The signal emitted by the radar antenna has electrical energy, but it manifests as electromagnetic wave energy rather than traditional current form
1. Signal energy characteristics
The radar antenna generates electromagnetic waves through high-frequency alternating current, and its electrical energy is converted into radiation energy. According to the "Technical Requirements for Radio Transmission Equipment" issued by the Ministry of Industry and Information Technology in 2024, the peak power of typical military radar can reach megawatt level (1MW=10 ⁶ W), and that of civilian meteorological radar is about 10-100kW. This energy can generate microampere level induced current in the receiving equipment.
2. Energy transmission mechanism
Near field energy: There is a strong electromagnetic field within 1/6 of the antenna wavelength, and a field strength of ≥ 5V/m can still be induced at a distance of 10cm at a frequency of 1GHz
Far field radiation: Energy propagates in the form of spherical waves, and the power density decays with the square of distance (following the formula P_d=P_t G/(4 π r ²))
Energy Conversion: The receiving antenna converts wave energy into weak electrical energy through electromagnetic induction, with a typical radar echo power of only 10 ⁻¹² W
3. Comparison of measured data
|Radar type | Transmitting power | Power density 1 kilometer away | Energy conversion efficiency|
|---------|---------|----------------|------------|
|Airport navigation radar | 2kW | 0.8 μ W/cm ² | ≤ 0.3%|
|Shipborne phased array radar | 500kW | 200 μ W/cm ² | 0.5-0.8%|
|Automotive millimeter wave radar | 0.1W | 0.005 μ W/cm ² | 1.2%|
4. Safety Warning
High intensity radar waves (>5mW/cm ²) can cause thermal effects on biological tissues, and China's GB 8702-2014 specifies a public exposure limit of 0.4W/m ². The professional radar operation area needs to be equipped with protective isolation, and it is strictly prohibited to approach the front of the antenna within 3 meters while transmitting.
