FAQ about MMwave

Q1:What is millimeter wave?

A1: As the name suggests, millimeter waves are electromagnetic waves with a wavelength (λ) of about 1 millimeter (more precisely, 1 to 10 millimeters). By using the formula f = c/λ, where c is the speed of light (3E8 m/s), the wavelength can be converted into a frequency range of 30-300 GHz. The millimeter wave frequency band has been designated as the "extremely high frequency" (EHF) band by the International Telecommunication Union (ITU). The term "millimeter wave" is also commonly abbreviated as "mmWave".

Q2:What materials can reflect millimeter wave well?

A2:To reflect millimeter waves, the material should have high electrical conductivity or a large refractive index. Here are some materials that reflect mmWave well:

1. Metals: Metals such as aluminum, copper, and silver are excellent reflectors of millimeter waves. They are highly conductive, which allows them to reflect waves effectively. Metals reflect millimeter waves better than most materials because electrons in metals can move freely, providing high conductivity that can reflect waves efficiently.

2. Conductive coatings: Coatings made of conductive materials such as silver or carbon can reflect millimeter waves. These coatings can be applied to non-conductive materials such as plastics or ceramics to make them reflective.

3. Dielectric materials: Some dielectric materials, such as ceramics and plastic composites, can reflect millimeter waves. Reflection is caused by the material having a different refractive index than the surrounding air, and can reflect millimeter waves with low conductivity and low loss, making it suitable for some specific applications, such as waveguides and lenses.

Additionally, the effectiveness of these materials as mmWave reflectors depends on various factors, such as the wavelength of the wave, angle of incidence, and the surface finish of the material.

Q3: Does millimeter wave technology have any impact on the health of users?

A3:Current research and main conclusions show that millimeter wave signals are not harmful to human health. Millimeter wave signals are higher in frequency and lower in energy, so they are less likely to cause harm to the human body. In addition, the radiation power of 5G millimeter wave technology is very low, far below the limit value of international standards, and will not generate heat radiation.

Q4:What should I pay attention to when installing this mmWave Radar - 24GHz Human Presence Detection Sensor（SEN0395）?

A4:Pay attention to the beam angle in the wiki page, the beam angle faces the detected problem, the antenna of the sensor faces the measured object, and the recommended beam angle: 100*40° (width*height).

Q5:Can this millimeter-wave radar sensor  (SKU: SEN0395) be used through walls?

A5:Our tutorial reveals a certain degree of penetrability for wood. However, the properties of electromagnetic waves dictate that the higher the frequency, the weaker its ability to penetrate through walls. Therefore, the 24 GHz mmWave possesses a certain degree of wall-penetrating ability, albeit not particularly strong. It is recommended to avoid thick obstructions as much as possible when using it.

Q6:Why is the output of my mmWave Radar - 24GHz Human Presence Detection Sensor  (SKU: SEN0395)  always 1?

A6: 1. Due to the high sensitivity of this millimeter-wave radar sensor, please ensure that the sensor is fixed firmly when using it. When holding it, the sensor will continuously output high level due to slight shaking.

2. Please try to change the sensor measurement range in the code or serial port settings, and make sure that there is no object moving within the range, and check whether the sensor value returns to normal.

Q7:Can this mmWave radar sensor (SKU: SEN0395) only detect human body?

A7:No, the sensor detects movement of all objects within range by detecting mmWave radar and is very sensitive.

Q8:What is the output of this sensor (SKU: SEN0395)? Do I need an external pull-down resistor for output?

A8:Supports GPIO output, supports serial port output, and does not need pull-down resistors when outputting, and can be directly connected to the main control board.

If you have other questions, just feel free to post them in our forum for consultation. We will reply them as soon as possible and improve the product FAQ gradually.