Plotting sin (x/x) function in terms of Mag(dB) over Frequency

x=linspace(-20,20);
y= sin(x)./x;
y1 = (10*log(y));
plot(x,y1,'-')

Warning: Imaginary parts of complex X and/or Y arguments ignored.

This is currrently the code i have running but not getting the resulting sin x/x plot, but more so a rectified version of it. i also wanted some help in changing the x axis from linear to frequency(preferably in rad/s), similar to how i changed y from linear to dB.

the sin x/x plot work when using just "plot(x,y)" but now when trying to change the axis to dB and Freq.

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Answer 1

[Paul]

Hi IFECHUKWU,

sin(x)/x can take on negative values, for example

x = 5*pi/4;
sin(x)/x

ans = -0.1801

Taking the log10 (as neeed for dB, not log) of a negative number yields a complex result

log10(ans)

ans = -0.7446 + 1.3644i

Not sure what kind of plot is expected after converting the result dB.

[IFECHUKWU IKE-ORJI]

my question was a bit unclear as i was referring to dBm not dB, so you would be right resulting the sin (x/x) waveform being rectified