Venkat Reddy Kandregula

Evaluating the performance of an antenna in the presence of electrically large structures is computationally challenging. In this context, three solver techniques – full-wave Finite Integration Technique (FIT), Unidirectional Advanced Method (UAM) and Hybrid Bidirectional Solver (HBS) are compared. The above solver techniques available in Computer Simulation Technology Microwave Studio (CST-MWS) are used to simulate a Printed Log-Periodic Dipole Antenna (PLPDA) enclosed in a fixture with foam mounted on an Unmanned Aerial Vehicle (UAV). The electromagnetic performance of all three solver methods is compared, thereby validating the accuracy, with realized gain differences of less than 0.2 dB, HPBW differences of less than 1°, and front-to-back ratio differences of less than 2-3 dB at all frequencies. The full-wave FIT solver takes 14 hrs at 6 GHz, but the UAM and HBS only take 1.2 and 1.6 hrs, respectively. In contrast to the HBS, the UAM offers the most computationally efficient solution for this class of problems by incorporating selective field recalculations that take into consideration the presence of the UAV body.

To evaluate the performance of a printed log-periodic dipole antenna (PLPDA) in outdoor environments, we present unmanned aerial vehicle (UAV)-based antenna measurements conducted in the far-field region. Non-tethered UAV flight operations were achieved by configuring commercially available UAVs separately as a transmitter (TX) and as a receiver (RX). UAVs configured in non-tethered mode provide flexibility in terms of altitude maintained by the UAV from the ground level. The TX section of the UAV consists of a portable signal generator and a PLPDA configured to transmit signals with an output power of +15 dBm at 0.8 and 3.5 GHz. Similarly, the RX section of the UAV is equipped with a real-time spectrum analyzer and an identical PLPDA. Using these two UAVs in TX and RX modes, the radiation pattern of the PLPDA was obtained in the azimuth plane. Since two identical PLPDAs were used, the realized gain of the PLPDA is evaluated using the two-antenna gain method. The test scenario involved the TX UAV hovering at the center while the RX UAV followed a circular trajectory around it. A comparison between the UAV measurements, anechoic chamber measurements, and simulated data demonstrates good agreement, validating the reliability of the measurements.

A dual function metasurface based on flip-chip Aluminium Gallium Arsenide (AlGaAs) PIN diodes is presented. Depending on the biasing state of the PIN diodes, the metasurface exhibits either a 1-bit reflection response or a transmission response. The design was optimized using the full 3D model of the AlGaAs PIN diodes. Simulations have been carried out using CST microwave studio to evaluate the performance of the dual function metasurface. The optimized metasurface demonstrates an average reflection loss of 0.3 dB and a transmission loss of 1.09 dB at 29 GHz. The corresponding simulation results were compared against both the simulated (obtained from a SPICE model developed in a circuit simulator) and measured S-parameters of the diodes. The transmission and reflection responses obtained at the operating frequency remain consistent across the three modelling approaches are presented and discussed.

A dual-pattern reconfigurable antenna comprising a torus-shaped metasurface controlled by flip-chip Aluminum Gallium Arsenide (AlGaAs) PIN diodes and a bicone antenna feed is investigated. A broadband bicone antenna operating between 14 and 34 GHz is initially optimized to enhance its realized gain and achieve 4.1 dBi at 29 GHz and 4.4 dBi at 30 GHz. The designed bicone is subsequently used as a feed for the torus-shaped metasurface. A torus-shaped metasurface capable of switching between reflection and transmission is investigated in two stages. Its geometry is optimized as a metallic reflector to reduce computational time. The dimensions of the reflector are optimized to improve the gains and lower the side lobe levels (SLL). The simulation of the reflector confirms that the torus reflector with the bicone feed achieves a realized gain of 16.3 dBi at 29 GHz and 17 dBi at 30 GHz. The proposed metasurface achieves transmission and reflection switching between 27.5 and 30.5 GHz by controlling the PIN diode state. Based on the results, the proposed system can operate in two distinct modes: omnidirectional and directional. The expected omnidirectional performance of the final system corresponds to that of the standalone bicone antenna, reduced by the metasurface insertion loss. In the directional mode, the realized gain and radiation pattern are determined by the combined response of the bicone antenna and torus-shaped metasurface reflector.

This paper presents a comprehensive survey of state-of-the-art UAV–based antennas and propagation measurements. Unmanned aerial vehicles (UAVs) have emerged as powerful tools for in situ electromagnetic field assessments due to their flexibility, cost-effectiveness, and ability to operate in challenging environments. This paper highlights various UAV applications, from testing large–scale antenna arrays, such as those used in the square kilometer array (SKA), to evaluating channel models for 5G/6G networks. Additionally, the review discusses technical challenges, such as positioning accuracy and antenna alignment, and it provides insights into the latest advancements in portable measurement systems and antenna designs tailored for UAV use. During the UAV–based antenna measurements, key contributors to the relatively small inaccuracies of around 0.5 to 1 dB are identified. In addition to factors such as GPS positioning errors and UAV vibrations, ground reflections can significantly contribute to inaccuracies, leading to variations in the measured radiation patterns of the antenna. By minimizing ground reflections during UAV–based antenna measurements, errors in key measured antenna parameters, such as HPBW, realized gain, and the front-to-back ratio, can be effectively mitigated. To understand the source of propagation losses in a UAV to ground link, simulations were conducted in CST. These simulations identified scattering effects caused by surrounding buildings. Additionally, by simulating a UAV with a horn antenna, potential sources of electromagnetic coupling between the antenna and the UAV body were detected. The survey concludes by identifying key areas for future research and emphasizing the potential of UAVs to revolutionize antenna and propagation measurement practices to avoid the inaccuracies of the antenna parameters measured by the UAV.

Evaluating the performance of an antenna using commercially available electromagnetic (EM) solvers such as Computer simulation technology (CST) studio suite has become crucial. In this context, a unidirectional advanced technique is used for simulating a Printed Log-Periodic Antenna (PLPDA) enclosed in a fixture with foam. This method employs a hybrid solver approach, in which the PLPDA with foam (source) is simulated using a transient solver, and the fixture (platform) is simulated using an integral equation solver. The proposed technique significantly reduces the simulation time and RAM usage while maintaining high accuracy. It is a viable alternative to traditional full-wave analysis, where the source and platform are simulated using a single solver or bidirectional simulation techniques. A comparative analysis with measured radiation patterns demonstrates the effectiveness of this method, providing a reliable and efficient solution for antenna design and performance evaluation.

Wireless systems have been upgraded over the past several years and as a result, drone-based communications have found a wide range of applications. This paper presents the performance of a printed log-periodic antenna, which operates in the frequency range from 0.7 to 6.5 GHz when mounted on the top of a drone. The effect of a metallic mast and a base plate is considered in our analysis. From our simulations, it is observed that an improvement in realized gain of 1.6 dB is obtained over a frequency band of 2 to 6.5 GHz. All simulations are performed using CST Studio Suite.

A Gregorian Dual Reflector configuration is proposed to scan an area ranging from -1.2° to 1.2°. The proposed configuration consists of a paraboloidal main reflector, elliptical sub-reflector operating at Ku-Band and sharing common feed point. Imaging arrangement is obtained by translation, rotation and focal length adjustment of the feed. An attractive feature of the imaging arrangement is that they are capable to scan one beam electronically and generate multi beam coverage in a limited field of view. As an application, a 0.6m diameter main reflector with a cluster of WR-51 waveguides is utilized to get an H.P.B.W of 1.8°.

In this article, Antenna with flag-shaped radiating elements in antipodal configuration is proposed. The design and the study focuses on geometrical parameters like length of the patch, width of the flared structure to enhance the operability of the antenna in Ku-band spectrum. The proposed antenna is designed and simulated in ANSYS HFSS ver15.0 and the characteristic features obtained after simulation indicates that the antenna operates from 11.1293 GHz to 19.18 GHz. The proposed antenna is configured into an array with 3-elements. The characterization of antenna array is done in terms of return loss, isolation and radiation performance. The array configuration has improved the directive radiation performance.