A direct-sampling receiver for synthetic thinned array radiometry

As analog-to-digital converter technology improves, direct RF sampling is emerging as a suitable architecture for radiometer systems. A digital front-end replaces the mixer stage found in a conventional receiver. The digital signal chain is immune to gain fluctuations and spurious noise sources which arise in analog systems. Direct-sampling is also a forerunner in the evolution of an integrated digital receiver for Synthetic Thinned Array Radiometry (STAR). The authors are developing a digital L-band direct-sampling radiometer to verify /spl Delta/T sensitivity predicted by statistical models. Less than 0.1 K sensitivity is possible at 1.4 GHz by using a 2-bit quantization scheme. Signal coherence is maintained due to the low phase noise characteristics of the A/D converter, making this technique ideal for aperture synthesis.