Detection of stationary objects using Radar technology
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Jan 22, 202410:03 AM
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Jan 22, 202410:03 AM
Applications using mmWave radar are mainly focused on the attributes detected from moving objects,such as vehicles and pedestrians, as the underlying principle of radar happens to be based on Doppler shift. On the contrary, radars are capable of detecting stationary objects too, but there are certain attributes that need to be considered while using it for such applications.
In this article, we will explore how Infineon's XENSIV™ 24 GHz/60 GHzradars can be used to detect static targets and the specific attributes that must be taken into account when using radar for such purposes, such as radar operating mode (Doppler, FMCW...), the amount of energy reflected by a target, chirp profile of the transmitted signal, angular resolution, reflectivity of the object, and algorithm used.
- Radar operating mode: Doppler or FMCW?
If you're deciding which radar system to use, then understanding the nature of your targets is crucial.
Doppler radar works by detecting the frequency shift of the radar signal as it bounces off a moving target. This is useful for detecting moving targets, but may have difficulty detecting stationary targets that don't produce a frequency shift. FrequencyModulated Continuous Wave (FMCW) radar, on the other hand, uses a continuous wave signal that is modulated in frequency to determine the range and velocity of targets. This makes it useful for detecting both moving and stationary targets. Therefore, if you need to detect stationary targets, FMCW radar may be a better option for you.
- RCS of the target
The radar cross-section (RCS) or otherwise known as the radar signature is a measure of how detectable a target is, as the cross-section of the target seen by the radar would determine how much radar energy is scattered back to the receiver by the target.Larger objects generally have a larger RCS, making them easier to detect. If there are multiple stationary targets and with different RCS, the one with higher RCS will have much more probability of being detected compared to the smaller one.During Fast Fourier Transform (FFT) processing, the side lobes of the one with a larger RCS might mask the ones of the lower RCS, especially if they are at the same distance. - Chirp profile of the transmitted signal
The chirp profile of the transmitted signal is an essential parameter, as it defines the range resolution and the maximum detection range for the radar. Range resolution is the ability of the target to differentiate between two closely spaced targets, which is given as:
Range Resolution = Speed of light / (2* Bandwidth swept by the chirp).
As the range resolution is dependent only on the bandwidth swept by the chirp, the higher the bandwidth, the better the resolution. But it also needs to be considered that the bandwidth needs to comply with the FCC regulations.
- Angular resolution
When analyzing radar data for detecting stationary objects, the information primarily extracted are the range and angle;velocity is not as relevant. To accurately identify a target and distinguish it from its surroundings, angular resolution plays a crucial role. It is the minimum angular separation needed between two stationary objects at the same range for the radar to recognize them as distinct entities. The higher the angular resolution, the more effective the radar is in distinguishing between multiple objects at the same range. - Reflectivity of the target
The reflectivity of a target is determined by the concentration of electric flux in the material, which is represented by its dielectric constant. While other environmental factors and physical attributes of the target can also impact the reflected signal, it's important to note that the material's reflectivity is a significant factor. A higher dielectric constant will result in a stronger reflected signal. If multiple objects with varying dielectric constants are present in the same environment, the object with the highest dielectric constant is more likely to be detected. - Algorithm used
The processing of the reflected signal plays a very important role in the detection of the stationary object. Specifically, the algorithm used for this purpose should be capable of eliminating the reflections from other surrounding objects and additionally, if there are multiple targets to be detected then the algorithm should be capable of multi-peak detection as well.
With the above suggested attributes,XENSIV™BGT60TR13C 60 GHz radaroperating in FMCW mode is well-suited for detecting moving targets and can be used in IoT-based applications. On the other hand, XENSIV™BGT60ATR24C with its automotive certification is an ideal choice for automotive applications.
References:
Infineon Radar Sensors
Infineon Product Selection Guide
Radar basics (FMCW) Online Training
- Tags:
- fmcw
- Radar
- Stationary objects
