INS/GNSS ultra-tight coupling based on VDFLL and CaKFPLL

In order to improve GNSS's anti-jamming ability under complex electromagnetic environment, an improved algorithm of INS/GNSS ultra-tight coupling (UTC) based on vector DLL (delay locked loop) and FLL (frequency locked loop) as well as cascade loop filter of phase-locked loop is proposed for low cost guided weapon navigation. The architecture of INS-aided GNSS vector tracking is analyzed, a discriminator-based pre-processing filter for vector tracking is devised to reduce the computational complexity, and an extended Kalman filter for PLL is given. A ballistic trajectory under jamming condition is also designed to test the UTC algorithm. Dynamic simulation test shows that the performance of UTC is better than that of stand-alone high dynamic tracking under interference environment. The UTC can lock GPS L1 C/A signal at J/S level of 48.6 dB which is about 12 dB bigger than stand-alone receiver.