System and method for generating very long ppm waveforms

A method for generating long Pulse Position Modulated (PPM) waveforms in a lidar, the method comprising:

• a) receiving an initial PPM code element and a desired maximum sidelobe height;
• b) generating a two-column lookup table, wherein one column of the lookup table includes differences between each code element and each of the other code elements, and the other column of the lookup table includes entries indicating a number of times a code element difference has been observed in the initial PPM code;
• c) selecting a candidate modulation level from a pool of available elements;
• d) identifying the differences between the selected candidate modulation value and each code values in the initial PPM code and incrementing the corresponding values in the lookup table;
• e) comparing the values of the lookup table against the desired maximum sidelobe height;
• f) when a value exceeds the desired maximum sidelobe height, discarding the candidate modulation level, decrementing the corresponding values in the lookup table and repeating steps c to e;
• g) when a value is below the desired maximum sidelobe height, appending the candidate modulation level to an end of the initial PPM code to update the initial code, and repeating steps c to g N times to generate a PPM waveform of length N, wherein N is an integer;
• h) transmitting the PPM waveform of length N by a transmitter toward a target;
• and
• i) receiving a waveform reflected from the target to determine a range to the target.