Noise Figure Verification and Optimization of an Undersampled Software Defined Radio Based Radar Receiver for a Phased Array Radar System
This paper aims to study practical applicable measurement and optimization methods of the noise figure of an undersampled radar receiver including the influence of aliasing caused by the analog-digital-conversion and the followed digital signal processing. For this, a measurement method is implemented that regards the convolution of noise components from adjacent frequency bands into the useful band which occurs through a weak band-limiting analog filter. A comparison with the common Y-Factor-Method noise figure measurement method for only the analog front-end is made and it is shown why this method is not suitable for undersampled systems. The results have shown that the weak slope steepness of the used analog bandpass filter leads to a degradation of the noise figure in the upper half of the receiving frequency band that could not be determined by common measurement methods.