2021/2
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- ItemHarmonic Suppression by Using T-shaped Spur-Line in a Compact Hairpin-Line Bandpass Filter(Společnost pro radioelektronické inženýrství, 2021-06) Das, Tarun Kumar; Chatterjee, SayanThis article exhibits the design of a fourth-order compact hairpin-line filter centered at 2.5 GHz and 3 dB fractional bandwidth of 5% along with a sharp roll-off factor and wide stopband characteristics required for Wireless Local Area Network (WLAN). Miniaturization of the conventional hairpin-line filter has been achieved by folding the open end arms twice towards the inward direction and accordingly, a size reduction of 42% has been obtained. Subsequently, T-shaped spur-lines with optimum dimensions have been incorporated at both the inner and outer edges of the coupled arms of the folded hairpin-line cell. Accordingly, two fourth-order folded filters with outer T-shaped and double T-shaped spur-lines have been designed and verified experimentally. An extended stopband with a rejection level of 39 dB up to 3.2f_0 along with a size reduction of 46% has been achieved.
- ItemDesign of Ultra-wideband Low RCS Reflecting Screen Based on Phase Gradient Metasurface(Společnost pro radioelektronické inženýrství, 2021-06) Ji, Kefeng; Gao, Jun; Cao, Xiangyu; Han, Jiangfeng; Yang, HuanhuanIn order to realize full phase coverage of 360° and abnormal reflection of incident wave, one kind of metasurface unit-cell with double diagonal opening cross petal and two types of one and two dimensional phase gradient metasurface with elements arranged on 6×6 array whose phase difference is 60°, were designed and constructed in this paper based on the abnormal reflection principle of phase gradient metasurface. By rotating the two phase gradient metasurfaces and arranging them in a spiral manner, three types of ultra-wideband low Radar Cross Section (RCS) reflecting screens with different unit configurations were devised. HFSS 14.0 was used for simulation experiment and the relative bandwidth of RCS reduction above 10 dB is respectively 34.5%、28.8% and 28.1%. Moreover, the peak value of RCS reduction can reach 44.9 dB. After testing the three reflecting screens in a microwave anechoic chamber, it was found that the measured results were basically in agreement with the simulation data, which verified the feasibility of the design. The design of reflecting screen proposed in this paper can provide a new method and approach for new ultra-wideband stealth technology.
- ItemStudy on the Composite Electromagnetic Scattering from 3D Conductor Multi-Objects above the Rough Surface(Společnost pro radioelektronické inženýrství, 2021-06) Liu, Ting; Zhang, Lin; Zeng, Zhi-Guo; Wei, Sheng-JunThe traditional algorithm for the composite electromagnetic scattering from 3D conductor multi-objects above the rough surface has such weaknesses as slow computation speed and large memory consumption. On the basis of the fast algorithm integrated with the traditional coupling method of moment and physical optics method, this paper uses the multilevel fast multipole method (MLFMA) and fast far-field approximation (FAFFA) to accelerate the multiplication of matrix vector between the object and environment, which greatly improves the computation speed and reduces the memory consumption. This paper adopts the dual Debye sweater permittivity model simulate the real sea surface environment, establishes the coupling MoM-PO model of composite scattering from multi-objects on and above the sea surface, and obtains the composite electromagnetic scattering coefficient in virtue of the interaction between object area and rough surface area calculated by the MLFMA and FAFFA. At the same time, the changes of composite scattering coefficient along with the change of object spacing, size, incident angles, tilt angle, type and sea surface wind speed are analyzed in detail. The computation results show that the hybrid method consisting of the method of moment accelerated by MLFMA and FAFFA and physical optics method brings higher accuracy and computation efficiency (the computation time and memory consumption are 62% and 82% of the method of moment respectively).
- ItemCipherCAD Testbed(Společnost pro radioelektronické inženýrství, 2021-06) Platenka, Vaclav; Mazalek, AntoninThe CipherCAD testbed is a unique workplace for the development, design, testing, verification and teaching of the communications systems. CipherCAD is at the core of the workplace, which is an application primarily designed for solving cryptographic tasks. The application can also be used for communicating with hardware communications devices. The workplace is used in the Department of Communications Technologies at the University of Defense. The article will present selected exam-ples used in this workplace. The introduction introduces CipherCAD and the possibilities for creating simple models. The first model to be selected shows how to control SDR IZ225 and process the signals received. The next model shows how selected modulated signals are gener-ated in real time, and their transmission throughout the whole chain of communications. The models that follow show how they can be used in the field of communications protocols, VoIP transfer and changing any of the parameters of the transmitted information.
- ItemParametric Geometrical Study of OOO-Microstrip Circuit with Dual-Band Bandpass NGD Behavior(Společnost pro radioelektronické inženýrství, 2021-06) Yang, Rong; Wan, Fayu; Nebhen, Jamel; Lallechere, Sebastien; Ravelo, BlaiseThis paper introduces a bandpass (BP) NGD circuit design engineering. The developed circuit is de¬signed and implemented using distributed microstrip tech-nology and operates with outstanding dual-band bandpass NGD performance added with low attenuation. The BP NGD topology presents an innovative geometrical shape represented by an OOO (triple O) structure composed of multi-parameter parallel transmission lines (TLs) based elements. The OOO type NGD circuit is mainly composed of different physical length TLs and two identical coupled lines (CLs). Then extensive parameter NGD analyses are elaborated to investigate on the influences of each physical size of OOO circuit on the NGD performances. Through the difference of physical length of transmission line, the delay can be adjusted. Through the results of simulation and measurement, it can be seen that the center frequency points are about 0.75 GHz and 1.46 GHz respectively, and the time delay is about –1.83 ns and –2.6 ns respectively.