On methods to determine bounds on the Q-factor for a given directivity

This paper revisit and extend the interesting case of bounds on the Q-factor for a given directivity for a small antenna of arbitrary shape. A higher directivity in a small antenna is closely connected with a narrow impedance bandwidth. The relation between bandwidth and a desired directivity is still not fully understood, not even for small antennas. Initial investigations in this direction has related the radius of a circumscribing sphere to the directivity, and bounds on the Q-factor has also been derived for a partial directivity in a given direction. In this paper we derive lower bounds on the Q-factor for a total desired directivity for an arbitrarily shaped antenna in a given direction as a convex problem using semi-definite relaxation techniques (SDR). We also show that the relaxed solution is also a solution of the original problem of determining the lower Q-factor bound for a total desired directivity. SDR can also be used to relax a class of other interesting non-convex constraints in antenna optimization such as tuning, losses, front-to-back ratio. We compare two different new methods to determine the lowest Q-factor for arbitrary shaped antennas for a given total directivity. We also compare our results with full EM-simulations of a parasitic element antenna with high directivity.Comment: Correct some minor typos in the previous versio

Hybrid Beamforming for dual-polarized antenna

International audienceRecently, dual-polarized antenna has attracted strong attention in Millimeter wave (mmWave) systems. It provides an additional degree-of-freedom in wireless communication, yielding higher throughput. Nowadays, with the development of antenna technology, dual-polarized large scale antenna arrays can be realized inexpensively. However, several challenges must be addressed when using dual-polarized antennas in practical transmission such as mobile phone rotation and non-ideal polarization isolation. We address these challenges in the frame of dual-polarized hybrid beamformers. In this paper, we analyze the performance of dual-polarized beamforming based on two popular techniques: Beam steering and Orthogonal Matching Pursuit. Three categories of dual-polarized beam steering are analyzed : (1) same ray : the two polarizations are sent on the same ray, (2) different ray-same polarization : the two polarizations are sent on different pathes, and the receiver uses the same polarization as the emitter, (3) different ray-different polarization : the receiver uses the orthogonal polarization w.r.t. the emitter. An algorithm to choose the rays and polarizations to use, taking the mobile rotation into account, is also developed. Moreover, we develop a hybrid beamforming algorithm inspired by Orthogonal Matching Pursuit that approaches the fully digital beamforming data-rate and outperforms beam steering. Its developed version-Orthogonal based Matching Pursuit-is also introduced to reduce the computational complexity and overcome the unavailability of the Angle of Arrival

Optimal Planar Electric Dipole Antenna

Considerable time is often spent optimizing antennas to meet specific design metrics. Rarely, however, are the resulting antenna designs compared to rigorous physical bounds on those metrics. Here we study the performance of optimized planar meander line antennas with respect to such bounds. Results show that these simple structures meet the lower bound on radiation Q-factor (maximizing single resonance fractional bandwidth), but are far from reaching the associated physical bounds on efficiency. The relative performance of other canonical antenna designs is compared in similar ways, and the quantitative results are connected to intuitions from small antenna design, physical bounds, and matching network design.Comment: 10 pages, 15 figures, 2 tables, 4 boxe

Convex optimization for the synthesis of matching filters

International audienceIn this work we study a particular filter synthesis problem in order to minimize the reflection coefficient of the global system consisting of filter and antenna. The matching problem is formulated as an optimization problem involving the minimization of a pseudo hyperbolic distance and the solution to this problem using H∞ approach yields a lower bound for the matching criterion related to the computation of a matching filter, with prescribed finite degree, under selectivity constraints

A multifunctional compact pattern reconfigurable antenna with Four radiation patterns for sub-GHz IoT applications

ABSTRACT: A compact pattern reconfigurable antenna with four radiation patterns is proposed for sub-GHz IoT applications. The antenna has two functional modes; Mode I has three uncorrelated patterns, while Mode II has electric and magnetic omnidirectional patterns. The resonant frequency of the antenna is 868 MHz with measured overlapped −6 dB impedance-bandwidths of 22 MHz and 20 MHz for Mode I and Mode II, respectively. The antenna is integrated in an 80×55 mm2 terminal. The radiating elements consist of two meandered slots and one meandered monopole. Four pattern configurations are obtained with an average peak gain of 0 dBi, and an average radiation efficiency of 43.3%. Two of the patterns are with 5 dB directivity, and the other two are omnidirectional patterns. Pattern reconfigurability is achieved using four PIN diodes. The antenna is fabricated on a low-cost FR-4 substrate. By removing FR-4 material inside the slots, slots’ radiation efficiencies were improved by 2.25 dB

Open-Source 4G Experimental Setup (Report)

In this work, we show how to set up a cellular LTE network for wireless experimentation and measurement, relying on commodity hardware and open-source software. We first deploy a complete LTE network on a single laptop and an SDR hardware. Then, we use it to evaluate the reception performance of a commercial smartphone. In the end, we propose a calibration technique which allows using a smartphone as a wireless power measurement tool by reducing the root-mean-square error of the RSSI, with respect to a reference power measured with a specialized spectrum analyzer, from 6.4 dBm to 2.4 dBm

Evaluating Smartphone Accuracy for RSSI Measurements

International audienceSmartphones are today affordable devices, capable of embedding a large variety of sensors such as magnetometers or orientation sensors, but also the hardware needed to connect them to most wireless communication technologies such as Wi-Fi, Bluetooth, or cellular networks. Therefore, they are handy devices able to perform Received Signal Strength Indicator (RSSI) measurements for a wide variety of applications such as cellular coverage maps, indoor localization, or proximity tracking. However, to the best of our knowledge, the accuracy of such measurements has never been rigorously assessed. The goal of this paper is to assess the accuracy of the RSSI measurements made with a Commercial Off-The-Shelf (COTS) smartphone in a variety of conditions, and how possible inaccuracies can be corrected. We primarily focus on the LTE RSSI, but we also extend our results to the Bluetooth RSSI. In this paper, we build a controlled experimental setup based on commodity hardware and on open-source software. We evaluate the granularity and limitations of the Android API that returns the RSSI. We explore how reliable the measurements in a controlled environment with a monopolarized antenna are. We show that the orientation of the smartphone, the position or orientation of the source, and the transmission power have a significant impact on the accuracy of the measurements. We introduce several correction techniques based on radiation matrix manipulations and on machine learning in order to improve measurement accuracy to less than 5 dBm RMSE, as compared to a professional equipment. We also explore the reliability of measurements made in an outdoor realistic environment. We show that whereas transmission diversity available in LTE base stations significantly improves the measured RSSI regardless of the smartphone orientation, the Bluetooth RSSI remains largely sensitive to the smartphone orientation

Evaluating Smartphone Accuracy for LTE Power Measurement

Smartphones are today relatively cheap devices that embed a large variety of sensors such as magnetometers or orientation sensors, but also the hardware to connect to most wireless communication technologies such as Wi-Fi, Bluetooth, or cellular networks. For this reason, companies, such as OpenSignal or Tutela use smartphones to make crowd-based measurements of the received power from the cellular infrastructure to help operators manage their infrastructure. However, to the best of our knowledge, the accuracy of such measurements has never been rigorously assessed. The goal of this paper is to assess how accurate are measurements of received power from a 4G (LTE) antenna when performed from a Commercial Off-The-Shelf~(COTS) smartphone in different environments. We first evaluate the granularity and limitations of the Android API that returns the received power. We explore how reliable are the measurements from a mono-polarized antenna in a fully controlled environment. We show that the orientation of the smartphone, the position of the source, and the distance to the source has a significant impact on the accuracy of the measurements. We introduce several calibration techniques based on radiation matrices manipulations and machine learning to calibrate the measurements, that is, to improve the accuracy to less than 5 dBm RMSE compared to a professional equipment. Finally, we explore how reliable are measurements in an outdoor environment, in the context of a multi-polarized antenna

Open-Source 4G Experimental Setup

International audienceIn this work, we show how to set up a cellular LTE network for wireless experimentation and measurement, relying on commodity hardware and open-source software. We first deploy a complete LTE network on a single laptop and an SDR hardware. Then, we use it to evaluate the reception performance of a commercial smartphone. In the end, we propose a calibration technique which allows using a smartphone as a wireless power measurement tool by reducing the root-mean-square error of the RSSI, with respect to a reference power measured with a specialized spectrum analyzer, from 6.4 dBm to 2.4 dBm