Learn How to Master Radar Signal Processing: Techniques for Distance and Velocity Measurement

In this technical discussion, we delve into the computational aspects of radar signal processing, particularly focusing on the Digital Signal Processing (DSP) and the role of Field-Programmable Gate Arrays (FPGAs) in managing the computationally intensive tasks.

The foundational structure of a radar system includes both a transmitter and a receiver. Our setup particularly considers a configuration with one transmit antenna and multiple receive antennas. At the core of the system is an oscillator tasked with generating a chirp—a signal with a frequency that varies over time. This chirp is essential for measuring velocity, as it needs to be emitted repeatedly, a concept we will elaborate on later.

As the chirp propagates, it splits into two paths. One path radiates freely into space, while the other is directed towards the receiver, entering through a mixer. This dual-path approach enables the radar to detect objects, such as a vehicle moving at velocity V and located at range R, with an angle of arrival θ. The received signals, weakened by distance, are then amplified and mixed to generate a beat frequency, which is subsequently digitized and processed to extract valuable data about the target’s distance and velocity.

We advance to a deeper examination of how distance measurement is achieved. By analyzing the time delay of the received chirp compared to the transmitted chirp, and applying the principles of chirp modulation, we can derive a formula that relates the beat frequency to the target’s range. This relationship is linear and is further refined through Fast Fourier Transform (FFT) to determine the precise range of the target.

Velocity measurement follows a similar principle but focuses on the phase change between consecutive chirps reflected off a moving target. By analyzing these phase changes, we can deduce the target’s velocity using Doppler FFT. This process requires careful consideration of the sampling frequency and the FFT’s resolution to ensure accurate velocity detection.

The discussion also covers the concept of angle of arrival, which necessitates the use of multiple antennas to pinpoint the direction from which the signal arrives. This technique involves comparing the phase difference of signals received by different antennas, allowing for the determination of the target’s direction.

The webinar then shifts to the practical aspects of implementing these principles in a radar system. We explore a case study of a short-range radar designed for specific operational requirements, including the sampling rate, bit resolution, and the number of chirps per frame. This segment emphasizes the importance of system design choices in achieving desired measurement accuracies and resolutions.

In summary, the main topics covered include:

• The integral role of FPGAs in handling DSP tasks within radar systems.
• The generation and significance of chirps in measuring distance and velocity.
• Mathematical foundations for calculating range and velocity from radar signals.
• The application of FFT in analyzing radar signal frequencies for distance and velocity determination.
• Techniques for enhancing the accuracy and resolution of radar measurements, including considerations for system design and signal processing algorithms.