X-band smart circular array antenna and control method thereof

Abstract

The application discloses an X-band intelligent circular ring array antenna and a control method thereof, and relates to the technical field of radar antennas.The antenna comprises a PCB base plate, a plurality of antenna elements are distributed radially on the front surface of the PCB base plate, the front surface of the PCB base plate is an analog circuit, and the back surface is a digital processing control circuit.The analog circuit comprises a power divider / combiner and a multi-path TR component, and the digital processing control circuit comprises an SPI control interface, a wave control circuit, a power supply and a modulation circuit.The application superimposes the windowed beam forming algorithm and the traditional beam forming superposition processing technology, overcomes the disadvantage that the main and side lobe suppression of the circular ring antenna array is relatively low, greatly reduces the false target false alarm probability, adopts the circular ring array + phased array technology to realize the X-band intelligent antenna, does not need a motor rotating device, adopts full digital beam forming, and has faster scanning speed, higher reliability, various scanning modes, can realize the beam pointing large-angle instantaneous movement, and overcomes the inertia disadvantage of mechanical scanning.

Description

Technical Field

[0001] This invention relates to the field of radar antenna technology, specifically to an X-band intelligent circular array antenna and its control method. Background Technology

[0002] Marine radar is divided into two technical routes: magnetron radar and solid-state radar. Solid-state radar uses pulse compression technology, which eliminates the drawbacks of magnetrons and has many advantages such as shorter warm-up time, longer service life, higher reliability, and lower electromagnetic radiation energy. It can provide excellent detection range and resolution. In particular, the low-power pulse transmission meets the upcoming radar low-radiation standards, making it more environmentally friendly. This allows it to operate safely in anchorage areas and docks and provide radar coverage throughout the voyage. It also has the potential to measure the Doppler frequency shift of targets and is the mainstream development direction for future marine radar. Currently, most of the world's major solid-state radars use microstrip antenna arrays + motor scanning. This method has the advantages of simple structure, low cost, and ease of implementation, but it also has disadvantages such as slow mechanical scanning speed, inability to achieve multi-beam scanning, and inability to perform staring tracking.

[0003] Existing technologies also include end-fire circular array antennas. Under special installation conditions, end-fire circular arrays have significant advantages. When the installation requires a very low antenna height and 360° scanning, using an end-fire circular array antenna is a very wise choice. Circular array antennas have the following characteristics compared to linear array antennas: 1) Linear arrays can theoretically provide a 180° scanning range, but as the angle increases, the beamwidth increases and the directivity deteriorates, so a range of ±60° in the normal direction is usually used. Circular arrays, on the other hand, can cyclically move the array excitation, providing 360° scanning without blind spots, and have the same array aperture in any orientation. 2) The far-field mode of the circular array is frequency-independent and can use broadband and ultra-wideband signals. Higher time resolution and ranging accuracy can be obtained through pulse compression technology. 3) Adaptable to some special installation occasions, such as conformal installation with cylindrical shells on aircraft; 4) 360° coverage eliminates the need for mechanical scanning devices such as motors, resulting in higher reliability and much faster scanning speed. It can even perform cross-scanning, unlike mechanical scanning which is limited by motor speed and makes it difficult to instantly shift the beam direction. The beam direction can be manipulated simply and flexibly. 5) With the same number of array elements, the sidelobe level of a linear array is usually lower than that of a circular array. Regardless of the number of elements and the radius of the circular array, the first sidelobe is about 8dB lower than the main lobe. In contrast, the first sidelobe of a uniform linear array is about 13dB lower than the main lobe, which is its disadvantage.

[0004] This application addresses the drawback of low main lobe and sidelobe suppression in circular arrays by improving the algorithm, and proposes an X-band intelligent circular array antenna and its control method. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide an X-band intelligent circular array antenna and its control method.

[0006] To achieve the above objectives, the present invention provides the following technical solution: an X-band intelligent circular array antenna, the antenna comprising a PCB chassis, wherein a plurality of antenna elements are radially distributed on the front side of the PCB chassis, the front side of the PCB chassis is an analog circuit, and the back side is a digital processing and control circuit, the analog circuit comprising a power divider / combiner and a multi-channel TR component, the digital processing and control circuit comprising an SPI control interface, a beam control circuit, a power supply and a modulation circuit, and each TR component comprising a transmit / receive switch, a balanced power amplifier, a limiting LNA, a 6-bit high-precision phase shifter, a 6-bit high-precision attenuator and a drive amplifier; The antenna also includes an FPGA chip, in which pre-stored beam control parameters are implemented to generate good beam control.

[0007] Taking the time of arrival at the center of the PCB chassis of the X-band intelligent circular array antenna as the reference time, the distance difference dk between each antenna element of the X-band intelligent circular array antenna along the beam direction and the vertical plane is obtained. The additional phase shift of the radar signal caused by the distance is: Where f is the operating frequency and C is the speed of light, the additional phase shifts of each antenna element can be canceled out by the phase shifter, thus achieving same frequency and phase. The signal output after combining N antenna elements is: The signal output after synthesis by the antenna elements is windowed, and the synthesized output after windowing is: Where wk is the windowing function, which includes the triangular window, Hamming window and Kaiser window.

[0008] Regarding the above and Multiplication and fusion processing.

[0009] Beneficial effects: Compared with existing technologies, this X-band smart circular array antenna technology has the following beneficial effects: This invention combines windowed beamforming algorithm with traditional beamforming technology to overcome the drawback of low main and side lobe suppression in circular ring antenna arrays, significantly reducing the false alarm probability. It employs a circular array + phased array technology to realize an X-band smart antenna, eliminating the need for a motor rotation device and abandoning mechanical scanning. Using fully digital beamforming, it offers faster scanning speed, higher reliability, and diverse scanning modes, enabling instantaneous large-angle beam pointing movement. It overcomes the inertia drawbacks of mechanical scanning, allows for pre-stored beam control parameters, and also allows users to download their own parameters, making it extremely convenient. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the analog circuit of the present invention; Figure 2 This is a schematic diagram of the beam synthesis algorithm of the present invention; Figure 3 This is a schematic diagram of the windowed beamforming algorithm of the present invention; Figure 4 This is a simulation diagram of the beamforming effect of the triangular window added to this invention; Figure 5 This is a simulation result of Gaussian window beamforming in this invention; Figure 6 This is a schematic diagram of the digital processing control circuit of the present invention; Figure 7 This is a schematic diagram of the X-band four-channel TR component of the present invention; Figure 8 This is a functional block diagram of the wave control circuit of the present invention; Figure 9 This is a schematic diagram of the operation of the intelligent circular antenna array of the present invention. Detailed Implementation

[0011] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0012] Please see Figures 1-9As shown, the present invention provides a technical solution: an X-band intelligent circular array antenna and its control method. The antenna includes a PCB chassis, on the front of which several antenna elements are radially distributed. The front of the PCB chassis is an analog circuit, and the back is a digital processing and control circuit. The analog circuit includes a power divider / combiner and a multi-channel TR component. The digital processing and control circuit includes an SPI control interface, a beam control circuit, a power supply and a modulation circuit. Each TR component includes a transmit / receive switch, a balanced power amplifier, a limiting LNA, a 6-bit high-precision phase shifter, a 6-bit high-precision attenuator, and a drive amplifier. The antenna also includes an FPGA chip, in which pre-stored beam control parameters are implemented to generate good beam control.

[0013] In practical use, a radar dome with good wave transmission performance needs to be designed to shield the antenna in order to achieve waterproof, windproof, and corrosion-proof effects.

[0014] This invention uses 48 antenna elements with a radius of... The basic principle of the present invention is illustrated by the example below: Using the arrival time at the center of the circle as the reference time, simple geometric calculations can be used to obtain the path difference (compared to the arrival time at the center of the circle) of each element. This is essentially the distance difference dk between each element along the beamline and the vertical plane. Elements above the vertical plane have negative distances and lead phase, while those below the vertical plane have positive distances and lag phase. The additional phase shift in the radar signal caused by this distance is: Where f is the operating frequency and C is the speed of light. A phase shifter can cancel out the additional phase shifts of each element, achieving in-phase and frequency-coordinated beams. These are then superimposed to obtain the desired beam direction. The basic principle is as follows: Figure 2 As shown.

[0015] The signal output after combining N primitives is: Its synthesis effect is as follows Figure 4 The blue line in the left-hand diagram shows 48 primitives with a radius R ≥ N × 2π. The main lobe width is approximately 8 dB wider than the sidelobe width. Clearly, the main and sidelobe suppression is relatively low and does not meet the requirements. Therefore, windowing is applied as follows: Figure 3 As shown, the synthesized output after windowing is Where wk is the windowing function, various window functions such as triangular windows, Hamming windows, and Kaiser windows can be used. Users can choose flexibly according to their needs. Figure 4 The left image shows the beamforming effect after adding a triangular window. Clearly, the first sidelobe has a better suppression effect and is significantly improved.

[0016] After horizontal beamforming with a triangular window, the main lobe width remains unchanged. Although the side lobes are significantly suppressed to about 10dB, this is still far from the 13dB suppression of a linear array.

[0017] from Figure 4 As shown in the left image, the sidelobes are misaligned, and multiplication may cause them to suppress each other, while the main lobes overlap, resulting in no change in beam width after superposition. Therefore, we performed two beamforming methods followed by further multiplication and fusion processing, achieving a more ideal effect, as shown below. Figure 4 As shown in the middle right figure, the suppression exceeds 23dB, which is ideal.

[0018] To further verify the effect, a Gaussian window function was used to generate the windowing coefficients. The simulation results are as follows: Figure 5 As shown in the figure, it can be seen that the suppression effect of adding a Gaussian window alone is better than that of the trigonometric function, with a main lobe-to-side lobe ratio exceeding 11dB. However, after synthesis, the suppression effects of the main lobe and side lobe are both more than 23dB, which is not much different and both are quite ideal.

[0019] Working Principle: To achieve the above objectives, this application employs a TR component to control its phase, thereby rapidly realizing the desired beam shape in a specified direction. The entire PCB chassis is circular, with the digital processing control circuit and analog circuit distributed on both sides to prevent interference. Figure 1 and 6 As shown.

[0020] The analog circuit's TR chip uses an X-band four-channel fully integrated TR chip, the schematic of which is shown below. Figure 7 As shown, this chip integrates digital and radio frequency (RF) circuits. The digital circuits include an SPI control interface, wave control circuitry, power supply, and modulation circuitry. The RF circuitry includes a pair of four-way power splitters / combiners and four TR (transmitter / receiver) modules. Each TR module includes a transmit / receive switch, a balanced power amplifier, a limiting LNA (with a 0.5W burn-out-resistant receiver limiter), a 6-bit high-precision phase shifter, a 6-bit high-precision attenuator, and a driver amplifier. The maximum transmit power is 27dBm, the receive noise figure is 3dB, and the phase shift accuracy is <4°RMS. The transmit / receive switching time is <100ns, making it particularly suitable for low-cost, short-to-medium range, small-scale two-dimensional phased-array radars, X-band communication systems, and test equipment. The SPI clock does not exceed 20MHz, uses a two-level buffer, and the total control word is 80 bits, as shown below. Figure 8 As shown.

[0021] To simplify user experience, we pre-store the beam control parameters in the FPGA. Users only need to control the beam index number via the SPI port, and the FPGA will automatically call the parameters to form the desired beam. This gives the antenna automatic beamforming capabilities without user intervention, reduces transmission parameters, and allows for fast switching. Users are responsible for controlling the transmit / receive switching and selecting the generated transmit signal waveform. Thus, the antenna becomes a relatively independent, intelligent phased array ring array, as illustrated in the diagram below. Figure 9 As shown.

[0022] from Figure 9 As can be seen, the default user-provided beam control pointing parameters are 720 sets of uniformly distributed beams, each with a 0.5° beam spacing. Users only need to input 10 bits of beam pointing to select a specific direction. Upon receiving this information, the FPGA calls the corresponding coefficients and downloads them to each TR component. This system allows users to read and download beam control coefficients, providing a maximum of 1024 sets of coefficients. Therefore, the minimum beam spacing is 360 / 1024 ≈ 0.35°. Typically, the pointing coefficients are generated uniformly beforehand, but users can customize the beams to be denser in some directions and sparser in others, allowing for non-uniform beam generation. Customization services can be provided to ensure optimal results. Furthermore, the user's scanning method is flexible and offers a wide range of options.

[0023] The beam switching rate is less than 100ns. Theoretically, the beam scanning speed can switch up to 10 million times per second. However, considering the propagation delay of light, for example, a range of 15 kilometers and a round trip of 30 kilometers, the transmission time is: 30 / C=30 / 300000=0.1ms. Therefore, the beam switching speed is no more than 10,000 times per second.

[0024] Based on the above scheme, considering the phase delay accuracy problem (6 bits), the simulation results show that the number of primitives is 48, the radius of the ring is 0.30m, and the coefficient windowing is applied using win=window(@gausswin ,N,1.8) to fuse the coefficients of the two beamforming processes together in advance to generate the synthesized beam control parameters.

[0025] The X-band intelligent ring array antenna technology of this invention overcomes some inherent shortcomings of mechanically scanned solid-state radar antennas, achieving flexible beam pointing control. It can utilize pre-stored beam control parameters or allow users to download their own parameters, which is very convenient. The scanning method is more flexible, allowing for uniform or non-uniform scanning; continuous or skip scanning; forward or reverse scanning (with arbitrary turning at any time); it can also achieve a staring function, enabling long-term monitoring of directions and targets of interest. After setting a quiet zone, it can directly skip over it, unlike mechanically scanned radar which requires rotation time. In addition, by omitting motors and other mechanical devices, the structure is more compact and reliable, and the scanning speed is faster. In particular, the innovative technology of superimposing windowed beamforming algorithms with traditional beamforming processing overcomes the drawback of low main and side lobe suppression in circular ring antenna arrays, greatly reducing the probability of false alarms.

[0026] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A control method for an X-band intelligent circular array antenna, characterized in that, The control method includes: Taking the time of reaching the center of the PCB chassis of the X-band intelligent circular array antenna as a reference, the distance difference dk between each antenna element of the X-band intelligent circular array antenna along the beam direction and the vertical plane is obtained. The additional phase shift of the radar signal caused by the distance is: , Where f is the operating frequency and C is the speed of light, the additional phase shifts of each antenna element are canceled out by a phase shifter, thus achieving same frequency and phase. The signal output after combining N antenna elements is: , The signal output after synthesis by the antenna elements is windowed, and the synthesized output after windowing is: , Where wk is the windowing function; Will and Multiplication and fusion.

2. An antenna for implementing the control method of an X-band intelligent circular array antenna as described in claim 1, characterized in that: The antenna includes a PCB chassis with several antenna elements radially distributed on the front. The front of the PCB chassis contains analog circuitry, while the back contains digital processing and control circuitry. The analog circuitry includes a power divider / combiner and multiple TR components. The digital processing and control circuitry includes an SPI control interface, beam control circuitry, power supply, and modulation circuitry. Each TR component includes a transmit / receive switch, a balanced power amplifier, a limiting LNA, a 6-bit high-precision phase shifter, a 6-bit high-precision attenuator, and a drive amplifier. The antenna also includes an FPGA chip, which stores pre-generated beam control parameters.

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