Millimeter wave transceiver and security inspection system

Abstract

The present application discloses a millimeter wave transceiver, which includes a millimeter wave frequency source, which provides a baseband source signal of at least two frequency signals; a power division unit, which is used to power divide the baseband source signal from the millimeter wave frequency source according to the number of frequency signals to obtain at least two baseband source signals; a frequency multiplication unit, which is used to multiply the frequency of each baseband source signal from the power division unit to generate at least two frequency signals; a timing unit, which provides a transmission timing for a transmission array switch, and provides a receiving timing for a receiving array switch; the transmission array switch, which is used to output each frequency signal from the frequency multiplication unit to a transmission antenna array according to the transmission timing of the timing unit; and the receiving array switch, which is used to output each frequency signal from the frequency multiplication unit to a receiving antenna array according to the receiving timing of the timing unit.

Description

Technical Field

[0001] The present invention relates to the field of living body security inspection, and in particular, to a millimeter wave transceiver. Background Art

[0002] In the field of security inspection, according to the biological nature of the inspected object, it is divided into live security inspection and non-live security inspection. Among them, live security inspection is mainly for human body detection, and non-live security inspection is mainly for luggage, parcels, etc. Since live security inspection needs to avoid causing damage to the living body, the detection technologies used mainly include metal detection, X-ray technology (for example, X-ray backscatter technology, X-ray transmission technology), millimeter wave holographic imaging and other technologies. Metal detection can only detect hidden metal targets, and can only alarm but not image, and requires manual inspection personnel to cooperate with body search. Due to its ionizing radiation characteristics, X-ray technology is harmful to security inspection operators and inspected living objects, and its use is limited in many occasions. Millimeter wave holographic imaging technology uses safe non-ionizing radiation waves to perform holographic imaging of the inspected target. It can not only detect metal objects hidden under fabrics, but also detect dangerous goods such as plastic pistols and explosives. This technology can obtain more detailed and accurate information due to three-dimensional imaging, which is convenient for computer-assisted identification.

[0003] According to the way of scanning the reflected wave (echo), millimeter wave holographic imaging technology can include planar scanning and cylindrical scanning. Figure 1 As shown, Figure 1 It is a schematic diagram of plane scanning and cylindrical scanning. The left figure shows cylindrical scanning, and the right figure shows plane scanning. In the right figure, taking the human body as an example, the width direction is from the left side to the right side of the human body, the height direction is from the feet to the head of the human body, and the thickness direction is from the front chest to the back of the human body. The direction perpendicular to the scanning plane formed by the transceiver antenna array is the distance direction, and the direction parallel to the scanning plane is the azimuth direction, that is, the direction of the plane determined by the width direction and height direction of the human body. Cylindrical scanning is to receive the reflected wave of the detected target by making a uniform circular motion of the transceiver antenna array around the detected target; plane scanning is to receive the reflected wave of the detected target by making a uniform linear motion of the transceiver antenna array parallel to the azimuth direction of the detected target.

[0004] According to the principle of synthetic aperture imaging, the image range and image azimuth resolutions are shown as follows:

[0005] δ 距离 =c / (2*B)

[0006] δ 方位 =λ / (4*sin(θ / 2))

[0007] In the above formula, c is the speed of light, B is the system operating bandwidth, λ is the wavelength, and θ is the antenna beam width.

[0008] The system operating bandwidth of existing millimeter wave body security inspection equipment is basically 5-10GHz. Taking the existing equipment as an example, the L3 equipment is 24.5-30GHz, and the R&S equipment is 70GHz-80GHz; substituting into the formula, it can be calculated that the azimuth resolution of L3 is 5mm, the range resolution is 30mm, and the azimuth resolution of R&S is 2mm, and the range resolution is 15mm.

[0009] It can be seen that for different system working bandwidths, the image resolution in range varies more than in azimuth, so increasing the system working bandwidth can effectively improve the image resolution. However, this is limited by the RF chip devices and antenna design and is difficult to achieve in the system. Summary of the invention

[0010] The present invention provides a millimeter wave transceiver to generate an ultra-wideband transmission signal and receive an ultra-wideband reflected wave signal.

[0011] The present invention provides a millimeter wave transceiver, the device comprising:

[0012] A millimeter wave frequency source, providing a baseband source signal of at least two frequency signals;

[0013] The power division unit is used to divide the baseband source signal from the millimeter wave frequency source according to the number of frequency signals to obtain at least two baseband source signals.

[0014] A frequency multiplication unit, used for multiplying the frequency of each baseband source signal from the power division unit to generate at least two frequency signals;

[0015] The array switch is used to output each frequency signal from the frequency multiplication unit to the transceiver antenna array.

[0016] Preferably, the frequency multiplication unit includes at least two frequency multipliers, each of which multiplies the frequency of a baseband source signal from the power division unit to obtain a frequency signal;

[0017] The device also includes,

[0018] A timing unit, providing a transmit timing for the transmit array switch, and providing a receive timing for the receive array switch;

[0019] The array switch comprises:

[0020] A transmitting array switch, used for outputting each frequency signal from the frequency multiplication unit to the transmitting antenna array;

[0021] The receiving array switch is used to output each frequency signal from the frequency multiplication unit to the receiving antenna array according to the receiving timing of the timing unit.

[0022] Preferably, the receiving antenna array has a rotation axis and at least two receiving antenna array elements arranged along the radial direction of the rotation axis.

[0023] The receiving antenna array is driven to rotate around the rotation axis to scan the reflected wave signal formed by the detection target reflecting the transmitting wave emitted by at least one transmitting antenna array element fixed to the circumferential envelope boundary formed by the rotation of the receiving antenna array.

[0024] Preferably, the at least two receiving antenna array elements are located on the same side of the rotating shaft in the radial direction of the rotating shaft, or are symmetrically distributed relative to the rotating shaft in the radial direction of the rotating shaft;

[0025] The interval between two adjacent receiving antenna array elements is equal, and the interval is greater than or equal to the wavelength of the transmitting wave.

[0026] Preferably, the at least one transmitting antenna array element is bilaterally symmetrically distributed on the boundary of a circular envelope formed by the rotation of the receiving antenna array in the height direction of the detected target;

[0027] The circular envelope boundary is a closed polygon formed by connecting end to end straight line segments circumscribing the circle formed by the rotation of the receiving antenna array; or, the circular envelope boundary is a closed circle with the rotation axis as the center and a radius greater than the rotation radius of the receiving antenna array;

[0028] Each of the at least one transmitting antenna array element has a direction that causes the transmitting beam to be oriented toward the center of the detected target scene.

[0029] Preferably, the timing unit provides a transmission timing for the transmission array switch, so that each of the at least one transmission antenna array element transmits transmission signals of at least two frequencies in time division; and after each transmission cycle, all the transmission antenna array elements enter a waiting state until the receiving antenna array rotates n degrees relative to the previous transmission cycle, and all the transmission antenna array elements enter the next transmission cycle to transmit the transmission wave of the transmission cycle, wherein n is less than or equal to 1 degree;

[0030] The timing unit provides a receiving timing for the receiving array switch, so that in a transmission cycle in which each transmitting antenna array element completes transmission in sequence, all receiving antenna array elements receive simultaneously.

[0031] The present invention also provides a security inspection system, which comprises:

[0032] Any of the above-mentioned millimeter wave transceiver devices transmits at least two frequency signals for being reflected by the detected object to form reflected waves, receives first reflected wave data of the at least two frequency signals reflected by the detected object,

[0033] An imaging module, used for converting the first reflected wave data from a circular scanning array into second reflected wave data of an equivalent array with a row direction and a column direction by interpolation, and reconstructing a reflection function based on the second reflected wave data;

[0034] A detection unit, used for performing detection based on the reconstructed reflection function;

[0035] The driving unit is used to drive the receiving antenna array to perform a circular scanning motion.

[0036] The present invention further provides a millimeter wave transceiver, the device comprising:

[0037] A millimeter wave frequency source provides a baseband source signal for an ultra-wideband signal synthesized by frequency bands; the number of the frequency bands is at least two,

[0038] The power division unit is used to divide the baseband source signal from the millimeter wave frequency source according to the number of frequency bands to obtain at least two baseband source signals.

[0039] A frequency multiplication unit, used for multiplying the baseband source signal of each channel from the power division unit to generate at least two complementary frequency band signals; the at least two complementary frequency bands are adjacent frequency bands, where the upper frequency band and the lower frequency band have partially overlapping frequency band ranges or overlapping frequencies;

[0040] The array switch is used to output each frequency band signal from the frequency multiplication unit to the transceiver antenna array of the frequency band.

[0041] Preferably, the frequency multiplication unit includes at least two frequency multipliers, each of which multiplies the frequency of a baseband source signal from the power division unit to obtain a frequency band signal.

[0042] Preferably, the transceiver antenna array has at least two rows of transmitting antenna elements and at least two rows of receiving antenna elements.

[0043] Each row of transmitting antenna array elements transmits a frequency band signal.

[0044] Each row of receiving antenna elements receives a frequency band signal.

[0045] The transmitting antenna array elements and receiving antenna array elements in the same frequency band are symmetrically distributed along the axis connecting the equivalent phase centers.

[0046] Preferably, the array switch comprises:

[0047] A transmitting array switch, used for outputting each frequency band signal from the frequency multiplication unit to the transmitting antenna array of the frequency band;

[0048] The receiving array switch is used to output each frequency band signal from the frequency multiplication unit to the receiving antenna array of the frequency band.

[0049] Preferably, the transceiver antenna array is scanned in a planar manner, or in a cylindrical manner;

[0050] Each transmitting antenna array element in the transmitting antenna array has a direction that makes the transmitting beam point to the center of the detected target scene.

[0051] The present invention provides a security inspection system, which comprises:

[0052] Any of the above-mentioned millimeter wave transceiver devices transmits an ultra-wideband signal to be reflected by the detected target to form a reflected wave, and receives the reflected wave of the ultra-wideband signal synthesized by the sub-frequency bands reflected by the detected target,

[0053] An imaging module is used to reconstruct a reflection function based on the received reflection wave data.

[0054] A detection unit, used for performing detection based on the reconstructed reflection function;

[0055] The driving unit is used to drive the transceiver antenna array to perform scanning motion.

[0056] The millimeter wave transceiver provided by the present invention performs power division and frequency multiplication based on the same baseband source signal to obtain signals of at least two frequencies or two complementary frequency bands for transmission and reception, thereby obtaining ultra-wideband transmission signals and reception signals without increasing the difficulty of hardware design, and improving the resolution of distance imaging; when applied to a security inspection system, uniformity of resolution in three-dimensional space is achieved, which is conducive to the efficient identification of concealed objects. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 A schematic diagram of plane scanning and cylindrical scanning.

[0058] Figure 2a and 2b A schematic diagram of a receiving antenna array of the present application.

[0059] Figure 3a-3f Schematic diagram of transmitting antenna array elements uniformly distributed on the circular envelope boundary.

[0060] Figure 4 A schematic diagram of the key blind spots of millimeter-wave human body security inspection imaging.

[0061] Figure 5 A schematic diagram of an antenna array for optimizing the antenna transmit beam.

[0062] Figure 6 The present invention is a schematic diagram of the existing plane scanning trajectory and human body posture when the detected target is a human body.

[0063] Figure 7A schematic diagram of the circular scanning trajectory and human body posture of this application.

[0064] Figure 8 A schematic diagram of the circular scanning trajectory of the transmitting antenna array and the human body posture based on the optimized antenna transmitting beam.

[0065] Fig. 9 A schematic diagram of the timing relationship between the transmitting antenna array and the receiving antenna array.

[0066] Fig.10 A schematic diagram of the imaging field of view model.

[0067] Fig.11 A schematic diagram of a process of the imaging method of the present application.

[0068] Fig.12 A schematic diagram of the circular scanning array scanning points and its equivalent array scanning points of the present application.

[0069] Fig.13 This is a schematic diagram of an ultra-wideband signal transceiver according to the first embodiment of the present invention.

[0070] Fig.14 A security inspection system using an ultra-wideband transceiver with frequency-band synthesis according to the embodiment of the present invention.

[0071] Fig.15 It is a schematic diagram of an imaging module of this embodiment.

[0072] Fig.16 A schematic diagram of the arrangement of the transmitting and receiving antenna arrays and the corresponding frequency bands of Example 2.

[0073] Fig.17 A schematic diagram of an ultra-wideband transceiver with frequency band synthesis.

[0074] Fig.18 A schematic diagram of a security inspection system using the transceiver device described in the second embodiment. DETAILED DESCRIPTION

[0075] In order to make the objectives, technical means and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings.

[0076] The present invention breaks through the limitation of devices and realizes ultra-wideband by combining several complementary frequency bands, thereby achieving uniformity of resolution in three-dimensional space, which is helpful for efficient identification of concealed objects.

[0077] Embodiment 1

[0078] In this embodiment, a receiving antenna array having a rotating shaft and at least two receiving antenna elements arranged in the radial direction of the rotating shaft performs a circular motion (rotation) around the rotating shaft to scan the reflected wave signal, wherein the reflected wave is formed by the beam emitted by at least one transmitting antenna element uniformly distributed on the circumferential envelope boundary formed by the rotation of the receiving antenna array and reflected by the detected target, and holographic imaging is performed based on the scanned reflected wave signal, wherein the at least two receiving antenna elements are symmetrically distributed relative to the rotating shaft in the radial direction of the rotating shaft, or at least two receiving antenna elements are located on the same side of the rotating shaft in the radial direction of the rotating shaft. In this way, within the receiving cycle formed by the receiving antenna array completing a rotation cycle, the set of scanning points in the scanning plane can be equivalent to an array of scanning points equally spaced in the row direction and the column direction, and imaging is performed based on the equivalent array plane. Preferably, each transmitting antenna element is uniformly fixed on the circumference formed by the circular plane motion of the receiving element, and transmits beams in sequence according to the scanning direction.

[0079] See also Figure 2a , 2b As shown, Figure 2a and 2b This is a schematic diagram of the receiving antenna array of the present application. The receiving antenna array has a rotating shaft, and the receiving antenna array rotates counterclockwise (or clockwise) around the rotating shaft under power drive, thereby realizing circular plane scanning. The receiving antenna array includes at least one row of receiving antenna array elements, each row includes at least two receiving antenna array elements, and the receiving antenna array elements are symmetrically distributed relative to the rotating shaft along the radial direction of the rotating shaft (such as Figure 2a ), or, at least two receiving antenna elements are located on the same side of the rotation axis in the radial direction of the rotation axis (such as Figure 2b ). Since the transmitting antenna elements of the present application do not rotate, the interval between two adjacent receiving antenna elements in each row can be greater than or equal to a central working wavelength (transmitting signal wavelength) λ. For example, the receiving antenna array is a linear array. Assuming that the entire linear array is 1 meter long and the central working wavelength is 10 mm, there are at most 100 receiving elements on a linear array. In this way, a larger receiving antenna element interval is beneficial to reducing the number of receiving antenna elements, thereby facilitating the lightweight receiving antenna array, and the receiving antenna array is easy to rotate. In view of the fact that multiple rows of receiving antenna elements do not significantly improve the imaging quality, preferably, the receiving antenna array is a linear array, that is, it only includes one row of equally spaced elements.

[0080] At least one fixed transmitting antenna array element is arranged on the circumferential plane of the receiving antenna array rotation. Preferably, increasing the number of transmitting antenna array elements irradiating the inspected object will help improve the imaging resolution. Multiple transmitting antenna array elements are evenly arranged along the circumferential envelope boundary so that the transmitting beam evenly irradiates the entire scene and improves the imaging quality. Figure 3a-3f As shown, Figure 3a-3f3e and 3f are schematic diagrams of transmitting antenna array elements uniformly distributed on the circular envelope boundary. The figure shows the distribution when the number of transmitting antenna array elements is 3, 4, and m. 3e and 3f are schematic diagrams of the number of transmitting antenna array elements being m. It should be understood that the circular envelope boundary can be formed by connecting a number of straight line segments circumscribed to the circumference formed by rotating the receiving antenna array to form a closed polygon, such as Figure 3a-3e The regular polygon shown in can also be a closed circle with the rotation axis as the center and a radius greater than the rotation radius of the receiving antenna array, such as Figure 3f Preferably, the transmitting antenna array element is bilaterally symmetrical in the height direction of the detected target. It should be understood that when there are multiple transmitting antenna array elements, the uniformly distributed arrangement of these transmitting antenna array elements can also be understood as a transmitting antenna array.

[0081] According to the imaging characteristics of millimeter-wave radar, the imaging resolution of any spatial point on the target is determined by the size of all transmitting antenna array elements that can illuminate the point. In the existing planar scanning and cylindrical scanning methods, due to the size and beam width of the transmitting antenna array, the resolution of planar scanning is poor on the side of the body, and the resolution of cylindrical scanning is poor on the inner thigh, see Figure 4 As shown, Figure 4 This is a schematic diagram of the key blind spots of millimeter-wave human body security inspection imaging. In the figure, the short thick solid line indicates the location of the blind spot.

[0082] In order to further improve the image resolution, for the transmitting antenna array, the transmit beam direction of each transmitting antenna array element can be adjusted so that more transmit beams reach the center of the scene. Figure 5 As shown, Figure 5 A schematic diagram of an antenna array for optimizing the antenna transmit beam. Take a row of transmit antenna elements as an example, Figure 3e The transmitting antenna array elements on one side of the middle polygon have their transmitting beams located in the middle of the side oriented toward a circular plane perpendicular to the rotation of the receiving antenna array, and the transmitting beams of the transmitting antenna array elements on both sides outside the middle of the side are oriented toward the scene center of the inspected target, so that more transmitting beams can illuminate the inspected target, especially the sides of the body, inner thighs, shoulders and other parts with poor theoretical resolution.

[0083] For example, if the number of transmitting antenna array elements on one side of the polygon is p, the p transmitting antenna array elements are divided into a first group of transmitting antenna array elements located in the middle, a second group of transmitting antenna array elements located on both sides of the middle, and a third group of transmitting antenna array elements. Preferably, the number of transmitting antenna array elements in the second group is equal to the number of transmitting antenna array elements in the third group. The transmitting beam of the first group of transmitting antenna array elements is directed toward a circular plane perpendicular to the rotation of the receiving antenna array, and the transmitting beams of the other two groups of transmitting antenna array elements are directed toward the scene center of the detected target.

[0084] Similarly, when there are fewer transmitting antenna elements, the transmitting antenna elements can be adjusted according to the required transmitting beam direction. For example, when the number of transmitting antenna elements in a row is less than 3, for example, as shown in 3a-3d, the transmitting beams of each transmitting antenna element are respectively directed toward the scene center of the detected object.

[0085] See also Figure 6 As shown, Figure 6 A schematic diagram of the existing plane scanning trajectory and human posture when the target is a human body. In order to reduce costs, the existing security inspection equipment has a narrow scanning surface width, and the target needs to be inspected in a specific posture to improve the resolution. For example, in the figure, the arm needs to be raised and lowered; for cylindrical scanning security inspection equipment, the arm needs to be raised high. The coordination of these specific postures will cause detection failure due to the short time the posture is maintained, and the imaging quality of the side of the body and the inside of the arm will be reduced due to non-standard postures.

[0086] See also Figure 7 As shown, Figure 7 A schematic diagram of the circular scanning trajectory and human body posture of this application. In the circular scanning plane, the arm of the target being inspected is naturally extended and straightened at any angle to the human body. Preferably, the angle is greater than 0 degrees. The posture is friendly and easy to maintain. Due to the sufficient transmission beam illumination of the transmitting antenna array elements and the scanning of the receiving antenna array elements, fine scanning imaging can be achieved in blind areas such as the inner side of the arm, the inner side of the thigh, and the side of the body.

[0087] See also Figure 8 As shown, Figure 8 It is a schematic diagram of the circular scanning trajectory of the transmitting antenna array and the human body posture based on the optimized antenna transmitting beam, wherein the gray area indicates that the transmitting antenna of the optimized antenna transmitting beam will be more toward the human body, which can increase the effective irradiation area, especially the sides, crotch, armpits, shoulders and other parts of the human body with poor resolution, thereby improving the imaging resolution.

[0088] The following takes four uniformly distributed transmitting antenna array elements as an example to illustrate the working process of transmitting by the transmitting antenna array element and receiving by the receiving antenna array.

[0089] In order to avoid the sparse scanning position of the receiving antenna array elements affecting the imaging, all transmitting antenna array elements are switched once every rotation of n degrees, where n is less than or equal to 1 degree after simulation test. When each transmitting antenna array element is working, all receiving array elements receive at the same time; in order to realize broadband millimeter wave signals, each transmitting antenna array element transmits a stepped frequency (SFCW) signal or a swept frequency continuous wave (FMCW) signal, which contains multiple frequencies. The mode in which the number of transmitting antenna array elements is less than the number of receiving antenna array elements and the receiving antenna array elements work simultaneously can significantly reduce the data acquisition time and ensure the accuracy of the scanning position. The following is a detailed description of the data acquisition process for a complete frame:

[0090] 1. The receiving antenna array rotates to an initial position. Since the receiving antenna array rotates around the rotation axis to form a circular scanning array, the initial position can be any position during the scanning process.

[0091] 2. Transmitting antenna element 1 works, transmitting stepped frequency signals or swept frequency continuous wave signals. During the switching of the transmitting frequency, all receiving antenna elements receive simultaneously. After transmitting antenna element 1 completes the transmission of each frequency signal, transmitting antenna element 1 stops transmitting and switches to transmitting antenna element 2, transmitting antenna element 3, and transmitting antenna element 4 to work in sequence. The transmission time of each transmitting antenna element is at the microsecond level to ensure that the displacement of the receiving antenna array during the transmission time period of the transmitting antenna element is very small, so that it can be compensated by the imaging algorithm or directly ignored. All receiving antenna elements receive simultaneously.

[0092] 3. After the four transmitting antenna elements complete transmission, they all stop transmitting and enter a waiting state until the receiving antenna array rotates 1 degree relative to the previous position and reaches the next receiving position.

[0093] 4. Repeat process 2 and 3 until the receiving antenna array scans the entire circumference, thereby completing a receiving cycle and obtaining a frame of image data. For example, when the receiving antenna array elements are symmetrically distributed relative to the rotating shaft along the radial direction of the rotating shaft, only 180 degrees need to be scanned. When the receiving antenna array elements are located on the same side of the rotating shaft in the radial direction of the rotating shaft, 360 degrees need to be scanned.

[0094] See also Fig. 9 As shown, Fig. 9 The diagram is a timing relationship diagram of a transmitting antenna array and a receiving antenna array. Each transmitting antenna array element transmits a transmitting signal of w frequencies; each transmitting antenna array element transmits in time, and when a transmitting antenna array element finishes transmitting, it switches to the next transmitting antenna array element until all transmitting antenna array elements have transmitted, thereby forming a transmitting cycle of the transmitting antenna array; in this transmitting cycle, all receiving antenna array elements receive at the same time; after the transmitting cycle ends, all transmitting antenna array elements enter a waiting state until the receiving antenna array rotates 1 degree, and when the receiving antenna array scans the entire circle, a receiving cycle is completed. The same switching order of the transmitting antenna array elements in each transmitting cycle is conducive to simplifying the transmission control, and the same order of the transmitting signals of the w frequencies transmitted by the transmitting antenna array elements each time is also conducive to simplifying the transmission control. It should be understood that the switching order of the transmitting antenna array elements in each transmitting cycle can be different, and the order of the transmitting signals of the w frequencies transmitted each time can also be different.

[0095] See also Fig.10 As shown, Fig.10It is a schematic diagram of the imaging field of view model. In the figure, the reflected wave data obtained at any scanning point position (theta, r, 0) in the circular scanning array formed by the rotation of the receiving antenna array around the axis of rotation is f(theta, r, w), where theta and r represent the position of the scanning point. From the definition of plane polar coordinates, theta represents the angle between the scanning point and the polar coordinate origin relative to the positive half axis of the x-axis, and r represents the length of the line connecting the scanning point and the polar coordinate origin; w is the carrier frequency of the reflected wave. The reflection function of any spatial point on the target under test is g(x, y, z). Assuming that the antenna beam is infinite, the data obtained at any scanning point position is the superposition of the reflected waves of all points on the target under test, which can be expressed mathematically as follows:

[0096] f(theta, r, w) = ∫∫∫g(x, y, z)*exp(-2j*k*d)dxdydz

[0097] Where k is the wave number corresponding to w, which represents the phase per unit distance change, d is the distance between any spatial point on the target and the scanning point (theta, r, 0), and the three-dimensional spatial coordinates of the target are (x, y, z).

[0098] The imaging process is to reconstruct the reflection function of the target according to the acquired reflection wave data, that is, to obtain g(x, y, z) from the above formula.

[0099] See also Fig.11 As shown, Fig.11 A schematic diagram of a flow chart of the imaging method of the present application. The method comprises:

[0100] Step 1101, obtaining a reflected wave signal received by a receiving antenna array as first transmitted wave data, wherein the reflected wave data obtained at any scanning point position (theta, r, 0) in a circular scanning array formed by the receiving antenna array rotating around a rotation axis is f(theta, r, w), and the data is scanned at equal intervals in the plane polar coordinate angle azimuth, radial azimuth, and frequency axis;

[0101] Step 1102, the acquired first reflected wave data is converted from equally spaced angles and radial directions to equally spaced row and column directions, i.e., the x-axis and y-axis directions of the two-dimensional equivalent array plane, through two-dimensional linear interpolation to obtain equivalent reflected wave data as second transmitted wave data.

[0102] Take the symmetrical distribution of the receiving antenna array elements along the radial direction of the rotation axis relative to the rotation axis as an example. Fig.12 As shown, Fig.12This is a schematic diagram of the scanning points of the circular scanning array surface and its equivalent array surface scanning points of the present application, wherein the left figure is the scanning point distribution of a receiving cycle, and the right figure is the equivalent scanning point distribution. In the equivalent array surface scanning points: the interval between adjacent receiving antenna array elements in the receiving antenna array can be equivalent to the interval between adjacent scanning points in the y-axis direction (column direction); since the displacement of the scanning point along the circumference for each rotation of the receiving antenna array is related to the rotation radius of the scanning point, the larger the radius, the larger the displacement along the circumference, so the interval between adjacent scanning points in the x-direction (row direction) is equivalent to the interval between adjacent scanning points in the y-axis direction. Preferably, the interval is less than or equal to one-half of the wavelength of the transmitted wave. Since the circular scanning array surface is centrally symmetrical, the equivalent array surface is also centrally symmetrical, so that an equivalent square array surface can be obtained. As shown in the figure, in one receiving cycle, the number of scanning points in the row direction of the equivalent array surface is equal to the number of scanning points in the column direction, and is also equal to the number of radial scanning points in the circular scanning array surface.

[0103] For each scanning point in the equivalent array, two-dimensional linear interpolation is performed according to the first reflected wave data of each scanning point in the circular scanning array to obtain the second reflected wave data of each scanning point in the equivalent array.

[0104] Mathematically expressed as:

[0105] f(x, y, w) = INTERP 2D [f(theta, r, w)]

[0106] Among them, f(x, y, w) is the reflected wave data of the scanning point (x, y) in the equivalent square array, INTERP 2D [] indicates two-dimensional linear interpolation.

[0107] After obtaining the transmission wave data of the equivalent array, the reflection function can be reconstructed using traditional near-field imaging methods, including but not limited to near-field three-dimensional imaging methods based on perturbation, near-field three-dimensional imaging methods based on compressed sensing, near-field three-dimensional imaging methods based on wave number domain, near-field three-dimensional imaging methods based on space domain, etc. For example,

[0108] Step 1103: perform a spatial two-dimensional Fourier transform on the second reflected wave data.

[0109] For each scanning point in the equivalent square array, the second reflection data of each frequency of the scanning point is subjected to a two-dimensional Fourier transform to obtain a two-dimensional Fourier transform result, which is expressed as follows:

[0110] F(kx,ky,w)=FFT 2D {f(x, y, w)}

[0111] Among them, FFT 2D {} represents two-dimensional Fourier transform,

[0112] Step 1104: phase shift processing.

[0113] The two-dimensional Fourier transform result is multiplied by a phase factor to perform matched filtering, thereby obtaining a phase shift processing result, which can be expressed mathematically as follows:

[0114]

[0115] Among them, k x , k y are the components of the wave number k in the x and y azimuth directions respectively, and R is the distance from the target to the circular scanning array, that is, the distance direction of the target.

[0116] Step 1105: three-dimensional space spectrum domain interpolation.

[0117] The phase shift processing result is subjected to one-dimensional STOLT interpolation so as to interpolate from the equally spaced frequency axis to the equally spaced kz axis to obtain the STOLT interpolation result, which is expressed as follows:

[0118]

[0119] Among them, STOLT k-kz {} indicates interpolation from the frequency axis k to the equally spaced kz axes;

[0120] Step 1106, three-dimensional inverse Fourier transform.

[0121] Perform a three-dimensional Fourier inverse transform on the STOLT interpolation result, and get the reflection function of any spatial point on the inspected target is g(x, y, z), which can be expressed as:

[0122]

[0123] in, Represents the three-dimensional inverse Fourier transform.

[0124] Step 1107: displaying a three-dimensional reflected wave image.

[0125] The amplitude of each spatial point is calculated, and then rendered and displayed to obtain the pixel amplitude, thereby obtaining the imaging result.

[0126] image(x,y)=RENDER{ABS[g(x,y,z)]}

[0127] Among them, ABS[] represents the calculation of the absolute value of the reflection function, that is, the pixel amplitude, and RENDER{} represents the rendering function.

[0128] See also Fig.13 As shown, Fig.13FIG. 1 is a schematic diagram of an ultra-wideband signal transceiver according to an embodiment of the present invention. The transceiver includes:

[0129] A millimeter wave frequency source, used to provide a baseband source signal for all frequency signals; the frequency signal includes at least two frequency signals, so as to improve the resolution of imaging;

[0130] The power division unit is used to divide the baseband source signal from the millimeter wave frequency source into multiple power divisions. The number of power divisions depends on the number of transmission signal frequencies. For example, if there are w transmission frequencies, the power divisions are w.

[0131] A frequency multiplication unit, used for multiplying the frequency of each baseband source signal from the power division unit to generate multiple frequency signals;

[0132] A transmitting array switch, used for outputting each frequency signal from the frequency multiplication unit to the transmitting antenna array according to the transmitting timing of the timing unit;

[0133] The receiving array switch is used to output each frequency signal from the frequency multiplication unit to the receiving antenna array according to the receiving timing of the timing unit, so that the receiving antenna array receives the reflected wave signal based on each frequency signal.

[0134] The timing unit provides a transmitting timing for the transmitting array switch and a receiving timing for the receiving array switch; wherein,

[0135] The transmission timing enables each of the at least one transmitting antenna array element to transmit the transmission signal of at least two frequencies in time division; and after each transmission cycle, all transmitting antenna array elements enter a waiting state until the receiving antenna array rotates n degrees relative to the previous transmission cycle, and all transmitting antenna array elements enter the next transmission cycle to transmit the transmission wave of the transmission cycle, where n is less than or equal to 1 degree. Specifically, for each transmitting antenna array element switch, the timing unit sequentially provides the timing of F1 to Fw to the transmitting antenna array element switch, such as Fig.13 In the example, the timing of F1 to Fw of the transmitting array element switch 1 is provided sequentially (in time division); for all transmitting antenna array element switches, similarly, the transmitting timing of each transmitting antenna array element switch is also provided sequentially (in time division), such as Fig.13 In the example, when the timing of F1 to Fw of the transmitting array element switch 1 ends, the timing of F1 to Fw of the next transmitting array element switch begins to be provided; that is, the w×m transmitting timing signals provided by the timing unit are provided in sequence, so that each transmitting antenna array element can transmit an ultra-wideband signal.

[0136] The receiving timing enables all receiving antenna elements to receive simultaneously during the transmission cycle in which each transmitting antenna element completes the transmission in sequence; specifically, for each receiving antenna element switch, the timing unit provides the receiving antenna element switch with the timing for receiving F1 to Fw simultaneously (in parallel), such as Fig.13 In the embodiment, the timings of F1 to Fw are provided to the receiving array element switches 1 to r at the same time, that is, the w×r receiving timing signals provided by the timing unit are provided in parallel, so that each receiving antenna array element can independently receive the ultra-wideband signal.

[0137] The transmission and reception of multiple frequencies can help improve the imaging resolution and the distance imaging effect.

[0138] See also Fig.14 As shown, Fig.14 For the security inspection system using the ultra-wideband transceiver device synthesized by frequency bands of this embodiment, the timing provided by the timing unit is briefly illustrated in the figure for ease of understanding. The system includes:

[0139] a transceiver, transmitting w frequency signals for being reflected by the detected object to form a reflected wave, and receiving the reflected wave reflected by the detected object based on the w frequency signals,

[0140] An imaging module is used to reconstruct a reflection function based on the received first reflection wave data,

[0141] A detection unit, for performing detection based on the reconstructed reflection function,

[0142] A driving unit, used for driving the receiving antenna array to rotate around a rotation axis to perform a scanning motion;

[0143] Furthermore, it may also include:

[0144] Display unit, used to display the reconstructed reflection function,

[0145] An alarm unit is used to output an alarm.

[0146] See also Fig.15 As shown, Fig.15 This is a schematic diagram of the imaging module of this embodiment. The imaging module is used to convert the first reflected wave data from the transceiver into the second reflected wave data of the equivalent array surface with row and column directions through interpolation from the circular scanning array surface, and reconstruct the reflection function based on the second reflected wave data.

[0147] The imaging module comprises:

[0148] an equivalent interpolation module, used for converting the first reflected wave data from the circular scanning array into second reflected wave data of an equivalent array with a row direction and a column direction by interpolation,

[0149] The reconstruction module is used to reconstruct the reflection function based on the second reflection wave data.

[0150] Embodiment 2

[0151] See also Fig.16 As shown, Fig.16 This is a schematic diagram of the arrangement of the transceiver antenna array and the corresponding frequency band of the second embodiment. The transceiver antenna array has three rows of transmitting antenna elements and three rows of receiving antenna elements. Each row of transmitting antenna elements transmits the first frequency band transmitting signal, the second frequency band transmitting signal, and the third frequency band transmitting signal respectively. Each row of receiving antenna elements receives the first frequency band receiving signal, the second frequency band receiving signal, and the third frequency band receiving signal respectively. For example, the frequency range of the first frequency band transmitting signal is 10-20GHz, the frequency range of the second frequency band transmitting signal is 20-30GHz, and the frequency range of the third frequency band transmitting signal is 30-40GHz. Correspondingly, the frequency range of the first frequency band receiving signal is 10-20GHz, the frequency range of the second frequency band receiving signal is 20-30GHz, and the frequency range of the third frequency band receiving signal is 30-40GHz. The transceiver antenna elements of the same frequency band are symmetrically distributed along the equivalent phase center connecting line to ensure that the data within all bandwidths are obtained at the same equivalent phase center. The scanning mode of the antenna can be planar or cylindrical.

[0152] Preferably, each row of transmitting antenna array elements may have a direction such that the transmitting beam is oriented toward the center of the detected target scene, for example, Figure 5 As shown, the number of transmitting antenna array elements in each row is p, and the p transmitting antenna array elements are divided into a first group of transmitting antenna array elements located in the middle, a second group of transmitting antenna array elements located on both sides of the middle, and a third group of transmitting antenna array elements. Preferably, the number of transmitting antenna array elements in the second group is equal to the number of transmitting antenna array elements in the third group. The transmitting beams of the first group of transmitting antenna array elements are oriented toward a circular plane perpendicular to the rotation of the receiving antenna array, and the transmitting beams of the remaining two groups of transmitting antenna array elements are oriented toward the scene center of the detected target.

[0153] See also Fig.17 As shown, Fig.17 A schematic diagram of an ultra-wideband transceiver for frequency band synthesis. The transceiver includes:

[0154] Millimeter wave frequency source, used to provide baseband source signals for all frequency bands;

[0155] A power splitter unit is used to perform multi-path power splitting on the baseband source signal from the millimeter wave frequency source. The number of power splitting paths depends on the number of frequency bands. For example, if there are three transmission frequency bands, the power splitting path is three paths.

[0156] The frequency multiplication unit is used to multiply the baseband source signal of each channel from the power division unit to generate multiple complementary frequency bands; the complementarity means that the upper frequency band and the lower frequency band in adjacent frequency bands have partially overlapping frequency band ranges or overlapping frequencies. For example, the upper frequency band is 10-20GHz, the lower frequency band is 15-25GHz, and the partially overlapping frequency band range is 15-20GHz, or the maximum frequency of the upper frequency band is equal to the minimum frequency of the lower frequency band, for example, the first frequency band range is 10-20GHz, the minimum frequency in this frequency band is 10GHz, and the maximum frequency is 20GHz, the second frequency band range is 20-30GHz, the minimum frequency in this frequency band is 20GHz, and the maximum frequency is 30GHz, wherein the maximum frequency of the first frequency band range is equal to the minimum frequency of the second frequency band, so the first frequency band is complementary to the second frequency band;

[0157] A transmitting array switch, used to output each frequency band signal from the frequency multiplication unit to the transmitting antenna array of the frequency band;

[0158] The receiving array switch is used to output each frequency band signal from the frequency multiplication unit to the receiving antenna array of the frequency band respectively, so that the receiving antenna array receives the signal from the receiving antenna array of the frequency band based on the frequency band.

[0159] Take three frequency bands as an example. The three frequency bands share the same millimeter wave frequency source, the power division unit divides one baseband source signal from the millimeter wave frequency source into three channels, and the three frequency multipliers respectively multiply the three power-divided baseband source signals to obtain the first frequency band signal, the second frequency band signal, and the third frequency band signal, respectively, wherein the first frequency band signal is output to the first transmitting array switch and the first receiving array switch, respectively, the second frequency band signal is output to the second transmitting array switch and the second receiving array switch, respectively, and the third frequency band signal is output to the third transmitting array switch and the third receiving array switch, respectively.

[0160] The transceiver of this embodiment performs power division and frequency multiplication on the baseband source signal from the millimeter wave frequency source, thereby obtaining an ultra-wideband signal composed of various frequency bands as a whole, thereby improving the resolution of range imaging without increasing the difficulty of hardware design.

[0161] See also Fig.18 As shown, Fig.18 A schematic diagram of a security inspection system using the transceiver device described in this embodiment. The security inspection system includes:

[0162] a transceiver, transmitting an ultra-wideband signal for being reflected by a detected target to form a reflected wave, and receiving the reflected wave reflected by the detected target,

[0163] An imaging module is used to reconstruct a reflection function based on the received reflection wave data.

[0164] A detection unit, used for performing detection based on the reconstructed reflection function;

[0165] The driving unit is used to drive the antenna array to perform scanning motion. In this embodiment, since the receiving antenna array and the transmitting antenna array are integrated, the antenna array includes the receiving antenna array and the transmitting antenna array.

[0166] Furthermore, it may also include:

[0167] Display unit, used to display the reconstructed reflection function,

[0168] An alarm unit is used to output an alarm.

[0169] In this article, relational terms such as first and second, etc. are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0170] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A millimeter wave transceiver, characterized in that: The device comprises, A millimeter wave frequency source provides a baseband source signal for an ultra-wideband signal synthesized by frequency bands; the number of the frequency bands is at least two, The power division unit is used to divide the baseband source signal from the millimeter wave frequency source according to the number of frequency bands to obtain at least two baseband source signals. A frequency multiplication unit, used for multiplying the baseband source signal of each channel from the power division unit to generate at least two complementary frequency band signals; the at least two complementary frequency bands are adjacent frequency bands, where the upper frequency band and the lower frequency band have partially overlapping frequency band ranges or overlapping frequencies; The array switch is used to output each frequency band signal from the frequency multiplication unit to the transceiver antenna array of the frequency band.

2. The device according to claim 1, characterized in that The frequency multiplication unit includes at least two frequency multipliers, each of which multiplies the frequency of a baseband source signal from the power division unit to obtain a frequency band signal.

3. The device according to claim 1, characterized in that The transceiver antenna array has at least two rows of transmitting antenna elements and at least two rows of receiving antenna elements. Each row of transmitting antenna array elements transmits a frequency band signal. Each row of receiving antenna elements receives a frequency band signal. The transmitting antenna array elements and receiving antenna array elements in the same frequency band are symmetrically distributed along the axis connecting the equivalent phase centers.

4. The device according to claim 3, characterized in that The array switch comprises: A transmitting array switch, used for outputting each frequency band signal from the frequency multiplication unit to the transmitting antenna array of the frequency band; The receiving array switch is used to output each frequency band signal from the frequency multiplication unit to the receiving antenna array of the frequency band.

5. The device according to claim 3, characterized in that The transmitting and receiving antenna array is scanned in a planar manner, or in a cylindrical manner; Each transmitting antenna array element in the transmitting antenna array has a direction that makes the transmitting beam point to the center of the detected target scene.

6. The device according to claim 4, characterized in that The receiving antenna array has a rotation axis and at least two receiving antenna array elements arranged in a radial direction of the rotation axis. The receiving antenna array is driven to rotate around the rotation axis to receive a reflected wave signal formed by reflection of a transmission wave emitted by at least one transmitting antenna array element fixed to a circumferential envelope boundary formed by the rotation of the receiving antenna array and being reflected by a detected target.

7. The device according to claim 6, characterized in that The at least two receiving antenna array elements are located on the same side of the rotating shaft in the radial direction of the rotating shaft, or are symmetrically distributed relative to the rotating shaft in the radial direction of the rotating shaft; The interval between two adjacent receiving antenna array elements is equal, and the interval is greater than or equal to the wavelength of the transmitting wave.

8. The device according to claim 6, characterized in that The at least one transmitting antenna array element is bilaterally symmetrically distributed on the boundary of a circular envelope formed by the rotation of the receiving antenna array in the height direction of the detected target; The circular envelope boundary is a closed polygon formed by connecting end to end straight line segments circumscribing the circle formed by the rotation of the receiving antenna array; or, the circular envelope boundary is a closed circle with the rotation axis as the center and a radius greater than the rotation radius of the receiving antenna array; Each of the at least one transmitting antenna array element has a direction that causes the transmitting beam to be oriented toward the center of the detected target scene.

9. The device according to claim 8, characterized in that Each of the at least one transmitting antenna array element transmits transmission signals of at least two frequencies in a time-sharing manner, and after each transmission cycle, all transmitting antenna array elements enter a waiting state until the receiving antenna array rotates n degrees relative to the previous transmission cycle, and all transmitting antenna array elements enter the next transmission cycle to transmit the transmission wave of the transmission cycle, wherein n is less than or equal to 1 degree; During a transmission cycle in which each transmitting antenna array element completes transmission in sequence, all receiving antenna array elements receive simultaneously.

10. A security inspection system, characterized in that: The system includes, A millimeter wave transceiver according to any one of claims 1 to 9, transmitting an ultra-wideband signal for being reflected by a detected target to form a reflected wave, receiving a reflected wave of the ultra-wideband signal synthesized by the sub-frequency bands reflected by the detected target, An imaging module is used to reconstruct a reflection function based on the received reflection wave data. A detection unit, used for performing detection based on the reconstructed reflection function; The driving unit is used to drive the transceiver antenna array to perform scanning motion.

Images