IoT is one of the popular topics for the past few years. The study achieves the data in the internet collecting and sharing by data transmission wired or wireless from information carriers. In most of IoT application, the main information devices are embedded systems and micro sensors. Due to the hardware limitations, most of information devices use the wireless transmission to do the data exchange like Wi-Fi, NFC, and Bluetooth. However, most of these devices are powered by batteries. In the other words, there are some problems that the user has to face: time limit, hard to replace batteries, and different specifications. In order to solve these problems, a dynamic antenna-based wireless power charger based on electromagnetic coupling of coil is proposed to replace traditional batteries in this chapter. Flexible printed circuit can allow the user changes in the circuit into a suitable shape by cutting, reversing, and coiling. In this way, the user can improve the electricity supply effect by adjusting the power of wireless transmission.
TopIntroduction
Currently, the Internet Of Things (IOT) is the popular implementation and research topic. Most IOT devices are integrated with sensor components, network component, and power component. Each IOT device obtains the information of environment by the sensors. However, these sensors need the power. Considering the physical implementation, connecting with the wire power line for all IOT devices is impossible. To exchange the battery which as the power source of the IOT device increases the cost of time and human resource. Therefore, to transmit the power wirelessly is the possible solution for the IOT devices.
Originally, most sensors are powered by wire line connection. These sensors can work with stable power. Considering the real implementation and environment, most sensors are movable or not located at only one location. Therefore, how to provide the power for the sensors or embedded systems becomes the research topic.
Today, most movable sensors or embedded systems use the battery as the power supply. In other words, using the battery as the power should reserve the space for the battery. Hence, the size of sensor or embedded system will be bigger for adopting the battery as the power provider. However, the battery should be exchanged to keep the stable power supply. In other words, the system users have to exchange the battery frequently. It will cost time and money.
Based on the concept: electromagnetic coupling of coil, many application were proposed. Most popular application is radio frequency identification (RFID) system. Radio Frequency Identification (RFID) is the popular wireless induction system used in IOT, personal payment, or customized individual services (Jian, 2009a, 2009b; Wu et al., 2011; Jian, 2012). When an independent RFID tag approaches the RFID antenna, the induction between RFID tag and antenna happens. At the same time, due to the electromagnetic coupling of coil, the RFID tag can receive the power from the antenna of RFID reader and active the chip embedded on RFID tag. Finally, the signal of data and be replied to RFID reader via wireless electromagnetic wave. Hence, the wireless services between the RFID tag user and the RFID reader (which includes the services) can be provided. In other words, the power can be provided to the RFID tag wirelessly. For example, the Taiwan Far Eastern Electronic Toll Collection Co., Ltd used the RFID based Electronic Toll Collection for the nationwide freeways (FETC, 2012).
Since the power can be transmitted from one device to another via wireless electromagnetic wave, no wire connection will be needed. It also means that the device can be powered based on electromagnetic wave without the battery (Ostaffe, 2015; Wu et al., 2015). Generally used wireless power transmission is implemented based on the single on demand designed coil or antenna. Some power transmission transmitters use the antenna (coil) arrays which are consisted of multiple small antenna or coil. However, due to the oscillator circuit designing of the transmitter, most of the single or arrays of the antenna (or coil) are designed with fixed size (area), fixed shape, or fixed turns of the coil. The antenna or coil is not extendable or dynamically changeable.
Unfortunately, the performance of induction between RFID tag and antenna depends on 1. the induction direction (angle) of the coil and electromagnetic field, 2. the total amount of coil, and 3. the area of the coil. If the power is not strong enough, the induction cannot be happened. Or, the chip embedded in the tag will not be acted. In addition, if the total amount of coil or the area of the coil is too small, the inducted electromagnetic field will not be enough. In addition, the induction range or distance will also affect the performance of the power transmission.