Interference between different radars can have disastrous consequences for radar functionality, leading to missed detections, blind-spots, reduced range, and ghost objects. Robust, reliable radar performance requires methods to identify and mitigate interference, or avoid it altogether. This white paper describes the mechanisms of interference and methods to mitigate interference, using algorithms designed for and hardware hooks designed into the TI family of radar devices.
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This white paper discusses the problem of radar-to-radar interference and how it can be managed in TI radar devices. Interference is a major issue for reliable radar functioning, as the number of deployed radars has increased in both automotive and industrial contexts. Thus, the likelihood that one radar’s transmission is received by another radar has also increased. Interference results in a host of issues, such as a degradation in the noise floor leading to missed detections, or blind spots at certain ranges or directions. It can also create ghost objects in certain cases (ghost targets are targets seen by the radar which do not exist).
This paper is only concerned with cases where FMCW radars interfere with each other.
The information presented here covers the following topics:
In FMCW radar a chirp, a signal with a linearly ramping frequency, is generated and transmitted (see Figure 2-1).
This transmitted signal is reflected from targets in its field of view and received at the receiver. The received signal is a delayed copy of the transmitted signal. The signal received is mixed down, using the transmitted signal, and then digitized to create ADC data. Because the reflected signal is a delayed version of the transmitted signal, the mixed down signal corresponds to a sinusoid whose frequency is proportional to this delay. The delay is itself proportional to the distance of the target.
Delays can never be negative. Thus, given a positive slope, all valid objects correspond to positive frequencies. With the tone frequency estimated by a Fourier transform, the delay can be estimated. Using the delay and light speed, the distance to the target can be estimated. Thus, the maximum distance that the receiver can detect is limited by the IF bandwidth. If the target’s frequency exceeds the IF bandwidth, it is filtered out.