Calibration Device and Method for Wideband Digital Phased Array Antenna Suitable for Cylindrical Conformal

Abstract

The present invention discloses a calibration device and method for a broadband digital phased array antenna suitable for cylindrical conformal. The device includes a calibration track, a conformal calibration frame, a microstrip antenna, a calibration chassis and an electric tractor. The conformal calibration frame is installed on the calibration track. The output of the calibration chassis is connected to the driving end of the electric tractor, and the electric tractor is used to drive the conformal calibration frame to slide on the calibration track. A plurality of calibration antennas are installed on the conformal calibration frame. The connection lines between the calibration antennas and the to-be-tested array elements are parallel to the normal directions of the to-be-tested array elements. The distances between each calibration antenna and each to-be-tested array element meet the antenna near-field test conditions. The microstrip antenna is deployed between two adjacent to-be-tested array elements, and the deployment direction is parallel to the moving direction of the conformal calibration frame. One end of the microstrip antenna is connected to a matching load, and the other end is connected to the calibration chassis through a microstrip line switch power divider. The calibration antenna is connected to the calibration chassis through a calibration frame switch power divider. The present invention can realize the calibration of the conformal digital broadband phased array antenna.

Description

Technical Field

[0001] The present invention relates to the technical field of phased array antenna calibration, and particularly relates to a calibration device and method for a wideband digital phased array antenna suitable for cylindrical conformal Background Art

[0002] The technical characteristics of phased array antennas are very superior, and there are many technical advantages compared with traditional reflector antennas. Its high-precision pointing, multi-target measurement and control capabilities, adaptive beamforming, and anti-interference capabilities are all very prominent, and it has been widely used in radar, communication, countermeasure and other fields. In the development of phased array technology, one of the vigorously developed directions is conformal phased array antennas. "Conforming" the antenna array surface to the carrier shape can greatly increase the applicable scenarios of the antenna. Especially for aircrafts running at high speeds and with strict restrictions on equipment weight and installation space, the conformal antenna configuration will not damage the aerodynamic shape of the aircraft. For ground-based carrier platforms, conformal antennas can endow them with certain camouflage capabilities.

[0003] However, the calibration of large conformal phased array antennas has always been a very difficult problem to solve. In order to obtain higher antenna gain, the antenna size is often large, while the conventional planar scanning probes in current large microwave anechoic chambers can generally only move in two dimensions and cannot meet the calibration requirements of large conformal array antennas. Building a three-dimensional probe requires extremely high construction costs and very complex robotic arm design support. The robotic arm itself is prone to the generation of multipath effects and is not applicable to large microwave anechoic chambers.

[0004] In addition, the calibration process of digital phased arrays with wideband signal bandwidth is more complex than that of digital phased arrays with narrowband signal bandwidth. Because the calibration of narrowband digital phased arrays only requires frequency domain compensation, and the process is relatively simple. For wideband phased arrays with a signal bandwidth above 100M, in addition to compensating the frequency domain part, the time domain part also needs to be compensated, otherwise some signals will be folded back.

[0005] In related technologies, the phased array antenna calibration method proposed in the patent application document with publication number CN111641463A is essentially an improvement of the planar calibration method. For a curved surface array, when using the planar calibration method, the calibration horn needs to be perpendicular to the antenna surface, so a three-dimensional calibration horn, that is, a three-dimensional probe, is required. This scheme proposes to use a turntable combined with a two-dimensional calibration horn, that is, a planar scanning probe, to replace the three-dimensional calibration horn to realize the calibration of the curved surface using the planar calibration method. However, the turntable must be designed in a linkage manner with the two-dimensional horn, that is to say, the angle of rotation of the turntable must be extremely precise, and at the same time, the turntable must traverse in all directions. Obviously, only through the two fixed angles of the first calibration position and the second calibration position mentioned in this scheme, the differences between array elements cannot be obtained.

[0006] The self - calibration method of the near - field channel calibration link of the spherical phased array antenna proposed in the patent application document with the publication number CN107783087A is essentially a curved - surface improved type of the planar multi - point method calibration. The core idea of the planar multi - point method calibration is calibration transfer. One of the most important conditions for the planar multi - point method to achieve calibration is that the antenna array surface must be symmetric. Once the antenna array surface is asymmetric, this scheme cannot be used. This is also the reason why the initial point in this scheme must be selected at the top of the spherical array antenna. Summary of the Invention

[0007] The technical problem to be solved by the present invention is how to achieve the calibration of the conformal digital broadband phased array antenna.

[0008] The present invention solves the above - mentioned technical problem by the following technical means:

[0009] In the first aspect, the present invention proposes a calibration device for a broadband digital phased array antenna suitable for cylindrical conformal. The calibration device includes a calibration track, a conformal calibration frame, a microstrip antenna, a calibration chassis, and an electric tractor. The conformal calibration frame is installed on the calibration track. The output of the calibration chassis is connected to the driving end of the electric tractor, and the electric tractor is used to drive the conformal calibration frame to slide on the calibration track;

[0010] A number of calibration antennas are installed on the conformal calibration frame. The connection lines between the calibration antennas and the to - be - measured array elements are parallel to the normal directions of the to - be - measured array elements. The distance between each calibration antenna and each to - be - measured array element is a fixed value D, and the fixed value D satisfies the antenna near - field test conditions;

[0011] The microstrip antenna is deployed between two adjacent to - be - measured array elements, and the deployment direction is parallel to the moving direction of the conformal calibration frame. One end of the microstrip antenna is connected to a matching load, and the other end is connected to the calibration chassis through a microstrip line switch for power distribution. The calibration antenna is connected to the calibration chassis through a calibration frame switch for power distribution.

[0012] Further, the fixed value D satisfies: where λ is the wavelength and r is the aperture of the antenna array element.

[0013] Further, the calibration antenna adopts a fixed - gain antenna.

[0014] Further, the time delays of the signals output by the calibration frame switch for power distribution are consistent and the initial phases are consistent. The time delays of the signals of the microstrip line switch for power distribution are consistent and the initial phases are consistent;

[0015] The lengths of the input cables from the calibration frame switch for power distribution to each calibration antenna are consistent and the specifications are the same. The lengths of the input cables from the microstrip line switch for power distribution to each microstrip antenna are consistent and the specifications are the same.

[0016] Further, a plurality of limiters are arranged at intervals on the calibration track, and the distance between adjacent limiters is the horizontal pitch of the array elements to be measured.

[0017] Further, the calibration chassis includes:

[0018] A calibration signal generation module for generating calibration signals, where the calibration signals include RF calibration signals or digital calibration signals;

[0019] A switch power distribution control module for sequentially turning on each on-off switch in the microstrip line switch power distribution or the calibration box switch power distribution according to the order of calibration control, and selecting the corresponding microstrip line antenna or calibration antenna;

[0020] A calibration data storage module for storing the digital signals collected by the microstrip line antenna for receiving calibration and the digital signals collected by the calibration antenna for receiving calibration, and storing the RF signals collected by the microstrip line antenna for transmitting calibration and the RF signals collected by the calibration antenna for transmitting calibration.

[0021] Further, the calibration chassis further includes:

[0022] A calibration processing module for performing self-calibration after the phased array antenna system is powered on, and compensating the obtained calibration error value into each channel of the phased array antenna system through FFT or an equalizer.

[0023] In a second aspect, the present invention proposes a calibration method for a wideband digital phased array antenna suitable for cylindrical conformal, using the calibration device for a wideband digital phased array antenna suitable for cylindrical conformal as described above to perform receiving calibration on the phased array antenna. The method includes:

[0024] After deploying the phased array antenna system to be measured in an anechoic chamber, the calibration device is installed for the phased array antenna to be measured. The phased array antenna system includes antenna elements and a DAM module;

[0025] After the phased array antenna system to be measured is powered on, the calibration chassis generates an RF calibration signal, and the RF calibration signal is stepwise transmitted to each microstrip line antenna through the microstrip line switch power distribution. After spatial coupling, it is received by the antenna elements to be measured and processed by the DAM module and then converted into a digital signal as microstrip line receiving calibration data and returned to the calibration chassis;

[0026] Without powering off the phased array antenna system to be tested, the calibration chassis generates a radio frequency calibration signal, and the radio frequency calibration signal is transmitted step by step to each of the calibration antennas through the calibration frame switch power divider. After spatial transmission, the antenna elements to be tested receive the signal and obtain digital signals through the DAM module for processing, and then return the digital signals to the calibration chassis to obtain the reception calibration data of one arch of antenna elements in the moving direction of the conformal calibration frame of the phased array antenna system;

[0027] The calibration chassis controls the electric tractor to tow the conformal calibration frame to slide a distance d on the calibration track, and then collects the reception calibration data of the next arch of antenna elements and returns it to the calibration chassis until the calibration chassis obtains the calibration data of all antenna elements of the phased array antenna system as the calibration frame reception calibration data, where d is the spacing of the antenna elements to be tested in the moving direction of the conformal calibration frame.

[0028] Further, after obtaining the calibration frame reception calibration data, the method further includes:

[0029] After the phased array antenna system is powered on, the calibration chassis generates a radio frequency calibration signal, and the radio frequency calibration signal is transmitted step by step to each microstrip antenna through the microstrip line switch power divider. After spatial coupling, the antenna elements to be tested receive the signal and obtain digital signals through the DAM module for processing, and then return the digital signals to the calibration chassis as the power-on reception calibration data;

[0030] The calibration chassis compensates the calibration error value into each channel of the phased array antenna system through FFT or an equalizer, where the calibration error value is the phase-frequency response after deducting the integer multiple time delay value for different frequency points calculated according to the calibration frame reception calibration data and the microstrip line reception calibration data.

[0031] Further, the time delay value is estimated by the multi-frequency point method or the linear frequency modulation signal time delay estimation method.

[0032] In a third aspect, the present invention also proposes a calibration method for a wideband digital phased array antenna suitable for cylindrical conformal. Using the calibration device for a wideband digital phased array antenna suitable for cylindrical conformal as described above to perform transmission calibration on the phased array antenna, the method includes:

[0033] After deploying the phased array antenna system to be tested in a microwave anechoic chamber, the calibration device is installed for the phased array antenna to be tested, and the phased array antenna system includes antenna elements and a DAM module;

[0034] After the phased array antenna system to be tested is powered on, a digital calibration signal is generated by the calibration chassis and transmitted to the DAM module for processing. After being converted into a radio frequency signal, it is emitted and spatially coupled to the microstrip antenna, and then power-divided by the microstrip switch to obtain microstrip transmission calibration data, which is transmitted to the calibration chassis;

[0035] Without shutting down the phased array antenna system to be tested, a digital calibration signal is generated by the calibration chassis and transmitted to the DAM module for processing. After being converted into a radio frequency signal, it is emitted, spatially coupled to the calibration antenna, and then power-divided by the calibration frame switch to obtain transmission calibration data of one arch of array elements, which is transmitted to the calibration chassis;

[0036] After the calibration chassis controls the electric tractor to tow the conformal calibration frame to slide a distance d on the calibration track, the acquisition of the transmission calibration data of the next arch of array elements is performed and returned to the calibration chassis until the calibration chassis obtains the transmission calibration data of all array elements of the phased array antenna system as the calibration frame transmission calibration data. Here, d is the spacing of the antenna array elements to be tested along the moving direction of the conformal calibration frame.

[0037] Further, after obtaining the calibration frame transmission calibration data, the method further includes:

[0038] After the phased array antenna system is powered on, a digital calibration signal is generated by the calibration chassis and transmitted to the DAM module for processing. After being converted into a radio frequency signal, it is spatially coupled to the microstrip antenna and then power-divided by the microstrip switch to obtain power-on transmission calibration data, which is transmitted to the calibration chassis;

[0039] The calibration chassis compensates the calibration error value into each channel of the phased array antenna system through FFT or an equalizer. Here, the calibration error value is the phase-frequency response after deducting the integer multiple delay value at different frequency points calculated according to the calibration frame transmission calibration data and the microstrip transmission calibration data.

[0040] The advantages of the present invention are as follows:

[0041] (1) Since there are many frequency points for wideband phased array calibration, when using the traditional planar near-field method for calibration, the required time is very long. When using the calibration device of the present invention for calibration, multiple calibration antennas work simultaneously, greatly improving the calibration efficiency, shortening the calibration time, and being suitable for calibrating the special-shaped cylindrical conformal phased array. At the same time, the overall operation of the calibration device is simple, the degree of automation is high, and it is especially suitable for calibrating a large number of phased array systems in engineering.

[0042] (2) The calibration device proposed by the present invention uses the overall method for calibration, and its calibration error source is single. Since the overall phase error does not affect beam synthesis, it can be directly applied after system compensation without further processing.

[0043] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is a schematic three-dimensional structure diagram of a calibration device for a broadband digital phased array antenna suitable for cylindrical conformal of an embodiment of the present invention;

[0045] Figure 2 is a schematic diagram of the laying of a microstrip antenna in an embodiment of the present invention;

[0046] Figure 3 is a schematic diagram of the transmission of a calibration signal in an embodiment of the present invention;

[0047] Figure 4 is a schematic flowchart of the reception calibration of a cylindrical conformal broadband digital phased array antenna in an embodiment of the present invention;

[0048] Figure 5 is a schematic flowchart of the transmission calibration of a cylindrical conformal broadband digital phased array antenna in an embodiment of the present invention.

[0049] DESCRIPTION OF THE REFERENCE NUMERALS:

[0050] 1 - calibration track; 2 - conformal calibration frame; 3 - microstrip antenna; 4 - calibration chassis; 5 - calibration antenna; 6 - phased array antenna; 7 - microstrip line switch power divider; 8 - calibration frame switch power divider; 9 - electric tractor; 10 - antenna element. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0051] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0052] As Figure 1 shown, the first embodiment of the present invention provides a calibration device for a cylindrical conformal broadband digital phased array antenna. The device includes a calibration track 1, a conformal calibration frame 2, a microstrip antenna 3, a calibration chassis 4, and an electric tractor 9. The conformal calibration frame 2 is installed on the calibration track 1. The output of the calibration chassis 4 is connected to the driving end of the electric tractor 9. The electric tractor 9 is used to drive the conformal calibration frame 2 to slide on the calibration track 1;

[0053] A number of calibration antennas 5 are installed on the conformal calibration frame 2. The connection lines between the calibration antennas 5 and the array elements to be measured are parallel to the normal directions of the array elements to be measured. The distances between each calibration antenna 5 and each array element to be measured are all a fixed value D, and the fixed value D satisfies the antenna near-field test conditions;

[0054] The microstrip line antennas 3 are deployed between two adjacent array elements to be measured, and the deployment direction is parallel to the moving direction of the conformal calibration frame 2. One end of the microstrip line antenna 3 is connected to a matching load, and the other end is connected to the calibration chassis 4 through a microstrip line switch power divider 7. The calibration antenna 5 is connected to the calibration chassis 4 through a calibration frame switch power divider 8.

[0055] It should be noted that the digital phased array antenna system 6 can be divided into antenna array elements 10 and DAM (Digital Array Module) modules according to different functional compositions. Among them, the antenna array element is the passive part of the phased array antenna, and can adopt various passive forms such as patch, dipole, and horn antennas; the DAM module is the active part of the phased array antenna, and at the same time is the backend part of the antenna array element, including components such as power amplifiers, A / D conversion modules, digital down-conversion, and equalizers, and is responsible for performing primary beam synthesis and filtering according to the beam pointing, and at the same time compensating and processing each channel according to the antenna calibration result.

[0056] The calibration purpose of the digital phased array antenna system 6 is to compensate for the frequency response differences between the active part and the passive part of the phased array antenna. For a phased array system with a narrowband signal bandwidth, multiple frequency points can be taken within its working bandwidth and calibrated sequentially; for a phased array system with a broadband signal bandwidth, the relative time delay value must be obtained through time delay estimation, and then the frequency response difference is compensated for calibration.

[0057] Those skilled in the art of this specialty can clearly understand that the above digital phased array antenna system 6 is a system commonly used in this specialty field. The composition and naming of each part are divided according to its functional modules. A digital phased array system with a re-arranged combination or naming of functional modules can all adopt the calibration method proposed by the present invention for calibration.

[0058] In the calibration device of the broadband digital phased array antenna applicable to cylindrical conformal proposed in this embodiment, the calibration chassis 4 is the central device of the calibration system, and is responsible for generating the timing pulse signals, various trigger pulses, generating calibration signals, performing calibration calculations, and calibration compensation required in the calibration process, etc. The calibration frame switch power divider 8 and the microstrip line switch power divider 7 are both controlled by the calibration chassis 4. According to the calibration timing of the calibration signals sent by the calibration chassis 4, the corresponding on-off switches in the calibration frame switch power divider 8 or the microstrip line switch power divider 7 are sequentially turned on to prevent bypass coupling interference.

[0059] Specifically, according to different calibration types, the signal flow also varies. During receive calibration: 1) When the calibration box receives calibration, the RF calibration signal is sent out from the calibration chassis 4, passes through the calibration box switch power divider 8, and is sent out by the calibration antenna 5 installed on the conformal calibration box 2. After spatial coupling, it is received by the antenna element under test. The RF calibration signal is processed by the DAM module and then becomes a digital calibration signal, which is transmitted to the calibration chassis 4 as receive calibration data for the calibration box, and calibration processing operations are performed; 2) When the microstrip line receives calibration, the RF calibration signal is sent out from the calibration chassis 4, passes through the microstrip line switch power divider 7 and is sent out by the microstrip line antenna 3. After spatial coupling, it is received by the antenna element under test. The RF calibration signal is processed by the DAM module and then becomes a digital calibration signal, which is transmitted to the calibration chassis 4 as receive calibration data for the microstrip line, and calibration processing operations are performed; 3) When power-on receive calibration is performed, the RF calibration signal is sent out from the calibration chassis 4, passes through the microstrip line switch power divider 7 and is sent out by the microstrip line antenna 3. After spatial coupling, it is received by the antenna element under test. The RF calibration signal is processed by the DAM module and then becomes a digital calibration signal, which is transmitted to the calibration chassis 4 as power-on receive calibration data, and calibration processing operations are performed. During transmit calibration: 1) The digital calibration signal is transmitted from the calibration chassis 4 to the DAM module, processed into an RF signal and sent out. After spatial coupling, it is received by the calibration antenna 5 installed on the conformal calibration box 2, passes through the calibration box switch power divider 8, and finally is transmitted to the calibration chassis 4 as transmit calibration data for the calibration box, and calibration processing operations are performed; 2) During microstrip line transmit calibration, the digital calibration signal is transmitted from the calibration chassis 4 to the DAM module, processed into an RF signal and sent out. After spatial coupling, it is received by the microstrip line antenna 3, passes through the microstrip line switch power divider 7, and the RF signal is transmitted to the calibration chassis 4 as transmit calibration data for the microstrip line, and calibration processing operations are performed; 3) During power-on transmit calibration, the digital calibration signal is transmitted from the calibration chassis 4 to the DAM module, processed into an RF signal and sent out. After spatial coupling, it is received by the microstrip line antenna 3, passes through the microstrip line switch power divider 7, and the RF signal is transmitted to the calibration chassis 4 as power-on transmit calibration data, and calibration processing operations are performed.

[0060] As a further preferred technical solution, the calibration antenna 5 installed on the conformal calibration box 2 and the antenna element under test of the phased array antenna system are equally spaced and conformal in the circumferential direction of the cylindrical conformal phased array antenna, that is, Figure 1 in the horizontal direction (Y direction) in where λ is the wavelength and r is the aperture of the antenna element. The distance between each calibration antenna 5 and each antenna element under test is a fixed value D, and D needs to meet the antenna near-field test conditions. The fixed value D satisfies:

[0061] In some preferred solutions, to make the position of the calibration box relative to the phased array antenna system more accurate, a fixed tooling can be used.

[0062] As a further preferred technical solution, the calibration track 1 is composed of two detachable tracks. After being laid and deployed, the calibration track 1 should be parallel to the axial direction of the cylindrical conformal phased array antenna, that is, Figure 1 the cylindrical direction (X direction) shown in the figure. Limiters should be installed at fixed positions on the calibration track 1. The distance between the limiters is the horizontal spacing d of the array elements to be measured. The conformal calibration frame 2 can slide along the cylindrical direction (X direction) on the calibration track 1 as shown in Figure 1 the figure.

[0063] The conformal calibration frame 2 can slide on the calibration track 1 at a fixed spacing d under the guidance of an electric traction device. After each slide, the calibration data of all array elements to be measured at different frequency points in the Y-direction plane of the antenna system will be collected. After completion, the next slide will be carried out until the calibration data collection work of the entire antenna array is completed.

[0064] As a further preferred technical solution, as shown in Figure 2 the figure, the microstrip antenna 3 is a pre-buried calibration antenna 5, which is deployed between two adjacent array elements to be measured. The microstrip line switch power divider 7 is similar to the calibration frame switch power divider 8, and both are controlled by the calibration chassis 4. According to the sequence of calibration control, the on-off switches corresponding to different microstrip lines are used to prevent bypass coupling interference.

[0065] In a preferred embodiment, the microstrip antenna 3 should be laid as close as possible to the array elements to be measured to obtain more accurate calibration data.

[0066] It should be noted that there are differences in the frequency response of the DAM module each time it is powered on. A system calibration needs to be performed after the DAM module is powered on. The purpose of this calibration is to collect and compensate for the time delay differences after the active components are powered on, without relying on any test environment. If there are no time delay differences in the active part of the phased array system, this step is not required, nor is it necessary to deploy the microstrip antenna 3 and the microstrip line switch power divider 7.

[0067] As a further preferred technical solution, the calibration antenna 5 uses a fixed-gain antenna. The time delays of the signals output by the calibration frame switch power divider 8 are consistent and the initial phases are the same. The time delays of the signals of the microstrip line switch power divider 7 are consistent and the initial phases are the same. The lengths and specifications of the input cables from the calibration frame switch power divider 8 to each calibration antenna 5 are the same. The lengths and specifications of the input cables from the microstrip line switch power divider 7 to each microstrip antenna 3 are the same. Otherwise, it will cause inconsistent frequency response characteristics of the calibration channels, thus affecting the final calibration results.

[0068] It should be noted that since the distances from the microstrip antenna to each array element are different, the microstrip antenna does not require a fixed gain.

[0069] As a further preferred technical solution, the calibration chassis 4 includes:

[0070] A calibration signal generation module for generating a calibration signal, where the calibration signal includes a radio frequency calibration signal or a digital calibration signal;

[0071] A switch power division control module for sequentially turning on each on-off switch in the microstrip line switch power divider 7 or the calibration box switch power divider 8 according to the order of calibration control, and selecting the corresponding microstrip line antenna 3 or calibration antenna 5;

[0072] A calibration data storage module for storing the digital signals collected by the microstrip line antenna 3 during calibration reception and the digital signals collected by the calibration antenna 5 during calibration reception, and storing the radio frequency signals collected by the microstrip line antenna 3 during calibration transmission and the radio frequency signals collected by the calibration antenna 5 during calibration transmission.

[0073] As a further preferred technical solution, the calibration chassis 4 further includes:

[0074] A calibration processing module for performing self-calibration after the phased array antenna system is powered on, and compensating the calibration error value into each channel of the phased array antenna system through FFT or an equalizer, where the calibration error value is the phase-frequency response after deducting the integer multiple time delay value at different frequency points calculated according to the calibration data received by the calibration box and the calibration data received by the microstrip line.

[0075] Further, as Figure 3 shown, the process of performing reception calibration on the phased array antenna by using the calibration device of the wideband digital phased array antenna applicable to cylindrical conformal proposed in this embodiment includes:

[0076] (1) After deploying the conformal phased array system to be measured in the microwave anechoic chamber, accurately measure the position of the phased array antenna system. After measurement, lay detachable calibration tracks on both sides of the conformal array so that the conformal calibration box can slide on the tracks. The distance D between the calibration antenna on the conformal calibration box and the antenna elements to be measured needs to meet the near-field condition.

[0077] It should be noted that the platform of the conformal phased array system to be calibrated is generally large and it is difficult to move accurately. In a preferred embodiment, after deploying the phased array system platform, perform precise positioning through a positioning device and then lay the calibration tracks. If the tracks are deployed first, it is difficult to deploy the phased array system to an accurate position. The sequence of deployment within this step can be selected specifically according to the specific embodiment.

[0078] (2) On the cylindrical direction (X direction) of the conformal phased array, lay a microstrip line antenna between every two antenna elements, and the directions of the microstrip lines are parallel to the calibration track direction (X direction). One end of the microstrip line is connected to a matching load, and the other end is connected to the microstrip line switch power divider.

[0079] (3) When the phased array system is powered on, a radio frequency calibration signal is generated by the calibration chassis, transmitted to the microstrip line switch for power splitting, and the radio frequency calibration signal is transmitted to each microstrip line antenna step by step according to the order of calibration control. After spatial coupling, it is received by the antenna elements to be measured, and the microstrip line received calibration data is obtained and returned to the calibration chassis for storage.

[0080] (4) Without shutting down the phased array system, a calibration signal is generated by the calibration chassis, transmitted to the calibration frame switch for power splitting, and the calibration signal is transmitted to each calibration antenna step by step according to the order of calibration control. After spatial transmission, it is received by the antenna elements to be measured, and the calibration data of one arch of array elements in the horizontal direction (Y direction) of the phased array system is obtained.

[0081] (5) Without shutting down the phased array system, after the calibration data acquisition of one arch in the horizontal direction (Y direction) of the conformal phased array system is completed, a completion signal is sent by the calibration chassis to control the electric tractor to tow the conformal calibration frame to slide on the track. Affected by the limiter, the sliding distance is fixed at d, where d is the distance between the array elements to be measured in the horizontal direction (X direction).

[0082] (6) Without shutting down the phased array system, repeat steps (4) - (5) so that the calibration antennas on the conformal calibration frame can collect the calibration data of all array elements of the entire conformal phased array system and return it to the calibration chassis for storage. The calibration data of all array elements of the conformal phased array system is named calibration frame received calibration data.

[0083] (7) After each power-on of the phased array antenna system, a calibration signal is generated by the calibration chassis, transmitted to the microstrip line switch for power splitting, and the calibration signal is transmitted to each microstrip line step by step according to the order of calibration control. After spatial coupling, it is received by the antenna elements to be measured, and the power-on received calibration data is obtained and returned to the calibration chassis for storage. This step does not require any of the aforementioned test environments, such as anechoic chamber, calibration track, conformal calibration frame, calibration frame switch for power splitting, etc.

[0084] (8) Perform calibration calculation, and the obtained calibration error value can be compensated into each channel of the phased array system through FFT or equalizer, so that the digital down-converted output signals of each channel can be superposed in the same direction to complete digital beamforming.

[0085] It should be noted that step (1) to step (6) have completed the darkroom calibration, and the subsequent steps do not need to be performed with the aid of any test environment. The purpose of the subsequent calibration is to solve the delay difference that may exist each time the DAM module is powered on. Due to the delay difference that may exist in the active part of the phased array system, that is, the DAM module, the effective compensation time obtained by the calibration calculation is the power-on time of the phased array system. After the system is shut down, step (7) to step (8) need to be repeated. In some embodiments, if the active part of the phased array system, that is, the DAM module, does not have a delay difference, step (7) is not required, and there is no need to install and deploy the entire microstrip line and its attached parts.

[0086] Furthermore, if Figure 3 As shown, the process of performing transmission calibration of the phased array antenna using the calibration device for the cylindrical conformal broadband digital phased array antenna proposed in this embodiment includes:

[0087] (1) After the conformal phased array system to be tested is deployed in a microwave darkroom, the position of the phased array antenna system is accurately measured. After the measurement, detachable correction tracks are laid on both sides of the conformal array so that the conformal correction frame can slide on the track. The distance D between the correction antenna on the conformal correction frame and the antenna array element to be tested must meet the near-field condition.

[0088] (2) In the cylindrical direction (X direction) of the conformal phased array, a microstrip line antenna is laid between every two array elements. The direction of each microstrip line is parallel to the correction track direction (X direction). One end of the microstrip line is connected to a matching load, and the other end is connected to a microstrip line switch power divider.

[0089] (3) The phased array system is turned on, and the calibration chassis generates a digital correction signal and transmits it to the DAM module for processing and conversion into an RF signal. The RF signal emitted by the DAM module is spatially coupled to the microstrip antenna and then divided by the microstrip switch power to obtain the microstrip transmission correction data, which is returned to the calibration chassis for storage.

[0090] (4) When the phased array system is not shut down, the digital correction signal generated by the calibration chassis is transmitted to the DAM module for processing and converted into a radio frequency signal before being emitted. After being spatially coupled to the correction antenna, the correction frame switch power is divided to obtain the transmission correction data of an arch array element and transmitted to the calibration chassis.

[0091] (5) When the phased array system is not shut down, after completing the transmission correction data collection of the conformal phased array system in the horizontal direction (Y direction), the calibration chassis sends a completion signal to control the electric traction device to pull the conformal correction frame to slide on the track. Affected by the limiter, the sliding spacing is fixed to d, where d is the spacing of the array elements to be measured in the horizontal direction (X direction).

[0092] (6) Without powering off the phased array system, repeat steps (4) - (5) so that the calibration antennas on the conformal calibration frame can collect the transmission calibration data of all elements of the entire conformal phased array system and return it to the calibration chassis for storage. The calibration data of all elements of the conformal phased array system is named calibration frame transmission calibration data.

[0093] (7) After each power-on of the phased array antenna system, the calibration chassis generates a digital calibration signal and transmits it to the DAM module for processing into a radio frequency signal. The radio frequency signal emitted by the DAM module is spatially coupled to the microstrip antenna and then power-divided by the microstrip switch to obtain the power-on transmission calibration data, which is returned to the calibration chassis for storage.

[0094] (8) Perform calibration calculations. By compensating the obtained calibration error values into each channel of the phased array system through FFT or an equalizer, the digital down-converted output signals of each channel can be superposed in the same direction to complete digital beamforming.

[0095] For the cylindrical conformal calibration device and method provided in this embodiment, the device can also be used for calibration of an elliptical cylindrical conformal antenna with a small curvature. When performing the calibration result calculation and processing at this time, various factors such as the path difference of each element, the normal angle between antennas, and the distance difference need to be calculated according to the coordinate positions of each element.

[0096] Since there are many frequency points for wideband phased array calibration, when using the traditional planar near-field method for calibration, the required time is very long. When using the calibration device described in this embodiment for calibration, multiple calibration antennas work simultaneously, greatly improving the calibration efficiency, shortening the calibration time, and adapting to the calibration of an irregular cylindrical conformal phased array. It solves the problems of large calibration errors and difficult beam synthesis during the calibration process of phased array systems with multi-plane and curved surface configurations. At the same time, the overall operation of the calibration device is simple, with a high degree of automation, and is particularly suitable for large-scale calibration of phased array systems in engineering. Moreover, the calibration device proposed in the present invention uses the overall method for calibration, and its calibration error source is single. Since the overall phase error does not affect beam synthesis, it can be directly applied after system compensation without further processing.

[0097] It should be noted that the calibration device based on the conformal phased array antenna system provided in the above embodiment is only named and illustrated by dividing the above functional modules. In actual applications, the above functions can also be completed by different functional modules according to different needs, that is, the modules in the embodiments of the present invention are decomposed and combined. For example, in some preferred solutions, a DBF (Digital Beam Forming) module is usually used for calibration data calculation. The names of the modules and steps designed in the embodiments of the present invention are only used to distinguish each module or step, and are not regarded as an improper limitation of the present invention.

[0098] In addition, asFigure 4 As shown in Figure 4 , the second embodiment of the present invention proposes a calibration method for a wideband digital phased array antenna suitable for cylindrical conformal. The phased array antenna is calibrated for reception by using the calibration device for a wideband digital phased array antenna suitable for cylindrical conformal as described above. The method includes the following steps:

[0099] S101. After deploying the phased array antenna system to be measured in a microwave anechoic chamber, install the calibration device for the phased array antenna to be measured. The phased array antenna system includes antenna elements and a DAM module;

[0100] S102. After the phased array antenna system to be measured is powered on, the calibration chassis generates a radio frequency calibration signal, and the radio frequency calibration signal is distributed step by step through the microstrip line switch and transmitted to each microstrip line antenna. After spatial coupling, it is received by the antenna elements to be measured and processed by the DAM module and then converted into a digital signal, which is returned to the calibration chassis as microstrip line reception calibration data;

[0101] S103. Without shutting down the phased array antenna system to be measured, the calibration chassis generates a radio frequency calibration signal, and the radio frequency calibration signal is distributed step by step through the calibration frame switch and transmitted to each calibration antenna. After spatial transmission, it is received by the antenna elements to be measured and processed by the DAM module, and then a digital signal is returned to the calibration chassis to obtain the reception calibration data of an arch of antenna elements in the moving direction of the conformal calibration frame of the phased array antenna system;

[0102] S104. The calibration chassis controls the electric tractor to tow the conformal calibration frame to slide a distance d on the calibration track, and then collects the reception calibration data of the next arch of antenna elements and returns it to the calibration chassis until the calibration chassis obtains the calibration data of all antenna elements of the phased array antenna system as the calibration frame reception calibration data. Here, d is the spacing of the antenna elements to be measured in the moving direction of the conformal calibration frame.

[0103] As a further preferred technical solution, after obtaining the calibration frame reception calibration data, the method further includes:

[0104] S105. After the phased array antenna system is powered on, the calibration chassis generates a radio frequency calibration signal, and the radio frequency calibration signal is distributed step by step through the microstrip line switch and transmitted to each microstrip line antenna. After spatial coupling, it is received by the antenna elements to be measured and processed by the DAM module, and then a digital signal is obtained and returned to the calibration chassis as the power-on reception calibration data;

[0105] It should be noted that the final calibration compensation result obtained from this step is only applicable to the power-on of the phased array system this time. If the time delay in the active channels of the phased array system can remain consistent after each power-on, this step is not required. The purpose of this step is to compensate for the time delay difference after each power-on of the active channels.

[0106] S106. The calibration chassis compensates the calibration error value into each channel of the phased array antenna system through FFT or an equalizer, where the calibration error value is the phase-frequency response after deducting the integer multiple time delay value for different frequency points calculated based on the calibration data received by the calibration frame and the calibration data received by the microstrip line.

[0107] As a further preferred technical solution, the calculation process of the calibration error value is as follows:

[0108] Assume that the signals obtained after Fourier transform of the signals of channels 1 and 2 of the phased array antenna system are X1(w) and X2(w), then the frequency response difference between channels can be expressed as:

[0109]

[0110] where τ is the integer multiple time delay of the active channel, is the phase-frequency response after deducting the integer multiple time delay value, j is a complex number, ω is the angular frequency, and A(ω) is the amplitude function.

[0111] For a phased array system with a wideband working bandwidth, the obviously varies at different frequency points, so it is impossible to directly separate and τ from the calibration result. Therefore, other methods are needed to estimate the time delay of the phased array system and substitute the estimated value into the above formula to obtain the compensation value at different frequency points. If the working bandwidth of the antenna system is narrowband, time delay estimation is not required, and the above frequency response difference can be directly compensated.

[0112] Among them, the process of estimating the time delay value using the multi-frequency point method in this embodiment is as follows:

[0113] Assume the i = 0, 1,..., 15th receiving channels, the j = 0, 1, 2nd frequency points, and the n = 0, 1,..., 15th samples are s ij (n), the frequencies of the three frequency points are f0, f1, f2 respectively, and f2 > f1 > f0; the two frequency differences are Δf 10 = f1 - f0, Δf 20 = f2 - f0. After collecting the 3 frequency points, a 16 * 3 * 16 matrix will be formed. Taking i = 0 as the reference channel, assume the time delay of i = 1 relative to i = 0 is τ.

[0114] a) Calculate the phase difference between receiving channels according to the following formula:

[0115]

[0116] a0, a1, and a2 can be obtained.

[0117] b) Calculate the phase difference between frequencies according to the following formula:

[0118] b 10 = conj(a0) * a1

[0119] b 20 = conj(a0) * a2

[0120] Two phase differences can be obtained:

[0121] c 10 = atan2(b 10 )

[0122] c 20 = atan2(b 20 )

[0123] c) Since the phase introduced by the fixed time delay in the frequency domain is linear, it can be obtained that:

[0124]

[0125] n = (c 10 / k - c 20 ) / (±2π)

[0126] where, Δf 10 , Δf 20 are known, that is, k is known, c 10 > 0, take the positive sign before 2π, otherwise take the negative sign.

[0127] d) The time delay estimate can be obtained as:

[0128] τ = (c 20 + 2π × n) / (2π × Δf 20 )

[0129] In the formula, n can be a positive number or a negative number.

[0130] The selection of the minimum frequency interval needs to meet the following requirements:

[0131]

[0132] It should be noted that there are various methods for wideband signal time delay estimation, such as the chirp signal time delay estimation method. After mixing the local signal with the received signal, passing it through a low-pass filter, and finally taking the modulus and searching for the peak value, the time delay estimation value can be obtained.

[0133] Further, according to the above method for delay estimation, calculate the relative delay τ1 during the process of the microstrip line receiving calibration data in step S102. The delay of τ1 includes the microstrip line delay and the receiving channel delay after the first power-on; calculate the relative delay τ2 for the calibration box to receive calibration data. The delay of τ2 includes the receiving channel delay after the first power-on; calculate the relative delay τ3 for power-on to receive calibration data. The delay of τ3 includes the microstrip line delay and the receiving channel delay after the second power-on.

[0134] Then construct τ3′ = τ3 + τ2 - τ1, where τ3′ is the receiving channel delay after the second power-on. Since the delay and frequency response of the laid microstrip line are processed by arithmetic operations, they will not affect the calibration result. Use τ3′ combined with the corresponding frequency to construct the phase values of each frequency point. And compensate it into each calibration channel to complete the calibration. Obviously, τ3′ after each power-on of the phased array system is different, and a new value can be obtained through the above method for compensation.

[0135] In addition, as Figure 5 shown, the third embodiment of the present invention proposes a calibration method for a wideband digital phased array antenna applicable to cylindrical conformal. Use the calibration device for a wideband digital phased array antenna applicable to cylindrical conformal as described above to perform transmission calibration on the phased array antenna. The method includes the following steps:

[0136] S201. After deploying the phased array antenna system to be measured in the anechoic chamber, install the calibration device for the phased array antenna to be measured. The phased array antenna system includes antenna elements and a DAM module;

[0137] S202. After the phased array antenna system to be measured is powered on, the calibration chassis generates a digital calibration signal and transmits it to the DAM module for processing to become a radio frequency signal and then emits it. After spatial coupling to the microstrip line antenna, it is power-divided by the microstrip line switch to obtain microstrip line transmission calibration data and transmit it to the calibration chassis;

[0138] S203. Without powering off the phased array antenna system to be measured, the calibration chassis generates a digital calibration signal and transmits it to the DAM module for processing to become a radio frequency signal and then emits it. After spatial coupling to the calibration antenna, it is power-divided by the calibration box switch to obtain the transmission calibration data of one arch element and transmit it to the calibration chassis;

[0139] S204. After the calibration chassis controls the electric tractor to tow the conformal calibration frame to slide a distance d on the calibration track, the acquisition of the transmission calibration data of the next arch element is performed and returned to the calibration chassis until the calibration chassis obtains the transmission calibration data of all elements of the phased array antenna system as the transmission calibration data of the calibration frame, where d is the spacing of the antenna elements to be measured along the moving direction of the conformal calibration frame.

[0140] It should be noted that the operation principles of transmission and reception are exactly the same, and will not be elaborated here.

[0141] In the description of this specification, the descriptions with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0142] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of these features. In the description of the present invention, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically and clearly defined.

[0143] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A calibration device for a broadband digital phased array antenna suitable for cylindrical conformal use, characterized in that: The calibration device comprises a calibration track, a conformal calibration frame, a microstrip line antenna, a calibration chassis and an electric tractor, wherein the conformal calibration frame is installed on the calibration track, the output of the calibration chassis is connected to the driving end of the electric tractor, and the electric tractor is used to drive the conformal calibration frame to slide on the calibration track; A plurality of correction antennas are installed on the conformal correction frame, the connection lines between the correction antennas and the array elements to be measured are parallel to the normal of the array elements to be measured, the distances between each correction antenna and each array element to be measured are fixed values ​​D, and the fixed value D meets the antenna near-field test conditions; The microstrip line antenna is deployed between two adjacent array elements to be measured, and the deployment direction is parallel to the moving direction of the conformal correction frame. One end of the microstrip line antenna is connected to a matching load, and the other end is connected to the calibration chassis via a microstrip line switch power divider. The correction antenna is connected to the calibration chassis via a correction frame switch power divider.

2. The calibration device for a wideband digital phased array antenna suitable for cylindrical conformal antenna according to claim 1, characterized in that: The fixed value D satisfies: ,in, is the wavelength, and r is the aperture of the array element to be measured.

3. The calibration device for a wideband digital phased array antenna suitable for cylindrical conformal antenna according to claim 1, characterized in that: The correction antenna adopts a fixed gain antenna.

4. The calibration device for a wideband digital phased array antenna suitable for cylindrical conformal antenna according to claim 1, characterized in that: The time delays and initial phases of the signals output by the correction frame switch power divider are consistent, and the time delays and initial phases of the signals output by the microstrip line switch power divider are consistent; The length and specification of the input cables from the correction frame switch power distribution to each correction antenna are consistent, and the length and specification of the input cables from the microstrip line switch power distribution to each microstrip line antenna are consistent.

5. The calibration device for a wideband digital phased array antenna suitable for cylindrical conformal antenna according to claim 1, characterized in that: A plurality of stoppers are arranged at intervals on the correction track, and the distance between adjacent stoppers is the spacing of the array elements to be measured in the horizontal direction.

6. The calibration device for a wideband digital phased array antenna suitable for cylindrical conformal antenna according to claim 1, characterized in that: The calibration chassis comprises: A correction signal generating module, used to generate a correction signal, wherein the correction signal includes a radio frequency correction signal or a digital correction signal; A switch power division control module, used to sequentially open the on-off switches in the microstrip line switch power division or the correction frame switch power division according to the correction control sequence, and select the corresponding microstrip line antenna or correction antenna; The correction data storage module is used to store the digital signals collected by the microstrip antenna receiving correction and the digital signals collected by the correction antenna receiving correction, and to store the radio frequency signals collected by the microstrip antenna transmitting correction and the radio frequency signals collected by the correction antenna transmitting correction.

7. The calibration device for a wideband digital phased array antenna suitable for cylindrical conformal antenna according to claim 1, characterized in that: The calibration chassis also includes: The correction processing module is used to perform self-calibration after the phased array antenna system is turned on, and compensate the correction error value to each channel of the phased array antenna system through FFT or equalizer, wherein the correction error value is the phase-frequency response after deducting the integer multiple delay value from different frequency points calculated based on the correction data received by the correction frame and the correction data received by the microstrip line.

8. A calibration method for a broadband digital phased array antenna suitable for cylindrical conformal, characterized in that: The phased array antenna is calibrated for reception using the correction device for a cylindrical conformal broadband digital phased array antenna as claimed in any one of claims 1 to 7, the method comprising: After the phased array antenna system to be tested is deployed in a microwave darkroom, the correction device is installed on the phased array antenna to be tested, wherein the phased array antenna system includes antenna elements and a digital array (DAM) module; After the phased array antenna system to be tested is turned on, the calibration chassis generates a radio frequency correction signal and transmits the radio frequency correction signal to each microstrip line antenna in steps through the microstrip line switch power division. After spatial coupling, the radio frequency correction signal is received by the antenna array element to be tested and converted into a digital signal after being processed by the DAM module as microstrip line reception correction data and returned to the calibration chassis; When the phased array antenna system to be tested is not shut down, the calibration chassis generates a radio frequency correction signal and transmits the radio frequency correction signal to each correction antenna in steps through the correction frame switch power division. After spatial transmission, the radio frequency correction signal is received by the antenna array element to be tested and processed by the DAM module to obtain a digital signal that is returned to the calibration chassis, thereby obtaining the reception correction data of an arch array element in the moving direction of the conformal correction frame of the phased array antenna system; After the calibration chassis controls the electric tractor to pull the conformal correction frame to slide a distance d on the correction track, the receiving correction data of the next arch array element is collected and returned to the calibration chassis until the calibration chassis obtains the correction data of all array elements of the phased array antenna system as the correction frame receiving correction data, wherein d is the spacing between the antenna array elements to be measured along the moving direction of the conformal correction frame.

9. The calibration method for a wideband digital phased array antenna suitable for cylindrical conformal use according to claim 8, characterized in that: After obtaining the correction frame to receive the correction data, in a test environment without the aid of a microwave darkroom, the method further includes: After the phased array antenna system is powered on, the calibration chassis generates a radio frequency calibration signal and transmits the radio frequency calibration signal to each microstrip line antenna in steps through the microstrip line switch power division. After spatial coupling, the radio frequency calibration signal is received by the antenna array element to be tested and processed by the DAM module to obtain a digital signal as the power-on reception calibration data and returned to the calibration chassis; The calibration chassis compensates the correction error value to each channel of the phased array antenna system through FFT or equalizer, wherein the correction error value is the phase-frequency response after deducting the integer multiple delay value from different frequency points calculated based on the correction data received by the correction frame and the correction data received by the microstrip line.

10. The calibration method for a wideband digital phased array antenna suitable for cylindrical conformal use according to claim 9, characterized in that: The time delay value is estimated by using a multi-frequency point method or a linear frequency modulation signal time delay estimation method.

11. A calibration method for a broadband digital phased array antenna suitable for cylindrical conformal, characterized in that: The phased array antenna is subjected to transmission correction using the correction device for a cylindrical conformal broadband digital phased array antenna as claimed in any one of claims 1 to 7, the method comprising: After the phased array antenna system to be tested is deployed in a microwave darkroom, the correction device is installed on the phased array antenna to be tested, wherein the phased array antenna system includes antenna array elements and a DAM module; After the phased array antenna system to be tested is turned on, the digital correction signal generated by the calibration chassis is transmitted to the DAM module for processing and converted into a radio frequency signal, which is then emitted and spatially coupled to the microstrip line antenna and then divided by the microstrip line switch to obtain microstrip line transmission correction data to be transmitted to the calibration chassis; When the phased array antenna system to be tested is not shut down, the digital correction signal generated by the calibration chassis is transmitted to the DAM module for processing and converted into a radio frequency signal before being sent out. After being spatially coupled to the correction antenna, the correction frame switch power is divided to obtain the transmission correction data of an arch array element and transmitted to the calibration chassis; After the calibration chassis controls the electric tractor to pull the conformal correction frame to slide a distance d on the correction track, the transmission correction data of the next arch array element is collected and returned to the calibration chassis until the calibration chassis obtains the transmission correction data of all array elements of the phased array antenna system as the correction frame transmission correction data, wherein d is the spacing between the antenna array elements to be measured along the moving direction of the conformal correction frame.

12. The calibration method for a broadband digital phased array antenna suitable for cylindrical conformal use according to claim 11, characterized in that: After acquiring the correction frame emission correction data, in a test environment without the aid of a microwave darkroom, the method further includes: After the phased array antenna system is powered on, the digital calibration signal generated by the calibration chassis is transmitted to the DAM module for processing and converted into a radio frequency signal. The radio frequency signal is spatially coupled to the microstrip line antenna and then divided by the microstrip line switch to obtain the power-on transmission calibration data to be transmitted to the calibration chassis. The calibration chassis compensates the correction error value to each channel of the phased array antenna system through FFT or equalizer, wherein the correction error value is the phase-frequency response after deducting the integer multiple delay value from different frequency points calculated based on the correction data transmitted by the correction frame and the correction data transmitted by the microstrip line.

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