5 Chirp Configuration Recommendations Using Sensing Estimator

If there is doubt about whether the chirp configuration is following the proper recommendations mentioned in this application note, use the sensing estimator to check the chirp settings. The Advanced Chirp Design and Tuning tab can check a chirp configuration to see if the settings comply with the graphs the previous sections. See Figure 5-1 for an example of the warnings given in the sensing estimator.

To evaluate the chirp configuration manually, consider the following settings:

1. TX Backoff
2. RX Gain
3. HPF setting
4. Frequency Slope

First, look at the HPF setting and Frequency Slope to make sure the requirements for RX gain are met. In the example pictured in Figure 5-1, HPF setting = 1400kHz and Frequency Slope, S (MHz/μs) = 240. This means the maximum RX gain is 36 (see Figure 4-1). In this case, the decision is made to change the RX gain to 36 or below to make sure that the maximum receiver gain constraint is met.

Next, look at the TX backoff for the frequency range. Here the frequency range is 57–63GHz so use the data in Figure 4-2. This shows the minimum TX backoff as 3. In this case, the decision is to change the TX backoff to 3 or above to make sure the minimum back off constraint is met.

With the changes of RX gain from 40 to 36 and the TX backoff from 0 to 3, there is little or no risk of ADC saturation and the errors in the sensing estimator are cleared.