“The short-range radio frequency (RF) circuits deployed for sensing in these Wi-Fi networks are built around radar technology. Unlike traditional hardware sensors, RF sensing is less expensive and unobtrusive. Due to the broadcast nature of RF signals, RF sensing can be used to monitor multiple objects and capture changes in the environment over large areas.
This article was compiled from Planet Analog by Masakazu Urade, Connectivity Solutions Manager, Socionext
In 2024, the IEEE will introduce a new Wi-Fi standard — 802.11bf — that turns wireless devices into sensors capable of collecting data about people and objects by calculating interference and bounces of signals in their physical space. Established Wi-Fi devices will be part of the network interactions used to determine the location of people and objects in a specific area.
The new standard will mark a major shift in data transmission, as sensors play an integral role in how information is captured, transmitted and utilized. It will also make Wi-Fi sensing ubiquitous and accelerate innovation in WiFi sensing technology.
Bottom CMOS RF Technology
The short-range radio frequency (RF) circuits deployed for sensing in these Wi-Fi networks are built around radar technology. Unlike traditional hardware sensors, RF sensing is less expensive and unobtrusive. Due to the broadcast nature of RF signals, RF sensing can be used to monitor multiple objects and capture changes in the environment over large areas.
RF or radar sensors use a waveform modulation scheme called frequency modulated continuous wave (FMCW). The waveform is optimized to detect objects in space and determine their velocity. This is also how smart devices can detect breathing patterns at close range.
Using multiple antennas can generate more detailed close-up images. This is because each antenna essentially “takes” a picture and uses that data to process motion information. A higher number of antennas enables finer angular resolution. 3D position and multi-object detection are a good example.
Take a smart home radar sensor, for example, which can monitor a person’s vital signs and track his or her breathing rate to understand how well they sleep. The device also uses radar for close-range gesture-based interactions.
Figure 1 New Wi-Fi sensor networks based on the 802.11bf standard require a single-chip solution based on RF CMOS. Source: Socionext
Notably, advanced CMOS integrated radars offer ultra-low power consumption while enabling smaller size – including mmWave RF circuits as well as A/D converters, filters, built-in dedicated engines for digital signal processing and standard SPI serial input/output, and a small Antenna-in-Package (AiP) housing.
Wi-Fi sense use cases
Internet of Things (IoT) devices rely on wireless communications using radio frequencies, such as Bluetooth Low Energy (BLE) and Low Power Wide Area (LPWAN). As the demand and usage of connected devices increases, developers seek sensors optimized for energy efficiency with new capabilities and longer battery life. Low-power CMOS digital and RF technologies provide this advantage. Additionally, as products become more compact, a system-on-chip (SoC) that integrates the entire system (CPU, RF, and other components) becomes more practical.
Originally developed for home appliances, low-power RF CMOS technology is now widely used in consumer and automotive applications. Radio waves are used in television broadcasting, data communications, and sensors for object detection. In order to accelerate the development of these products, SoC devices allow optimization adjustments to meet the different specifications of customers. Its low power consumption also makes it a very suitable design choice.
Figure 2 A wide range of applications will benefit from this Wi-Fi sensor. Source: Socionext
Here are some use cases that can benefit from RF CMOS-based SoCs:
Broadcast: Stream video directly on TVs, mobile devices and in-vehicle infotainment systems.
LPWA network: Use wireless communication to transmit various sensory data from IoT devices.
Ka-band satellite communications: Connect anytime, anywhere.
Vehicle-to-vehicle (V2X): for vehicle-to-vehicle and vehicle-to-infrastructure communications to support autonomous driving.
79 GHz RF Radar: Supports advanced driver assistance system (ADAS) applications.
24 GHz RF Radar: Capable of detecting suspicious persons and approaching objects and automatically triggering alarms and video recording before an event occurs.
60 GHz RF Radar: Multi-antenna and wide-bandwidth FMCW chips such as 2TX and 4RX MIMO can perform various sensing functions, such as detecting the location of multiple people in a vehicle. It can also detect vital signs, which helps prevent drivers from accidentally leaving babies, children or pets alone in the vehicle.
In July 2021, the US Federal Communications Commission (FCC) issued a press release stating that the US government recognizes the increasing utility of mobile radar equipment using the 60 GHz band to perform innovative and life-saving functions. Advanced radar technology can also be used for anti-theft and enable a range of smart in-vehicle features including seat occupancy monitoring, infant/pet detection and death prevention, driver status monitoring and contactless precision operation.
Wi-Fi Sensor SoC
Socionext has developed an RF-CMOS single-chip solution that includes an RF core, analog-to-digital integration and a small package design. It integrates a compact low-power RF CMOS circuit and a high-precision RF sensor antenna.
Below is an example of an RF CMOS SoC that highlights the integration details of various technologies.
Figure 3 RF sensing applications require highly integrated SoC designs. Source: Socionext
Over the years, Socionext has developed analog IP to meet the low power and small size requirements of various applications. This enables companies to integrate multiple analog and digital building blocks into a single chip while optimizing mobile designs for low noise.