24GHz Millimetre-Wave Radar

24GHz millimetre-wave radar is a short-range automotive radar sensor operating on the 24GHz frequency band, primarily used for close-range detection functions such as Blind Spot Detection (BSD) and Lane Change Assist (LCA).

💡 Operating Principle and Key Characteristics

Most 24GHz radars utilise Frequency Modulated Continuous Wave (FMCW) technology. By transmitting and receiving continuously frequency-modulated microwave signals, the system relies on the frequency shift between transmitted and received signals to accurately calculate target distance and speed. Its operating wavelength is around 12.5 mm.

Its primary technical attributes clearly outline its operational capabilities and limits:

• Limited available bandwidth: The internationally standard ISM band bandwidth is typically only 250MHz, which restricts its theoretical range resolution to roughly 60 cm.

• Moderate detection range: As a short-range sensor, its effective detection range generally spans from 0.15 metres to 30 metres, mainly catering to close-proximity environmental sensing.

• Relatively low cost: Backed by mature technology, the hardware cost of a 24GHz radar is significantly lower than that of a 77GHz unit, with unit costs hovering around the RM500 mark.

🚗 Primary Applications

In automotive Advanced Driver Assistance Systems (ADAS), 24GHz radar leverages its cost-effectiveness and capable short-range sensing to carry out the following supporting functions:

• Blind Spot Detection (BSD): Mounted inside the rear bumper corners, it monitors vehicles approaching within the side and rear blind spots, helping drivers execute lane changes safely.

• Lane Change Assist (LCA): When initiating a lane change, if the system detects a vehicle closing in rapidly from behind, it warns the driver via visual indicators on the wing mirrors or audible alerts.

📉 Current Market Trends: Rapidly Superseded by 77GHz Radar

Although 24GHz radar was previously the go-to solution for blind-spot monitoring systems, performance constraints and evolving regulatory standards are seeing it phased out in favour of advanced 77GHz radar technology.

• Performance bottlenecks: Compared to 77GHz radar, 24GHz units are bulkier, have shorter detection ranges, and deliver poorer range resolution (making it difficult to distinguish between two closely positioned objects).

• Regulatory shifts: China's Ministry of Industry and Information Technology (MIIT) has banned the production and import of automotive radars in the 24.25–26.65GHz band, standardising 76–79GHz as the dedicated automotive radar spectrum. This regulatory push has accelerated the adoption of 77GHz radars. Boasting a substantial bandwidth of up to 800MHz, 77GHz radar improves range resolution down to around 20 cm with higher velocity measurement accuracy, making it far better suited as the primary sensor for advanced active safety features such as Autonomous Emergency Braking (AEB) and Adaptive Cruise Control (ACC).