Automotive radar sensors are a staple in modern vehicles, enabling advanced driver assistance systems (ADAS) and autonomous driving features.
Depending on their use cases, automotive radar modules transmit and receive mmWave signals in the range of 76 – 81 GHz to enable autonomous driving features. In-cabin radar applications, such as that for passenger sensing, operate at mmWave frequencies of 58 – 62 GHz.
It is very important to characterize the radar chipset designs for their respective applications before they move downstream for assembly into automotive radar modules. Signal analysis is a process that helps engineers extract the radar signal characteristics such as chirp rate, modulation type and sequence, pulse repetition interval (PRI) and amplitude.
Developing automotive radar requires testing to minimize propagation loss, phase noise, IQ, frequency response errors, and noise that impact the evaluation modules. The challenge is in testing the automotive radar transmitter and receiver in a simple, streamlined fashion, allowing for a fast and reliable development cycle.
Measuring automotive radar in the high-frequency E-band of 60 GHz or 79 GHz presents challenges. Radar system losses tend to be very high at these high frequencies, and the measurement setup will need low-loss wave guides and low-loss connectors, which are costly.
Frequency Demodulation
Frequency demodulation is a common method to help automotive radar developers to effectively extract information from the radar signal for characterizing its performance.
Here’s how you can demodulate a typical automotive radar signal to test the quality of the transmission signals:
- Use a 60-90 GHz transceiver module to down-convert the E-band frequencies to baseband frequencies of 6 GHz or lower.
- Measure the down-converted signals with a real-time oscilloscope or a digitizer.
- Analyze your demodulated signals on a vector signal analysis software platform that can provide measurements like time and frequency domain, as well as custom OFDM modulation analysis.
Below are some signal measurement examples using the Keysight vector signal analysis software:
Acquisition spectrum:
Figure 1: Measuring bandwidth, along with start and stop frequencies, akin to a standard swept-tuned spectrum analysis measurement. We can use markers to determine the swept bandwidth of the signal.
Acquisition time:
Frequency deviation:
Figure 3: Measuring how frequencies deviate over time. These measurements are important as radar device manufacturers will have specifications that they must meet for frequency sweep time and frequency modulated linearity.
Explore the various Keysight tools that can help accelerate and improve your automotive radar design validation and iteration cycles:
Watch this product video on how to speed up your tests with the latest Keysight MXR series oscilloscopes.
Take a tour of the Keysight PathWave vector signal analysis software demodulation and vector signal analysis. This tool is compatible with signal analyzers, network analyzers, oscilloscopes and many more test instruments.