BoBr_4596421, start and kill inputs of the PWM can be used to enable the PWM at the rising edge of the signal and disabling it at the falling edge of the signal. But, the PWM period has to anyway be changed in firmware. So, there might be issue in synchronizing the 2 PWM outputs which needs to be taken care. For example - the first PWM might disable the second PWM before the output reaches 42 kHz.
ClMe_4503246, can you please make sure that the sensor will work with digital output? The sensor might require a Chirp signal similar to the one described in this link.
The steps to create a similar chirp signal -
1. Generate sample points of the chirp signal (probably using MATLAB).
2. Store the sample point values in a buffer.
3. Use DMA to write the buffer values into the DAC to generate the output.