2022 Vol. 37 No. 1
2022, 37(1): 1-7.
DOI: 10.12265/j.cjors.2020170
Abstract：
In order to solve the problem of near-field electromagnetic scattering simulation in an interactive scene of missile and target, this paper presents a calculation model based on near-field shooting and bouncing rays (SBR) under the influence of antenna patterns. According to the antenna patterns and the complex geometry between the ship and the sea surface, the electric field intensity received by the surface elements satisfying the far-field conditions of physical optics is given. The scattering fields of all surface elements are determined by the bouncing ray method. Further, the near-field radar cross section of the ship target is measured with vector superposition. The results of the model are in good agreement with the numerical computations in FEKO, which can be used to analyze the near-field scattering characteristics of ships on sea surface.
In order to solve the problem of near-field electromagnetic scattering simulation in an interactive scene of missile and target, this paper presents a calculation model based on near-field shooting and bouncing rays (SBR) under the influence of antenna patterns. According to the antenna patterns and the complex geometry between the ship and the sea surface, the electric field intensity received by the surface elements satisfying the far-field conditions of physical optics is given. The scattering fields of all surface elements are determined by the bouncing ray method. Further, the near-field radar cross section of the ship target is measured with vector superposition. The results of the model are in good agreement with the numerical computations in FEKO, which can be used to analyze the near-field scattering characteristics of ships on sea surface.
2022, 37(1): 8-14.
DOI: 10.12265/j.cjors.2021016
Abstract：
In order to solve the problem of spectrum allocation in cognitive radio networks, we propose a cooperative reinforcement learning spectrum allocation algorithm based on user experience quality. which simulates the secondary users in the cognitive network as agents in the reinforcement learning, and introduces a cooperation mechanism between the secondary users. New users can absorb and learn from the reinforcement learning experience of other users, and obtain the best spectrum allocation plan at a faster speed. In addition, the price game factor between the primary user and the secondary user is introduced in the spectrum allocation process, allowing the primary user to price the authorized spectrum according to their own situation, and the impact of different spectrum prices on the income of the secondary user is studied, making the algorithm closer to the real scene. In terms of system evaluation, the average opinion score model is used to visually display the service quality of system users. Simulation results show that the algorithm can effectively improve user service quality and system communication performance, and provides an effective solution for understanding the spectrum allocation among users.
In order to solve the problem of spectrum allocation in cognitive radio networks, we propose a cooperative reinforcement learning spectrum allocation algorithm based on user experience quality. which simulates the secondary users in the cognitive network as agents in the reinforcement learning, and introduces a cooperation mechanism between the secondary users. New users can absorb and learn from the reinforcement learning experience of other users, and obtain the best spectrum allocation plan at a faster speed. In addition, the price game factor between the primary user and the secondary user is introduced in the spectrum allocation process, allowing the primary user to price the authorized spectrum according to their own situation, and the impact of different spectrum prices on the income of the secondary user is studied, making the algorithm closer to the real scene. In terms of system evaluation, the average opinion score model is used to visually display the service quality of system users. Simulation results show that the algorithm can effectively improve user service quality and system communication performance, and provides an effective solution for understanding the spectrum allocation among users.
2022, 37(1): 15-22.
DOI: 10.12265/j.cjors.2020196
Abstract：
In order to solve the problems of insufficient objective evaluation and lack of evaluation basis for the classification and identification of radar emitter signals, a group evaluation method based on interval fuzzy principle, fuzzy cross entropy and multi-criteria compromise method is proposed. Firstly, the signal-noise ratio (SNR) classification evaluation model is established by the interval fuzzy principle, and the SNR weight is obtained by optimization based on the Hamming distance. Secondly, the hierarchical model is integrated with the group decision matrix by combining SNR weight and interval intuitionistic fuzzy weighted average operator, and the attribute weight is calculated by the entropy maximizing method. Finally, based on the framework of multi-criterion compromise method, the fuzzy cross entropy is adopted to realize feature scheme sequencing. The simulation results show that the proposed method is able to give the sorting identification feature evaluation ranking results consistent with the actual simulation experiment, and is better than the ideal point approach method, which verifies the feasibility and effectiveness of the proposed method.
In order to solve the problems of insufficient objective evaluation and lack of evaluation basis for the classification and identification of radar emitter signals, a group evaluation method based on interval fuzzy principle, fuzzy cross entropy and multi-criteria compromise method is proposed. Firstly, the signal-noise ratio (SNR) classification evaluation model is established by the interval fuzzy principle, and the SNR weight is obtained by optimization based on the Hamming distance. Secondly, the hierarchical model is integrated with the group decision matrix by combining SNR weight and interval intuitionistic fuzzy weighted average operator, and the attribute weight is calculated by the entropy maximizing method. Finally, based on the framework of multi-criterion compromise method, the fuzzy cross entropy is adopted to realize feature scheme sequencing. The simulation results show that the proposed method is able to give the sorting identification feature evaluation ranking results consistent with the actual simulation experiment, and is better than the ideal point approach method, which verifies the feasibility and effectiveness of the proposed method.
2022, 37(1): 23-32.
DOI: 10.12265/j.cjors.2021003
Abstract：
Starting from the equivalent replacing radiation model of a single pair of unshielded multi-core wires with a single pair of large current injection, a test method for strict equivalent radiation of a single pair of large current injection is proposed. Taking the unshielded four-core wire as the test object, the terminal response law of the unshielded multi-core wire is explored, and it is found that each pair of wires can not be strictly equivalent at the same time. The equivalent test method of tightening the coupling channel of unshielded wire is proposed and verified by the test. The test results prove that the proposed method of equivalent injection of bulk current tightening can replace the strong field irradiation test, which solves the problem of the passing ability test of the weapon equipment system.
2022, 37(1): 33-39.
DOI: 10.12265/j.cjors.2020235
Abstract：
With the rapid development of electronic industry technology, the electrostatic discharge(ESD) sensitivity voltage of electronic products has been lowered than the 50 V human body model(HBM) voltage. However, the existing ESD protected area (EPA) configuration standard works only for the electronic products whose ESD sensitive voltage is not less than 100 V. In order to study the configuration of EPA to achieve ultra-low human charge voltage, this paper investigates on the human walk experiment according to the ANSI/ESD S20.20 standard. Under high humidity conditions, the ESD mitigation floor and shoes with resistance widely below the 109 Ω standard are selected in the experiment for testing the system resistance of the human body and the walk charge voltage. Based on the short-term experimental data, the Chebyshev inequality is used to extrapolate the possible maximum voltage in a certain probability level which approves practical significance. The performed empirical research highlights innovatively that although the HB walk voltage is positively correlated with its system resistance, the discreteness is relatively large. If the system resistance is the only parameter used to control the HB charge voltage, we can not achieve good enough results. A risk assessment related to EPA protection reliability is determined based on the extrapolated voltage with suggestions to reduce EPA failures.
With the rapid development of electronic industry technology, the electrostatic discharge(ESD) sensitivity voltage of electronic products has been lowered than the 50 V human body model(HBM) voltage. However, the existing ESD protected area (EPA) configuration standard works only for the electronic products whose ESD sensitive voltage is not less than 100 V. In order to study the configuration of EPA to achieve ultra-low human charge voltage, this paper investigates on the human walk experiment according to the ANSI/ESD S20.20 standard. Under high humidity conditions, the ESD mitigation floor and shoes with resistance widely below the 109 Ω standard are selected in the experiment for testing the system resistance of the human body and the walk charge voltage. Based on the short-term experimental data, the Chebyshev inequality is used to extrapolate the possible maximum voltage in a certain probability level which approves practical significance. The performed empirical research highlights innovatively that although the HB walk voltage is positively correlated with its system resistance, the discreteness is relatively large. If the system resistance is the only parameter used to control the HB charge voltage, we can not achieve good enough results. A risk assessment related to EPA protection reliability is determined based on the extrapolated voltage with suggestions to reduce EPA failures.
2022, 37(1): 40-47.
DOI: 10.12265/j.cjors.2021004
Abstract：
In order to study the influence of sea surface temperature (SST) on the numerical simulation of low atmospheric ducts, the influence of different SST on the numerical simulation of lower atmospheric ducts over the South China Sea (SCS) was studied based on WRF model. The results show that the simulation of lower atmospheric ducts events is affected greatly by SST accuracy and the update frequency. The experiment scheme of the SST provided by US National Oceanic and Atmospheric Administration (NOAA) has the best simulation results with the accuracy of 68.2%, and its lowest mean error and standard deviation of duct-bottom heights are less than the other schemes, followed by climate forecast system reanalysis (CFSR) SST, which might be attributed to good numerical simulation of relative humidity and air temperature profiles. Besides those, nested grid pattern also affects the numerical simulation of atmospheric ducts. Using the best scheme, the duct characteristic parameters of the sub-grid simulation are more accurate, and the accuracy rate of the simulation and the duct probability increase by 11.8% and 10.4% respectively, with the false alarm rate decreased by 2.4%. This study provides technical support for accuracy numerical prediction of low atmospheric ducts over the South China Sea.
In order to study the influence of sea surface temperature (SST) on the numerical simulation of low atmospheric ducts, the influence of different SST on the numerical simulation of lower atmospheric ducts over the South China Sea (SCS) was studied based on WRF model. The results show that the simulation of lower atmospheric ducts events is affected greatly by SST accuracy and the update frequency. The experiment scheme of the SST provided by US National Oceanic and Atmospheric Administration (NOAA) has the best simulation results with the accuracy of 68.2%, and its lowest mean error and standard deviation of duct-bottom heights are less than the other schemes, followed by climate forecast system reanalysis (CFSR) SST, which might be attributed to good numerical simulation of relative humidity and air temperature profiles. Besides those, nested grid pattern also affects the numerical simulation of atmospheric ducts. Using the best scheme, the duct characteristic parameters of the sub-grid simulation are more accurate, and the accuracy rate of the simulation and the duct probability increase by 11.8% and 10.4% respectively, with the false alarm rate decreased by 2.4%. This study provides technical support for accuracy numerical prediction of low atmospheric ducts over the South China Sea.
2022, 37(1): 48-57.
DOI: 10.12265/j.cjors.2020242
Abstract：
From the perspective of estimating the target angle of arrival (AOA), in this paper, the problem of how to counter the interference of off-board active decoys based on the monopulse radar system is studied. The signal model under the condition of centroid jamming formed by the off-board active decoy is established, and the statistical characteristics of target and off-board active decoy jamming echoes are analyzed. Based on this, two methods of AOA estimation, the improved maximum likelihood estimation method and moment estimation method, are proposed. The Monte Carlo simulation experiment are conducted to study the performance of the angle estimators for various values of subpulses N, signal-to-interference ratio (SIR), signal-to-noise ratio (SNR), etc. The asymptotic statistical properties of the probability distribution function (PDF) of the target AOA are also studied. The accuracy of the proposed methods and algorithm complexity are compared with the existing methods and the Cramér-Rao lower bound (CRLB) as well. The results show that the PDF of target AOA obeys the Gaussian distribution asymptotically, and the estimation performance of the proposed method is closer to the square root of CRLB as the increase of the number of subpulses N, SIR and SNR. Theoretical analysis and simulation experiments verify the feasibility of the proposed methods.
From the perspective of estimating the target angle of arrival (AOA), in this paper, the problem of how to counter the interference of off-board active decoys based on the monopulse radar system is studied. The signal model under the condition of centroid jamming formed by the off-board active decoy is established, and the statistical characteristics of target and off-board active decoy jamming echoes are analyzed. Based on this, two methods of AOA estimation, the improved maximum likelihood estimation method and moment estimation method, are proposed. The Monte Carlo simulation experiment are conducted to study the performance of the angle estimators for various values of subpulses N, signal-to-interference ratio (SIR), signal-to-noise ratio (SNR), etc. The asymptotic statistical properties of the probability distribution function (PDF) of the target AOA are also studied. The accuracy of the proposed methods and algorithm complexity are compared with the existing methods and the Cramér-Rao lower bound (CRLB) as well. The results show that the PDF of target AOA obeys the Gaussian distribution asymptotically, and the estimation performance of the proposed method is closer to the square root of CRLB as the increase of the number of subpulses N, SIR and SNR. Theoretical analysis and simulation experiments verify the feasibility of the proposed methods.
2022, 37(1): 58-66.
DOI: 10.12265/j.cjors.2021257
Abstract：
In order to design a phased array feed with high performance, the relationship between PAF parameters and aperture efficiency is given through the study of optimal sampling of focal field of reflector antenna. The optimal sampling range and element spacing of PAF are summarized, and the calculation formula of element number is derived. The phased array feed of a 9 m antenna is designed. The antenna aperture efficiency is greater than 51% when the scanning range is ±3° in the frequency range of 4−7 GHz, which verifies the effectiveness of the design method. The approach in this paper can be used to guide the engineering design of phased array feed.
In order to design a phased array feed with high performance, the relationship between PAF parameters and aperture efficiency is given through the study of optimal sampling of focal field of reflector antenna. The optimal sampling range and element spacing of PAF are summarized, and the calculation formula of element number is derived. The phased array feed of a 9 m antenna is designed. The antenna aperture efficiency is greater than 51% when the scanning range is ±3° in the frequency range of 4−7 GHz, which verifies the effectiveness of the design method. The approach in this paper can be used to guide the engineering design of phased array feed.
2022, 37(1): 67-72.
DOI: 10.12265/j.cjors.2021008
Abstract：
Spectrum sensing is one of the most important technologies in cognitive radio. Based on the mutational unbiased bases (MUB) matrices and goodness of fit test, a novel spectrum sensing method based on the traditional Kolmogorov-Smirnov (KS) test is proposed in this paper. Specifically, by using MUB matrices to process the received samples, new samples with low correlation are generated, and thus, the number of samples is enlarged, and its sensing performance is improved. Simulation results show that when the number of received samples is limited and the noise is subject to Gaussian distribution, detection probability of the proposed method is higher than the traditional KS test method.
Spectrum sensing is one of the most important technologies in cognitive radio. Based on the mutational unbiased bases (MUB) matrices and goodness of fit test, a novel spectrum sensing method based on the traditional Kolmogorov-Smirnov (KS) test is proposed in this paper. Specifically, by using MUB matrices to process the received samples, new samples with low correlation are generated, and thus, the number of samples is enlarged, and its sensing performance is improved. Simulation results show that when the number of received samples is limited and the noise is subject to Gaussian distribution, detection probability of the proposed method is higher than the traditional KS test method.
2022, 37(1): 73-78.
DOI: 10.12265/j.cjors.2020251
Abstract：
In order to adapt to the propagation characteristics of the ionosphere and make HF antenna better match the ionospheric environment, an HF log-periodic antenna working on dual-mode propagation is designed. The antenna is composed of two log-periodic antennas in the vertical direction. The low elevation mode and high elevation mode are produced in the proposed antenna by in-phase excitation and inverse excitation respectively. The simulation and test show that the voltage standing wave ratio(VSWR) of the proposed antenna is less than 2.5 in the range of 6−30 MHz. The elevation of the antenna is of 20° and the gain is of 12 dBi for low elevation mode; for another mode, the elevation varying from 44° to 60° and the gain of 10 dBi are obtained. The proposed antenna works on two modes, which effectively improves the coverage ability of the conventional HF log-periodic antenna. The design lays a foundation for the further research of multipath separation of high frequency signals.
In order to adapt to the propagation characteristics of the ionosphere and make HF antenna better match the ionospheric environment, an HF log-periodic antenna working on dual-mode propagation is designed. The antenna is composed of two log-periodic antennas in the vertical direction. The low elevation mode and high elevation mode are produced in the proposed antenna by in-phase excitation and inverse excitation respectively. The simulation and test show that the voltage standing wave ratio(VSWR) of the proposed antenna is less than 2.5 in the range of 6−30 MHz. The elevation of the antenna is of 20° and the gain is of 12 dBi for low elevation mode; for another mode, the elevation varying from 44° to 60° and the gain of 10 dBi are obtained. The proposed antenna works on two modes, which effectively improves the coverage ability of the conventional HF log-periodic antenna. The design lays a foundation for the further research of multipath separation of high frequency signals.
2022, 37(1): 79-86.
DOI: 10.12265/j.cjors.2021005
Abstract：
Considering the Earth’s curvature effect, the positioning accuracy of very low frequency(VLF) emission sources is studied by using a long-distance multi-station time difference positioning algorithm based on a spherical model. By the Monte-Carlo simulation method, the spatial distribution of the root mean square error (RMSE) of positioning results is calculated for the two typical station geometries of the square- and star-shaped stations in the four-stations receiving system. The influence of three factors of station geometry, baseline length, and master station selection on positioning accuracy is analyzed. The results show that increasing the baseline length can effectively improve the positioning accuracy, but the improvement effect decreases as the baseline increases. Compared with the square-shaped stations, the star-shaped geometry has more advantages. The overall positioning error in the detection area is lower without a directional distribution, so it is more suitable for blind source positioning. For the star-shaped configuration, the positioning accuracy of the master station at the center of the triangle is better than that at other positions. The research results have a significant reference value for the actual receiving site setting of the long-distance VLF source positioning system
Considering the Earth’s curvature effect, the positioning accuracy of very low frequency(VLF) emission sources is studied by using a long-distance multi-station time difference positioning algorithm based on a spherical model. By the Monte-Carlo simulation method, the spatial distribution of the root mean square error (RMSE) of positioning results is calculated for the two typical station geometries of the square- and star-shaped stations in the four-stations receiving system. The influence of three factors of station geometry, baseline length, and master station selection on positioning accuracy is analyzed. The results show that increasing the baseline length can effectively improve the positioning accuracy, but the improvement effect decreases as the baseline increases. Compared with the square-shaped stations, the star-shaped geometry has more advantages. The overall positioning error in the detection area is lower without a directional distribution, so it is more suitable for blind source positioning. For the star-shaped configuration, the positioning accuracy of the master station at the center of the triangle is better than that at other positions. The research results have a significant reference value for the actual receiving site setting of the long-distance VLF source positioning system
2022, 37(1): 87-92.
DOI: 10.12265/j.cjors.2020265
Abstract：
As one of the important components in the time division duplex (TDD) subsystem of wireless communications, filtering switch, which integrates two functions of filter and switch, has been widely concerned and studied. At present, most of the reported filtering switches are realized by microstrip lines. However, the loss of microstrip filtering switch cannot meet the requirements of the communication systems. A switchable bridge-type coupling structures for dielectric filters is presented in this paper. The coupling structure is constructed by a section of metal strip on the printed circuit board (PCB) and two metal probes inserted in the adjacent dielectric cavities. Shunt PIN diodes are loaded at the metal strips so that the coupling path can be switched on or off by controlling the bias conditions of the PIN diodes. For demonstration, a fourth-order dielectric filtering switch is implemented and measured for 5G applications. It features an on-state low loss of 1.2 dB and an off-state isolation of 50 dB in measurement. The proposed design features lower insertion loss and higher isolation as compared with the traditional microstrip filtering switches.
As one of the important components in the time division duplex (TDD) subsystem of wireless communications, filtering switch, which integrates two functions of filter and switch, has been widely concerned and studied. At present, most of the reported filtering switches are realized by microstrip lines. However, the loss of microstrip filtering switch cannot meet the requirements of the communication systems. A switchable bridge-type coupling structures for dielectric filters is presented in this paper. The coupling structure is constructed by a section of metal strip on the printed circuit board (PCB) and two metal probes inserted in the adjacent dielectric cavities. Shunt PIN diodes are loaded at the metal strips so that the coupling path can be switched on or off by controlling the bias conditions of the PIN diodes. For demonstration, a fourth-order dielectric filtering switch is implemented and measured for 5G applications. It features an on-state low loss of 1.2 dB and an off-state isolation of 50 dB in measurement. The proposed design features lower insertion loss and higher isolation as compared with the traditional microstrip filtering switches.
2022, 37(1): 93-98.
DOI: 10.12265/j.cjors.2020262
Abstract：
This paper presents a method for designing concurrent dual-band high-efficiency power amplifier with a novel output matching circuit. The output matching circuit consists of a harmonic control circuit and a fundamental impedance matching circuit. The harmonic impedance of the transistor is tuned to reduce the waveform overlap between the drain voltage and the drain current. The optimum fundamental impedance of the transistor at two desired frequencies can be matched to 50 Ω by the proposed fundamental impedance matching circuit. In order to verify the feasibility of the method, a dual-band high-efficiency power amplifier working at 1.9/2.6 GHz is designed using Cree’s 10W transistor CGH40010. The realized dual-band high-efficiency power amplifier achieves the maximum power-added efficiency (PAE) of 72.5% and 67.8%, respectively, while an output power of 39.8 and 40.03 dBm is delivered by the PA at the measured frequencies of 1.9 and 2.6 GHz. The proposed dual-band power amplifier reduces the circuit complexity and provides a novel power amplifier structure for multi-mode and multi-band communication systems.
This paper presents a method for designing concurrent dual-band high-efficiency power amplifier with a novel output matching circuit. The output matching circuit consists of a harmonic control circuit and a fundamental impedance matching circuit. The harmonic impedance of the transistor is tuned to reduce the waveform overlap between the drain voltage and the drain current. The optimum fundamental impedance of the transistor at two desired frequencies can be matched to 50 Ω by the proposed fundamental impedance matching circuit. In order to verify the feasibility of the method, a dual-band high-efficiency power amplifier working at 1.9/2.6 GHz is designed using Cree’s 10W transistor CGH40010. The realized dual-band high-efficiency power amplifier achieves the maximum power-added efficiency (PAE) of 72.5% and 67.8%, respectively, while an output power of 39.8 and 40.03 dBm is delivered by the PA at the measured frequencies of 1.9 and 2.6 GHz. The proposed dual-band power amplifier reduces the circuit complexity and provides a novel power amplifier structure for multi-mode and multi-band communication systems.
2022, 37(1): 99-105.
DOI: 10.12265/j.cjors.2020260
Abstract：
In order to meet the ever-increasing requirements on high-precision channel modeling for future wireless communications, a method to select the electromagnetic parameters for ray-tracing channel simulation has been proposed, which addresses the challenging practical issue in ray-tracing channel simulation, namely, how to accurately determinate the environmental electromagnetic parameters. In the proposed method, a local radio environment map is firstly constructed with the measured radio propagation data in a small part of the whole simulation area. Then, based on the perceptual hash algorithm, the measured radio environment map is quickly compared against the ray-tracing simulated radio environment map. By adjusting the electromagnetic parameters in the simulation environment, the simulated results get close to the measurement results. For reflective surfaces composed of multiple types of materials, a rasterization method is further proposed to improve the accuracy of channel prediction. The proposed method has been employed to obtain environmental electromagnetic parameters and perform ray-tracing simulation verification. Laboratory test results show that the root mean square error of the received power is 2.7 dB when using the proposed method, which is smaller than that when using the traditional method with electromagnetic parameters querying from the material library. This method can be employed to avoid field measurement, especially for those hard-reaching environment, and can also be used to update (or supplement) the electromagnetic parameters queried from the material library.
In order to meet the ever-increasing requirements on high-precision channel modeling for future wireless communications, a method to select the electromagnetic parameters for ray-tracing channel simulation has been proposed, which addresses the challenging practical issue in ray-tracing channel simulation, namely, how to accurately determinate the environmental electromagnetic parameters. In the proposed method, a local radio environment map is firstly constructed with the measured radio propagation data in a small part of the whole simulation area. Then, based on the perceptual hash algorithm, the measured radio environment map is quickly compared against the ray-tracing simulated radio environment map. By adjusting the electromagnetic parameters in the simulation environment, the simulated results get close to the measurement results. For reflective surfaces composed of multiple types of materials, a rasterization method is further proposed to improve the accuracy of channel prediction. The proposed method has been employed to obtain environmental electromagnetic parameters and perform ray-tracing simulation verification. Laboratory test results show that the root mean square error of the received power is 2.7 dB when using the proposed method, which is smaller than that when using the traditional method with electromagnetic parameters querying from the material library. This method can be employed to avoid field measurement, especially for those hard-reaching environment, and can also be used to update (or supplement) the electromagnetic parameters queried from the material library.
2022, 37(1): 106-112.
DOI: 10.12265/j.cjors.2020276
Abstract：
The hybrid implicit-explicit FDTD (HIE-FDTD) method is used to numerically simulate the graphene absorber. The intraband conductivity of graphene is introduced into the HIE-FDTD method through the auxiliary difference equation (ADE) and the conformal technology is used to complete the characteristic analysis of the designed new graphene absorber. Numerical results show that the absorption rate of the absorber can reach 99.8% near 2.68 THz, and the working frequency of the absorber can be adjusted by controlling the chemical potential of graphene and the width of the ring in the terahertz frequency band. The ring-shaped absorber designed in this paper has a simple structure and has potential applications in terahertz devices such as detectors, sensors, and filters.
The hybrid implicit-explicit FDTD (HIE-FDTD) method is used to numerically simulate the graphene absorber. The intraband conductivity of graphene is introduced into the HIE-FDTD method through the auxiliary difference equation (ADE) and the conformal technology is used to complete the characteristic analysis of the designed new graphene absorber. Numerical results show that the absorption rate of the absorber can reach 99.8% near 2.68 THz, and the working frequency of the absorber can be adjusted by controlling the chemical potential of graphene and the width of the ring in the terahertz frequency band. The ring-shaped absorber designed in this paper has a simple structure and has potential applications in terahertz devices such as detectors, sensors, and filters.
2022, 37(1): 113-120.
DOI: 10.12265/j.cjors.2020275
Abstract：
The airborne/vehicle multi-system communication, measurement and control, detection and other multi-wireless systems coexist, multiple antennas are scattered correspondingly, and the interference between the antennas are serious. Meanwhile, the airborne/vehicle conformal antenna needs to have strong carrying capacity. This paper designs a low profile bearable dual band CP directional slot antenna suitable for car shells in a shared aperture. The antenna body adopts the form of open slots to realize the miniaturization and broadband performance, and the microstrip line is used to feed the slot via the coupling. The shared aperture dual band antenna is realized by slotting and embedding high-frequency antenna in the low-frequency antenna. The circular polarization is realized by using the multi-feed method. The antenna is filled with substrate FR4, the maximum thickness of which is 5% of the wavelength corresponding to the lowest frequency. This hybrid metallic and dielectric stereoscopic structure greatly enhances the carrying capacity of the antenna. The measured results show that the impedance bandwidth of the antenna is 75 MHz (0.303−0.378 GHz) and the axial ratio bandwidth is 50 MHz (0.32−0.37 GHz) in UHF band. In the L-band, the impedance bandwidth of the antenna is 550 MHz (1.18−1.73 GHz), and the axial ratio bandwidth of the antenna is 420 MHz (1.1−1.52 GHz). When the pressure reaches 390 kg/cm2, the antenna can still work normally with a deformation of 3%. The measured results are basically consistent with the simulation results. The antenna has the characteristics of low profile, shared aperture, dual band and circular polarization, which provides a novel and practical antenna structure for vehicle wireless communication system, and can be embedded in the vehicle shell as part of the shell.
The airborne/vehicle multi-system communication, measurement and control, detection and other multi-wireless systems coexist, multiple antennas are scattered correspondingly, and the interference between the antennas are serious. Meanwhile, the airborne/vehicle conformal antenna needs to have strong carrying capacity. This paper designs a low profile bearable dual band CP directional slot antenna suitable for car shells in a shared aperture. The antenna body adopts the form of open slots to realize the miniaturization and broadband performance, and the microstrip line is used to feed the slot via the coupling. The shared aperture dual band antenna is realized by slotting and embedding high-frequency antenna in the low-frequency antenna. The circular polarization is realized by using the multi-feed method. The antenna is filled with substrate FR4, the maximum thickness of which is 5% of the wavelength corresponding to the lowest frequency. This hybrid metallic and dielectric stereoscopic structure greatly enhances the carrying capacity of the antenna. The measured results show that the impedance bandwidth of the antenna is 75 MHz (0.303−0.378 GHz) and the axial ratio bandwidth is 50 MHz (0.32−0.37 GHz) in UHF band. In the L-band, the impedance bandwidth of the antenna is 550 MHz (1.18−1.73 GHz), and the axial ratio bandwidth of the antenna is 420 MHz (1.1−1.52 GHz). When the pressure reaches 390 kg/cm2, the antenna can still work normally with a deformation of 3%. The measured results are basically consistent with the simulation results. The antenna has the characteristics of low profile, shared aperture, dual band and circular polarization, which provides a novel and practical antenna structure for vehicle wireless communication system, and can be embedded in the vehicle shell as part of the shell.
2022, 37(1): 121-128.
DOI: 10.12265/j.cjors.2020241
Abstract：
The emerging fleet of non geo-stationary orbit (NGSO) satellite constellations are able to connect a large number of terminals all around the world. Moreover, NGSO constellation system has high dynamic characteristics in the domains of space, time, frequency, and coding, etc. Most NGSO satellite systems use the same frequency band as geo-stationary orbit (GSO) constellation systems. Therefore, it is inevitable to bring time-varying interference to GSO satellite systems in the sharing frequency bands. The problem of how to generate the maximum uplink radiated power of NGSO constellation is solved in this paper. The generation method of the equivalent is equivalent isotropically radiated power (EIRP) mask in the uplink of NGSO satellite constellation system is improved by introducing the latitude range of non-GSO earth stations, the visible GSO arc, the minimum separation angle at the earth stations, the earth stations directional antenna gain. A simulation example is shown in this paper. Through simulation analysis, it can be known that the more detailed operating parameters of the working system to be got, especially the related avoidance strategies and mitigation techniques, the more accurate results can be simulated, which is closer to the true value of the NGSO constellation system. The proposed method can be used to calculate the EIRP mask in order to participate in the uplink equivalent power flux density (EPFD) calculation in article 22 of ITU Radio Regulations.
The emerging fleet of non geo-stationary orbit (NGSO) satellite constellations are able to connect a large number of terminals all around the world. Moreover, NGSO constellation system has high dynamic characteristics in the domains of space, time, frequency, and coding, etc. Most NGSO satellite systems use the same frequency band as geo-stationary orbit (GSO) constellation systems. Therefore, it is inevitable to bring time-varying interference to GSO satellite systems in the sharing frequency bands. The problem of how to generate the maximum uplink radiated power of NGSO constellation is solved in this paper. The generation method of the equivalent is equivalent isotropically radiated power (EIRP) mask in the uplink of NGSO satellite constellation system is improved by introducing the latitude range of non-GSO earth stations, the visible GSO arc, the minimum separation angle at the earth stations, the earth stations directional antenna gain. A simulation example is shown in this paper. Through simulation analysis, it can be known that the more detailed operating parameters of the working system to be got, especially the related avoidance strategies and mitigation techniques, the more accurate results can be simulated, which is closer to the true value of the NGSO constellation system. The proposed method can be used to calculate the EIRP mask in order to participate in the uplink equivalent power flux density (EPFD) calculation in article 22 of ITU Radio Regulations.
2022, 37(1): 129-136.
DOI: 10.12265/j.cjors.2020269
Abstract：
This paper compares and analyzes the methods of using the ITU semi-empirical model and three electron impact models to predict the ionospheric absorption attenuation of the skywave links. The international reference ionosphere model and the mass spectrometer incoherent scattering atmosphere model are used to construct the background ionosphere and background atmosphere. In the constructed background environment, using the three-dimensional ray tracing method to simulate and analyze the relationship between the ionospheric absorption attenuation and the radio frequency, the elevation angle, and the great circle distance calculated by the semi-empirical model and the three electron impact models. Shortwave communication test experiments with the great circle distances of 100 km, 200 km, and 400 km are conducted, and the accuracy of each prediction method is analyzed. According to the test results, there is little difference in the performance of the two models during the day. But during sunset, the ionospheric absorption attenuation predicted by the electron impact model is better than the ITU semi-empirical model used in the past. At the larger frequency of the available frequency band, the actual measurement values are closer to the electron collision model. Simulations and experiments have confirmed that the predicted values of the three electron collision models are similar. According to the actual data, the neutral composition of the atmosphere can be obtained.
This paper compares and analyzes the methods of using the ITU semi-empirical model and three electron impact models to predict the ionospheric absorption attenuation of the skywave links. The international reference ionosphere model and the mass spectrometer incoherent scattering atmosphere model are used to construct the background ionosphere and background atmosphere. In the constructed background environment, using the three-dimensional ray tracing method to simulate and analyze the relationship between the ionospheric absorption attenuation and the radio frequency, the elevation angle, and the great circle distance calculated by the semi-empirical model and the three electron impact models. Shortwave communication test experiments with the great circle distances of 100 km, 200 km, and 400 km are conducted, and the accuracy of each prediction method is analyzed. According to the test results, there is little difference in the performance of the two models during the day. But during sunset, the ionospheric absorption attenuation predicted by the electron impact model is better than the ITU semi-empirical model used in the past. At the larger frequency of the available frequency band, the actual measurement values are closer to the electron collision model. Simulations and experiments have confirmed that the predicted values of the three electron collision models are similar. According to the actual data, the neutral composition of the atmosphere can be obtained.
2022, 37(1): 137-145.
DOI: 10.12265/j.cjors.2020224
Abstract：
A novel sum-difference side lobe suppression array antenna applied in secondary surveillance radar (SSR) system is designed in order to solve the suppression problem with the traditional sum-difference array antenna. The antenna consists of front array, back element antenna, beam forming network and RF cables. The difference beam is formed by front array and back element antenna, of which the amplitudes and phases is optimized by genetic algorithm. By using this method, a good coverage of the side lobe of the sum beam is obtained in operating bandwidth. The simulation and test results of the antenna show that the characteristics of the sum beam is the same as the conventional sum-difference antenna, meanwhile, the difference beam can achieve 100% coverage in azimuth of the side lobe of the sum beam with a relative band width of 13.2%.
A novel sum-difference side lobe suppression array antenna applied in secondary surveillance radar (SSR) system is designed in order to solve the suppression problem with the traditional sum-difference array antenna. The antenna consists of front array, back element antenna, beam forming network and RF cables. The difference beam is formed by front array and back element antenna, of which the amplitudes and phases is optimized by genetic algorithm. By using this method, a good coverage of the side lobe of the sum beam is obtained in operating bandwidth. The simulation and test results of the antenna show that the characteristics of the sum beam is the same as the conventional sum-difference antenna, meanwhile, the difference beam can achieve 100% coverage in azimuth of the side lobe of the sum beam with a relative band width of 13.2%.
2022, 37(1): 146-152.
DOI: 10.12265/j.cjors.2020228
Abstract：
In order to study the methods and estimation strategies applicable to the regional ionospheric total electron content (TEC) modeling, this paper compares and analyzes several modeling methods and estimation strategies under the traditional single-layer hypothesis. Based on the data of 17 continuously operating reference stations in the middle latitudes of my country, the TEC modeling is carried out. The modeling methods used 4×3 polynomial model, 2nd order polynomial model, 4th order spherical harmonic series model, and the estimation strategy used piece-wise constant estimation strategy and piece-wise linear estimation strategy. On the basis of the traditional single-layer assumption, this paper also proposes a three-layer ionospheric TEC model, which can respectively give the TEC of the bottom ionosphere, peak height ionosphere and top ionosphere. The research results show that, the fitting effect of the total electron content in the zenith direction of several models is in good agreement with the ionospheric grid map published by the European Orbit Determination Center. Among them, the 4th order spherical harmonic series model and the piece-wise linear estimation strategy have the best effect. Through the three-layer ionospheric model, the relationship between the TEC and the ionospheric height can be obtained. The multi-layer ionospheric model has important application value for space target monitoring and low-orbit satellite aerospace measurement and control.
In order to study the methods and estimation strategies applicable to the regional ionospheric total electron content (TEC) modeling, this paper compares and analyzes several modeling methods and estimation strategies under the traditional single-layer hypothesis. Based on the data of 17 continuously operating reference stations in the middle latitudes of my country, the TEC modeling is carried out. The modeling methods used 4×3 polynomial model, 2nd order polynomial model, 4th order spherical harmonic series model, and the estimation strategy used piece-wise constant estimation strategy and piece-wise linear estimation strategy. On the basis of the traditional single-layer assumption, this paper also proposes a three-layer ionospheric TEC model, which can respectively give the TEC of the bottom ionosphere, peak height ionosphere and top ionosphere. The research results show that, the fitting effect of the total electron content in the zenith direction of several models is in good agreement with the ionospheric grid map published by the European Orbit Determination Center. Among them, the 4th order spherical harmonic series model and the piece-wise linear estimation strategy have the best effect. Through the three-layer ionospheric model, the relationship between the TEC and the ionospheric height can be obtained. The multi-layer ionospheric model has important application value for space target monitoring and low-orbit satellite aerospace measurement and control.
2022, 37(1): 153-161.
DOI: 10.12265/j.cjors.2020205
Abstract：
Ship target detection in SAR images has important applications in military and civilian fields. However, with the improvement of SAR image imaging capabilities, SAR imaging scenes are getting larger and larger, and there are two difficulties in ship target detection: first, ship targets account for a very small proportion of the entire image, and they are difficult to be separated from the surrounding background; second, the targets of docked ships are usually densely arranged, and it is difficult to distinguish among targets. Currently, commonly used anchor box based detection methods are likely to cause missed detection of ship targets in SAR images of large scenes. In order to solve the above problems, this paper proposes a ship detection method based on the target center point in the large scene SAR images. Based on the fast segmentation of land and sea, the anchor free detector CenterNet is used to locate the center point of the target through key point estimation, and the target boundary is obtained from the center point information regression to achieve target detection, thus effectively avoiding the problem of missing detection based on the anchor frame detection method. Tests based on the public dataset SAR-ship-Dataset show that the method can accurately detect ship targets in SAR images of large scenes, with a detection rate of 92.4%; for densely arranged targets, compared with SSD, YOLO, Fast-RCNN, etc, the method in this paper can also obtain the optimal detection performance.
Ship target detection in SAR images has important applications in military and civilian fields. However, with the improvement of SAR image imaging capabilities, SAR imaging scenes are getting larger and larger, and there are two difficulties in ship target detection: first, ship targets account for a very small proportion of the entire image, and they are difficult to be separated from the surrounding background; second, the targets of docked ships are usually densely arranged, and it is difficult to distinguish among targets. Currently, commonly used anchor box based detection methods are likely to cause missed detection of ship targets in SAR images of large scenes. In order to solve the above problems, this paper proposes a ship detection method based on the target center point in the large scene SAR images. Based on the fast segmentation of land and sea, the anchor free detector CenterNet is used to locate the center point of the target through key point estimation, and the target boundary is obtained from the center point information regression to achieve target detection, thus effectively avoiding the problem of missing detection based on the anchor frame detection method. Tests based on the public dataset SAR-ship-Dataset show that the method can accurately detect ship targets in SAR images of large scenes, with a detection rate of 92.4%; for densely arranged targets, compared with SSD, YOLO, Fast-RCNN, etc, the method in this paper can also obtain the optimal detection performance.
2022, 37(1): 162-167.
DOI: 10.12265/j.cjors.2020246
Abstract：
In order to predict the omnidirectional propagation characteristics of radar waves over the sea surface, a radio wave propagation model based on cylindrical coordinate parabolic equation is proposed and used to study the coverage range of marine radar. In this paper, the forward parabolic equation in cylindrical coordinate system is derived from Helmholtz equation. By using the orthogonality of trigonometric functions in the general solution of the parabolic equation, the excitation coefficients of each wave propagation modes are solved, and the stepwise iterative algorithm of the cylindrical coordinate parabolic equation is realized by combining the split step Fourier method, to predict the propagation characteristics of the radio waves in space. Numerical examples show that the method proposed in this paper can overcome the azimuth limitation of the traditional three-dimensional cartesian coordinate parabolic equation method, which propagates about 30° along the axis, and realizes the omnidirectional calculation. Compared with quasi-three dimensional parabolic equation, it has higher calculation accuracy. Based on the proposed method, the influences of atmospheric waveguide and rough sea surface on radar detection performance are studied, the simulation results have important significance for constructing digital battlefield at sea.
In order to predict the omnidirectional propagation characteristics of radar waves over the sea surface, a radio wave propagation model based on cylindrical coordinate parabolic equation is proposed and used to study the coverage range of marine radar. In this paper, the forward parabolic equation in cylindrical coordinate system is derived from Helmholtz equation. By using the orthogonality of trigonometric functions in the general solution of the parabolic equation, the excitation coefficients of each wave propagation modes are solved, and the stepwise iterative algorithm of the cylindrical coordinate parabolic equation is realized by combining the split step Fourier method, to predict the propagation characteristics of the radio waves in space. Numerical examples show that the method proposed in this paper can overcome the azimuth limitation of the traditional three-dimensional cartesian coordinate parabolic equation method, which propagates about 30° along the axis, and realizes the omnidirectional calculation. Compared with quasi-three dimensional parabolic equation, it has higher calculation accuracy. Based on the proposed method, the influences of atmospheric waveguide and rough sea surface on radar detection performance are studied, the simulation results have important significance for constructing digital battlefield at sea.
2022, 37(1): 168-174.
DOI: 10.12265/j.cjors.2020273
Abstract：
In order to meet the demand for power amplifiers in multi-standard and multi-mode systems in 5G communications, a new reconfigurable dual-band matching circuit structure is proposed. First, a distributed PIN switch is added to the output matching network. Disconnect the two dual-band output matching circuits to achieve good matching; then, the broadband input matching network designed based on the theory of band-pass filters can achieve good matching in the 1.5 GHz−2.5 GHz frequency band. To verify the effectiveness of the method, we used CGH40010F GaN transistor, designed and processed a reconfigurable dual-band power amplifier working at 1.6 GHz & 2.1 GHz, 1.8 GHz & 2.3 GHz. The actual measurement results show that the power added efficiency of the reconfigurable dual-band power amplifier (power added efficiency, PAE) are greater than 46.2%, and the saturated output power is greater than 39.09 dBm. The power amplifier has the characteristics of circuit complexity and low design difficulty, and each band has high output power and power added efficiency, which provides a feasible solution for design reconfigurable power amplifiers.
In order to meet the demand for power amplifiers in multi-standard and multi-mode systems in 5G communications, a new reconfigurable dual-band matching circuit structure is proposed. First, a distributed PIN switch is added to the output matching network. Disconnect the two dual-band output matching circuits to achieve good matching; then, the broadband input matching network designed based on the theory of band-pass filters can achieve good matching in the 1.5 GHz−2.5 GHz frequency band. To verify the effectiveness of the method, we used CGH40010F GaN transistor, designed and processed a reconfigurable dual-band power amplifier working at 1.6 GHz & 2.1 GHz, 1.8 GHz & 2.3 GHz. The actual measurement results show that the power added efficiency of the reconfigurable dual-band power amplifier (power added efficiency, PAE) are greater than 46.2%, and the saturated output power is greater than 39.09 dBm. The power amplifier has the characteristics of circuit complexity and low design difficulty, and each band has high output power and power added efficiency, which provides a feasible solution for design reconfigurable power amplifiers.
