Antenna Rotation Research Articles

Design and Implementation of Wind Speed-Based Radar Antenna Safety System Prototype

Air defense radar is a system that detects the presence of one or more air objects at a certain distance, altitude, and direction. One type of air defense radar used by the Indonesian National Armed Forces (TNI) is the Thomson TRS 2215D. An essential part of the radar is the rotating part of the radar antenna support called the antenna pivot. The rotation of the radar antenna must constantly be monitored and controlled for rotational stability at a speed of 6 Rotations per Minute (RPM) with a maximum wind speed of 120 km/h to prevent damage to the driving gear. Stormy weather with high wind speeds can cause the rotation speed of the radar antenna to be uncontrollable, which can cause damage. The solution offered in this study is to build a safety system that will lock the radar antenna automatically when the wind speed is detected to exceed tolerances and maintain the security of the radar antenna and its support system. The safety system was designed using an ESP32 Wi-Fi device equipped with an anemometer wind speed sensor, a Liquid Crystal Display (LCD) monitor, a Direct Current (DC) motor, and a Blynk Internet of Things (IoT) application. The test was conducted in a simulation using a multi-meter and oscilloscope measuring instrument. Testing the radar antenna's safety system prototype on a laboratory scale shows that the safety system can work as designed. The system can lock the radar antenna when the airflow is set at a speed of 54 km/h or 15 m/s, communication with the Blynk server works well, and the ESP32 device can transmit data at a maximum distance of 14 meters.

Design and implementation of high-rigidity and high-precision satellite antenna rotating unit

The satellite antenna rotating unit is an important component that drives the satellite antenna to rotate in orbit, mainly composed of a stepper motor, harmonic reducer, and rotating transformer. This type of rotating unit has the advantages of small size, lightweight, high-rated output torque, and long rotating life. The high-stiffness and high-precision satellite antenna rotation unit is based on the existing antenna rotation unit. Through comprehensive improvement design, the measured closed-loop control has a rotation accuracy of better than 0.005°, a torsional stiffness of better than 6.5 Nm/(Å), a rotation accuracy of 6 times higher than the existing antenna rotation unit, a torsional stiffness increase of 13 times, and a rated output torque increase of 2.4 times. The article introduces the development of components, measurement of torsional stiffness, and measurement of rotational accuracy for the high-stiffness and high-precision satellite antenna rotating unit. Finally, the development conclusion is given. The successful development of a high-stiffness and high-precision satellite-borne antenna rotation unit can not only meet the precise pointing control requirements of the mechanical movable antennas and terahertz antennas of the narrow beam with a width of 0.2° but also solve practical problems such as jitter in ground testing of data transmission or relay antennas and unstable pointing of point beam antennas in orbit.

Monostatic microwave imaging of cancerous breast phantom with a frequency to time domain conversion technique

AbstractThe letter presents a method of frequency to time domain conversion of Scattering Parameter data for microwave imaging applications. The time to frequency domain conversion was initially tested in the MATLAB. The testing was conducted in a realistic microwave imaging environment with an antenna and a heterogeneous breast phantom. Note that, the time domain signal obtained from the Vector Network Analyzer (VNA) as well as the time domain signal obtained with the introduced process is similar indicating efficiency of the proposed method. An ultra‐wideband (UWB) signal is transmitted from the transmitting Antipodal Vivaldi Antenna to the breast phantom and the received signals are collected by the same antenna over a monostatic process. A total of 36 antenna rotations were considered while scanning the phantom from various orientations. All the data stored in the VNA is extracted and the proposed frequency to time domain conversion technique was applied to it. Finally, the Delay and Sum beamforming algoirithm was used to reconstruct the target image.

Modeling the control of a radar antenna rotation system

Following the constitutional provision stating that “Mongolia has an armed force for self-defence” [1], and fulfilling its duty to safeguard its territory, borders, and national security, the technical equipment of the radar station, which monitors the current airspace, is undergoing rapid development. This involves updating and improving the system, as well as transitioning from analogue to digital, with the automation process progressing swiftly day by day. For Mongolia, it is very important to determine the angle of rotation of the radar antenna used in the armament of the Air Force of the Armed Forces and determine the target detected in the airspace. This paper introduces a novel hardware and software solution for simulating the control of a radar antenna rotation system and processing the output signal of a Selsin sensor to determine the rotation angle. Due to the confidentiality of military information, this article does not include device brands, specifications or bibliography. Радарын антены эргэлтийн системийн удирдлагыг загварчлах нь Хураангуй: "Монгол Улс нь өөрийгөө хамгаалах зэвсэгт хүчинтэй байна"[1] гэсэн үндсэн хуулийн заалтын хүрээнд өөрийн нутаг дэвсгэр, хил хязгаар, үндэсний аюулгүй байдлыг хамгаалах үүргийнхээ дагуу одоо ашиглагдаж буй агаарын орон зайд хяналт тавих радиолокацын станц (цаашид радар гэх)-ын техник хэрэгслүүдийг шинэчлэх, сайжруулах, аналог системээс дижитал буюу тоон системд шилжүүлэх, автоматжуулах ажлыг өдрөөс өдөрт маш хурдацтайгаар хөгжүүлсээр байна. Монгол Улсын хувьд Зэвсэгт хүчний Агаарын цэргийн зэвсэглэлд ашиглагдаж буй радарын антены эргэлтийн өнцгийг тодорхойлж агаарын орон зайд илэрсэн бай/цель/-г оновчтой илрүүлж тогтоох нь нэн чухал юм. Энэхүү өгүүллээр радарын антены эргэлтийн системийн удирдлагыг загварчилсан ба эргэлтийн өнцгийг тодорхойлох сельсин мэдрэгчийн гаралтын дохиог боловсруулах техник хангамжийн болон программ хангамжийн шинэ шийдлийг танилцуулж байна. Цэргийн мэдээллүүд нууцлалын зэрэгтэй тул энэхүү өгүүлэлд төхөөрөмжийн марк, техникийн үзүүлэлт мөн ном зүйг дурдах боломжгүй юм. Түлхүүр үгс: Сельсин, энкодер, хөдөлгүүр, радар, тоон дохио

Multimaterial Additively Manufactured Transmissive Spin‐Decoupled Polarization‐Maintaining Metasurfaces

AbstractTaking advantage of multimaterial additive manufacturing, this work demonstrates a kind of polarization‐maintaining metasurface (MS) for spin‐decoupled beam shaping. The wavefronts of the two spin states, i.e., the left‐hand circular polarization (LHCP) and the right‐hand circular polarization (RHCP), can be independently manipulated while the output spin state remains the same as the input. The meta‐atom is implemented with dual‐polarized antennas at the top and the bottom with phase delay lines connecting them. The dual‐polarized antenna on the receiving side is fixed to receive the LHCP/RHCP incident waves, while the dual‐polarized transmitting antenna is rotated, providing the opposite phase shifts for the LHCP and RHCP. The absolute value of the phase shift is the same as the transmitting antenna's rotation angle. Meanwhile, varying the length of phase delay lines introduces 2π phase shifts for both LHCP and RHCP inputs. Thus, combining the two phase‐shifting degrees of freedom, the LHCP and RHCP wavefronts can be independently controlled while the polarization is not flipped after transmitting through the MS. One MS produces vortex beams with different topological charges for LHCP and RHCP. The other achieves spin‐decoupled focusing. The multilayered MSs are conveniently printed using multimaterial additive manufacturing without postprocessing.

Metallo-Dielectric Millimeter-Wave Huygens’ Quarter-Wave and Half-Wave Plates

A novel metallo-dielectric Huygens’ unit cell is proposed that can be designed to operate either as a quarter-wave plate (QWP) or as a half-wave plate (HWP). The unit cell is based on a single-layer perforated dielectric, with straight (non-metallized) and 45° (metallized) elliptical holes. The novelty of the unit cell is its suitability for millimeter-wave implementation in printed-circuit board (PCB) fabrication due to the absence of metallic patterns of small line widths and gaps. As an example of their applicability, the wave plates are demonstrated in the near-field of 60-GHz band diffusion-bonded slot array antennas. The unit cell operating as a QWP is demonstrated in full-wave simulations and experimentally for linear-to-circular polarization conversion, whereby the combination of a linearly-polarized (LP) antenna and the QWP produces a circularly-polarized (CP) wave. Measurement results of the antenna and the QWP show ≤ -10-dB reflection from 59 to 63 GHz (6.6%), ≤ 3-dB axial ratio from 59.5 to 61.5 GHz (3.3%), and an overall efficiency ≥ 77% from 59.5 to 61.5 GHz. The unit cell operating as a HWP is demonstrated in full-wave simulations for polarization rotation of the LP antenna, and for changing the sense of rotation of a right-hand CP antenna into left-hand circular polarization.

Antenna Beampattern Matched Optimum Coherent Detection in High-Resolution Mechanically Scanning Maritime Surveillance Radars

Mechanically scanning radars are still widely used in ocean guard and surveillance areas nowadays, owing to simple structure, light weight and low cost. The antenna rotation causes amplitude modulation of target returns along pulses by the antenna azimuth beampattern. The traditional coherent detection that ignores this modulation suffers from some performance loss. In this paper, an antenna beampattern matched optimum coherent detector and a dual-threshold detection scheme are proposed for high-resolution mechanically scanning maritime surveillance radars. Firstly, it is shown that the modulation of target returns is determined by the antenna azimuth beampattern, scan rate, and pulse repetition interval (PRI) and the antenna scanning also affect the temporal correlation of sea clutter. Secondly, the antenna beampattern matched optimum coherent detector is given in compound-Gaussian sea clutter with inverse Gamma distributed texture and the pulse scanning mode is used to deal with unknown target azimuth angle in the matched filter. Thirdly, to mitigate the high computational cost of the pulse scanning mode, a dual-threshold scheme is given, which searches all pulse-range cells by short-time integration and further confirms suspected cells whose test statistics are between the two lower and higher thresholds in the search by long-time integration. Moreover, two fast recursive clutter covariance matrix inversion algorithms along pulses and range cells are presented, which bring a great reduction in computational complexity. Finally, real measured radar data is used to verify the proposed detector and scheme and the experimental results show that it behaves better in detection of small targets than the traditional detectors.

Mathematical model of phased array antenna aperture in the presence of errors in the position of antenna elements

The analysis of the directional characteristics of a phased array antenna is one of the main problems in the development of an antenna. The key issue in carrying out this analysis is an adequate representation of the directional characteristics of the phased array antenna with known directional patterns and the set-up as part of the aperture of antenna elements. There are many works considering the directional characteristics of the antenna, taking into account the mutual connection between the antenna elements. A number of works are devoted to the study of the directional characteristics of a phased array antenna in the presence of random errors of the amplitude-phase distribution in the radiating aperture. However, the issues related to the influence of the antenna elements installation error in the radiating aperture on the directional characteristics of the phased array antenna practically did not receive their consideration. With this in mind, this article discusses a mathematical model of the radiating aperture of a phased array antenna in the presence of errors in the antenna elements installation. At the same time, the installation error means not only the displacement of the antenna elements, but also its rotation relative to three axes, due to a violation of the shape of the radiating aperture. The objective of the article is to investigate the influence of the antenna element installation errors, including the displacement and reversal of the antenna elements in the radiating aperture, on the directional characteristics of the phased array antenna, based on strict consideration of the relationship between the directional characteristics of the phased array antenna and the parameters of the antenna elements installation in the radiating aperture. The main results obtained in the article are as follows. 1. A mathematical model of the radiating aperture of the phased array antenna, taking into account the errors of installation of the antenna elements in the aperture, including displacement of the phase center of the antenna elements and rotation of the antenna elements relative to the plane of the radiating aperture at three angles. 2. Investigation of the main patterns of changes in the directional characteristics of the phased array antenna due to the presence of errors in the antenna elements installation in the radiating aperture of the phased array antenna. In particular, errors in the installation of antenna elements practically do not lead to a change in the main beam either in width or in level. The most significant changes in the directional characteristics are manifested as follows: the structure and level of the side lobes of the directional patterns of the phased array antenna change; there is a cross-polarized component in the directional pattern, which, unlike the main component, is weakly directional. The developed mathematical model and the obtained simulation results allow us to determine the relationship between the parameters of the antenna elements installation errors as part of the phased array antenna aperture with a change in the amplitude, phase and polarization directional pattern, on the basis of which requirements for the accuracy of the parameters of the radiating aperture and the accuracy of the antenna elements installation can be formulated. These results are most significant for communication and radar systems that use orthogonal polarization signals when receiving and radiating.

КОМБІНОВАНЕ КЕРУВАННЯ БЕЗРЕДУКТОРНИМ ДУГОСТАТОРНИМ ЕЛЕКТРОПРИВОДОМ АНТЕНИ СУДНОВОЇ РАДІОЛОКАЦІЙНОЇ СТАНЦІЇ З НЕЧІТКИМ РЕГУЛЯТОРОМ ШВИДКОСТІ

The synthesis of a fuzzy proportional-integral-differential speed regulator of the arc stator electric drive of the rotation of the radar station antenna with combined control was carried out. The structural diagram of the fuzzy regulator was developed, the input and output linguistic variables are defined, the rule base was compiled, the dependence surfaces of the output control variable on the input coordinates are obtained. A simulation model of an electric drive in the Matlab system with a synthesized fuzzy logic regulator based on a two-phase model of an asynchronous arc-stator motor was built. Modeling of the nominal and the most difficult mode of operation of the electric drive was carried out, graphs of transient processes were obtained, which confirm its operability even under conditions of extreme loads. Refreces 9, figures 7, table 1.

Study the noise effect on the edges and cross correlation of TV images

The noise that associated with TV images is considered to be a very important problem that complicates the developments of these systems. Because of that, it makes the interpretation and analysis of informative images a very difficult process, and lessens their advantages. The most common type of these images are TV images transmitted by antenna work with (VHF, UHF) frequency and Satellite Transmission. Because TV images move through a complicated system in generating the TV or video signal, coding them, transmitting them, and receiving them by decoding and passing with different sets until appearing on screen. This will lead to a loose and fraud for a part of the information sent in the wave. As a result, it will be affected by an additive noise (Gaussian noise) which leads to deforming and destroying the quality of these images.
 This research aimed at studying the effect of the noise influence of this noise on edge as well as study of the relation between the statistical operators that include the mean and standard deviation (µ, σ) of edge’s regions for the components RGB and illumination component L as a function of time and as a function of antenna rotation.
 As well as we studied the relation between (µ, σ) and signal to noise ratio SNR for the cross correlation of edge's regions and for a homogeneous regions as well as for image as a whole once as a function of time and the other as a function of the angle of antenna rotation as in the first.

Clutter suppression and target energy focussing for airborne rotating antenna radar using improved Space‐time adaptive processing

AbstractRotating antenna radar is widely used on the airborne platform to extend the range of the radar detection airspace. However, the echo signal received by an airborne rotating radar is spread in the Doppler domain due to the platform motion and the antenna rotation. In the process of a long‐time integration, the antenna rotation harms the signal‐to‐noise ratio and reduces the performance of target detection when using conventional processing methods. Although conventional space‐time adaptive processing (STAP) has been used successfully to suppress clutter on an airborne radar, it does not take into account the antenna rotation. It decreases the performance of clutter suppression on the airborne rotating antenna radar. The signal model of airborne rotating antenna radar is analysed and the STAP technique to the rotating antenna scenario is improved to effectively suppress clutter and focus on target energy. Firstly, the echo of the airborne rotating antenna radar is modelled. Secondly, the factors affecting the Doppler difference of the array elements are investigated. Thirdly, an improved STAP method is proposed. Finally, the effect of antenna rotation on clutter Doppler characteristics and the clutter suppression and target energy focussing on the effects of the improved STAP technique are investigated. Experimental results demonstrate the effectiveness of the proposed method.

Synthesizing Shaped-Beam Cylindrical Conformal Array Considering Mutual Coupling Using Refined Rotation/Phase Optimization

A novel method of synthesizing shaped-beam cylindrical conformal array by rotating the antenna elements and optimizing their excitation phases is presented. Rotation of antennas on curved surface is mathematically described by rotating its vectorial active element pattern (VAEP) in its local coordinate system (LCS). Then the scalar patterns and polarization unit vectors of all the rotated VAEPs are properly transformed and then interpolated at a unified angle sampling grid in a common coordinate system, where they are summed to obtain an approximated array expression. With this expression, element rotations and phases can be optimized using the constriction factor particle swarm optimization (CF-PSO) to synthesize desired shaped-beam pattern with controlled sidelobe level (SLL) and cross-polarization level (XPL). However, since rotations on curved surface introduce considerable variations to the element curvature and mutual coupling (MC), the synthesized array pattern would have considerable errors. A refined strategy is adopted then to improve the synthesis accuracy. The proposed method uses uniform amplitude weighting, thus saving many unequal power dividers. Three typical shaped pattern synthesis examples are provided to show the effectiveness of the proposed method. A cylindrical array prototype with 24 rotated U-slot loaded patch antennas is fabricated and measured for practical validation.

An Improved Adaptive Median Filtering Algorithm for Radar Image Co-Channel Interference Suppression.

In order to increase the accuracy of ocean monitoring, this paper proposes an improved adaptive median filtering algorithm based on the tangential interference ratio to better suppress marine radar co-channel interference. To solve the problem that co-channel interference reduces the accuracy of radar images’ parameter extraction, this paper constructs a tangential interference ratio model based on the improved Laplace operator, which is used to describe the ratio of co-channel interference along the antenna rotation direction in the original radar image. Based on the idea of between-class variance, the tangential interference ratio threshold is selected to divide co-channel interference into high-ratio regions and low ones. Moreover, an improved adaptive median filter is used to process regions of high ratio based on the median of sub-windows, while that of low-ratio regions is processed by the adaptive median filter based on the median of current windows. Radar-measured data from Bohai Bay, China are used for algorithm validation and experimental results show that the proposed filtering algorithm performs better than the adaptive median filtering algorithm.

Anti-Jamming Method and Implementation for GNSS Receiver Based on Array Antenna Rotation

Global navigation satellite system (GNSS) array antenna receivers are effective for suppressing wideband jamming. However, its anti-jamming performance decreases sharply when the number of wideband interference surpasses the number of array elements. Since a large number of jammers are often used in navigation countermeasures, it is crucial to keep array antenna receivers available in such conditions. Aiming at this issue, two main tasks were performed in this research and are presented in this paper: Firstly, the direction sensitivity of the sup-freedom anti-jamming performance is revealed and an anti-jamming method for array antenna receivers based on antenna rotation is proposed. Secondly, in order to determine the optimal rotation angle rapidly, a variable-step iteration algorithm based on gradient descent is proposed. Theoretical analysis and simulation show the effectiveness of the proposed anti-jamming method and the efficiency of the implementation algorithm. In a typical airborne scenario with a maximum azimuth difference of 90°, the anti-jamming ability of the proposed method improved by 21~26 dB and 5~10 dB for arrays adopting the PI (power inversion) and MVDR (minimum variance distortionless response) algorithms, respectively. The iterative efficiency improved by 78.35–99.63% in comparison with a traversal of 0.1° search resolution. The proposed method and algorithm are not limited to airborne scenarios and they might be influential to anti-jamming algorithms in the data domain.

Underground transient electromagnetic real-time imaging system for coal mine water disasters

Due to advantageous sensitivity to low resistance and noncomplicated operation, transient electromagnetic methods are the most widely used geophysical methods for advanced detection of coal-mining-disaster water bodies. To realize real-time imaging, we developed a wireless antenna attitude angle measuring instrument based on an electronic compass, which measures antenna attitude angle real-time. According to attitude angle information sent through WiFi to the host of transient electromagnetic real-time imager instruments, current transmission, signal acquisition, and antenna rotation angle information are achieved for real-time imaging. We studied the direct algorithm of the apparent resistivity of the whole-space transient electromagnetic field in overlapping loop mode based on double-logarithmic-transform piecewise least-squares fitting, which not only ensures accuracy but also accelerates calculation. On-site detection was carried out in a coal mine, and the detection results are generally consistent with the drilling results.

A Sidelobe Suppression Method for Circular Ground-Based SAR 3D Imaging Based on Sparse Optimization of Radial Phase-Center Distribution

Circular ground-based SAR (GBSAR) is a new 3D imaging GBSAR with the potential of acquiring high-quality 3D SAR images and 3D deformation. However, its donut-shaped spectrum and short radius of antenna rotation cause high sidelobes on 3D curved surfaces, resulting in 3D SAR images with poor quality. The multi-phase-center circular GBSAR with full array can effectively suppress sidelobes by filling the donut-shaped spectrum to be the equivalent solid spectrum, but it requires a larger number of phase centers, increasing system cost and engineering difficulties. In this paper, a sidelobe suppression method for circular GBSAR 3D imaging based on sparse optimization of radial phase-center distribution is proposed to suppress high sidelobes at low cost. By deriving the point spread function (PSF) of multi-phase-center circular GBSAR and taking the peak sidelobe level (PSL) and integrated sidelobe level (ISL) of the derived PSF as multi-objective functions, we solve the multi-objective optimization problem to optimize the sparse distribution of radial phase centers. The advantage of the proposed method is that the solved optimal radial phase-center distribution can effectively suppress the 3D sidelobes of circular GBSAR with a limited number of phase centers. Finally, the sidelobe suppression effect of the proposed method is verified via 3D imaging simulations.

Luminescence modulation by twisting the branches of organic building blocks in uranyl-organic frameworks

Twisting the branches of an organic molecule will enhance luminescence; however, this is often accompanied by the rotation of the branches that will reduce luminescence, offering a contradiction. Thus, deep insight into this contradiction and creating some effective solutions to make a good trade-off have become critical but challenging. Here, we report a smart structural design to fine-tune the twisting of the branches of triangular organic building blocks through steric hindrance, including anchoring of organic units or further construction of uranyl-organic metal-organic frameworks (U-MOFs). Both theoretical calculations and experimental results disclose that the fluorescence performance in the solid for both organic ligands and corresponding U-MOFs highly correlates with the twisting of the branches, and both the anchoring of organic units and the construction of U-MOFs would be effective tools to modulate the trade-off between twisting and rotation, and that rotation could play a key role in promoting a turn-on antenna effect. • The relationship between twisting and rotation is disclosed in U-MOFs • Adjusting steric hindrance gives a trade-off between twisting and rotation • Luminescence in U-MOFs is fine-tuned by twisting the branches • Rotation could play a key role in turn-on antenna effect Twisting and rotation of organic linkers co-exist in the solid state of metal-organic frameworks, one increasing luminescence and the other decreasing luminescence. Yin et al. find that steric hinderance and coordination of uranyl ions can control the twisting of branches of organic building blocks, offering good trade-off between twisting and rotation.

Dynamic characteristics analysis of high speed rotating thin film antenna

The thin-film antenna is in a state of high-speed rotation in space, and studying the influence of its structure size on its vibration characteristics can avoid the occurrence of resonance. The rotational vibration characteristics of thin film antenna are studied by using the Absolute Nodal Coordinate Formulation (ANCF) with improved computational efficiency. The triangular element is used to mesh the thin film antenna, the kinetic energy, strain energy and external force potential energy of the element are calculated. The mass matrix and stiffness matrix of the element are transformed into the overall mass matrix and stiffness matrix through Boolean matrix. According to the rotation equivalent model, the centrifugal force potential energy generated by the high-speed rotation of the thin film antenna is transformed into the centrifugal force stiffness matrix. The relationship between rotational speed and natural frequency of thin film antenna under different structural sizes is analyzed. By analyzing the critical speed generated by the front traveling wave and the back traveling wave, the theoretical basis for the structural design of thin film antenna is improved.

Improving the Reverberation Chamber Performance Using a Reconfigurable Source Stirring Antenna Array

An antenna array composed of 16 asymmetric distributed monopoles on a circular dielectric substrate is proposed to use as a reconfigurable source stirrer in a reverberation chamber (RC). The distance between antennas is above λ2 to ensure the isolation between antennas below −15 dB. In order to ensure the mutual independence of the stirring modes of the antenna array, the 16 monopoles are asymmetrically distributed on both sides with X and Y as axes. The stirring efficiency of a stirrer is related to its size, and usually a higher stirring efficiency means a larger stirrer. The source stirring technique can achieve high efficiency, but the rotation of a source stirring antenna is limited to the radius of the turntable in an RC. To solve this problem, we propose to use an antenna array as a reconfigurable source stirrer, which can achieve a high efficiency of source stirring. As the antenna array can achieve source stirring and mechanical stirring at the same time, the source stirring section is not limited to the radius of the turntable; the switch between the selected antennas of the antenna array can increase the actual stirring samples of the stirring. Thus, the efficiency can be improved significantly and has been verified by the measurement results. The volume occupied by the conventional mechanical stirrer is reduced, which improves the working volume. The figures of merit, such as the field uniformity (FU), the independent sample numbers, the average K-factor, and the total scattering cross-section (TSCS), are measured and compared to the conventional mechanical stirring, mechanical stirring, and source stirring of the antenna array. Measurement results of the reconfigurable stir are illustrated below. FU has the best convergence and the lowest value, below 0.5 dB. The independent sample number is the largest. K-factor is the lowest, and most ranges are below −15 dB. Additionally, the proposed method has the largest TSCS, above 2 m2. These confirm that the proposed reconfigurable source stirring technique outperforms other three stirring techniques significantly. The antenna array can be easy to disassemble and install in different RC. With a wide range of working band, the proposed method can be applied to 5G OTA testing.

Polarimetric Calibration Technique for a Fully Polarimetric Entomological Radar Based on Antenna Rotation

For entomological radar, the polarization information of the target is usually used to estimate the biological parameters, such as orientation, body length, and mass, of the insect. Thus, the accuracy of polarization measurement directly affects the performance of the biological parameters’ estimation. The polarization measurement error is mainly caused by the imbalance of amplitude and phase between two polarization channels and the crosstalk of the dual-polarization antenna. In order to obtain the correct polarization information of the target, the polarimetric calibration of the entomological radar is required. This paper proposes a new polarimetric calibration technique based on antenna rotation, which does not require the calibrator to have a specific polarization scattering matrix (PSM). Compared with the currently existing calibration techniques, no prior knowledge of the calibrator PSM is required (in fact, any fixed-point target can be used as a calibrator); thus, the errors introduced by the mechanical process can be avoided. Simulations and data measured by radar verify the effectiveness of the method. This method has the potential to be extended to other fully polarimetric radar systems in the future, such as fully polarimetric weather radar, fully polarimetric synthetic aperture radar (SAR), and so on.