Noncircularity of Demodulated Radar Signal

The output of the quadrature demodulator is generally regarded as a complex signal that is circular if only the demodulator is well balanced. In the paper we analyze properties of quadrature demodulators, particularly digital one, and show that the output is noncircular also if the input signal is nonstationary. Then we find sources of this noncircularity and show that they stem from transients of the low-pass demodulator filter. This is quite important because nonstationary inputs are quite typical in radar where power of echoes depends strongly on range. In the first sections we also review complex random signals and properties of circularity and properness

On the ambiguity function for accelerating target in FMCW radar, Journal of Telecommunications and Information Technology, 2007, nr 1

In the paper, we are concerned with FMCWradar detection of an accelerating target, echo of which is buried in an additive white Gaussian noise. We derive and analyze three-dimensional generalized ambiguity function for target range, velocity and acceleration. We interpret known properties of this function and obtain new ones, which allows us to specify resolutions and regions of unambiguity for range, velocity and acceleration. The obtained resolutions we express in terms of corresponding Cramer-Rao bounds