Logarithmic Chirp Specifications

Introduced in Digital Audio Acquisition and Generation Toolkit 2021 Q2

The following specifications apply to the Configure Chirp (N Ch) VI when configuring a logarithmic chirp signal.

Start frequency range

≤PDM rate/32, corresponding to 96 kHz at 3.072 MHz PDM rate

Stop frequency range

≤PDM rate/32

Pre-chirp duration range

0 to 232 − 1 PDM samples, or approximately 23 minutes at PDM rate of 3.072 MHz

Chirp duration range

0 to 232 − 1 − Pre-chirp duration samples

The logarithmic chirp rate range, in seconds, is defined by the following equation:

Logarithmic chirp rate range = ± ( Stop freq / Start freq ) / Chirp duration

Refer to the following table for maximum chirp rates at different PDM rates.

Table 4. Maximum Logarithmic Chirp Rate at Different PDM Rates
Maximum Logarithmic Chirp Rate PDM Rate = 600 kHz PDM Rate = 800 kHz PDM Rate = 2.4 MHz PDM Rate = 3.072 MHz PDM Rate = 4.8 MHz
Range ±105 octave/s ±140 octave/s ±422 octave/s ±541 octave/s ±845 octave/s
Minimum chirp time for 10 octaves 95 ms 71 ms 24 ms 18.5 ms 12 ms