Design And Verification Of Built-In If Data Record And Playback Function In Gnss Receivers

GNSS signal simulators can generate many ideal scenarios, but they are difficult to accurately model a specific realistic scenario for a real existed complex environment. Therefore it is required to record and playback the real signals (RF or IF) to debug the receiver performance in the realistic and comprehensive scenarios. This paper proposes a scheme of GNSS receiver with built-in IF data record and playback (RP) function. The system architecture and the design structure of software and hardware are described. The built-in RP function was designed to be independent and compatible with the GNSS receiver; the data format of IF signal (e. g. data rate and bit width) was designed to be flexible; the IF data high-speed transmission scheme was optimized to guarantee the continuity and stability. The built-in RP function was verified by comparing the IF playback results with the real-time live results of the receiver. Results indicate that: the maximum recording speed in real-time continuous IF data transmission can reach no less than 208Mbps; if the playback format is the same as the live-receiver's, the average difference of the carrier noise ratio (CNR) is less than 0.15dB, where the sampling rate and bit width have some influence on CNR. The positioning results in GNSS receiver's playback and live working are almost the same. Compared to the existing dedicated RP systems, the proposed built-in RP function shares the same RF front-end module with the receiver, and therefore gain the advantages of more real playback IF signal, cost-saving, and convenience to use. The built-in RP adds no hardware cost and limited software expense to the receiver. It is a promising value-added function of GNSS receivers, especially for the professional products. Furthermore, this work sets the stage for the IF RP design of GNSS/ INS deep integration systems, where the signal playback is a necessary function.