Deep Coupled Integration of CSAC and GNSS for Robust PNT

Abstract

Global navigation satellite systems (GNSS) are the most widely used positioning, navigation, and timing (PNT) technology. However, a GNSS cannot provide effective PNT services in physical blocks, such as in a natural canyon, canyon city, underground, underwater, and indoors. With the development of micro-electromechanical system (MEMS) technology, the chip scale atomic clock (CSAC) gradually matures, and performance is constantly improved. A deep coupled integration of CSAC and GNSS is explored in this thesis to enhance PNT robustness. “Clock coasting” of CSAC provides time synchronized with GNSS and optimizes navigation equations. However, errors of clock coasting increase over time and can be corrected by GNSS time, which is stable but noisy. In this paper, weighted linear optimal estimation algorithm is used for CSAC-aided GNSS, while Kalman filter is used for GNSS-corrected CSAC. Simulations of the model are conducted, and field tests are carried out. Dilution of precision can be improved by integration. Integration is more accurate than traditional GNSS. When only three satellites are visible, the integration still works, whereas the traditional method fails. The deep coupled integration of CSAC and GNSS can improve the accuracy, reliability, and availability of PNT.

Performance Enhancement of GNSS/MEMS-IMU Tightly Integration Navigation System Using Multiple Receivers

“…where, Zρ R i is the pseudo-range rates measurement vector, and the Eρ 1 R i is the relative velocity projected onto a unit Line-Of-Sight (LOS) vector [20], and the D XYZ ENU is the velocity conversion matrix from the E-N-U coordinates to the ECEF (earth-centered-earth-fixed) coordinates. Vρ R i is the pseudorange rate measurement noise, and the Equation (10) is the linearized version of the measurement models, more details are illustrated in the references [23], [24]. Combing the pseudo-range measurement vector and the pseudo-range rates measurement vector, the measurement vector of the MR-TI system is:…”

Research on a chip scale atomic clock driven GNSS/SINS deeply coupled navigation system for augmented performance

“…The CSAC is fabricated using the microelectromechanical systems technique and atom excitation technique, which allows several orders of magnitude higher‐frequency reference than the widely utilised TXCO. The power consumption, size, and cost of the CSAC are considerably improved and definitely better than those of the traditional rubidium atomic clocks [9–15]. In addition, with the commercialisation of CSAC, the atomic frequency reference applications have been extended, especially integrating into portable GNSS receivers.…”

“…As aforementioned, timing is at the core of ranging, measuring and positioning determination in GNSS receivers. Thus, CSAC can enhance the performance of the GNSS receivers including enhanced resistance to jamming and interference [10–12], faster acquisition time [13] and more reliable receiver operation [14–18].…”

Implementation and performance evaluation of a fast relocation method in a GPS/SINS/CSAC integrated navigation system hardware prototype

“…The size, weight, power, and cost of CSAC are considerably better than those of traditional rubidium atomic clocks. CSAC has higher than 10 -10 at 1 s stability [8,9,10,11]. For PNT applications, CSAC can be treated as the time reference and improves timing accuracy.…”