System and method for generating repeatable PPM waveforms

A lidar for generating repeatable Pulse Position Modulated (PPM) waveforms to determine a range to a target comprising:

• a processor for a) creating a modulation pool, based on a maximum nominal pulse repetition frequency (PRF) and a specified final PPM code length of N, wherein N is an integer greater than 1;
• b) obtaining a seed code;
• c) eliminating bad modulation levels from the modulation pool to generate a good modulation pool;
• d) selecting a modulation level from the good modulation pool;
• e) concatenating the selected modulation level to the seed code to generate an i-element modulation sequence, wherein i is an integer index greater than 1;
• f) repeating steps c to e N times to generate an N-element modulation sequence;
• g) selecting a PRF less than the maximum nominal PRF;
• h) generating a concatenated repeatable base PPM waveform by applying the N-element modulation sequence to the selected PRF, wherein
• eliminating bad modulation levels comprises:
• discarding modulation levels that cause a baud collision between any pair of code elements in the base PPM waveform;
• discarding modulation levels that cause a baud collision between any pair of code elements in the base PPM waveform and a concatenated code formed by concatenating the base PPM waveform to itself;
• and discarding modulation levels that lie equidistant between the elements in the base PPM waveform, and code elements in the concatenated code;
• a transmitter for transmitting the concatenated repeatable base PPM waveform toward the target;
• and
• a receiver for receiving a waveform reflected from the target to determine the range to the target.