2021/2

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    Design 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, Huanhuan
    In 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.
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    Amplitude-modulated, Cosine PE and WP Pulses: Theory and Applicability
    (Společnost pro radioelektronické inženýrství, 2021-06) Lager, Ioan E.; Stumpf, Martin
    The amplitude-modulated, cosine power-exponential (PE) and windowed-power (WP) pulses are discussed, by insisting on their time-domain normalization. Illustrative examples of signatures and their correspondent frequency-domain behavior are given. These examples compellingly demonstrate the possibility to replace non-causal pulses of prevalent use by causal, or even time-windowed, pulses with closely resembling signatures.
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    CipherCAD Testbed
    (Společnost pro radioelektronické inženýrství, 2021-06) Platenka, Vaclav; Mazalek, Antonin
    The 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.
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    Harmonic Suppression by Using T-shaped Spur-Line in a Compact Hairpin-Line Bandpass Filter
    (Společnost pro radioelektronické inženýrství, 2021-06) Das, Tarun Kumar; Chatterjee, Sayan
    This 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.
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    A Wideband Conductor Backed Coplanar Waveguide Fed Implantable Antenna Operable in Different Tissues for Biotelemetry Applications
    (Společnost pro radioelektronické inženýrství, 2021-06) Okan, Tayfun
    A wideband biocompatible implanted antenna is designed for wireless biotelemetry applications at industrial, scientific and medical (ISM) band (2.4-2.48 GHz). The antenna is fed by a conductor backed coplanar waveguide (CB-CPW) structure and two H-shaped slots are etched side by side on the patch of the antenna to create a resonance at the desired frequency. The experimental and simulation measurements are performed by using skin, fat and muscle tissue layers. The impedance bandwidth (S_11≤-10 dB) of the proposed antenna is measured as 0.406 GHz (2.272 - 2.678 GHz), when the fabricated antenna is implanted inside a three-layered human body mimicking gel. By using the advantage of having a wide bandwidth, the designed antenna is analyzed inside different tissue types and tissue thicknesses. For every obtained simulation and experimental result, it is observed that the antenna always covers the ISM band, which is the most significant contribution of this study. The size of the implantable antenna is 16×13×1.93 mm3, where both sides of the antenna is covered by a superstrate material to extend the life of the antenna inside the tissue.