| Nowadays, with the rapid development of global navigation satellite system(GNSS), which not only brings great convenience to people's life, but also is an important symbol of a country's comprehensive national strength and international status. GNSS spatial signal is an important part of GNSS, whose quality is the most important condition to guarantee the normal operation of navigation receiver. USA and Europe have built relatively GNSS signal quality monitoring system, which has played an important role in test, operation and quality assurance process of GPS and Galileo. China is currently building Beidou system, so there is an urgently need to conduct in-depth study of signal quality assessment whether in orbit test or the long-term quality monitoring process.This paper focuses on two aspects of GNSS signal quality assessment: firstly, based on the GNSS signal system and analysis of baseband signal, a set of signal index which is closely related to navigation performance is studied and an assessment framework is built. Then, for GNSS signal at low SNR, high-resolution waveform reconstruction technique is proposed, thus its index value can be accomplished in complex environment where the noise interference is large. The main contents can be summarized as follows:(1) The signal quality evaluation index of current signal quality assessment method is very complex. In order to monitoring the abnormal signal, the signal quality evaluation system proposed in the paper includes the index of time domain, frequency domain, modulation domain and related domain and so on, which involves more information.(2) Without large-aperture and high-gain antenna, navigation signal received by the ground is submerged in the noise. In order to reproduce the signal waveform characteristics, a navigation baseband signal waveform reconstruction technology is proposed, which can accomplish the recovery of baseband signal waveform farthest, so that extraction of signal quality index value can be done at low SNR. |
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