Event Details
Brightness Distribution Errors in Synthetic Aperture Systems due to Perturbations in Receiver Transfer Functions
Presenter: Chamira Edussooriya
Supervisor: Dr. Len Bruton and Dr. Pan Agathoklis
Date: Thu, August 2, 2012
Time: 13:00:00 - 00:00:00
Place: EOW 430
ABSTRACT
ABSTRACT
The transfer functions of receivers employed in typical synthetic aperture systems are slightly mismatched due to small random perturbations of circuit parameters. To gain insight regarding effects of these perturbations on the performance of synthetic aperture systems, brightness distribution (BD) errors caused by perturbed receiver transfer functions are theoretically and numerically analyzed. In the theoretical analysis, the BD errors caused by perturbations in the transfer functions of low noise amplifiers (LNAs) and anti-aliasing filters (AAFs) are considered, and the characteristics of the additive BD error and its effects on synthesized BDs are thoroughly analyzed. Second, the conditions that should be satisfied by the transfer functions of digital beamformers to eliminate the BD errors caused by their phase responses are examined. The sufficient condition to eliminate these BD errors is that the transfer functions of digital beamformers are matched, and, interestingly, the phase responses are not necessary to be linear.
In the numerical analysis, the BD errors caused by typical tolerances of passive L and C elements used to implement the AAFs and those caused by the random variations of gain from LNA to LNA are quantified through simulations. The percentage error of the synthesized BDs with the perturbed AAFs is substantial at frequencies near the passband edge of the AAFs. The percentage error due to the random variations of the gains of the LNAs is moderate throughout the interested bandwidth.