White Paper: Test & Measurement

Automotive Radar Sensors – Transmit Signal Analysis and Inference Tests

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Road safety is a global challenge at present and will be in the future. Automotive radar has become a keyword in this area and pushes again a step forward to increase driving comfort, crash prevention, and even automated driving. In the automotive radar market, high performance and reliability, combined with low unit size and price, are mandatory.

A single car may carry in excess of ten sensors. These radars shall not interfere with each other or any other device. It follows that test and measurement of such radar sensors needs to be just as fast, as reliable, cost-effective, and straightforward to use during development as well as in production.

Just like all other signal transmission via radio frequency (RF) systems, radar can be distorted by other RF systems transmitting at the same time. If such radio frequency interferences (RFI) happen, the functionality of a system can suffer severely and it may react unpredictably.

Apart from time, the likelihood of interference depends, for example, on the used frequency bands of such systems (e.g. 76-81 GHz or around 24 GHz band for automotive radar), the distance between the individual transmitters (e.g. many cars in front of each other), the waveform (chirp rate, timing, receive bandwidth, and filter stages), and the emitted power. The worst scenario for this interference would be the creation of artificial ghost targets, the malfunction of the automotive sensor, or a blind automotive sensor.

This application note highlights signal measurements and analysis of automotive radars that are crucial during the development and verification stages. Particular emphasis is placed on a setup to verify the functionality of a radar in case of radio interference. It covers the theoretical background of automotive radar signals, the analysis of those signals, and the test and measurement solutions provided by Rohde & Schwarz. Furthermore, a measurement setup is shown to also address radio interference test for two kinds of radars.

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