ICACT20220074 Slide.17
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Thank you for your attention!
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ICACT20220074 Slide.16
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In this paper, we have proposed an ESPAR antenna based WPT system and presented the 3x3 ESPAR antenna design method and performance evaluation results that can be effectively used in the WPT system.
In detail, the design specifications of the 3x3 ESPAR antenna that can operate in the 2.45 GHz band have been presented, and through beam pattern analysis, it has been confirmed that the designed antenna can effectively support the front direction of the antenna from 60° to 90° in elevation.
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ICACT20220074 Slide.15
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These figures show example beam patterns of the 3x3 ESPAR antenna. These are captured from the top.
The left-side figure shows the beam pattern when a reactance set for direction #0 is applied to the antenna.
and the maximum beam gain is about 7.47 dBi.
The right-side figure shows the beam pattern when a reactance set for direction #5 is applied to the antenna and the maximum beam gain is about 7.5 dBi.
The beam patterns are well formed in the target direction according to the reactance set.
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ICACT20220074 Slide.14
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This table shows the reactance sets for generating the finally selected beam patterns under the condition of having a beam gain of 7 dBi.
This data can be used by the MCU to control the reactance values of the ESPAR antenna.
The MCU can use this reactance data to effectively generate a beam pattern in a targeted direction depending on the situation.
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ICACT20220074 Slide.13
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These figures shows the direction of beam patterns that have higher directivity than 7 dBi.
That is, it shows the beam direction when the antenna is viewed from the front, and [0, 0] means the front with an elevation angle of 90°.
In addition, 17 patterns selected to effectively support a wide range are shown.
The small circles are candidate beam patterns of directional 7 dBi or more, and the large red circles indicate the selected beam patterns.
By using the reactance sets corresponding to the selected 17 beam patterns, beamforming can be effectively performed for the power receivers in various locations.
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ICACT20220074 Slide.12
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This figure shows the direction and gain of beamforming according to 256 reactance combinations as vectors.
The elevation angle of the generated beam pattern can be changed from about 60° to about 90° when the bottom surface is 0° and the front direction is 90°.
That is, it can support a 60° range in the front direction.
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ICACT20220074 Slide.11
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This figure shows the S-parameter characteristics according to the reactance combination of the designed 3x3 ESPAR antenna.
The set of reactance applied to each passive element is from {-1, -1, -1, -1, -1, -1, -1, -1} to {-150, -150, -150, -150, -150, -150, -150, -150}.
Looking at the S-parameter characteristics as it changes over 256 steps when -10 dB is the standard, this antenna can support the 2.45 GHz band and operate under most conditions.
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ICACT20220074 Slide.10
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To confirm the beamforming characteristics of the designed ESPAR antenna, a simulation has been performed while changing the reactance value applied to each passive element to -1 or -150.
Since each of the eight passive elements has two reactance states, 256 simulations have been performed.
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ICACT20220074 Slide.09
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This figure shows the specification of the designed antenna.
In this paper, we design an ESPAR antenna that consists of a two-dimensional array to overcome the shortcomings of a general two-dimensional array antenna and present reactance sets that enable effective 3D beamforming.
The antenna design and simulation are performed using the CST antenna design program, and the beam pattern characteristics extracted from the CST are analyzed using the MATLAB program.
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ICACT20220074 Slide.08
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This figures show the antenna structure we designed.
An ESPAR antenna consists of an active element with one RF chain connected to the center and passive elements with variable reactance around it.
In the antenna, the beam pattern is changed according to the reactance value of each passive element.
In order to perform beamforming in a desired direction, after designing an antenna, it is necessary to identify a beam pattern generated by applying each reactance set.
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ICACT20220074 Slide.07
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To solve this problem of the phase array type antenna structure, this paper presents a method to apply an ESPAR antenna capable of beamforming using a single RF chain to an MPT system.
In this paper, we also design an ESPAR antenna using microstrip patch elements that can be used on the power transmitter side for effective MPT system design and evaluate how wide a designed antenna can support.
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ICACT20220074 Slide.06
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In general, to use beamforming technology, an antenna composed of multiple elements is required. In addition, an RF chain composed of active elements consuming power is connected to each element.
That is, when the number of antennas of the array antenna increases, the number of RF chains also increases, which may cause problems such as interference between circuits, heat generation, increase in form factor size, and increase in power consumption.
When a conventional array antenna is used in an MPT system, the power transmission efficiency of the overall system may decrease due to an increase in power consumption caused by multiple RF chains.
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ICACT20220074 Slide.05
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This figure shows the block diagram of the MPT system. The MPT system consists of a wireless power transmitter and a wireless power receiver.
In the MPT system, the overall power transmission efficiency is greatly affected by the distance-dependent attenuation, impedance matching, and RF-DC conversion efficiency.
Therefore, an effective impedance matching circuit configuration and a high-efficiency RF-DC rectifier should be used in the power receiver.
In addition, in the power transceiver, it is necessary to overcome the decrease in power transmission efficiency due to path loss by increasing the antenna gain of the transmitter and the receiver by using a plurality of antennas.
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ICACT20220074 Slide.04
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However, there is a disadvantage in that the network configuration for beamforming is complicated.
The ESPAR antenna has the advantage of being able to perform beamforming without such a complicated circuit configuration.
When the ESPAR antenna is applied to an WPT system, a low-complexity and high-efficient WPT system can be designed.
Through the simulations, it is confirmed that the ESPAR antenna can support a wide range forward through 3D beamforming.
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ICACT20220074 Slide.03
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Recently, wireless power transfer (WPT) to the IoT sensors wirelessly over the far distance has been attracted too much and this WPT system is based on the radio frequency (RF) antenna technology.
In this paper, we propose an WPT system to multiple IoT sensor system using an electronically steerable parasitic array radiator (ESPAR) antenna based on microstrip patches.
An ESPAR antenna design method and evaluation results for the WPT system are also presented. The WPT system is characterized by very low power transmission efficiency due to path loss of the RF signal.
Therefore, the WPT system mainly utilizes a beamforming technique using multiple antennas to improve this characteristic. A phased array antenna is generally used for beamforming.
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ICACT20220074 Slide.02
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This is an outline of my presentation.
Firstly, I will introduce some background about WPT system and Beamforming.
Next, I will show the antenna structure for 3D beamforming.
Finally, I will conclude.
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ICACT20220074 Slide.01
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Hello. I am Changyoung An and working at Chungbuk National University, South Korea. The title of our paper is “Beamforming Design of the Wireless Power Transfer System into Multiple IoT Sensors”.
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