AN84 データシートの表示（PDF） - Silicon Laboratories

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AN84

DIGITAL HYBRID WITH THE Si305X DAAS

Silicon Laboratories 

AN84

%%%%%%%%%% Near end echo (H2)

% Calculate Zline

Zcline=1./(j*2*pi*f*Cline);

Zline=R1line + R2line.*Zcline./(R2line+Zcline);

% Calculate Zref, assume perfect ACT

R1ref=[eps eps 270 220 370 320 370 275 120 350 eps 600 900 900 600 270];

R2ref=[600 900 750 820 620 1050 820 780 820 1000 900 1e9 1e9 1e9 1e9 750];

Cref =[eps eps 150 117 310 230 110 132 110 210 30 2160 1000 2160 1000 150]*1e-9;

Zcact=1./(j*2*pi*f*Cref(Nact));

Zact=R1ref(Nact) + R2ref(Nact).*Zcact./(R2ref(Nact)+Zcact);

C9r=0*1e-9;

Ycact2=(j*2*pi*f*C9r);

Zact=1./(1./Zact + Ycact2);

%%%%%

HL=2*Zline./(Zact+Zline);

HL(1)=0;

% Add extra group delay to match measurements

gde=-0.225;

Hd=-Ht.*Hr.*(HL-1).*exp(j*2*pi/16000*gde*[0:length(Ht)-1]);

Hd=[Hd conj(fliplr(Hd))];

% Estimate impulse response to match

hd=real(ifft(Hd));

% Truncate coefficients and express in [0 255]

hdh=round(hd(5:12)*64);

ind=find(hdh<0);

hdh(ind)=hdh(ind)+256;

echo = Ht.*Hr.*(HL-1).*exp(j*2*pi/16000*gde*[0:length(Ht)-1]);

hyb_coef = [0 0 0 0 hd(5:12)];

dig_hyb = freqz(hyb_coef,1,w);

figure

plot(f,abs(echo),'-',f,abs(dig_hyb),'-.',f,abs(echo+dig_hyb),':')

axis([0 4000 0 0.4])

legend('echo','digital hybrid response','cancelled signal')

8

Rev. 0.6

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