Fourier coefficients for range identification in FMCW radar systems
Shel D. Dalton · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1999
Frequency-modulated continuous wave radar systems have been used for many years to determine range and velocity in a wide variety of military and commercial applications. The modulation waveform can be sinusoidal, triangular or sawtooth. Each form has its advantages, but, since the triangular and sawtooth modulation can be approximated with a sinusoidal modulation, the analysis in this paper will concentrate on sinusoidal modulation. For moving targets, the envelope of the signal used for determining the Doppler frequency is a function that varies according to the range. If the mixing is performed with a sine wave that is the nth multiple of the modulation frequency, then the envelope is an nth-order Bessel function that varies according to the range. These envelopes can be used on their own to determine range based on tabulated values of the Bessel function. A second approach is to use the difference between two Bessel functions of different orders to identify a certain range. The choice of Bessel functions depends on the carrier frequency and the target range. Amplifiers can be used to modify the identification range.