Factors influencing the measuring accuracy of radar detection.

Radar sensors are becoming increasingly relevant, including in the industrial sector. Thanks to technical progress, this sensor technology is also attractive to integrators without specific expertise in radar development. In order to better explain the technology’s functions and characteristics as well as their relationship in practical use, InnoSenT is providing you with important background information about the measuring accuracy of radar and its influencing factors in this article.

How accurately can a radar measure?

There is both good and bad news. Unfortunately, there is no direct answer as to how precise radar measurements are. It depends on the technical design of the sensor, which is usually based on the subsequent use. During development, radar experts must take into account a variety of physical effects and influencing factors in order to achieve maximum measurement accuracy for the product and its application. They find the ideal balance between the parameters of transmission and reception power and other product requirements such as range or cycle time.

The measurement accuracy of radars

The accuracy of sensors indicates how precisely the various measured variables / radar data can be determined. It indicates the smallest measurable difference. For example, how precisely speed is determined and what measuring deviations might occur when. This deviation rate is described as plus/minus tolerance.

Caution – risk of confusion: the accuracy is sometimes accidentally equated with the radar solution. But the radar resolution describes a radar’s capability to distinguish objects. It indicates how well objects in close proximity can be distinguished from each other. This is particularly relevant to multi-target detection or exact positioning in space. The accuracy indicates how precisely the radar outputs the values of the individual measured dimensions.

Factors influencing measurement accuracy

The precision of the radar depends largely on the ratio of transmission to reception power. If the sensors have higher transmission and reception power, the measurement is more precise, because the data quality is higher. In addition, the more measurement data is available, the more valid the object information is.

Developers are working on different aspects to achieve an optimum signal-to-noise ratio. In addition, other interfering signals from the environment, for instance, can affect the detection process. Several factors and effects thus impact detection accuracy.

We have listed below what aspects have to be taken into account to enable the greatest-possible measuring accuracy for you.

Influencing factors associated with SNR (signal-to-noise ratio)

• The measurement time

The more measuring cycles (frames) are available, the better the accuracy of the measurement. If a radar monitors an object, the sensor receives more measuring points over time and the sensor has more data available to it for analysis. If the information regarding the object is as extensive as possible, this makes the detection result particularly robust, reliable, and all the more accurate.

However, very fast measurements are often required in the end use, for example in order to trigger a technical response as quickly as possible in the course of object detection. This means developers usually have to find the correct balance between detection time and accuracy for the respective application. Because if information is meant to be available as quickly as possible, for instance, the measuring time may have to be shortened.

• The frequency

At higher frequencies, such as 60 or 77 GHz, there are generally also larger bandwidths available. The bandwidth determines how many different signals the modulated radar sends and receives as reflections.

The transmitted frequency pulse can span the entire bandwidth, meaning that at higher frequencies, more frequencies are available for modulation. At high frequencies, the radar sends and receives more signals and can associate them with a target more clearly due to the narrower, precise peaks. This enables better resolution and accuracy.

In the detection of moving objects, the Doppler effect causes a frequency shift, causing the radar signal to be compressed or expanded over time. And radar developers make use of this effect for measuring speeds. At a higher transmission frequency, the Doppler frequency is also higher. This enables speeds to be determined more precisely, since lower movement speeds can be measured.

• The transmission power

If the radar emits a stronger signal, it also receives back a larger amount of energy after the signal is reflected from an object. A higher transmission power also impacts the noise, since while the latter remains the constant, the radar signal then becomes significantly more intense. The problem, however, is that not just any transmission power is permitted. It is subject to strict regulations which ensure even utilisation of the frequencies. This is meant to avoid overloads, disturbances, or health and safety risks.

• The reception power

How well a radar receives individual detection depends on the antenna gain and thus the antenna design.

• The distance

If radar waves spread freely, the signal becomes weaker and weaker at longer distances. Distant objects reflect only a fraction of the already weak signal. The radar thus receives fewer measuring points to analyse. The detection thus becomes less and less accurate over the distance.

• The components

In the development of a radar unit, the component costs and performance must be weighed against each other. High-quality components for the circuit, for example, cause significantly lower noise.

Further influencing factor in multi-target detection

• The angular resolution

When a single target is being detected, the signal-to-noise ratio plays a particularly crucial role in accuracy. In detecting multiple targets, however, resolution (capability to distinguish targets) also plays an important role. A radar’s resolution helps makes target detection more distinct. A higher resolution means that targets can be distinguished via several dimensions. Objects positioned close to each other can thus be distinguished from each other more clearly.

Influences due to unknown measuring conditions

• The object

Radar is better at detecting some shapes and materials and worse with others. Here, the RCS, or radar cross-section of an object, plays an important role and indicates how likely it is for a target is to be detected. Objects with a higher RCS value can be detected more precisely.

• The environment

In practice, rarely do optimum measuring conditions prevail – with no interfering factors. Other technical equipment or objects in the coverage area may cause interference or spreading loss. In addition, weather conditions can have a negative impact on measurement accuracy. False detections caused by wind movement can only be reduced through complex filter functions.

Capability to optimise measurement accuracy

If the hardware of the radar system has already been optimised, further optimisation of the measuring accuracy is subsequently possible by means of intelligent algorithms. Different filters for suppressing noise and interfering signals or to compensate for various effects that occur during measuring make the measurement result more accurate.

An example of this is the use of the tracking function. With it, the system clusters individual radar detections into a single object and tracks it over time. The following generally applies to subsequent signal processing: the better the measured values and the less the signal is dispersed, the more accurate the tracking is, since the algorithms have less to compensate for.

Some of the challenges relating to measuring accuracy can be compensated for in the technical implementation, while others are almost inevitable even despite high-end technology. For example, external influences such as local conditions, weather, and the object to be detected cannot generally be clearly predicted during product development. Manufacturers usually have to find a compromise or the right balance between the various influencing factors in order to achieve maximum measuring accuracy for the radar system’s specific end use.

Application examples

High-precision radar measurement in the millimetre range is no problem for radar experts like InnoSenT. One example product is the iSYS-6030 radar system. It impresses with its high resolution and precision in distance measurement. The company specially developed the product for the application areas of fill level measurement and collision protection, which put high demands on measuring accuracy.

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Information on this advanced sensor technology

The demand for sensors is increasing due to trends such as digitalisation, automation in industry & logistics, smart homes & cities, and autonomous driving. But the development and integration of radar units is a complex topic, and the technical terms and functions raise many questions for users. Our radar experts have put together comprehensive information to help you get started in the world of radar.