High Gain Microstrip Active Antenna Utilizes as Transmitter and Receiver with Linear and Circular Polarization

In this research paper, a high gain microstrip active antenna is operating as transmitter and receiver at the same time with linear and circular polarization operations. This proposed work contains five essential parts such as high gain and broadband applications. Firstly, mainly is dealing with passive patch antennas. These selected passive antennas enjoy both high gain and broadband applications. Part two intends to convert the selected passive patch antennas into an active antenna. Part three intended to improve the performances of the proposed active integrated antennas. Part four enhancement elements (which is known as parasitic elements) are utilized in order to increase the gain of selected antennas. Part five, this proposed active integrated antennas will be converted from linear polarization (LP) into circulation polarization (CP). All the selected antennas will simulate by using models of ADS Agilent.

CREATION AND APPROBATION OF A LOW-FREQUENCY RADIO ASTRONOMY ANTENNA FOR STUDIES OF OBJECTS OF THE UNIVERSE FROM THE MOON'S FARSIDE

Purpose: Theoretical and experimental studies of the active antenna – an element of the low-frequency radio telescope antenna array for the future observatory on the farside of the Moon. Design/methodology/approach: To study the active antenna, consisting of a complex-shaped dipole and a low-noise amplifier, we used its mathematical model in the form of a two-port network, whose electrical parameters are set by the scattering matrix, the noise parameters being set by the covariance matrix of the spectral densities of noise waves. This model allows ma[1]king the correct analysis of the signal-to-noise ratio at the active antenna output with account for the external and internal noise sources. The modelling results were compared with those of experimental measurements of antenna characteristics. A series of radio astronomy observations were made with the developed antenna under the Earth environmental conditions. Findings: A numerical analysis of the radio telescope active antenna parameters has been made in a wide frequency range of 4–40 MHz. Two versions of the low-noise amplifier were developed to operate in the active antenna under the space and Earth environmental conditions. Under the Earth conditions, it has been experimentally proven that the range of problems, which such radio telescopes can effectively solve at low frequencies, is quite wide – from the solar research to the search for cosmological effects. Conclusions: The results of numerical simulations and experimental measurements obtained in this work have shown a satisfactory agreement between them for the most of the frequency range. The results of this work can be useful in the research and development of active antennas designed for operation at the decameter and hectometer wavelength ranges, particularly those intended for using under the space environmental conditions. Keywords: active antenna, Moon, radio astronomy observations, sensitivity

Investigations on Monolithic Radome Interactions with Active Electronically Scanned Array on Fighter Platform

The conventional fighter aircrafts are often equipped with fire control radar (FCR) using mechanically scanned antenna (MSA) with passive slots enclosed with monolithic conical radome. When the fighter platforms get upgraded with the modern active electronically steered array (AESA) FCR for better mission capabilities, even though radome change is desirable for optimum performance of AESA, it may not be feasible due to development time. This necessitate the evaluation of AESA radar with the existing monolithic radome. Hence active antenna aperture radiation pattern is required to be assessed with monolithic radome. To address this issue, simulation is preferred over physical testing, due to the reduced cost, time and complexity in measurements and ability to verify compatibility. In the present paper, the influence of monolithic radome on the active antenna radiation patterns are simulated and analysed. The characterisation studies helped for better optimisation of active aperture, optimum size for new radome development and additional space on fighter platforms that can be used for integration of new subsystems. Simulations are performed at two different locations of antenna inside radome. Experimental validations have been carried out to prove the efficacy of simulated results, which are in agreement.

A Cross-Mode Universal Digital Pre-Distortion Technology for Low-Sidelobe Active Antenna Arrays in 5G and Satellite Communications

A cross-mode universal digital pre-distortion (CMUDPD) technology is proposed here to linearize low-sidelobe active antenna arrays with non-uniform fixed power levels for each branch, which are desired in satellite communications with stringent requirements to minimize interference. In low-sidelobe arrays formed by nonuniform amplitude excitation, conventional digital pre-distortion (DPD) techniques require multiple feedback paths for either one-to-one or average linearization of the PAs, which increases system complexity and is infeasible for large-scale arrays. This is because the power amplifiers (PAs) usually operate in different modes where the supply voltages, bias voltages, and input power levels are different. The proposed CMUDPD method aims at solving this issue by intentionally arranging the PAs to work in different modes but with shared nonlinear characteristics. Based on the nonlinear correlation established among the PAs’ different operating modes, a single feedback path is sufficient to capture the common nonlinearity of all the PAs and determine the parameters of the CMUDPD module. The concept is explained in theory and validated by simulations and experiments using GaN PAs operating with three significantly different output power levels and two orthogonal frequency division multiplexing (OFDM) signal bandwidths.