Low-Profile ESPAR Antenna for RSS-Based DoA Estimation in IoT Applications

Abstract

In this paper, we have introduced a low-profile electronically steerable parasitic array radiator (ESPAR) antenna that can successfully be used to estimate the direction-of-arrival (DoA) of incoming signals in wireless sensor network (WSN) applications, in which the height of the complete antenna has to be low. The proposed antenna is over three times lower than high-profile ESPAR antenna designs currently available in the literature for the DoA estimation; it can provide eight unique main beam directions and relies on simplified beam steering, which makes it applicable to simple and inexpensive WSN nodes. Measurements using our fabricated ESPAR antenna prototype indicate that relying solely on the received signal strength values recorded at the antenna output port, it is possible to achieve accurate DoA estimation results with error levels similar to those available for high-profile ESPAR antennas relying on the similar energy-efficient simplified beam steering concept and having 12 unique main beam directions. As a consequence, the overall time required for the DoA estimation using the proposed antenna can be reduced by 33%. INDEX TERMS Switched-beam antenna, electronically steerable parasitic array radiator (ESPAR) antenna, direction-of-arrival (DoA), received signal strength (RSS), Internet of Things (IoT), smart city.

Miniaturization of ESPAR Antenna Using Low-Cost 3D Printing Process

“…Recently, ESPAR antennas have successfully been adopted to energy-efficient wireless sensor network (WSN) nodes operating in the 2.4 GHz industrial, scientific and medical (ISM) frequency band by connecting passive monopoles' ends to single-pole, double-throw (SPDT) switches [3], [4]. SPDT switches are used for shorting some of the monopoles to the ground, while leaving the rest of them open.…”

RSS-Based DoA Estimation Using ESPAR Antenna for V2X Applications in 802.11p Frequency Band

“…Electronically steerable parasitic array radiator (ESPAR) antenna [1]- [4] is a simple yet powerful concept that enables beam steering capabilities in wireless sensor network (WSN) nodes that rely on inexpensive radio transceivers and energyefficient microcontrollers. Such antennas have a single radiating element in the middle, which is connected to a radio frequency (RF) transceiver output, and a number of passive (also referred to as parasitic) elements that surround it being placed on a circumference with equal distances among them.…”

“…Among various ESPAR antenna concepts already available in the literature for the 2.4 GHz frequency band, the design using single-pole, double-throw (SPDT) switches, that enable connecting passive elements' ends to the ground or leaving them open and can be controlled from digital input output (DIO) ports, seems to be particularly interesting [3], [4]. Using such simplified and energy-efficient beam steering concept, one can control the main beam from a simple and inexpensive microcontroller connected to the SPDT switches and provide direction-of-arrival (DoA) estimation capability with single degree accuracy to a WSN node [5], which can be used to increase the connectivity of the whole network [6], [7].…”

“…Using such simplified and energy-efficient beam steering concept, one can control the main beam from a simple and inexpensive microcontroller connected to the SPDT switches and provide direction-of-arrival (DoA) estimation capability with single degree accuracy to a WSN node [5], which can be used to increase the connectivity of the whole network [6], [7]. It has been shown that relying solely on received signal strength (RSS) values recorded at ESPAR antenna output one can estimate DoA of unknown signals impinging the antenna with 2° precision, being the maximum estimation error, for signal-to-noise ratio (SNR) equal to 20 dB [4], [5].…”

A Measurement-Division Model for TDOA-Based Source Bearing Estimation With Unknown Propagation Speed

“…Recently the source bearing estimation problem has been of considerable interest, particularly in Internet of Things and gunshot localization [1]. The source signal enables a point positioning if it is a spherical wave; however, it is only applicable to estimating the source direction if it is a plane wave from a far-field source [2].…”