Analog and digital hybrid two-dimensional phased array radio frequency multiple-beam intelligent imaging system

[0022] The block diagram of the analog-digital hybrid two-dimensional array RF multi-beam intelligent imaging system is shown in figure 1. An analog-digital hybrid two-dimensional array radio frequency multi-beam intelligent imaging system includes an antenna array and a corresponding receiving channel array. The receiving channel array has N×M receiving units, that is, there are N groups of units in the direction of the first dimension, and M groups of units in the direction of the second dimension, and the groups here can be rows or columns. In other words, the array can be placed horizontally or vertically.

[0023] Each receiving unit in the receiving channel array includes: antenna input circuit, such as input balun or RF filter; RF receiving low noise amplifier for amplifying the RF signal; one or two-stage downconverter, downconverting the input RF signal Frequency conversion to baseband signal; RF bandpass filter or IF filter and baseband filter for filtering out interfering signals; The baseband signal is weighted by the required angle and amplitude to achieve coherent reception of multiple signals; the local receive clock generation circuit generates the required local oscillation clock signal for downconverter; the receive beam controller is used to control each receiving unit. Phase and amplitude of multiple beams; the receiving data interface circuit is responsible for receiving control commands from the system for controlling the phases and amplitudes of multiple beams to achieve beam scanning coverage.

[0024] The analog-digital hybrid two-dimensional array RF multi-beam intelligent imaging system simulates coherent superposition of all the receiving units in the array in the first dimension, performs spatial filtering in space, and then generates M groups of simulations in the direction of the first dimension multi-beam signal. Suppose the number of beams is n.

[0025] The analog-digital hybrid two-dimensional array radio frequency multi-beam intelligent imaging system further includes: a parallel analog-to-digital converter unit for converting analog signals of M groups of n-beams into digital multi-beam signals of M groups of n-beams; parallel digital signal processing two-dimensional imaging The unit is used to convert the two-dimensional digital beam signals of M groups of n-beams into two-dimensional digital image signals, and achieve scanning coverage through time-division scanning to complete the synthesis of the entire image.

[0026] From the aspect of engineering realization, the receiving channel array of the analog-digital hybrid two-dimensional array radio frequency multi-beam intelligent imaging system can also be decomposed into multiple receiving sub-matrix units to help reduce development and manufacturing costs, such as figure 2 shown. Decomposable multiple receiver sub-matrix units also means modularity, structuring and building blocks.

[0027] The receiving channel array of the analog-digital hybrid two-dimensional array radio frequency multi-beam intelligent imaging system can be decomposed into a parallel one-dimensional analog receiving channel array. One-dimensional analog receive channel arrays and receive units can be decomposed into physically realizable integrated circuit chip structures, see image 3. In an integrated circuit chip, multiple receiving units can be integrated, and each receiving unit includes: an antenna, an antenna input circuit, a low-noise amplifier, a band-pass filter, a one-stage or two-stage downconverter, and a multi-channel complex weighting factor unit , local clock generator and corresponding control unit (not shown). In the RF receive channel structure of the one-stage downconverter, the downconverter is a quadrature balanced downconverter, which can be realized by an active or passive mixer. In the two-stage downconverter RF receive channel structure, the second downconverter is a quadrature balanced downconverter, which can also be implemented by active or passive mixers.

[0028] Multiple complex weighting factor units are implemented by parallel complex weighting factor units, and each complex weighting factor unit completes

[0029]

[0030]

[0031] Here i is a three-dimensional vector subscript, i=i(k,l,b), where k, and l are the position coordinates of the receiving unit in the array, and b is the subscript of the bth beam. yi and xi are the output and input of the ith complex weighting factor unit, respectively, and is the angle by which the complex weighting factor element is to be rotated. Δθ i ,Δφ i are the phase difference values ​​of two adjacent receiving units in the first dimension and the second dimension, respectively. a i is the weighting factor, It is an inherent correction value to compensate for the system phase error. The complex weighting factor unit is implemented by analog linear circuit units, such as broadband operational amplifiers, vector unit amplifiers, and many other deformation structures.

[0032] Parallel digital signal processing 2D imaging unit including: amplitude detection/or power detection; digital signal processor and controller; artificial intelligence visual neural network or image recognition and processing unit; wireless or wired transmission interface for display interface, see Figure 4.

[0033]The analog-digital hybrid two-dimensional array radio frequency multi-beam intelligent imaging system further includes: a power-controllable radio frequency radiation source unit is used to generate a uniform radiation source field covering the target. The power controllable RF radiation source unit can be realized by several distributed subunits, see Figure 5.

[0034] The analog baseband multi-beamforming complex factor weighting matrix unit of each receiving unit in the receiving array is connected to the input of a parallel multiplexing complex weighting factor unit based on the output of the baseband low pass filter. The multiplex complex weighting factor unit weights the signals of a plurality of specific incident angles according to a plurality of specific complex weighting factor matrices in the direction of the first dimension, so that a plurality of received signals from different incident angles have a plurality of different incidents in the first dimension The signal phase synchronization is achieved in the corresponding direction of the angle, and the in-phase superposition is performed on the output contact to form a parallel analog baseband multi-beam signal output. The controller generates a plurality of specific complex weighted control signals to control the required phase shift angle, and also controls the brightness, the viewing angle width, the power intensity of the emission source, and the static and dynamic parameters of various parameters during system operation. set up.

[0035] There are two methods for the next processing. The first method is to output the parallel analog baseband multi-beam signal of the first dimension in the receiving array, and convert it into a parallel digital baseband multi-beam signal of the first dimension through a parallel analog-to-digital converter. , and then form a second dimension two-dimensional digital beam signal on the output of the parallel digital baseband multi-beam signal of the first dimension.

[0036] The second method is to first perform amplitude detection or power detection on the output signal of the parallel analog baseband multi-beam signal in the first dimension, and then convert it into a narrowband signal, and then convert it into a parallel digital baseband in the first dimension by the analog-to-digital converter. multi-beam signal. The second dimension digital beamforming is performed on the narrowband parallel digital baseband multi-beam signal output of the first dimension. The advantage of the second method is that the conversion rate of the analog-to-digital converter is further reduced, but the imaging effect is less than the first direct analog-to-digital conversion, because the amplitude detection or power detection can destroy the coherence of the signal.

[0037] The analog-digital hybrid two-dimensional array radio frequency multi-beam intelligent imaging system is also characterized in that, in the second dimension, amplitude detection and two-dimensional baseband multi-beam image signal formation are performed by a digital signal processor or other hardware.

[0038] The analog-digital hybrid two-dimensional array radio frequency multi-beam intelligent imaging system is also characterized in that the artificial intelligence visual neural network is used to identify and filter the image features of the two-dimensional baseband multi-beam image to detect the graphics of sensitive objects. For example, it is very meaningful in human body safety detection, because people's coats are transparent under microwaves, and the outlines of people's bodies are fully exposed. In this application, the detected person is unacceptable. With the artificial intelligence visual neural network, machine vision is used to complete target filtering, hide sensitive human body parts, and only detect dangerous goods and weapons. Panoramic images can be displayed when suspicious objects and objects are found. The panoramic image includes the video image generated by the optical camera, the two-dimensional image generated by the radio frequency multi-beam intelligent imaging system, and the superimposed image of the two, etc. The artificial intelligence visual neural network also provides the speed of detection.

[0039] The analog-digital hybrid two-dimensional array radio frequency multi-beam intelligent imaging system is also characterized in that multiple specific incident angles in the first dimension can be changed according to the instructions of the receiving beam controller to achieve global scanning or local scanning, and dynamically adjust the imaging Viewing angle width.

[0040] The analog-digital hybrid two-dimensional array radio frequency multi-beam intelligent imaging system is also characterized in that multiple specific incident angles in the second dimension can be changed according to the instructions of the receiving beam controller to achieve global scanning or local scanning, and dynamically adjust the imaging angle. Viewing angle width.

[0041] The analog-digital hybrid two-dimensional array radio frequency multi-beam intelligent imaging system is also characterized in that the complex weighting factor in the second dimension can be implemented by a digital signal processor based on a multi-stage basic butterfly structure.

[0042] The analog-digital hybrid two-dimensional array radio frequency multi-beam intelligent imaging system is also characterized in that the two-dimensional array radio frequency multi-beam intelligent image forming and display screen can be centralized or separate through wireless or wired communication to connect the two-dimensional array radio frequency Multi-beam intelligent image forming part, display screen and man-machine interface part. It can also be wirelessly connected to intelligent communication terminal devices, such as smart phones and handheld terminals, and can communicate and interact with people through human-machine interfaces such as keyboards and screens.

[0043] The analog-digital hybrid two-dimensional array radio frequency multi-beam intelligent imaging system is also characterized in that it has intelligent radiation intensity irradiation control, which can automatically adjust the radiation intensity of the controllable radio frequency radiation source according to the distance of the scene, so as to achieve the best detection range of the image. The distance of the scene can be realized by methods such as infrared ranging or radio ranging. The optimal detection amplitude of the image enables the detection of a specific target to achieve the highest recognition rate.

[0044] The analog-digital hybrid two-dimensional array radio frequency multi-beam intelligent imaging system is also characterized in that a local oscillator with variable frequency can perform receiving down-conversion detection at at least one different frequency. Since the target object has different absorption and reflection characteristics for different frequencies, receiving down-conversion detection at different frequencies provides more different images. After the compounding of various images, the amount of image information is increased, thereby increasing the level of the image. In the artificial intelligence imaging system, through self-learning, the best detection range and effect can be achieved.

[0045] The analog-digital hybrid two-dimensional array radio frequency multi-beam intelligent imaging system is also characterized in that it has intelligent brightness control, which can automatically adjust the image brightness according to the image amplitude of the scene to achieve the best detection amplitude of the image. At the same time, if the amplitude of the irradiated power signal is not uniform in space, the brightness can be compensated by predistortion. Predistortion usually increases the detection gain in the area with low spatial illumination illumination, and compresses the detection gain in the area with high spatial illumination illumination.

[0046] The analog-digital hybrid two-dimensional array radio frequency multi-beam intelligent imaging system is either a fixed large equipment, a portable small equipment, or an unmanned flying object.