arXiv subjects

Mahdi Fartookzadeh

Publications and source records attributed to Mahdi Fartookzadeh.

5 recordsLinked to original sources

arXiv2024

On the Time-Range Dependency of the Beampatterns Produced by Arbitrary Antenna Arrays: Discussions on the Misplaced Expectations from Frequency Diverse Arrays

In the recent years constructing time-invariant spatial-focusing beampatterns by using frequency diverse arrays (FDAs) is conveyed in several papers. Further than time-invariant spatial-focusing beampatterns, the unfeasibility of constructing range-dependent time-invariant beampatterns is demonstrated in this paper. It is indicated that the beampatterns produced by antenna arrays including FDAs are not independently controllable in time, t, and range, r, dimensions, in the farfield. Inappropriate applications of the FDAs having time-invariant spatial-focusing beampatterns in two recent papers are also discussed.

physics.class-ph↗

arXiv2021

Comments on Combining Switched TMAs and FDAs to Synthesize Dot-Shaped Beampatterns

The idea of frequency diverse array (FDA) has been invigorated in the recent years by supposing to have the ability of stopping the electromagnetic wave propagation and producing secretive direct connections between distant points. However, it was based on a theoretical mistake in a series of published papers beginning from 2014. In fact, the issue was not very clear since 2018; hence the researchers should be very careful in relying on the papers of this topic.

eess.SP↗

arXiv2020

Frequency Diverse Arrays (FDAs) vs. Phased Arrays: On the Application of FDAs for Secure Wireless Communications

Application of range-angle focusing frequency diverse array (FDA) for secure wireless communication has been proposed in recent years. However, it can be proven that the FDAs are not suitable for secure wireless communication and the same properties of the focusing FDA can be obtained by using traditional phased arrays, more effectively. Besides, in this paper, it is indicated that FDAs are not good candidates for constructing time-variant focusing beampatterns, while constructing time-invariant focusing beampatterns is impossible at all. Furthermore, some incorrect considerations about the FDAs are highlighted.

eess.SP↗

arXiv2018

Enhancement of Dual-Band Reflection-Mode Circular Polarizers Using Dual-Layer Rectangular Frequency Selective Surfaces

A new kind of dual-band reflection-mode circular polarizers (RMCPs) is introduced with wide bandwidth and wide-view at the operating frequencies. The proposed RMCPs are based on dual-layer rectangular patches on both sides of a substrate, separated by a foam or air layer from the ground plane. Required TE susceptance of the first layer patches to produce circular polarization is calculated using the equivalent transmission line model. Dimensions of the RMCP are obtained using parametrical study for the two frequency bands, 1.9-2.3 GHz and 7.9-8.3 GHz. In addition, it is indicated that the accepted view angle and bandwidth of the proposed dual-layer RMCP are improved compared with the single layer RMCP, significantly. Moreover, a tradeoff is observed for the dual-layer RMCP on the bandwidths of X band and S band that can be controlled by propagation angle of the incident wave. The proposed RMCP has 30.5 % and 33.7 % bandwidths for less than 3 dB axial ratio with incident angles θmax=50° and θmin=35°. Finally, simulation results are met by the measurement for three angles of the incident wave.

physics.class-ph↗

arXiv2018

Comments on Frequency Diverse Array Antenna Using Time-Modulated Optimized Frequency Offset to Obtain Time-Invariant Spatial Fine Focusing Beampattern

In the recent papers [1-4] including above paper time modulated frequency diverse arrays (FDAs) have been presented to obtain time invariant spatial patterns. The presented FDAs in [1-3] have the feature of time-invariant spatial focusing which means they have a constant maximum in a time duration, T, at a point with desired range, r, and angle, θ. In [4] the pattern is time invariant, yet, not focused. However, in this communication it is indicated that the patterns are obtained using incorrect definition of time in some equations. The equation system of [3] is explained here that can be extended to [1, 2, 4], explicitly.

eess.SP↗