The P1 code is a modified version of the Frank code where the DC frequency term is in the middle of the pulse instead of at the beginning.
The default P1 code Code Order is N = 4.
The P1 code has N2 elements and is defined as:
i,j
Where i and j range from 1 to N. For example, the P1 code with N = 4, by taking phase value modulo 
is given by the following sequence:
0
0
4x4
The figure below shows the spectrum of a 10 us pulse using P1 Coded phase modulation, where N = 10.
