Electronically-steered Antennas Research Articles

Enabling In-Flight Connectivity with the new Generation of Electronically Steered Antennas

In-flight communication (IFC) services offered to passengers and crew are of great importance to the air transport sector. The improvement of the satellite capacity with High Throughput Satellites (HTS) in GEO and the advent of MEO and LEO constellations will support the forecast growth of the IFC market. Antenna equipment for satellite communications will need to address multiple scenarios from G2G (Gate-to-Gate) to multi-operation under GEO-MEO-LEO systems. Under these conditions, antennas with the ability to track multiple satellites and having superior performance and reliability will play a key role. Electronically steered antennas (ESA) have emerged as a viable solution in response to these demands. The EU-funded LESAF project proposes an ESA solution of reduced size and greater efficiency for the next generation of in-flight connectivity services. This will be managed through the requirements definition, system analysis, technology assessment, prototyping and validation of ESAs. The project has successfully passed the first milestone corresponding to requirements consolidation, baseline architecture definition and candidate technology trade-offs. Multi-beam Electronically Steered Antennas, separated apertures for both transmission and reception, a flexible modular approach coupled with planar multilayer integration and an advanced beamformer design are the basis for the proposed concept. The following project phase will be focused on the design and validation of an antenna demonstrator aimed at proving the superior added value of ESAs technological solution for the aviation industry needs.

Hardware Demonstration of Extremely Compact Optical True Time Delay Device for Wideband Electronically Steered Antennas

An optical true time delay device is demonstrated that is capable of supporting 112 antennas with 81 different delays (>; 6 bits) in a volume 16 × 5 × 4 including the box with electronics. It uses a free-space design based on the White cell, and alignment is made simple, fast, and robust by the use of slow-tool diamond turning of many optics on a single substrate. Pointing accuracy of the 12 objective mirrors is better than 10 μrad, and surface roughness is ≈ 45 nm RMS. Delays vary from 0 to 25 ns in 312.5 ps increments. Short delays are implemented using delay rods of high refractive index, and long delays using folded mirror trains. Total insertion loss from fiber to detector was 7.82 dB for the no-delay path, and 10.22 dB for the longest lens train. A three-state tip-style MEMS micromirror array is used to select among the delays, with tilt angles ±1.4° plus flat, and switching time <; 100 μs for the entire array. An InP wideband optical combiner photodetector array converts the optical signal to RF with 20 GHz bandwidth. The unit survived temperature cycling 0 to 50 C and random vibration on three axes (9.84 g RMS) with no degradation of signal.

Target Existence Based Resource Allocation

Assume an electronically steered antenna (ESA) radar. In between the search mode operations (where the radar completes one scan of the surveillance area), we may optimize performance by judiciously updating individual tracks. The optimization is often translated into the choice of the next track to update. We propose a resource allocation scheme designed to minimize the response time to changing target situation; i.e., confirmation of new tracks following new targets, and termination of tracks without targets. The resource allocation cost is a function of the probability of target existence of individual tracks. Approximative expressions are derived and verified. Simulation results show that resource allocation based on this cost significantly improves the response time of the system to the changes in target situation. As a spurious benefit, some of the sensor time is liberated for other activities.

Radar Optimal Times Detection Allocation in Multitarget Environment

This paper deals with the problem of the management of electronically steered antenna (ESA) in multitarget environments. Radars are used to detect, locate and identify targets. In this paper we focus on the detection of several aerial targets in a fixed given time. The difficulty of such detection lies in the fact that targets may be located anywhere in the space, but radars can only observe a limited part of it at a time. As a result, it is necessary to change their axis position over time. This paper describes the main steps to derive an optimal radar management in this context: the modeling of the radar, the determination of a criterion based on the target detection probability and the temporal optimization process leading to sensor management strategy. An optimization solution is presented for several contexts and several hypotheses about prior knowledge concerning the targets' locations. First, we propose a method for the optimization of the radar detection probability in a single target environment. It consists in the decomposition of the detection step into an optimal number of independent elementary detections. Then, in a multitarget context with deterministic prior knowledge, we present an optimal time allocation method which is based on the results of non linear programming. finally, in a multitarget context with probabilistic prior knowledge, results in search theory are used to determine an optimal temporal allocation.