Accurate delay tracking in multipath environments is one of the prerequisites of modern GNSS receivers. Several solutions have been proposed in the literature, both feedback and feedforward. However, this topic is still under active research focus, especially for mass-market receivers, where selection of lowcomplexity, nonpatented methods is preferred. Among the most encountered delay tracking structures implemented in today's receivers, we have the narrow correlator and the double-delta correlators. Both are heavily covered by various patents. The purpose of this paper is to introduce a new, generic structure, called multiple gate delay (MGD) structure, which covers also the patented correlators but offers much more flexibility in the design process. We show how the design parameters of such a structure can be optimized, we argue the performance of this structure via detailed simulation results based on various simulators, such as Matlab/Simulink-based tool, GRANADA, and we test the implementation feasibility of MGD structures on actual devices, via SystemC and FPGA prototyping. One of the main advantages of the proposed structure is its high degree of flexibility, which allows the designer to choose among, to the authors' knowledge, nonpatented solutions with delay tracking accuracy comparable with that of the current state-of-art trackers.
The Cutting edge Reconfigurable ICs for Stream Processing (CRISP) project aims to create a highly scalable and dependable reconfigurable system concept for a wide range of tomorrow's streaming DSP applications. Within CRISP, a network-on-chip based many-core stream processor with dependability infrastructure and run-time resource management is devised, implemented, and manufactured to demonstrate a coarse-grained core-level reconfigurable system with scalable computing power, flexibility, and dependability. This chapter introduces CRISP, presents the concepts, and outlines the preliminary results of a running project.
This paper demonstrates the effect of radio frequency (RF) front-end (FE) free-running local oscillator (FRO) phase noise (PN) on the phase component of the Global Navigation Satellite System (GNSS) code correlation product. It is observed that as FE PN increases, it adversely affects the stability of the phase component of the code correlation. The tracking loops in baseband processing of a GNSS receiver attempt to lock on to the frequency, delay and phase of the correlation product. Until these parameters are varying within acceptable bounds, set by the dynamics handling capability of the tracking loops, the tracking loops are able to successfully track the satellite signal. However, PN increases the variation in phase of the correlation product calculated over consecutive epochs and may also cause loss of tracking lock if these variations go beyond phase locked loop (PLL) pull-in range thresholds. This paper studies the relation between FRO PN and phase component of correlation through numerical analysis, and software simulations by artificially contaminating GNSS signal stream with PN of increasing variance and checking the result on the standard deviation (SD) of the phase component of correlation product. Based on these results, this paper recommends certain maximum limits on the FE PN in order to keep the SD of phase component below the onesigma phase error limits of the PLL used in typical GNSS tracking loops.
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