Comments on: First order digital PLL for tracking constant phase offset http://www.dsplog.com/2007/06/10/first-order-digital-pll-for-tracking-constant-phase-offset/ Signal Processing for Communication Fri, 10 Feb 2012 01:03:15 +0000 hourly 1 http://wordpress.org/?v=3.3.1 By: tien http://www.dsplog.com/2007/06/10/first-order-digital-pll-for-tracking-constant-phase-offset/#comment-29025 tien Tue, 11 May 2010 06:00:01 +0000 http://www.dsplog.com/2007/06/10/first-order-digital-pll-for-tracking-constant-phase-offset/#comment-29025 thanks thanks

]]> By: Krishna Sankar http://www.dsplog.com/2007/06/10/first-order-digital-pll-for-tracking-constant-phase-offset/#comment-24244 Krishna Sankar Sun, 28 Mar 2010 09:27:19 +0000 http://www.dsplog.com/2007/06/10/first-order-digital-pll-for-tracking-constant-phase-offset/#comment-24244 @venkat: Does your transmit signal contain phase information? Did the code work in no noise case? @venkat: Does your transmit signal contain phase information? Did the code work in no noise case?

]]> By: venkat http://www.dsplog.com/2007/06/10/first-order-digital-pll-for-tracking-constant-phase-offset/#comment-23550 venkat Thu, 18 Mar 2010 06:39:06 +0000 http://www.dsplog.com/2007/06/10/first-order-digital-pll-for-tracking-constant-phase-offset/#comment-23550 Hello Krishna, I have referred your example on first order PLL for constant phase tracking.It was very useful. http://www.dsplog.com/2007/06/10/first-order-digital-pll-for-tracking-constant-phase-offset/ But in the example a complex carrier is being used at the transmitter and receiver.Practically , when I use a cosine carrier at Tx. and cosine,sine carriers at Rx.(as in costas loop) , can the same loop filter be used ? I have tried to simulate the above situation in the following script but was unable to estimate the phase. Please help me………. % MODULATION clc; clear all; close all; [b,a] = butter(1,0.0156,’low’); % low pass filter to remove nterm_i = 0; % double frequency component dterm_i = 0; nterm_q = 0; dterm_q = 0; n_sym = 10; % number of symbols fs = 12.8e6; t = 0:1/fs:100e-6 – 1/fs; fc = fs/8; % carrier freuency theta = 70*pi/180; % phase offset r = 0.1e6; % symbol rate oversamp = fs/r; sym = randint(n_sym,1)*2-1; in = 0; for ind=1:1:n_sym tmp(1:oversamp) = sym(ind); in = [in tmp]; end tx = in(2:end); tx_carrier = cos(2*pi*fc*t + theta); tx_out = tx.*tx_carrier; % first order pll alpha = 0.05; phiHat = 0; for ii = 1:1:length(t) % Remove carrier rx_i(ii) = tx_out(ii)*cos(2*pi*fc*t(ii) + phiHat); rx_q(ii) = tx_out(ii)*sin(2*pi*fc*t(ii) + phiHat); % low-pass IIR filter for I-channel iir_in_i(ii) = rx_i(ii); iir_out_i(ii) = b(1)*iir_in_i(ii)+ nterm_i + dterm_i; nterm_i = b(2)*iir_in_i(ii); dterm_i = a(2)*iir_out_i(ii); % low-pass IIR filter for Q-channel iir_in_q(ii) = rx_q(ii); iir_out_q(ii) = b(1)*iir_in_q(ii)+ nterm_q + dterm_q; nterm_q = b(2)*iir_in_q(ii); dterm_q = a(2)*iir_out_q(ii); % demodulating circuit xHat = 2*(iir_out_i(ii)>0) -1 ; % symbol estimate phiHatT =angle(conj(xHat)*rx_i(ii)); % phase error estimate angle(iir_out_i(ii) + i*iir_out_q(ii));% % accumulation phiHat = alpha*phiHatT + phiHat; % phase accumulator output % dumping variables for plot phiHatDump(ii) = phiHat; end plot(phiHatDump*180/pi,’-'); Hello Krishna,
I have referred your example on first order PLL for constant phase tracking.It was very useful.
http://www.dsplog.com/2007/06/10/first-order-digital-pll-for-tracking-constant-phase-offset/
But in the example a complex carrier is being used at the transmitter and receiver.Practically , when I use a cosine carrier at Tx. and cosine,sine carriers at Rx.(as in costas loop) , can the same loop filter be used ?
I have tried to simulate the above situation in the following script but was unable to estimate the phase. Please help me……….

% MODULATION

clc;
clear all;
close all;

[b,a] = butter(1,0.0156,’low’); % low pass filter to remove
nterm_i = 0; % double frequency component
dterm_i = 0;
nterm_q = 0;
dterm_q = 0;

n_sym = 10; % number of symbols
fs = 12.8e6;
t = 0:1/fs:100e-6 – 1/fs;
fc = fs/8; % carrier freuency
theta = 70*pi/180; % phase offset
r = 0.1e6; % symbol rate
oversamp = fs/r;
sym = randint(n_sym,1)*2-1;
in = 0;
for ind=1:1:n_sym
tmp(1:oversamp) = sym(ind);
in = [in tmp];
end
tx = in(2:end);
tx_carrier = cos(2*pi*fc*t + theta);

tx_out = tx.*tx_carrier;

% first order pll
alpha = 0.05;
phiHat = 0;

for ii = 1:1:length(t)

% Remove carrier
rx_i(ii) = tx_out(ii)*cos(2*pi*fc*t(ii) + phiHat);
rx_q(ii) = tx_out(ii)*sin(2*pi*fc*t(ii) + phiHat);

% low-pass IIR filter for I-channel
iir_in_i(ii) = rx_i(ii);
iir_out_i(ii) = b(1)*iir_in_i(ii)+ nterm_i + dterm_i;
nterm_i = b(2)*iir_in_i(ii);
dterm_i = a(2)*iir_out_i(ii);

% low-pass IIR filter for Q-channel
iir_in_q(ii) = rx_q(ii);
iir_out_q(ii) = b(1)*iir_in_q(ii)+ nterm_q + dterm_q;
nterm_q = b(2)*iir_in_q(ii);
dterm_q = a(2)*iir_out_q(ii);

% demodulating circuit
xHat = 2*(iir_out_i(ii)>0) -1 ; % symbol estimate
phiHatT =angle(conj(xHat)*rx_i(ii)); % phase error estimate angle(iir_out_i(ii) + i*iir_out_q(ii));%

% accumulation
phiHat = alpha*phiHatT + phiHat; % phase accumulator output
% dumping variables for plot
phiHatDump(ii) = phiHat;
end

plot(phiHatDump*180/pi,’-’);

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