Application Of Frequency Domain Interference Suppression Algorithm In High Precision GNSS Surveying Receivers

At present, there are four independent satellite navigation systems in the world, which are called the Global Navigation Satellite System(GNSS). The Chinese Bei Dou Satellite Navigation System has been established and put into use since the end of 2012. With more than one GNSS, the user can not only use more satellites, but also receive signals from multiple frequencies. The utility of multi-system is an effective method to improve the position accuracy and reliability. GNSS can be used for navigation, time transfer and survey. High precision measurement technology has increasing application areas, however, there are many electromagnetic interferences in the practical working environment, among which the narrowband interference is commonly observed. The frequency-domain interference suppression techniques are simple to implement and is usually adopted to eliminate the narrowband interference. Therefore, an approach of frequency-domain anti-jamming algorithm with a threshold for interference detection is employed and applied to a GNSS surveying receiver, and the validity of the selected approach is verified by simulation and receiver test in this thesis.First, the principle of the frequency domain anti-jamming algorithm is investigated. The characteristics of the various components of the algorithm are analyzed, including overlap structures, window features, time-frequency domain transformations and etc. The N-sigma algorithm and the simplified interference suppression algorithm are compared and investigated, after which the design parameters of each part of the proposed algorithm are determined. The correlation of signal and interference are analyzed via simulations. Interference signals of different types are generated, such as continuous waves, sweep waves, narrowband noise and etc. The input signal to the anti-jamming algorithm is composed of the desired signal, additive white Gaussian noise and these different interferences. The adopted anti-jamming algorithm is used to remove these interferences from the input signal, and the correlation change of the remaining signal is analyzed. Then, the tracking loop model is generated to track the remaining signal after interference elimination. The standard deviations of the PN code phase error and the carrier phase error are calculated, and the measurement accuracy is analyzed under different interference conditions. In the end, the frequency domain anti-jamming algorithm is implemented in a GNSS surveying receiver. This thesis proposes a solution for the problem of resource and power consumption constraints. An anti-interference test under a zero baseline condition is conducted to the receiver with the proposed algorithm. The effects of interference suppression with a fixed signal level and different interference types are tested. The impact on the receiver’s pseudorange and carrier range measurement accuracy is analyzed. The test results and analysis show that the frequency domain anti-jamming algorithm can suppress different interferences with a fixed signal level, but the measurement accuracy and baseline solution results of the receiver is effected differently. Under the test condition, the affected results still meet the accuracy requirement. Therefore, the selected approach of frequency-domain anti-jamming algorithm can be applied to a GNSS surveying receiver.