Ch 29.rar_lte positioning_positioning_positioning lte

%-------------------------------------------------------------------------- % Example 3: Serial search acquisition algorithm. Matlab code % Author: Marco Pini, Istituto Superiore Mario Boella %-------------------------------------------------------------------------- clear all; close all; clc Rc = 0.5e6; % Code Rate [chip/s] Fs = 8e6; % Sampling Frequency [Hz] Fc = 2e6; % Carrier Frequency [Hz] c_loc = [1 -1 1 -1 -1 -1 -1 1 -1 ... 1 -1 -1 -1 1 -1 -1 1 1 1 -1]; % PRN code L = length(c_loc); % Code Length [chip] N = floor(Fs*L/Rc); % Code Length [samples] % --------- Generate the incoming signal, with 3 periods of c_loc --------- c_in = [c_loc c_loc c_loc]; % sample the spreading codes k = 0:3*N-1; c_in_sampled = c_in(floor(k*Rc/Fs)+1); % c_in code sampled @ Fs D = 4*Fs/Rc; % code delay [samples] sigma = 0.5; % modulate the spreading code sampled @ Fs and add noise c_in_sampled_noise = circshift(c_in_sampled,[0 D]).*cos(2*pi*Fc.*k/Fs) ... + (sigma)*randn(1,3*N); % ------------------------------------------------------------------------- % ----------------------- Generate the local code ------------------------- k = 0:N-1; % samples vector c_loc_sampled = c_loc(floor(k*Rc/Fs)+1); % c_loc code sampled @ Fs % ------------------------------------------------------------------------- for idx_freq = 1:10, fd = Fc-50e3 + 10e3*idx_freq; % local carrier frequency [Hz] loc_cos = cos(2*pi*fd.*k/Fs); % In-phase local carrier loc_sin = sin(2*pi*fd.*k/Fs); % Quadrature local carrier % prepare the local signal, multipling local code and carriers Loc_cos = c_loc_sampled.*loc_cos; Loc_sin = c_loc_sampled.*loc_sin; for idx_shift = 0:N-1, % correlate incoming and local signals Corr(idx_freq,idx_shift+1) = ... (c_in_sampled_noise(1+idx_shift:N+idx_shift)*Loc_cos').^2 + ... (c_in_sampled_noise(1+idx_shift:N+idx_shift)*Loc_sin').^2; end end % plot correlation functions x_axis = [0:(N-1)]./Fs.*Rc; % Prepare x-axis [chip] y_axis = Fc-5e3 + 1e3.*[1:10]; figure(1), surf(x_axis,y_axis,abs(Corr));%, shading shading, xlabel('Delay [chip]') ylabel('Freq [MHz]') title('Cross Ambiguity Function')