I am trying to calculate the maximum unambiguous range for FMCW automotive radar.
In automotive, the pulse repetition rate (Tp) is typically 50 – 60ms. My equation is as follows:
where c is the speed of light. This becomes
Have I done the above correctly? 7 million metres seems wrong. Is it different as automotive is using FMCW?
Looking here
For example, a given radar with a linear frequency shift with a
duration of 1 ms, can provide a maximum unambiguous range of less than
150 km theoretically. This value results from the remaining
necessarily overlap of the transmission signal with the echo signal
(see Figure 1) to get enough time for measuring a difference
frequency. Most this range can never be achieved due to low power of
the transmitter. Thus always remains enough time for a measurement of
the difference frequency.
This suggests my calculation is correct but for FMCW the chirp duration is used (in the example 1ms), as answered by Neil_UK
Best Answer
It depends how the radar is working. If it times the difference between transmission and reception of the pulse, then the correct unambiguous range is given by taking 50mS as the time of flight, and doing the appropriate thing with \$c\$, which gives you 7500km.
However, it's unlikely that is how it's working. It's more likely to be using a higher rate of modulation within the pulse. In that case, you need to take the repetition rate of the actual modulation used to sense the distance.