Haystack Radar
Haystack Radar
Haystack Radar
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Resolving Doppler<br />
Tx signal: cos(2πf o t)<br />
Doppler shifted: cos[2π(f o + f D )t]<br />
Multiply by cos(2πf o t) -> Low pass filter -> cos(2πf D t)<br />
BUT, the sign of f D is lost (cosine is an even<br />
function)<br />
So, instead use<br />
exp(j2πf D t) = cos(2πf D t) + jsin(2πf D t)<br />
Generate this signal by mixing cos and sin via two<br />
oscillators (same frequency, 90 o out of phase)<br />
<strong>Haystack</strong> 2003-23<br />
AJC 7/20/11<br />
Components are called I (In phase) and Q<br />
(Quadrature): Aexp(j2πf D t) = I + jQ<br />
MIT <strong>Haystack</strong> Observatory
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