Advances in the Internet of Things depend on emerging wireless technologies that use little energy and fit in cramped quarters.
It looks as though the success of wearable technology such as smart watches and fitness bands could hinge on low-energy versions of wireless communication technology. The low-energy technology getting the most attention is Bluetooth 4.1 low energy (BLE) specification, which is being marketed as Bluetooth Smart. This is a less power-hungry version of Bluetooth and was first adopted in 2010.
One reason BLE reduces energy consumption is that it eliminates issues related to continuous battery use and constant pairing and re-pairing, which were problems in the earlier versions. Also, BLE devices use less power because they stay in idle mode except when transferring critical data. To keep down energy consumption in devices with small batteries, BLE-equipped notebooks, smartphones, tablets and other consumer electronic devices act as primary devices to send and receive data from secondary BLE devices, such as heart rate monitors, smart watches or any other wearable products.
BLE also makes possible the use of what’s called beacon technology. The industry analyst firm ABI Research says over the last twelve months, the use of iBeacons/BLE beacons really took off among retailers. The firm predicts BLE beacon shipments over the next five years could climb to a point where 60 million BLE units get sold in 2019. Another analyst firm, IHS, calls 2015 the year indoor positioning takes off. Though indoor positioning is possible with WiFi, Bluetooth beacons offer better accuracy. With Bluetooth beacons, you can navigate not just to a store, but also to an aisle or even a specific product.
Bluetooth Smart semiconductors shipped briskly in 2014. Analyst estimates put the global BLE and Smart Ready market at $5,572 million and shipments of as much as 2.7 billion units by 2020, up from just 49 million units in 2013. Expectations are for a compound annual growth rate of 9.38% between 2014 and 2020. Analysts also see BLE taking the lead in annual wireless sensor network (WSN) shipments. The analyst firm ON World projects that by 2018, IEEE 802.15.4, BLE and WiFi will make up more than 80% of the WSN unit shipments.
Hardware vendors are responding to the need for reduced power consumption with innovative ideas on several fronts. In BLE ICs, recent developments include the IS1870 and IS1871 BLE RF ICs, and the BM70 module from Microchip Technology. The power profile of these devices minimizes current consumption, and form factors are as small as 4 × 4 mm for the RF ICs and 15×12 mm for the module. The module options include RF regulatory certifications, or non-certified (unshielded/antenna-less) for smaller and more remote antenna designs that will undergo end-product emission certifications.
To handle beacon applications, the module supports stand-alone “hostless” operation—in other words, it boots from a Flash memory so there’s no need for an external host processor to download code or run a driver. Microchip’s BLE devices include an integrated, certified Bluetooth 4.2 firmware stack that facilitates communications at up to 2.5 times faster data transfer speeds and connection security, with government-grade (FIPS-based) secure connection support.
On another front, electronic components manufacturer TDK has devised a number of components with low-power IoT and BLE applications in mind. These devices include RF components and modules based on surface acoustic wave (SAW), bulk acoustic wave (BAW) and SESUB (semiconductor embedded in substrate) technology, tiny and flat multilayer inductors, a variety of advanced sensor technologies, and miniaturized ultra-flat coils for wireless charging.
Consider one particular BLE module. With its miniature footprint of just 3.5 × 3.5 mm and slim insertion height of 1.0 mm, the SESUB-PAN-D14580 is billed as the world’s smallest BLE module. It is nearly 65% smaller than modules that employ discrete components and consumes about a quarter of the power needed by classic Bluetooth devices. It works from 3-V supply voltage and consumes just 5.0 mA when transmitting, 5.4 mA when receiving and 0.8 µA in standby mode.
Based on TDK SESUB integration technology, the module incorporates a DA14580 Bluetooth 4.1 chip from Dialog Semiconductor. Its substrate layers optimally route all the I/Os to a BGA on the module’s bottom surface, to better let designers access the integrated Bluetooth IC. The module makes available all terminals of the discrete chip. The quartz oscillator, capacitors and various other peripheral components mount on the same substrate. The miniature size and low current consumption lets the Bluetooth module handle battery-powered wearable applications where small size, light weight and low power consumption are essential. Mass production started in July 2015.
It isn’t just communication chips that are getting attention. Power supply makers are designing low-power components specifically for wearable devices such as smart watches. An example is the TDK µdc-dc converters, which have a relatively small 2.9×2.3-mm footprint with an insertion height of 1 mm. The integrated power modules occupy 65% of the space taken up by conventional discrete components. They have a 92% power efficiency and under light loads, the modules go into a power-save mode using pulse frequency modulation with a typical quiescent current of 24 µA.
It also looks as though a lot of low-power communication electronics will get juice through some kind of wireless charging scheme. A complicating factor is that there is no such thing as a wireless charging standard. Several technologies are in use, including magnetic inductance, magnetic resonance, radio wave charging, microwave charging and laser beam charging.
Magnetic inductance uses an electromagnetic field to transfer power. In magnetic resonance charging, wireless energy transmission between transmitter and receiver is done through tank circuits tuned to same frequency. Radio wave charging uses radio waves to transmit power to receivers at distances ranging as far as 30 ft.
Currently, about 90% of wireless charging takes place through magnetic inductance. Two organizations are trying to develop harmonized standards for wireless charging. The Wireless Power Consortium (WPC) is involved in creating standards specifically for magnetic inductance. The other organization is a recent merger of the Power Matters Alliance (PMA) and the Alliance for Wireless Power (A4WP)—a new name for the merged organizations has yet to be determined. One goal of the hook-up is to promote interoperability among the various wireless charging schemes.
Wireless charging takes place in what can only be described as cramped quarters; in most wearables, there is little room for charging components such as inductive pick-up coils. But the level of signal strength is proportional to the number of coil turns and to the third power of loop radius. So manufacturers have developed special inductive coils optimized for both small spaces and maximizing signal levels.
For example, Tx coils from TDK handle WPC low-power (≤ 5 W) specifications that include single primary coils with magnetic alignment (specifications A1 and A9) and without magnets (specifications A10 and A11). A linear array with three coils is also available for chargers that allow free positioning with an array. All Tx coils use WPC-approved ferrite sheets. Extremely thin flexible sheets are available.
TDK Rx coils come in thicknesses from 0.50 to 1.12 mm as a way of meeting the varying requirements for wireless charging applications. All Rx coils are designed with magnetic attractor materials to support magnetic alignment. The lineup also includes Rx coils with a combined antenna for near field communications (NFC). Rx modules include an Rx coil with attractor and control unit. The modules feature a thin maximum thickness of just 1.0 mm. Three small Rx coils target wearables; their dimensions are as small as 22×12 mm and the coils are designed for a maximum output of 2 W.