电子信息科技有限公司 | Cylindrical scanning microwave imaging method |
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