all_files.zip_BLUTOOTH_bluetooth_gfsk bluetooth_gfsk解调_matlab

function bitstream = symbolDecision(Isig,Qsig,type) % Symbol Decision / detection of symbols and output the bits. % Usage: bitstream = symbolDecision(Isig,Qsig,type) % Isig and Qsig: The in-phase and quadrature signals (should be % down-converted and samplerate converted). % type: modulation scheme % bitstream: the detected bitstream fs = 4e6; % sample frequency of input signal Ts = 1/fs; % sample time T = 1e-6; % symbol time L = length(Isig); Nsymbols = L*Ts/T; % number of symbols in input signal bitstream = []; %%%% QPSK %%%% if type == 1 start = 1; for idx=1:Nsymbols final = start+T*fs-1; % calculate angle in the middel of a sample period cc = Isig(round(median(start:final))) + j*Qsig(round(median(start:final))); phi = angle(cc); start = final+1; % which of the elementary angles is phi closest to? phitest(1) = abs(pi/4 - phi); phitest(2) = abs(3*pi/4 - phi); phitest(3) = abs(-3*pi/4 - phi); phitest(4) = abs(-pi/4 - phi); [phimin, phiIdx] = min(phitest); % append the bitstream switch phiIdx case 1, bitstream = [bitstream 0 0]; case 2, bitstream = [bitstream 0 1]; case 3, bitstream = [bitstream 1 1]; case 4, bitstream = [bitstream 1 0]; end end end % type == 1, QPSK %%%% DQPSK %%%% if type == 2 oldphi = 0; start = 1; for idx = 1:Nsymbols final = start+T*fs-1; % calculate angle in the middel of a sample period cc = Isig(round(median(start:final))) + j*Qsig(round(median(start:final))); phi = angle(cc); deltaphi = phi - oldphi; % the angle change % make sure that deltaphi lies between -pi and pi if deltaphi > pi; deltaphi = deltaphi - 2*pi; elseif deltaphi < -pi deltaphi = deltaphi + 2*pi; end % which of the elementary angles is deltaphi closest to? phitest(1) = abs(pi/4 - deltaphi); phitest(2) = abs(3*pi/4 - deltaphi); phitest(3) = abs(-3*pi/4 - deltaphi); phitest(4) = abs(-pi/4 - deltaphi); [phimin, phiIdx] = min(phitest); % append the bitstream switch phiIdx case 1, bitstream = [bitstream 0 0]; case 2, bitstream = [bitstream 0 1]; case 3, bitstream = [bitstream 1 1]; case 4, bitstream = [bitstream 1 0]; end oldphi = phi; % store the old angle start = final+1; end end % type == 2, pi/4-DQPSK %%%% 8DPSK %%%% if type == 3 oldphi = 0; start = 1; for idx = 1:Nsymbols final = start+T*fs-1; % calculate angle in the middel of a sample period cc = Isig(round(median(start:final))) + j*Qsig(round(median(start:final))); phi = angle(cc); deltaphi = phi - oldphi; % the angle change % make sure that deltaphi lies between -pi and pi if deltaphi > pi; deltaphi = deltaphi - 2*pi; elseif deltaphi < -pi deltaphi = deltaphi + 2*pi; end % which of the elementary angles is deltaphi closest to? phitest(1) = abs(0 - deltaphi); phitest(2) = abs(pi/4 - deltaphi); phitest(3) = abs(pi/2 - deltaphi); phitest(4) = abs(3*pi/4 - deltaphi); phitest(5) = abs(min(pi - deltaphi,pi + deltaphi)); % extra check if deltaphi is exactly -pi or pi phitest(6) = abs(-3*pi/4 - deltaphi); phitest(7) = abs(-pi/2 - deltaphi); phitest(8) = abs(-pi/4 - deltaphi); [phimin, phiIdx] = min(phitest); % append the bitstream switch phiIdx case 1, bitstream = [bitstream 0 0 0]; case 2, bitstream = [bitstream 0 0 1]; case 3, bitstream = [bitstream 0 1 1]; case 4, bitstream = [bitstream 0 1 0]; case 5, bitstream = [bitstream 1 1 0]; case 6, bitstream = [bitstream 1 1 1]; case 7, bitstream = [bitstream 1 0 1]; case 8, bitstream = [bitstream 1 0 0]; end oldphi = phi; % store the old angle start = final+1; end end % type == 3, 8DPSK %%%% GFSK %%%% if type == 4 start = 1; for idx = 1:Nsymbols final = start+T*fs-1; for frek = 1:2 % for each frequency inti = sum(Isig(frek,start:final)); % integrate in symbol period intq = sum(Qsig(frek,start:final)); sumIQ(frek) = inti^2 + intq^2; % Squared and summed end compare = sumIQ(1) - sumIQ(2); % append the bitstream if compare >= 0 bitstream = [bitstream 1]; elseif compare < 0 bitstream = [bitstream 0]; end start = final + 1; end end % type == 4, GFSK