RF Wireless World

Phase_noise_dBc = -25; % integrated phase noise in dBc
Phase_noise_cutoff = 1000e2; % cutoff frequency of PSD
Phase_noise_floor = -125; % phase noise floor in dBc/Hz
Phase_noise_fs = 100e6; % sampling frequency
in=mapper_out_ori;
in=in';
out=RX_PN(in,Phase_noise_dBc,Phase_noise_cutoff,Phase_noise_floor,Phase_noise_fs)
figure;plot(real(out),imag(out),'c+');title('constellation with phase noise');

function out = RX_PN(in,dBc, cutoff, floor, Fs)
[M N] = size(in);
ltx = 2^(fix(log2(M-0.5))+2); % ltx will always be at least 2xM
if cutoff/(Fs/ltx)<16,
ltx = 16*Fs/cutoff;
ltx = 2^(fix(log2(ltx-0.5))+1);
end
PhaseNoise = frequency_synth_lorenzian(dBc, cutoff, floor, Fs, ltx).';
Nphn = length(PhaseNoise);
if Nphn<M
error(['Phase noise vector must be longer than' num2str(Nsamples)])
end
Nstart = fix(rand(1,1)*(Nphn-M)); % random staring point
PhaseNoise = PhaseNoise(Nstart:Nstart+M-1);
% Add phase noise to data
out = zeros(size(in));
for k=1:N
out(:,k) = in(:,k).*PhaseNoise.';
end

function y = frequency_synth_lorenzian( K, B, p2, Fs, ltx);
global d
Ns = ltx; % Number of samples for ifft calculation
df = Fs/Ns; % frequency resolution
k = [0:1:Ns/2-1, -Ns/2:1:-1]; % frequency index range
% frequency range: f = k * df
p2o = p2;
p2 = 10^(p2/10); % in V^2/Hz
p2 = p2*df; % in V^2/df
Ko = K;
K = 10^(K/10); % in V^2
B = B/df; % 3-dB bandwidth index
% Low frequency part is defined by Lorenzian function
SSBmask = sqrt( K*B/pi./([1:Ns/2].^2+B^2) );
% High frequency part is defined by the noise floor of the system p2
SSBmask = max(SSBmask, sqrt(p2)*ones(size(SSBmask)));
%-- Phase noise PHI(f, f>0) is first generated as a wide band signal
PHI = sqrt(0.5) * abs( randn(1,Ns/2) + j*randn(1,Ns/2) );
PHI = PHI .* exp(j*2*pi*rand(1,Ns/2));
%-- Phase noise PHI(f, f>0) is shaped according to the wanted mask
PHI = PHI .* SSBmask;
%-- Phase noise PHI(f) is then generated from PHI(f, f>0)
% (no phase noise on the carrier)
PHI = [0 PHI(1:Ns/2-1) conj(PHI(Ns/2:-1:1))];
NoisePower = 10*log10( sum(abs(PHI).^2) );
if (0) f = k(2:Ns/2)*df;
PHI_f = 20*log10(abs(PHI(2:Ns/2))/sqrt(df));
SSBmask_f = 20*log10(SSBmask(1:Ns/2-1)/sqrt(df));
% normalisation to get PHI(f) in dBc/Hz, and not dBc/df
figure(20),semilogx(f, PHI_f, 'b-','linewidth',1);
hold on; grid on; zoom on;
semilogx(f, SSBmask_f, 'r-','linewidth', 2);
axis([f(1) f(end) p2o-10 SSBmask_f(1)+10]);
end; %-- Correction for the integrated phase noise power:
PHI = PHI * 10^((Ko-NoisePower)/20);
%-- Phase noise phi(t) in the time domain
phi = ifft(PHI,Ns)*Ns;
%-- Local oscillator signal lo(t) in the time domain
lo = exp(j*phi);
%-- Local oscillator signal LO(f) in the frequency domain
if (0)
LO = fft(lo,Ns)/Ns;
f = k(2:Ns/2)*df;
LO_f = 20*log10(abs(LO(2:Ns/2))/sqrt(df));
SSBmask_f = 20*log10(SSBmask(1:Ns/2-1)/sqrt(df));
figure(21);semilogx(f, LO_f, 'k-','linewidth',1);
hold on; grid on; zoom on;
semilogx(f, SSBmask_f, 'r-','linewidth',2);
axis([f(1) f(end) p2o-10 SSBmask_f(1)+10]);
end; %-- Prepare lo(t) for efficient use in dbbm_fe
y = lo(1,1:ltx*fix(Ns/ltx));
y = reshape(y,ltx,fix(Ns/ltx));