Behaviour of ADC nonlinearities in multichannel antenna array digitiser systems

Abstract

With the wide use of analogue to digital converters (ADCs) in multi channel array applications, their nonlinearity effects on array performance is of great interest. This paper examines the behaviour of ADC nonlinearities in multi channel arrays, with particular emphasis on the mechanisms that lead to an improvement in the effective spurious free dynamic range (SFDR). The paper reviews some previously published work, and provides some important extensions. These include the consideration of the effect of distinct array channel nonlinearities with memory. The paper illustrates that the spatial dimension provided with multi channel array digitisers allows the nonlinear distortion products to be separated from the signals of interest, and makes it possible for the apparent SFDR to increase. Further, the paper explains how the SFDR improvement is dependent on the nonlinearity characteristics, including the degree of similarity between the array channel nonlinearities, and the presence of memory.