A Multi-antenna GNSS-over-fiber System with High Vertical Precision

A novel multi-antenna global navigation satellite system over fiber (GNSS-over-fiber) system with real-time microwave-photonics-based fiber-length-difference monitoring is proposed. In the architecture, GNSS signal transmission from two or more remote antennas to the local processing center is realized based on radio-over-fiber techniques. A novel microwavephotonics-based fiber length measurement scheme is applied to compensate the line bias delay between different GNSS channels due to the fiber-length variation. Then the carrier phase single difference (SD) algorithm, instead of the carrier phase double difference (DD) algorithm, can be used to improve the vertical precision of multi-antenna GNSS system. Experimental results show that the vertical positioning precision with SD algorithm is about 1.3 mm which is 3.15 times better than that with DD algorithm. Meanwhile, the horizontal positioning precision is about 1.5 mm which is on the same level compared with the system with DD algorithm.