# Logarithmic Chirp Specifications

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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:

$\text{Logarithmic chirp rate range}=\text{}±\left(\text{Stop freq / Start freq}\right)/\text{Chirp duration}$

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

Table 1. 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