With the growing electromagnetic traffic, Electronic Warfare (EW) systems need to be accurate or use new characterizing parameters in order to discriminate at best radar pulses. An accurate study of the Instantaneous Frequency Law (IFL) and Rate (IFR) offers some new opportunities. Multi-linear methods such as the Highorder Ambiguity Function (HAF) or any General Representation of Phase Derivatives (GRPD) are often used to estimate those parameters but not in an EW context. In this article, we first describe conditions for which those modulations can be estimated. Then, HAF and GRPD are studied in an EW context and their performances are compared to Cramer-Rao Bounds (CRB) to find the most appropriate one.