A transmission-type multi-beam switching antenna based on coding metasurface is designed. The U-shaped slot microstrip antenna is used as a source element, and the coding metasurface above the microstrip antenna is used to control multiple beams. The coding metasurface have two kinds of particles with different transmissivity responses to TM wave, corresponding to two basic coding element 0 and 1 respectively. PIN diodes are loaded on the metasurface. The designed antenna can dynamically switch between 4 beams or 2 beams by controlling the on or off state of PIN diodes.
A broadband substrate integrated waveguide (SIW) H-plane horn antenna with back-lobe suppression for Ka-band application is proposed in this paper. Based on the traditional H-plane SIW horn antenna, by loading a folded metal wall behind the horn aperture, the backward radiation is suppressed. Moreover, for better impedance matching, the substrates are directly extended and metal lines are loaded on the upper and lower substrates separately. Simulation results show that the designed antenna bandwidth reaches 39.9% (from 25.1 to 37.6 GHz). The simulated result also indicates that the proposed antenna achieves stable radiation patterns with the average gain of 9.9 dBi, as well as back-lobe level of larger than 10 dB. Importantly, the front to back ratio (FTBR) of the antenna is better than 20 dB over the operating band basically.
A frequency tunable helical filter using distilled water is presented. The filter frequency tunability is realized by using distilled water loaded helical resonator. Due to the high dielectric constant of distilled water, adjusting the volume of distilled water can change the equivalent electrical length of the helix, thus realizing the frequency reconfiguration. A third-order tunable cavity filter is designed. The simulation results show that the center frequency tuning of the proposed BPF is ranged from 315 to 425 MHz and the insertion loss is varied within 0.3 dB -1dB. This tunable filter has great potentials for the radar communication system.
To study the role of the multiple scattering effect of ice particles when retrieving the microphysical parameters of cirrus using millimeter-wave radar, spherical and non-spherical ice particles' models with gamma size distributions were first established. Then, the XFDTD (X Finite Difference Time Domain) software, GMM (Generalized Multi-particle Mie) and simple addition method were used to calculate the radar cross section(RCS) values for the ice particle models at 94 GHz. Therefore, multiple scattering effects must be considered in practical meteorological detection.
A method to obtain the echoes of UAV swarm from the echoes of a single UAV is presented by vector superposition. UAV swarm can be regarded as an extended target. Therefore, the echoes of UAV swarm can be simulated by the vector superposition which is generally applied in extended target. The echo characteristics of two different UAV swarms are studied in time domain. The research work of this paper will help to further obtain the relevant characteristics of UAV swarms by coherent accumulation.
A C-band microwave power transfer (MPT) system is designed and investigated in the article. The transmitting microwave power is greater than one kilowatt. The phased arrays are used to transmit large amounts of power to the receiving terminal. The high power feed system between the source and transmitting antenna is a waveguide splitter to reduce loss as much as possible. There are 256 quadrate patches to constitute a sub-array with size of 42 cm. The transmitting arrays are consisted of four sub-arrays and each sub-array is etched on Rogers 4003C substrate with ε r = 3.55 and 32 mil thickness. The transmitting antenna gain is 30.8 dBi and the return loss greater than 10 dB. The rectifying patch antenna consist of a high efficiency receiving antenna and rectifier circuit at 5.8 GHz. The single GaN diode conversion efficiency of radiofrequency to direct current (RF-DC) was tested more than 70% with 33 dBm input power and 430Q-load. In the process of study, the practical transmission power and efficiency are more than 1.5kW and 10%, respectively. The excellent performance of the MPT system indicates that they are suitable for wireless power supply application with ten meters.
The L-band polarization ratio (PR) is analyzed on the basis of the SAR data acquired by the airborne radar UAVSAR. And two new empirical PR models are proposed based on 60 quad-polarization images. One of the new empirical PR models is a function of incidence angle only, while the other has additional dependence on scatter coefficient. Unlike the forms of some PR models which are functions of wind speed, the new PR models for L-band data do not depend on wind speed, which makes the models more convenient for application. Finally, another 60 quad-polarization UAVSAR images are used to validate the performance of the new PR models. Meanwhile, the behavior of an empirical PR model proposed by other scholars is also presented for comparisons. From the results we can conclude that the PR predicted by the new model which includes scatter coefficient is more consistent with the measurements.
An ultra-wideband polarization reconfigurable slot antenna based on liquid metal (LM) is proposed. The Polymethylmethacrylate (PMMA) structure with microchannels are loaded on the upper and lower sides of the Rogers5880, to provide conditions for polarization reconfiguration. The left-hand circular polarization (LHCP), right-hand circular polarization (RHCP), and linear polarization (LP) are achieved by injecting LM into microchannels in different directions. The simulation results show that the proposed antenna achieves - 10dB impedance bandwidth of 81.5% (2.29-5.44GHz) in LP state, -10dB impedance bandwidth of 48.3% (2.78-4.55GHz) and 3 dB axial ratio bandwidth (ARBW) of 51.1% (2.61-4.40GHz) in CP state.
Millimeter-wave (mmWave) is crucial autonomous driving for its wide bandwidth and low I complex vehicular communication scenarios, the shad of large vehicles has a significant influence on th to-vehicle (V2V) channel. Thus, it is necessary to channel characteristics in this case. This paper uses a ray-tracing simulator to research the influence of the and the beam switching technology on the V2V c the “See-Through situation”. Finally, through the ext channel parameters, the characteristics of the V2V (the mmWave band are explored. Conclusions can project ideas for the design of the vehicular communication li
In this paper, an antenna array for phased array antenna operating in Ka-band (32 - 38GHz) is presented. The proposed antenna is dipole, and the dielectric layer we used is low-temperature co-fired ceramic (LTCC). The active VSWRs of E-plane, D-plane and H-plane are less than 2.25, 2.75 and 2.57 while scanning to 30°, without oversampling the aperture. An antenna array with 64 elements is simulated, and the simulation results show that the proposed antenna array has a scanning angle from -30° to +30° with low gain decrease and good active VSWR. The simulated maximum gain of the antenna array is about 24.6dBi at 35GHz. The proposed phased array antenna has a good application prospect in radar systems.
A near-field time-domain shooting and bouncing rays (TDSBR) method is proposed to analyze the transient scattered near-fields from a composite target-ocean scene illuminated by far-field antenna sources. The time-domain far-field incident sources can be obtained by a convolution of pulsed excitation with the inverse Fourier transform (IFT) of antenna radiation far-fields. The TDPO near-field integral expressions for dielectric surface are reduced to closed-form expressions by applying locally expanded phase approximations and surface partitioning. The forward and backward tracing technique and the equivalent mirror antenna method are used to obtain the ray bouncing path in the composite scene under antenna radiation. Numerical examples are presented to demonstrate the efficiency and accuracy of the proposed method.
A compact dual-band antenna system with artificial magnetic conductor (AMC) reflector and operating in ISM band is proposed. The monopole antenna fed by coplanar waveguide is used as the main radiator. The circular AMC array below the antenna can greatly improve the performance of the antenna and enhance the isolation between the antenna and the human body. At 2.45 GHz and 5.8 GHz, the antenna gains are 3.35dBi and 7.03dBi, respectively. In addition, it can work normally in the corresponding frequency band on human tissue and when bent to a certain extent. Therefore, the antenna can be a promising candidate antenna for wireless body area network (WBAN) applications.
An ultra-wideband CPW-to-stripline transition is proposed in this paper. The entire transition structure is based on a multilayered PCB structure using thin dielectric substrates. The electromagnetic coupling and matching designed between CPW and stripline is completed by resin plating on multilayer dielectric plate. At the same time, a back-to-back structure of the CPW-to-strip line transition is simulated and optimized in the full-wave commercial electromagnetic simulation software. A prototype of the back-to-back transition structure was fabricated and measured, and the experimental results indicate that the VSWR is less than 1.25, the insertion loss is less than -0.3 dB in the entire frequency band within 2-18GHz. Its good performance together with simple structure and usage of thin dielectric substrates making it a good candidate in feeding the vivaldi antenna.
Sea surface sometimes become dynamic, non-uniform, anisotropic and random. In this paper, a dynamic sea surface is established based on the Monte Carlo method and with the help of JNOSWAP sea spectrum simulation, and the influence of the wind speed and wind zone of the blue-green laser passing the sea surface on the backscattering coefficient and transmission coefficient is discussed. The results show that the backscattering coefficient of the sea surface at a large incident angle is greater than that of a small incident angle. This is due to the occlusion effect of the sea surface; When the blue-green laser passes through the sea, the maximum transmission coefficient appears at the position of the refraction angle. As the wind speed and wind area increase, the transmission coefficient decreases. This work provides support for the research on key technologies and basic theories of cross-medium target laser detection by gas-sea blue-green lasers and wireless optical communication.
In order to investigate the generation and scattering characteristics of vortex electromagnetic (EM) beam, a uniform circular array (UCA) is used to generate the vortex EM beam. The scattering field, total field and radar cross section of vortex EM beam illuminating a sphere are calculated, respectively. Results indicate that phase difference of each dipole in UCA has exceedingly significant effect on the incident field, furthermore, it affects the scattering characteristics and the modal spectrum of the scattering field. It reveals that the scattering field and total field illuminated by vortex EM beam are also vortex fields, in addition, topological charges of scattering field and total field have high consistencies with incident field, these can provide a theoretical basis for the research of vortex EM beam radar detection.
The measurement campaign for point-to-area propagation at radio wave frequency 90.5 MHz is introduced and the measured basic transmission loss is compared with the Recommendation ITU-R P.1546-6 model. The experiment was carried out in Beijing, China. It can be concluded from the comparison that the measured loss is greater than the predicted loss in most circumstances.
In order to solve the problem that the application mechanism of scattering information of background of surface features in the design process of altimeter fuze is not clear, a simulation method of altimeter fuze based on Ulaby model is proposed. This method is based on the Ulaby model to model the target characteristics of background of surface features. The target characteristics information is used as the input information of fuze detection in the missile target encounter process, adopting the digital signal processing method. The response characteristic model of fuze target detection is established, and the response simulation of fuze detection to the time-varying scattering characteristics of background of surface features in the process of missile target encounter is carried out, and the response characteristics of echo and IF signal processing are clearly reproduced. The experimental results show that Ulaby model can be used to distinguish different background of surface features types. The target type information is added as another dimensional fuze detection information, and the detection accuracy is further improved by combining the height information.
In this paper, different polarized antenna arrays based on high-order mode(HOM) are presented for the fifth-generation communication, respectively. Firstly, two linearly polarized antenna arrays are demonstrated with high gain and high efficiency thanks to the low-cost property of HOM. In one of them, 3 x 4 slots are excited simultaneously by the high-order mode. A TE 340 HOM cavity excited 2x2 slot antenna array is presented in another one. Then, two circular antenna arrays are proposed based on the HOM phase distribution. A sequentially rotated feeding network is introduced for antennas' better performance. Last but not least, an 8x 8 dual circularly polarized antenna array is proposed, showing the huge potential of HOM in antenna design with miniaturized size, high gain, and high efficiency. Four sequentially rotated patches fed by high-order mode are set as a subarray to form dual circular polarization. It is concluded that the HOM fed antenna arrays feature high gain, high efficiency, and diverse polarizations.
The OAM vortex electromagnetic wave are generated by using the particular circular phased microstrip antenna array, which can provide more efficient and reliable transmission of information. Based on the theoretical analysis of OAM, the proposed phased microstrip antenna array can generate vortex electromagnetic waves carrying OAM at a center frequency of 6 GHz. The excitation is carried out by using the phase difference between adjacent antenna elements as a constant value, and a circular antenna array with a double-layer circular microstrip antenna as the antenna element is designed. By controlling the phase difference between the antenna elements, the orbital angular momentum with OAM mode numbers of 0, 1, 2, 3 are obtained. It is known from the results that by designing antenna array with different structures and changing the phase difference between the antenna elements, vortex electromagnetic waves carrying good orbital angular momentum can be obtained.
With the development of integrated joint operations technology, unmanned aerial vehicle (UAV) plays a more and more important role in modern warfare and civil science and technology. Compared with manned aircraft, UAV has many advantages in manufacturing and maintenance costs. However, the command and control of UAV depends entirely on the remote operation of ground control station, and its dependence on electromagnetic signals makes UAV more susceptible to interference and threat from complex external electromagnetic environment, and the consequences caused by interference are more serious, which may lead to control failure and crash. In this paper, the composition and characteristics of the complex electromagnetic environment faced by UAV are combed, and the interference coupling mechanism of UAV to external electromagnetic environment is studied. Furthermore, based on the interference coupling mechanism of complex electromagnetic environment to UAV, the anti-interference test of VUAV in complex electromagnetic environment is studied and carried out, and the anti-interference ability of UAV to signals of different systems is verified.
