What is Skew?

Skew is defined as the difference in propagation delay between two or more signal paths.

Skew is of greatest concern  between two conductors of a differential pair.

If both path lengths aren’t matched precisely, skew in a  differential pair can lead to  increased Insertion Loss, Impedance Mismatch, Crosstalk and EMI.

Low skew between multiple paths can be important in a parallel bus.


http://www.sabritec.com/technotes/PDF/High_Speed_Digital_Tutorial.pdf

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What is Nyquist Frequency?

http://www.dnr.state.oh.us/tabid/8170/Default.aspx

Nyquist Frequency

The Nyquist frequency is the bandwidth of a sampled signal, and is equal to half the sampling frequency of that signal. If the sampled signal should represent a continuous spectral range starting at 0 Hz, the Nyquist frequency is the highest frequency that the sampled signal can unambiguously represent.

Example

If a signal is sampled at 22050 Hz, the highest frequency that can be expected to be present in the sampled signal is 11025 Hz. Thus, to attain this expectation, the continuous signal should be run through a low-pass filter with a cut-off frequency below 11025 Hz; otherwise, the phenomenon of aliasing would be encounterd.

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Data Communications Class Notes

http://www.okstate.edu/elec-engr/scheets/ecen4533/

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FFT komutu kullanarak matlabda basit DFT

clear all;
for n =1:20,
    sign1(n)=0.5*cos(2*pi*n/10); % transfer edilecek sinyal
end

XK(1:20)=0;
for k =1:20
    for n=1:20
    XK(k)=XK(k)+sign1(n)*exp(-j*2*pi*n*k/20); %matrisle transfer et
    end
end

%using fft command
XK2=fft(sign1,20); %fft komutu kullanarak transfer et
XK2(1)=[];
stem(XK); %cizdir
plot();
stem(XK2) %cizdir

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Great Windows tools

http://rainmeter.net/cms/Final25
http://www.infoworld.com/d/applications/top-15-free-tools-every-windows-desktop-063?page=0,0
Microsoft synctoy 2.1

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Good practical source on antennas

http://wndw.net/pdf/wndw2-en/ch04-antennas.pdf

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Simple DFT using FFT command in matlab

clear all;
for n =1:20,
    sign1(n)=0.5*cos(2*pi*n/10); %sinal to convert, f=10 Hz
end

XK(1:20)=0;
for k =1:20
    for n=1:20
    XK(k)=XK(k)+sign1(n)*exp(-j*2*pi*n*k/20); %convert with math
    end
end

%using fft command
XK2=fft(sign1,20); %convert with command
XK2(1)=[];
stem(XK);
plot();
stem(XK2)

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