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diff --git a/octave/impulse_noise.m b/octave/impulse_noise.m
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-% impulse_noise
-% David Rowe May 2017
-%
-% Experiments with impulsive noise and HF radio
-
-format;
-more off;
-rand('seed',1)
-
-% DFT function ------------------------------------------------
-% note k is on 0..K-1 format, unlike Octave fft() which is 1..K
-
-function H = calc_H(k, K, a, d)
-  L = length(d);
-  H = 0;
-  for i=1:L
-    H += a(i)*exp(-j*2*pi*k*d(i)/K);
-  end
-endfunction
-
-% -----------------------------------------
-% PWM noise simulation
-% -----------------------------------------
-
-function pwm_noise
-
-  Fs   = 10E6;   % sample rate of simulation
-  Fsig = 1E6;    % frequency of our wanted signal
-  Fpwm = 255E3;  % switcher PWM frequency
-  T    = 1;      % length of simulations in seconds
-  Nsam = T*Fs;  
-  Nsamplot = 200;
-  Apwm = 0.1;
-  Asig = -40;    % attenuation of wanted signal in dB
-
-  % generate an impulse train with jitter to simulate switcher noise
-
-  pwm = zeros(1,Fs);
-  Tpwm = floor(Fs/Fpwm);
-  pulse_positions_pwm = Tpwm*(1:T*Fpwm) + round(rand(1,T*Fpwm));
-
-  h_pwm = zeros(1,Nsam);
-  h_pwm(pulse_positions_pwm) = Apwm;
-  h_pwm = h_pwm(1:Nsam);
- 
-  % add in wanted signal and computer amplitude spectrum
-
-  s = 10^(Asig/20)*cos(2*pi*Fsig*(1:Nsam)/Fs);
-
-  h = h_pwm+s;
-  H = fft(h);
-  Hdb = 20*log10(abs(H)) - 20*log10(Nsam/2);
-
-  figure(1); clf;
-  subplot(211)
-  plot(h(1:Nsamplot));
-  subplot(212)
-  plot(Hdb(1:Nsam/2));
-  axis([0 T*2E6 -120 0]); xlabel('Frequency Hz'); ylabel('Amplityude dBV'); grid;
-
-  printf("pwm rms: %f signal rms: %f noise rms\n", std(h_pwm), std(s));
-endfunction
-
-% -----------------------------------------
-% Single pulse noise simulation
-% -----------------------------------------
-
-function pulse_noise
-
-  % set up short pulse in wide window, consisting of two samples next
-  % to each other
-
-  K = 1024;
-  a(1) = a(2) = 1; d(1) = 10; d(2) = d(1)+1;
-  h = zeros(1,K);
-  h(d(1)) = a(1);
-  h(d(2)) = a(2);
-
-  % mag and phase spectrum, mag spectrum changes slowly
-
-  figure(2); clf;
-  Hfft = fft(h);
-  subplot(311)
-  stem(h(1:100));
-  axis([1 100 -0.2 1.2]);
-  subplot(312)  
-  plot(abs(Hfft(1:K/2)),'+');
-  title('Magnitude');
-  subplot(313)
-  plot(angle(Hfft(1:K/2)),'+');
-  title('Phase');
-
-  % simple test to estimate H(k+1) from H(k) --------------------
-
-  % brute force calculation
-
-  k = 300;
-  H = zeros(1,K);
-  H(k-1) = calc_H(k-1, K, a, d);
-  H(k)   = calc_H(k, K, a, d);
-  H(k+1) = calc_H(k+1, K, a, d);
-
-  % calculation of k+1 from k using approximation that {d(i)} are
-  % close together compared to M, i.e it's a narrow pulse (assumes we
-  % can estimate d using other means)
-
-  Hk1_ = exp(-j*2*pi*d(1)/K)*H(k);
-
-  % plot zoomed in version around k to compare
-
-  figure(3); clf;
-  plot(H(k-1:k+1),'b+','markersize', 10, 'linewidth', 2);
-  hold on; plot(Hk1_,'g+','markersize', 10, 'linewidth', 2); hold off;
-  title('H(k-1) .... H(k+1)');
-  printf("H(k+1) match: %f dB\n", 20*log10(abs(H(k+1) - Hk1_)));
-endfunction
-
-% Run various simulations here ---------------------------------------------
-
-%pwm_noise
-pulse_noise
-