Local oscillator uncorrelated phase noise analysis for millimeter-wave passive imager BHU-2D frequency synthesizer

In this paper, a nontrivial local oscillator uncorrelated phase noise analysis is proposed for frequency synthesizer of a passive millimeter-wave Synthetic Aperture Interferometric Radiometer (SAIR) imager BHU-2D designed for concealed weapon detections on human bodies with high imaging rates. The frequency synthesizer provides local oscillator signals for both millimeter-wave front-ends and intermediate frequency I/Q demodulators for the receivers. The influence of local oscillator uncorrelated phase noise in different offset frequency ranges on the visibility phase errors have been systematically investigated, and the corresponding system-level visibility specifications are drawn. The integrated RMS phase error has been applied to set uncorrelated phase noise requirements in the most critical offset frequency range for visibility error control. The synthesizer design is given, and measurement results have proved that the visibility phase error requirement is achieved by the PN analysis method proposed with system-level visibility error tests performed. To conclude, the phase noise effects on SAIR visibility phase errors are investigated by theory, and are properly limited by the PN requirement analysis method to ensure that the system-level visibility phase error specification is satisfied.