cordic_mixer.m

FPGA可实现的

function [Xout,Yout] = CORDIC_mixer(Sn,theta)
% CORDIC algorithm used in NCO and DDC
%  Sn : input signal
%theta: the phase of the cosine and sine wave
% Ir: output signal for I arm after mixer
% Qr: output signal for Q arm after mixer

N_cordic=16;
K_cordic=1;
word_length=12;
for k=0:N_cordic-1
    K_cordic=K_cordic/sqrt(1+0.25^k);
end
x0=K_cordic*Sn;   % when mixing with input signal s(n),x0=s(n)
y0=0;
while(theta>pi||theta<-pi)
    if(theta>pi)
        theta=theta-2*pi;
    else
        theta=theta+2*pi;
    end
end
z0=theta;
    if(z0>0)
        d0=1;
    else
        d0=-1;
    end
        x(1)=0;
        y(1)=x0*d0;
        z(1)=z0-d0*pi/2;
        for i=1:N_cordic
            if(z(i)>=0)
                d(i)=1;
            else
                d(i)=-1;
            end
            x(i+1)=x(i)-d(i)*y(i)*2^(-(i-1));
            y(i+1)=y(i)+d(i)*x(i)*2^(-(i-1));
            z(i+1)=z(i)-d(i)*atan(2^(-(i-1)));
        end
        Xout=x(N_cordic+1);% cos
        Yout=y(N_cordic+1);% sin

    Ir= round(Xout*(2^word_length-1));
    Qr= round(Yout*(2^word_length-1));