Main Lobe Of Radiation Pattern Research Articles

Stable-Sample-Level-Based Digital Predistortion for 2-D Millimeter-Wave Phased Array Steering

This letter proposes a stable-sample-level (SL)-based digital predistortion (DPD) technique for 2-D phased array with fixed-position over-the-air (OTA) feedback (FB) to overcome significant SL fluctuation when the beam is steered. It is achieved by optimizing the phase of the beamformer based on the DPD requirement, which can control the SL at a given value without affecting the main lobe of radiation pattern, relaxing the requirement of FB dynamic range. The radiation pattern and DPD performances are measured on a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4 \times 4$ </tex-math></inline-formula> phased array at 26 GHz. The measured results show that the proposed method can realize the stable SL with good DPD performance.

Synthesis of a Luneburg lens with a flat surface using quasi-conformal transformation optics

Annotation In modern systems of radiolocation, navigation and communication, the requirements for antennas are becoming higher requirements every year, namely: operation in a wide frequency range, the ability to change of direction of the main lobe of the radiation pattern. Antenna systems with similar characteristics can be built using dielectric antenna beamforming structures. One of these structures is the Luneberg lens, the peculiarity of which is its spherical symmetry. However, the curved surface of this lens significantly complicates the placement of transmitting and receiving elements along it, which increases the complexity of constructing the entire antenna system. This paper proposes an algorithm for constructing a Luneberg lens with a flat surface. The lens was synthesized using the method of quasi-conformal optical transformations, the mathematical algorithm of which is also described in this work. The paper also presents the results of mathematical modeling of the antenna system using a Luneberg lens with a flat surface at different positions of the emitter relative to the center of the lens, as well as different cut angles. The simulation results show that the synthesized lens can be used to construct a multi-beam antenna system that allows the direction of the main lobe of the antenna radiation pattern to be rearranged over a wide range of angles. However, the scanning angles of this system are limited by the lens geometry, the larger the maximum scanning angle we choose, the more significant the influence of the side lobes on the radiation pattern becomes.

Radiation pattern control of core shell nanoantenna by manipulation of nonlinear properties

In this article, a new structure of core–shell spherical nanoparticle as nanoantenna has been evaluated in which the main lobe direction of its radiation pattern is controllable. In other words, the main lobe direction of core–shell nanoantennas are rotated by using of nonlinearity and pumping secondary wave. As a matter of fact, a unique method is presented in order to turn and tune the radiation pattern of nanoantenna in a considered direction. The control of core shell nanoantenna’s main lobe direction is done by manipulation of the nonlinear properties and an excitation wave as secondary pump. Specifically, Increase in pumping leads to motivate the nonlinear properties of the proposed nanoantenna, therefore the main lobe of radiation pattern is turned slowly and its direction is changed. Based on this method, the designers can implement the structures which have been the controllable scatterings in specific directions. Basically, we indicated that it is possible to control the main lobe direction by means of nonlinear perturbation in core–shell nanoantenna and incidence of secondary wave. For more study, the effect of existence of substrate under spherical nanoantenna is investigated and variation of its pattern is also illustrated. The constituent materials of structures have nonlinear properties. The obtained results in final section show that the substrate also plays effective role in directing of nanoantenna’s beam. Turning lobe direction of presented nanoantenna is evaluated on 600 THz as well.

Agile radiation pattern control of metamaterial microstrip antenna

We are interested in this work, with the antenna radiation pattern agility. The aim is to control the radiation pattern using an agile metamaterial lens. This latter is based on an agile metamaterial. For this purpose we design an agile metamaterial unit cell which can flip between two different behaviors. The first one corresponds to an effective medium with a refractive index close to zero and the second one corresponds to an effective medium having a refractive index greater than unity. This agile lens is used to enhance a microstrip antenna gain and control its radiation pattern. The maximum realized gain obtained is up to 12 dB. The radiation pattern main lobe can be rotated from −47° to 47° in the E-plane and from −33° to 33° in the H-plane. We obtain also a main lobe beam width of 32° in the E-plane and 46° in the H-plane.

A New On-Line/Off-Line Adaptive Antenna Array Beamformer for Tracking the Mobile Targets

An adaptive antenna array system adjusts the main lobe of radiation pattern in the direction of desired signal and points the nulls in the direction of undesired signals or interferers. The essential goal of beamforming is to reduce the complexity of weighting process and to decrease the time needed for adjusting the antenna radiation pattern. In this article a new adaptive weighting algorithm is proposed for both least mean squares (LMS) and constant modulus (CM) algorithms. It is appropriate and applicable for antenna array systems with moving targets and also mobile applications as well as sensor networks. By predicting the relative velocity of source, the next location of the source will be estimated and the array weights will be determined using LMS or CM algorithm before arriving to the new point. For the next time associated to the new sampling point, evaluated weights will be used. Furthermore, by updating these weights between two consecutive times the effects of error propagation will be eliminated. Therefore, in addition to reduction in computational complexity at the time of weight allocation, relatively accurate weight allocation can be obtained. Simulation results of this investigation show that the angular error related to both LMS-based and CM-based algorithms is less than the conventional LMS and CM algorithms at different signal to noise ratios (SNRs). On the other hand, due to considering off-line process, online computational complexity of new algorithms is slightly low with respect to previous ones.