Research Of High Dynamic Vector GPS Receiver’s Tracking Algorithm And Implemention

With the development needs of the defense and military, the dynamics of missiles, fighter planes and other advanced weapons is increasing, which makes traditional GPS receiver can no longer do positioning and navigation work, and must be improved. Under high dynamic environment, due to the big relative velocity and its rate between the receiver and satellite, the received GPS signal will contain a big Doppler frequency shift and its rate of change. If the traditional structure and algorithms are used to track the signal, it must increase loop bandwidth to remain locked. But this would increase the loop noise which can also cause the tracking loop losing lock. If you do not increase the loop bandwidth, carrier Doppler frequency shift often exceeds the loop’s tracking range, which will also result in a loop losing lock. Aiming at the satellite positioning problem under the conditions of high dynamic, this paper designed of new receiver structures and algorithms, mainly including carrier tracking based on immune particle swarm optimization particle filter and vector-based structure of pseudo-code tracking.First, the carrier loop tracking algorithm design. Carrier tracking problem under high dynamic environment is actually can be understood as the estimation of the GPS carrier’s frequency and the frequency’s first and second derivative. Under high dynamic conditions, these carrier parameters not only change relatively fast, but also have a strong nonlinearity. Foregoing considerations, the particle filter method which adapts to non-linear systems is proposed to estimate the carrier’s four parameters. However, due to the particle filter is prone to exist particle degradation and sample dilution, the paper proposes immune particle swarm optimization particle filtering algorithm to improve it. The new algorithm can avoid the particle filter’s problem. It can dynamically adjust loop bandwidth according to the user’s motion state, and is not limited by the nonlinearity and flicker noise problems. So it is possible to better tracking on the carrier signal of the high dynamic.The second is the design of the pseudo-code tracking methods. The pseudo-code’s frequency is lower than the carrier’s, and can be assisted by carrier loop. Therefore it has a small nonlinearity and subjects to the impact of high dynamic weakly. However, traditional code loop ignores the correlation of each satellite channel, so there is no interaction between channels. This paper design a vector delay locked loop, VDLL, to track the C/A code. The difference between vector structure and the traditional structure is that each channel is no longer self-loop, but passing the observed pseudoranges and pseudorange rates directly to the navigation filter module, and then get each channel’s control amount for pseudo-code NCO. The benefit of such a structure is the full use of the correlation of the respective channels, information is more sufficient, and the estimated control amount is more accurately. But channels under this structure may be too closely associated and are relatively fragile. This paper proposes optimizing the available satellite combination by monitoring the satellites’ signal quality, elevation and geometric distribution, so it can improve positioning accuracy, and avoid seriously incorrect positioning results.Finally, use traditional methods and vector based GPS receiver designed in this paper to process simulated data and real collection data. The simulation results are compared and analyzed. The results show that the designed method has a dynamic resilience enhancement than the traditional one, and the positioning error also decreases, which proves the validity of the receiver tracking algorithms designed in this paper.