Determining linearity of wideband FMCW-systems based on low-cost Six-Port technology

This paper describes a new method for high accuracy determination of instantaneous frequency and linearity of frequency modulated continuous wave systems. The presented setup reduces the frequency measurement to a phase measurement based on Six-Port interferometer with a delay line. To extend the range of possible input frequencies and power levels, a calibration method and the appropriate correction algorithm is introduced. Evaluation of linearity and frequency of the input signal is obtained without the use of computationally intensive Fourier transform which allows the signal processing based on low-cost micro-controllers.