How to perform end-of-line production testing to ensure automotive radar performance

As automotive radar continues to evolve and its role in advanced driver assistance systems (ADAS) increases, the test environment must enable fast, simple, and repeatable test processes. This article describes how to use a radar echo generator for end-of-line production testing to ensure the functionality and quality of automotive radar sensors.

As the practical implications of building truly safe vehicles become increasingly apparent, we are still a long way from building and certifying fully autonomous vehicles for use on public roads. Despite this, the adoption of advanced driver assistance systems (ADAS), such as lane keeping, adaptive cruise control, and collision avoidance mechanisms, is accelerating. As ADAS implementations increase, so too does the number of radar systems providing situational awareness on each vehicle.

These radar systems need to measure the distance, radial velocity and size of objects near the vehicle by calculating the radar echo delay, Doppler shift and amplitude. Obviously, these tests must guarantee accuracy and consistency. In the automatic emergency braking system (AEBS), small distance measurement errors are critical, whether it is safe parking or collision avoidance.

OEMs and their component manufacturers need to ensure that the radar modules installed on vehicles can work safely and stably not only when delivered, but also during the vehicle's life span for many years. The challenge of testing key radar performance parameters such as Doppler shift and range accuracy is that it is time-consuming and expensive. This does not meet the needs of production line testing, which requires fast and simple end-of-line testing to ensure the quality and functionality of the radar before the system is delivered to the customer. Modern, lean and versatile production lines require small and highly reliable test systems that ensure excellent test repeatability, customizable configuration, simple operation and maximum efficiency.

The way to deal with this challenge is to use the R&S AREG100A automotive radar echo generator from Rohde & Schwarz for testing. The R&S AREG100A supports user-defined delay lines and can simulate targets in the 24 GHz ISM band and the 77 GHz and 79 GHz E bands. A total of up to four static targets at different distances can be simulated, each with a different radar cross-section, and the target speed can be simulated by controlling the frequency offset. The echo generator supports all common automotive radar bands, the 24 GHz ISM band, and the E band RF front end.

The radar echo generator works by receiving the radar signal from the radar under test within a defined frequency band, converting it to an intermediate frequency (IF), and then introducing a fixed time delay (simulating distance), Doppler shift (simulating radial velocity), and attenuation (simulating target size). After up-converting the IF signal to RF, it is sent back to the radar under test, which receives and processes it and reports the detected target distance, Doppler shift, and radar cross-section. 

It can provide ADAS-based safety for automotive radar sensors, so it has attracted much attention from standardization bodies. With the publication of the EU Radio Equipment Directive (RED) and the relevant applicable standards, the mandatory framework has become law in Europe. The R&S AREG100A is the core equipment of the RED conformance test system for automotive radar sensors. The echo generator has a calibrated IF output to test the equivalent isotropic radiated power (EIRP) of the radar sensor. By connecting the R&S NRP8S power meter to this IF output, it is possible to check whether the radar sensor's EIRP complies with electromagnetic compatibility standards such as ETSI EN 301091-1 and ETSI EN 302264-1. There is also an IF port on the radar echo generator that can be used to connect the signal to a spectrum analyzer (such as the R&S FSW8) to perform spectrum measurements such as spurious emission tests. It is also possible to connect an analog or vector signal generator (including the R&S SMW200A in a 6 GHz configuration) to the IF input port, so that any interfering signals can be superimposed on the echo to test the radar's immunity to interference. The radar echo signal and the loaded interference signal share the RF front end in the R&S AREG100A and are then up-converted to the radar band, which simplifies the test setup. The test setup based on AREG100A does not require complex millimeter-wave test and measurement equipment, allowing test engineers to focus all their attention on test execution.

The test of radar system must ensure the consistency of environment, so that the results will not be invalidated by stray signals or unexpected reflections from other interference sources. To address this problem, Rohde & Schwarz launched the R&S ATS1500A shielded chamber, which provides a repeatable RF shielded environment for far-field testing of automotive radar sensors. In combination with a precise 2D positioner, azimuth and elevation coverage tests of automotive radar sensors can be easily performed. With the help of the positioner, the antenna pattern of the automotive radar sensor can also be accurately measured.

To develop test procedures using this combination of tools and facilities more quickly and eventually automate them, Rohde & Schwarz is launching the QuickStep test executive software, which can also be used to generate test reports. Using QuickStep to control the R&S AREG100A automotive radar echo generator and other test and measurement equipment, user-defined, fully automated functional and quality tests of automotive radar sensors can be performed.

The integration of these tools ultimately enables fast, consistent, high-quality checks of automotive radar system functionality, giving OEMs and their customers confidence that current ADAS features and future automotive autonomous driving systems will work accurately, reliably, and consistently over the life of the vehicle.