2021/4

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A Novel Unidirectional High-Gain Cascaded Square Ring Antenna for WLAN Base Station Applications
(Společnost pro radioelektronické inženýrství, 2021-12) Yadav, Subash Chandra; Rao, V. Sivavenkateswara; Duttagupta, S. P.
This paper designs a unidirectional high gain, low-cost cascading ring antenna with coaxial feeding and metal without the dielectric. The designed antenna suits for high power transfer applications such as Radar communications, wireless local area network (WLAN), and base stations. The use of gap-coupled cascading rings in the design enhances the gain to 13.4 dBi at the resonance frequency of 2.45 GHz, improving the side lobes level and front-to-back ratios. The proposed antenna has symmetrical half power beam width (HPBW) in H-plane and E-plane of 37 degree and 36.5 degree, respectively. The cross-polarization field component of the antenna is below -25 dB in H-plane, and below -45 dB in E-plane is obtained from the measurements. The measured antenna has 10 dB bandwidth of 95 MHz i.e., 2.405-2.50 GHz that covers the ISM 2.45 GHz band. The designed antenna is planar in structure with compact radiating rings of size 1.16λ×0.4λ×0.1λ. The measured and HFFS simulated results are found in good agreement.
Synthesis of Dual-Beam Patterns by Exploiting Time-Modulation in Unequally Spaced Linear Arrays
(Společnost pro radioelektronické inženýrství, 2021-12) Patra, Somnath; Mandal, Sujit Kumar; Mahanti, Gautam Kumar; Pathak, Narendra Nath
In this paper, a novel approach for synthesizing multiple radiation patterns with reduced hardware complexity in the feed network by exploiting the additional degree of freedom ‘time’ in time modulated unequally spaced linear array (TMUSLA) is presented. In the proposed approach, with a suitable common set of element position of TMUSLA, the desired dual-beam pattern with low sidelobe level (SLL) is obtained by simply controlling the ON-OFF time sequence of the RF switches connected to the array elements. To show the effectiveness of the proposed array synthesis method, two dual beam patterns - first one as pencil (sum) beam (PB) and flat-topped beam (FTB) pattern, and the second one as sum and difference pattern with different constraints have been synthesized. For the successful generation of the desired power patterns, differential evolution (DE) algorithm is employed to obtain the optimum possible solution in terms of common element position, time-modulation, switching sequences and applicable excitation phase for the desired shape beam patterns. The superiority of the proposed approach with the favourable improved performance have been demonstrated by comparing the realized patterns with the state-of-the-art relevant reported works.
A New Method for Designing Modified Compact Microstrip LPF with Sharp Roll-Off and Wide Stopband
(Společnost pro radioelektronické inženýrství, 2021-12) Hoseinabadi, Abbas; Tavakoli, Mohammad Bagher; Fatemi, Mohammad Jalal Rastegar; Setoudeh, Farbod
A new method for designing a compact microstrip lowpass filter (LPF) with wide stopband width (SBW) and sharp roll off (ROF) is presented. In proposed designing procedure, high impedance microstrip lines are bent to achieve an LPF with compact size. Then, to compensate for the effect of bending microstrip lines, the lengths of the lines are mathematically modified. Moreover, adding a suppressing cell composed of Radial stub resonator and a Butterfly stub resonator increases the SBW. Also, an elliptic filter structure is used to obtain sharp ROF. In this work, an LPF with 1.12 GHz cutoff frequency, 0.147 λg  0.133 λg filter size; where λg is the guided wavelength at cutoff frequency, the SBW equal to 13.4 GHz, and the ROF more than 201 dB / GHz, is designed, simulated and fabricated to demonstrate efficiency of the proposed method. Also, the other conventional characteristics for the fabricated LPF such as 0.3 dB insertion loss, 14.4 dB return loss, and suppression factor equal to 2.2, are in the appropriate range of their amounts.
Experimental Characterization of Aircraft Electromagnetic Protections
(Společnost pro radioelektronické inženýrství, 2021-12) Krutilek, David; Raida, Zbynek; Drinovsky, Jiri
In the paper, an original construction of a coaxial flange for measurements of shielding efficiency of composite materials is presented. The measurement procedure is conceived as a differential method to suppress influence of a flange. Attention is turned to measurements of carbon composites used in aerospace industry. The studied materials exhibit a significant ability to shield electromagnetic radiation. The shielding efficiency is rising with material thickness and with the number of fiber-to-fiber contacts. The optimal composite structure consists of 4 layers of carbon composite; more layers do not influence the shielding efficiency significantly.
Development an Analytical Method for Pattern Synthesis of Arbitrary Shaped Planar Arrays
(Společnost pro radioelektronické inženýrství, 2021-12) Boozari, Mahdi; Khalaj-Amirhosseini, Mohammad
In practice, it is often necessary to design an array that will yield desired radiation pattern. For this purpose, several time-consuming algorithms are introduced in the literature. In this paper, an analytical method is presented to synthesize the radiation pattern of planar and ring arrays. In this method, two new parameters are defined to reconstruct the array factor and simplify the calculation complexity. To accomplish this, we use the double integral to generate two distinct Sinc functions from a bivariate function utilizing the sampling theory notion. This stage generates a set of linear equations that, when solved, yields the complex excitation coefficients. The proposed method is verified by presenting several practical examples. Also, the performance of the method is compared with that of other approaches. The results show that the proposed method is a good candidate for synthesizing a prescribed pattern of planar arrays.

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