Millimeter-Wave Basics

What is millimeter-wave detection?

Millimeter-wave detection is a radar technology used for detecting objects and providing information about their distance, speed, and angle. This non-contact sensing technology operates within a frequency spectrum range of 24GHz to 300GHz. Due to its use of short wavelengths, it can offer sub-millimetre level ranging accuracy. Additionally, this technology can penetrate non-metallic materials such as plastic, wall panels, and clothing, and is unaffected by environmental conditions such as rain, fog, dust, and snow.

What are the measurement range and accuracy of millimeter waves

ICLEGEND MICRO millimetre-wave sensors can detect human presence in real-time within the required range of the scene and accurately identify movement for monitoring purposes, thereby enabling the control of smart devices to start and stop. In scene applications, the sensing distance of millimeter-wave radar is related to the "detection target," "detection environment," hardware configuration, and antenna design, and needs to be tested and evaluated according to the specific product application scenario.

What are the differences between millimeter-wave sensors and common general sensors

Millimeter-wave sensors apply to various radar application scenarios. Millimetre-wave sensors have lower transmission power and better sensing performance than radar using 5.8G/2.4G/sub-1G/sub-10G electromagnetic wave types. Unlike common sensing technologies such as infrared, ultrasonic, laser, and cameras, millimeter-wave sensors have different requirements for detection environments. In principle, complementary applications can be achieved using various sensors, allowing sensing needs to be maximally met.

What are the differences between the 24GHz and 77GHz frequencies in millimeter waves

The 24GHz frequency band is an ISM band (unlicensed and open for use) and has been used in radar applications for a longer time, making the commercial technology relatively more mature. The 77GHz frequency band offers advantages in bandwidth and antenna miniaturization. Despite its higher development difficulty and production costs, it has gradually begun to be used in automotive radar in recent years. Consequently, these frequencies are suitable for different applications. The 24GHz band is mostly used in industrial applications, while the 77GHz band is more commonly used in automotive applications.

Are the application fields of millimeter-wave and TOF sensors the same

TOF (Time-of-Flight) optical sensors are more commonly used with camera-based image recognition to assist with autofocus. Environmental conditions significantly affect TOF products; for example, their sensing capability drops considerably in rain or fog. Mature TOF products on the market generally have an effective detection range of 10 meters. In contrast, millimeter-wave sensors can be used in all-weather and all-time environments. High-performance millimetre-wave sensors have a longitudinal detection range of over 200 meters, making them suitable for broader applications.

Are millimeter-wave sensor sensitivities affected by weather conditions (such as rain and fog)

Millimetre-wave sensors emit electromagnetic signals that do not rely on the medium of the detected object for propagation. Due to their inherent wavelength characteristics, they possess excellent penetration properties (with higher energy than centimetre waves) and diffraction properties (with longer wavelengths than light waves). They are not sensitive to obstructions from non-metallic materials. Experiments have shown that millimetre waves can effectively penetrate materials such as gypsum board, glass, plastic, and dry-walled surfaces, and are not affected by rain, fog, dust, and other environmental conditions.

Application Performance and Relevance

Is common road traffic speed measurement done using millimeter-wave speed measurement

Common traffic regulation speed measurement methods currently in use include ground-installed inductive loops, ultrasonic speed measurement, infrared speed measurement, laser speed measurement, millimetre-wave radar, and video speed measurement. The commonly used "surveillance cameras" for road regulation typically use millimeter-wave radar in conjunction with high-speed cameras to capture images.

What is the speed measurement principle of millimeter-wave sensors

Millimeter-wave radar speed measurement is based on the Doppler principle. When the emitted electromagnetic wave encounters a target with relative motion, the frequency and phase of the radar's echo signal will change accordingly. By detecting the phase difference of the intermediate frequency signal, the radar can calculate the target's speed relative to the radar.

Can millimeter-wave signals penetrate glass media? Will they weaken the reflected signal

In common cases where drones, robotic vacuum cleaners, and other robots collide with glass, the primary reason is that these robots typically use cameras, infrared, and other optical sensors, which cannot recognize exterior glass walls. Using millimetre-wave sensors can effectively detect transparent obstacles like glass, thereby significantly reducing collision risks.

What are the measurement range and angle for millimeter-wave sensors?

The distance accuracy is constrained by bandwidth and signal-to-noise ratio and is not dependent on the distance itself. Gesture recognition applications require high bandwidth support and are generally for short-distance applications. Currently, Silicon Integrated's millimeter-wave sensor SoCs support a sweep bandwidth of 4GHz.