GNSS is the system which gives correct position to user by using received signal from more than four satellites located in the far distance. In the early days of GNSS history, GNSS was only used for positioning for military purposes, but later was open to the public, GNSS is also used for navigation and time synchronization, etc. GNSS is very useful, but as shown above, the GNSS has weakness that satellite signal used in GNSS becomes weaker than thermal noise level when the signal arrives at the earth. Since GNSS signal is vulnerable to interference, a jamming signal has a fatal effect on GNSS. Accordingly, many experts have devised a jamming countermeasure technology. In this paper, the anti-jamming techniques using SVD and FFT are analyzed and compared. Tone Jamming, multi-tone jamming and chirp jamming used often will be considered when the anti-jamming techniques are compared.

Keywords: anti-jamming, SVD, FFT