As we all know, traditional radar technology is widely applied in various fields, such as airborne, shipborne, and ground-based radar for target detection and imaging. In daily life, we can utilize radar sensors for applications like car reversing/driving assistance, weather forecasting, traffic management, resource exploration, and many more.
With the expanding range of Internet of Things (IoT) applications, many IoT applications rely on embedded sensors to perform critical measurement tasks or serve as essential components of control circuits. The development of new sensors can enable new applications, and radar sensors have become a vital design unit in IoT and embedded design.
Radar sensing technology has become one of the latest “cross” sensor technologies.
In recent years, rapid advancements in semiconductor technology have significantly reduced the size and power consumption of many radar systems. The use of millimeter wave, ultra-wideband technology, and multiple input multiple output (MIMO), combined with innovative signal processing techniques and increasingly powerful chips, has enhanced radar’s sensing capabilities.Radar sensing is a wireless sensing technology that analyzes received target echo characteristics to extract and discover the target’s location, shape, motion characteristics, and trajectory, and can further infer the characteristics of the target and the environment.Its function is similar to that of human eyes and ears. Compared to other sensors, radar sensing has many unique advantages. For example, unlike visual sensors, radar is not affected by light conditions and can penetrate obstacles, better protecting personal privacy. Compared to ultrasonic technology, radar sensing can detect objects at greater distances and does not harm people or animals.
Of course, the working principle of radar is not new. The roots of radar (Radio Direction And Ranging) can be traced back to experiments conducted by Heinrich Hertz in the 1880s using radio waves. Before World War II, it was developed into a practical air defense tool by Sir Robert Watson-Watt and others. All radar systems are based on the principle of reflecting radio waves away from the target. However, in practice, various implementation schemes can affect cost, complexity, and performance. Most IoT, automotive, and embedded applications typically use “short-range” radar architectures. Unlike traditional high-power radar systems used for navigation and military/defense, short-range radar systems operate at relatively short distances from their targets (i.e., 100 meters compared to 100 kilometers).
Additionally, there are several types of short-range radar, including continuous wave (CW) Doppler, frequency-modulated continuous wave (FMCW), pulse Doppler, and ultra-wideband (UWB). Both CW Doppler and FMCW can be widely used as RF chipsets and operate at low power levels, which is often crucial in IoT and embedded design.
Embedded short-range radar has become one of the latest “cross” sensor technologies used in IoT and smart lighting, playing an increasingly important role in IoT applications.When applications benefit from measuring or detecting the presence, speed, direction, and distance of distant objects, short-range radar may be a seriously considered candidate technology.
From smart streetlights to motion detection, from blood pressure monitoring to heart rate monitoring.
Currently, some applications have exceeded the general public’s imagination of radar technology, such as space occupancy detection for buildings and smart homes (IoT), surrounding and area security, lighting and HVAC control, automatic doors and gate control, robotics, smart streetlights (increasing brightness along the path of approaching vehicles), drones and drone altimeters, industrial fluid/solid level sensing, and speed measurement.
The application of radar sensing technology allows smart streetlights to respond differently based on the different states of targets.When no target is present, the streetlight can turn completely off. When a target appears, it can intelligently control whether nearby streetlights should turn on or the degree of brightness based on the distance and speed of the target, thus reducing energy consumption and minimizing wear on the streetlights, extending their lifespan.
Using radar sensors to explore advanced parking vehicle detection methods effectively and conveniently solves various types of parking vehicle detection issues.A 24GHz radar sensor network can effectively collect urban parking space information, and the data is transmitted to the parking management control center, making the allocation of parking spaces more intelligent. Radar sensors, as newly added devices, are installed facing downward on streetlights and building walls. The information obtained from these positions can accurately infer which areas still have available parking spaces. If the radar sensors are installed at higher positions, they can scan wider areas, making it easier to detect parked vehicles in a row. The matchbox-sized sensors emit microwave pulses, which reflect off the street and vehicles, obtaining corresponding location information.
Radar-based motion recognition technology can be applied in various scenarios.For instance, in sports, this technology can detect the motion status and trajectory of people and balls. In home environments, it can also be used for fall detection to prevent elderly falls. Currently, our technology can interpret human motion status and trajectories by processing radar data.
As people’s living standards continue to improve, their attention to health is also increasing. Real-time, fast, and convenient detection of heart rate and respiratory frequency has become an inevitable trend. Traditional detection devices are not easy to carry and have poor real-time operability.Radar waves are electromagnetic waves that do not change with environmental factors such as temperature and light, greatly enhancing the product’s anti-interference capability and stability. By using radar wave RF transceiver modules to detect heart rate and respiratory signals, non-contact detection can be achieved, making it convenient and reliable. Radar waves can easily penetrate clothing and skin to complete heart rate and respiratory frequency detection. Although the amplitude of heart rate and respiratory signals is small, the radar RF transceiver module has adjustable sensitivity, enabling effective detection of heart rate and respiratory signals.
Earlier this year, media reported a foreign company named Blumio that uses radar technology for innovative blood pressure monitoring. The company’s product integrates radar technology into an arm ring worn on the upper arm (the typical location for measuring blood pressure, as it is at the same height as the heart). The product utilizes two radar antennas to detect the pulse pressure wave between heartbeats, and then calculates the speed between the two antennas to deduce the monitored individual’s blood pressure. Unlike traditional blood pressure monitors, it does not need to be connected to bulky machines and can measure continuously.
In the field of radar blood pressure and heart rate measurement, domestic startup companies are also keeping pace. The core team members from Qualcomm, Broadcom, Spreadtrum, and others are researching a non-contact arterial radar BioRF technology at Yuexiang Trend Technology (LOHAS TECH). This technology captures superficial arterial signals through radar, avoiding errors caused by measuring capillaries with optical sensors, achieving accurate measurements.
BioRF radar heart rate measurement—arterial blood vessels
BioRF uses near-field sensing technology to detect pulse wave signals from superficial arteries throughout the body, supporting the development of more imaginative medical-grade products and algorithms through system design. BioRF arterial radar features non-compression and high sensitivity in continuous smart blood pressure monitoring, capable of accurately sensing superficial arterial pulses, detecting both proximal and distal arteries. It locks onto pulse signals in three seconds and completes a measurement in ten seconds without the need for cuff pressure.
Interestingly, a product introduced by an application engineer from ADI at the recent IMS2018 International Microwave Technology Exhibition also achieves similar body signal monitoring functions. ADI is developing a solution to monitor human heart rate and respiratory rate.
ADI product application engineer demonstrating radar heart rate monitoring solution at IMS2018
Demonstration materials show that this complete system solution includes an antenna, a 24GHz radar, a low-speed ADC, and a fixed-point DSP all integrated onto a single circuit board, which can be directly used as a vital signs monitoring system. When a person sits in front of this product, it sends extremely low-power radar signals to their body, and by reading the signals, it can obtain the person’s heart rate and respiratory rate information.
The on-site engineer directed the circuit board transmitting extremely low radar power at the demonstration model’s chest. On the demonstration platform’s system computer interface, the radar RF chip collects wireless signals, converts them to intermediate frequency signals, and a low-speed ADC digitizes the data. The DSP sensor and algorithm can read respiratory rate and heart rate data, which is transmitted to the computer via USB for real-time heart rate reading.According to ADI’s application suggestions, such systems can be used for monitoring driver health to track driver heart rate information and analyze driver status, and can also be placed in child seats or strollers to monitor infants’ health. This device can also be used in a room to measure the heart rates of people inside, among other innovative applications.
Conclusion
Currently, low-cost radar sensing technology and available design tools are abundant. These radar sensors can provide real-time information about the presence, motion, angular position, speed, and distance from the sensor ranging from a few centimeters to hundreds of meters, meeting the performance and functionality requirements in IoT, embedded, and smart lighting applications.Similar to the past low-cost MEMS accelerometers, this may also promote the development of entirely new, unexpected categories of IoT products.The innovative applications mentioned in this article are just the tip of the iceberg of radar applications.
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