A new phase-shifting interferometry analysis technique has been developed to overcome the errors introduced by nonlinear, irregular, or unknown phase-step increments. In the presence of a spatial carrier frequency, by observation of the phase of the first-order maximum in the Fourier domain, the global phase-step positions can be measured, phase-shifting elements can be calibrated, and the accu...

BACKGROUND Time-resolved three-dimensional, three-directional phase-contrast magnetic resonance velocity mapping (4D PC-MRI) is a powerful technique to depict dynamic blood flow patterns in the human body. However, the impact of phase background effects on flow visualizations has not been thoroughly studied previously, and it has not yet been experimentally demonstrated to what degree phase off...

Uncompensated phase errors present in synthetic-aperture-radar data can have a disastrous effect on reconstructed image quality. We present a new iterative algorithm that holds promise of being a robust estimator and corrector for arbitrary phase errors. Our algorithm is similar in many respects to speckle processing methods currently used in optical astronomy. We demonstrate its ability to foc...

One major problem of phase-referencing VLBI observations are phase errors due to the unknown tropospheric zenith delay at each antenna. These errors degrade the quality of the phase-referenced image and limit the achievable astrometric accuracy. We will present and compare two independent methods to estimate the zenith delay offset at each antenna. The zenith delay offsets can then be used to c...

Based on available GPS reference network observations we developed, implemented and tested a procedure to estimate carrier phase multipath corrections. This procedure consists of three steps: detection and localization of multipath affected satellite signals, daily estimations of multipath errors, and combination of these daily estimates to corrections for undifferenced L1 and L2 phase measurem...

In this paper, a nontrivial uncorrelated phase noise analysis is proposed for frequency synthesizer of a passive millimeter-wave Synthetic Aperture Interferometric Radiometer (SAIR) imager named BHU2D-U designed for concealed weapon detections on human bodies with high imaging rates. This synthesizer provides local oscillators both for millimeter-wave front-ends and intermediate frequency IQ de...

We present a framework for modelling atmospheric phase errors and their correction by both the fast-switching and water vapour radiometeric techniques. Notable features are simulating three dimensional turbulent volumes instead of flat phase screens, considering three representative configurations of ALMA and parametrisation in terms of phase fluctuations on a 300m baseline, allowing referencin...

An arrayed waveguide grating (AWG) at 760 nm is demonstrated with an insertion loss smaller than 0.5 dB. Interface roughness and waveguide length errors contribute much more to scattering loss and phase errors at 760 nm than at longer wavelengths, thus requiring improved design and fabrication. This Letter details how this is achieved by minimizing interfacial scattering, grating side-order exc...