Seasat – Technical Challenges – 8. Focusing Challenges
In modern systems, synthetic aperture radar (SAR) echoes are sampled in a complex fashion using IQ-demodulation. The I and Q components are samples of the same signal that are taken 90 degrees out of phase. Separating I and Q in this way allows measurement of the relative phase of the components of the signal, and is a requirement for the SAR focusing algorithm. The Seasat platform used an older method to sample echoes, storing real (not complex) returns in offset video format.