clc; clear; close all;

% parameters
fs1 = 48e6; % sample rate 1
fs2 = 122.88e6; % sample rate 2
ratio_up = fs2/gcd(fs1,fs2); % upsample ratio
ratio_dn = fs1/gcd(fs1,fs2); % downsample ratio
interp = 8; % interpolation factor
sumbol_num = 16;

% standard pn sequence
pn_seq = comm.PNSequence('Polynomial','x^7+x^6+1', ...
  'InitialConditions',[zeros(1,6),1],'SamplesPerFrame',2^7-1);
PRBS7 = pn_seq();
PRBS7_polar = 1-2*[PRBS7;0];

% square shaping 
data_fs1 = kron(repmat(PRBS7_polar,sumbol_num,1),ones(interp,1)); 

% upsample
data_fs1_up = upsample(data_fs1,ratio_up);

% anti-aliasing filter
fir = fir1(1024,6e6/48e6/max(ratio_up,ratio_dn)*2*pi,'low');

% filtering & downsample
data_fs2 = downsample(conv(data_fs1_up,fir,'same'),ratio_dn);

% quantize & export fir coefficients
coe_gen(round(fir/max(abs(fir))*(2^15-1)),'lpf_125k.coe','filter');