The ROHM Group owns various wireless communication technologies, including Bluetooth and ZigBee LED by wireless LAN, as well as specific low-power wireless technologies for the 920MHz frequency band opened in Japan in July 2012.
Through the technology integration with LAPIS semiconductor, a group company, ROHM has product advantages ranging from wireless communication ICs to modules, and provides communication ICs and modules that fully utilize the radio characteristics of various communication standards in accordance with customer needs. Especially for wireless communication ICs, LAPIS Semiconductor is proud of its low-power RF-CMOSNote1Technology and high performance MODEMNote2technology to achieve the industry’s highest level of low power consumption and wireless performance, which is also a major feature of this type of product.
The “High Frequency components and Module Technology Series” is divided into two phases. This issue is the first issue, and will introduce the “920MHz frequency band specific low-power wireless communication module” from the many wireless communication ICs and module products owned by ROHM. The second phase will also be launched in the near future, introducing “wireless LAN module technology”, so stay tuned!
Background introduction
In recent years, awareness of energy conservation has been rising in various fields, and countries are expanding their investment in the efficient use of energy. Among them, in the residential area, the attention of HEMS (Home Energy Management System), which monitors the power supply and demand between devices through network connection, and then effectively controls the devices, has been increasing. In order to “visualize” the power required for energy management, more advanced energy management and control systems that often use smart touch and the like are expected.
Against this background, Japan opened the 920 MHz band in July 2012, which is a radio frequency band that does not easily interfere with existing radio waves, has low power consumption, and enables long-distance data communication. Table 1 below summarizes the characteristics of ZigBee and wireless LAN in the 2.4GHz frequency band, as well as the 400MHz and 920MHz frequency bands for specific low-power wireless. 920MHz has excellent radio wave coupling properties compared to 2.4GHz using ZigBee and wireless LAN, so stable communication can be ensured even in places with walls and obstacles. When used at home, wireless devices such as microwave ovens and wireless mice use 2.4GHz, and the radio waves are very mixed. In Contrast, the 920MHz band is less prone to radio interference. In addition, the occupied frequency range of the 400MHz frequency band, which is also a specific low-power wireless radio, is narrow, so the communication speed is slow. To sum up, it can be said that the 920MHz frequency band is the most suitable frequency band for HEMS (Figure 1).
In addition, the 900MHz frequency band has been used in the United States, China, South Korea, and Australia, and Europe is also studying the opening up.
[表1] Wireless performance comparison
[图1] Comparison of Wireless Methods for HEMS
Roma920MHzFrequency band specific low power wireless module technology
＜Low power consumption＞
ROHM developed the 920MHz band specific low-power wireless module “BP3596” for HEMS (Figure 2). The biggest feature of this product is the industry’s top low power consumption, which is achieved by the “ML7396B” wireless communication IC “ML7396B”, which is known for its low power consumption by LAPIS Semiconductor, a subsidiary of the ROHM Group. It can be built into various devices such as smart touch products and home appliances, and can build a low-power wireless network. “Low power consumption” is very important for devices such as sensor devices, where it is difficult to supply AC power. The cost of battery replacement for battery-powered devices is too high, so there is an urgent need for no battery replacement for about 10 years. Although battery capacities vary, ROHM’s 920MHz band-specific low-power wireless modules have excellent low-power consumption performance, so even battery-operated devices can be used for 10 years without battery replacement.
＜Built-in Antenna＞
Built-in chip antenna, can be used without high frequency design. When installed in a device with a metal casing, the metal casing acts as a shield against radio waves, resulting in no communication. The product has a built-in antenna connector, and communication can be ensured by simply connecting an external antenna to the antenna connector.
＜Acquired radio law certification＞
It has been certified by Japan’s domestic radio law, so it can be used as a wireless device immediately after being installed in the whole machine without the need for a wireless communication test. Customers who do not have high-frequency circuit design capabilities and wireless characteristic measurement devices can also use it easily.
The 16-bit serial number used in the network is marked on the label. A QR code is also printed on the label, and the QR code contains the serial number information. When assembled into the machine, read the QR code output label to easily mark the serial number on the housing.
The EEPROM is built into the module, and not only the serial number but also the adjustment value of the output power is written. Therefore, it can be used without complicated adjustment of the wireless device.
[图2] BP3596 Dimensions
＜Easy connection of hardware＞
When the microcontroller for RF control is connected to the RFIC, the SPI (5pin) and EEPROM pass through the I2C(2pin), GPIO connection. The wiring diagram with the microcontroller for RF control is shown in Figure 3. It can be seen that it can be easily connected with a small number of wires.
[图3] Microcontroller Wiring Diagram for RF Control
＜Supported radio frequency band of each country＞
The 900MHz frequency band is expected to become a frequency band that can be used by all countries in the world. The United States, China, South Korea, and Australia have adopted the 900MHz frequency band as a sub-GHz frequency band that does not require application, and international cooperation in frequency allocation has made progress. ROHM’s BP3596 can respond to the radio frequency band of each country by adjusting the module (the radio wave specification of each country is negotiated separately).
BP3596how to use
BP3596 is a module covering to the physical layer. Therefore, when using it, the client needs to prepare a higher-level protocol than the MAC layer. An example of the protocol stack configuration when used in home appliances is shown in Figure 4.
The structure of the protocol stack that satisfies ECHONET Lite is shown in Figure 4, which is connected to the whole machine through BP3596 and the microcontroller board. As long as such a protocol stack is provided, the change of the main body on the host side can be minimized, so that a specific low-power wireless radio in the 920MHz band can be installed. Of course, it can also be directly stored in the HOST form.
[图4] Protocol stack configuration example
A schematic diagram used in an actual house is shown in Figure 5. This product can realize the great role of HEMS, namely “visualization” and “effective control” of power supply and demand. Each terminal in the home is installed with a specific low-power wireless module in the 920MHz frequency band, and networking is realized through a specific low-power wireless.It integrates the power supply and demand information of each device into the home gatewayNote3(Home Gate Way), the monitor screen displays the supply and demand situation, realizes the “visualization” of power, and comprehensively manages the equipment through the home gateway to effectively control the equipment.
Not only that, but the power status can be checked via the network from the home gateway via the wireless LAN.
[图5] Example of HEMS configuration
from now on
ROHM is advancing the development of specific low-power wireless modules with built-in wireless LAN and API interchangeable protocol stacks, taking advantage of the technology accumulation of wireless LAN modules (BP3591, etc.) that have already been mass-produced (Figure 6). Customers who have done wireless LAN development in the past can use this resource to greatly speed up development.
[图6] Conceptual Outlook for a Specific Low-Power Wireless Module with Built-in Protocol Stack
(In the upcoming “Series II”, we will focus on the wireless LAN module (BP3591/BP3580, etc.) technology in the picture, so stay tuned.)
In the future, ROHM will continue to provide customers with easier-to-use modules. By combining ROHM’s sensors with specific low-power wireless modules in the 920MHz frequency band, we will develop a product that not only saves energy, but also provides a more convenient, more comfortable, more secure, and safer life. products and make more contributions to mankind.
<Terminology>
Note 1: CMOS
CMOS (Complementary Metal Oxide Semiconductor), complementary metal oxide semiconductor, a voltage-controlled amplifier device, is the basic unit of CMOS digital integrated circuits.
Note 2: MODEM
The English name of the modem. A general term for a modulator and a demodulator combined.
Note 3: Home Gateway
A home gateway is a device that connects multiple computers to the Internet using a single Internet connection. Clients rely on the home gateway to provide Internet access.
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