New test bench from Löhnert Elektronik provides full-surface coverage of automotive radomes with the R&S QAR from Rohde & Schwarz

Löhnert Elektronik is integrating the R&S QAR imaging tester from Rohde & Schwarz into its new end-of-line test benches for automotive radomes. Now the test benches can reproducibly test the reflection and transmission of these sensor covers over their entire surface at cycle rates of less than ten seconds.

In late 2019, Löhnert Elektronik, a specialist in custom test benches, was looking for a reliable automotive radome tester for its new test bench and chose the R&S QAR quality automotive radome tester from leading T&M manufacturer Rohde & Schwarz. The R&S QAR is presently the only tester on the market that can test these radomes quickly and over their full surface area.

Automotive radomes are protective covers for vehicle radar sensors. They must have good and uniform transmission characteristics over their entire surface for radar signals in the 77 GHz and 79 GHz bands (E band). Otherwise, angle errors and distortions can occur and the maximum detection distance can be reduced.

Conventional test solutions for production lines are based on measuring only a few points using a radar reference sensor and with reflectors attached to the cover. It is not possible to measure the uniformity of the entire surface with this approach.

Reproducible detailed image of the radome structure with transmissivity

The R&S QAR quality automotive radome tester tests the entire radome. It is based on distributed planar arrays of transmit and receive antennas operating in the E band. The system performs spatially resolved reflection measurements, allowing reliable evaluation of radome performance within seconds. The user can see at a glance whether the material has any defects. The millimeterwave images reproducibly show how much of the radar signal is reflected by the radome and how much is transmitted unhindered through the radome (transmissivity). The system reveals even the smallest inhomogeneity in the material.

A reliable and fast end-of-line test bench for radomes

Löhnert Elektronik has already launched the first test bench with the automotive radome tester. The rotary indexing machine contains different type-specific holders for the objects under test (component nests) and two test stations for transmission and reflection reference measurements. The machine is driven by the Löhnert instant scripting RunTime (LisRT V3) software together with a Siemens SPC controller. The radomes can be placed in the test holders either manually or by a robot. The system identifies them by a barcode or a data matrix code (DMC).

Normalization of the test equipment (self-adjustment to changed operating conditions) is possible directly on the line without losing much time. This is done using the test stations with their test plates. The measurement accuracy and function can also be verified directly on the line without reconfiguration. The test bench can easily be adapted to new radomes and specifications. Löhnert Elektronik simply exchanges the component nests and modifies the evaluation masks in the software. These extremely reliable and fast end-of-line test benches are now available for automotive radomes up to around 200 mm in diameter.