In this paper, a new signal processing based methodology is suggested in order to measure the load impedance with high accuracy and resolution. This methodology is characterized by a chirp signal with Gaussian envelope which enables one to achieve time localization and to assign energy in the frequency band of interest. A normalized time-frequency cross correlation function is utilized to evaluate the reflection coefficient, and a cross time-frequency distribution function is used to acquire the phase difference between the input and the reflected signals. In this paper, the real experiments are achieved on a coaxial cable which is the typical transmission line in the electrical wiring system by using the time-frequency domain reflectometry (TFDR) system and terminal resistors to verify the performance of the suggested methodology. The experimental results of the TFDR based impedance measurement are compared with those of the commercial time domain reflectometry (TDR) system.