Even such a wireless standard uses subgiga

Some wireless standards use subgiga instead of 2.4GHz because subgiga has advantages over 2.4GHz.

These wireless standards are not often called sub-giga but are called by their respective designations (Wi-Sun for Wi-Sun).
Therefore, the term "sub-giga" is often used only for communications using proprietary protocols.

[Application 1] Factory sensor network

IoT and smart factories are progressing, but wireless is used for monitoring and remote control of facilities and equipment using sensors.

There are many obstacles in the factory, and it is an application that can take advantage of the features of Sub-Giga, which is strong against going around.
Conventionally, sub-giga (426 MHz band) was used, but the use of 920 MHz band, which has more channels and a better radio wave environment, is progressing.

[Application 2] Preventive maintenance of bridges, tunnels, etc.

Transportation infrastructure such as bridges and tunnels is regularly inspected to ensure safety. However, the inspection frequency is not so high.

By placing sensor nodes to detect anomalies at various locations in bridges and tunnels, and using Subgiga to collect and analyze the acquired information, constant monitoring becomes possible.
As a result, safety can be further enhanced, and it is useful for planning efficient inspection plans.

It is also expected to be used for monitoring landslides in mountains.

In such applications, it is often the case that a power supply cannot be secured, so it is necessary to operate with cells/batteries. In addition, it is assumed that sensor nodes will be installed in places where installation or replacement is not easy. (On/under bridges, in tunnels, in mountains, etc.)
Therefore, low power consumption design of the sensor node is required, and sub-giga is the most suitable for low power design compared to 2.4 GHz.

Also, even in environments with obstacles such as trees, it is easier to obtain a communication distance with sub-giga than 2.4GHz, which is one of the reasons why sub-giga is preferred.

[App ③] Drone

Drones are gradually becoming popular for hobbies and aerial photography, but in the future it is expected to expand to commercial applications such as logistics, agriculture, forestry and fisheries, surveying, and infrastructure management.

Drones are expected to use multiple frequencies, such as sub-giga, which is good at long-distance communication, for operation, and 2.4 GHz, which is good at high-speed data communication, for image transfer.

As sub-giga, in addition to 920MHz, which does not require a radio station license, 169MHz, which requires a license, is expected to be used. 169MHz is a newly opened frequency band, and it has the property that it is easier to obtain communication distance than 920MHz.

Si4x6x family (radio chips)

Si4x6x is the second generation product of the "EZRadioPRO" family, which is a high-performance, high-performance radio chip, and has greatly improved functions and performance from the first-generation Si4x3x family (mentioned above).
There are three product types: transceivers (transmit and receive), transmitters (transmit only), and receivers (receive only), and variations in transmit power are also available.

Since the wireless chip does not operate by itself, it becomes possible to operate by preparing an external controller (such as a microcomputer) and controlling it via a serial interface.
The control of Si4x6x adopts command-based control method instead of register-based. This has the advantage of reducing the design burden of the control software and increasing the reusability of the software.

In terms of function and performance,

• The same chip can support a wide range of frequencies from 119 to 1050MHz
• High output is possible without using an external PA (amplifier)
• high reception sensitivity
• Low power consumption

and many other features.
It is a product that combines the characteristics of experts, such as the beauty of the spectrum at the time of output and the high anti-interference performance (blocking).

Of course, I think that the large number of adoption results in Japan will be a reliable factor for recruitment.

The figure below is a typical circuit of Si446x (transceiver). As with the EFR32FG introduced next, it is necessary to optimize the component constants of the matching circuit according to the frequency you want to use.

EFR32FG Family (SoC)

The EFR32FG (Flex Gecko) family is a wireless microcontroller with an Arm® Cortex®-M4F core. FG1, FG12, FG13, FG14 and 4 families have been commercialized as of September 2018.

The basic structure is the same as the EFR32MG (Mighty Gecko) family introduced in the Zigbee edition, but the wireless protocols that can be installed are different. (Zigbee and Bluetooth cannot be implemented in EFR32FG)

The peripherals of the microcomputer part are also very rich, including serial interfaces such as SPI, I2C, and UART, analog peripherals such as ADC, DAC, and comparators, and hardware accelerators for encryption/decryption.

There are various variations of this EFR32FG, including those that support only sub-giga, those that support only 2.4GHz, and those that support both sub-giga and 2.4GHz.

The transmission output is basically +20dBm (+16.5dBm for FG1 only), but the output can be lowered by setting to comply with the radio laws of each country. Also, the product type is only a transceiver.

Compared to the 2-chip configuration of a wireless chip (Si4x6x) + control microcomputer, the EFR32FG is a single chip, enabling space-saving design.
Also, with two chips, it's a lot of work to check the operation first, but with one chip, it's a big advantage that the sample code that has been confirmed to work is provided.

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