Optimal path-control for dual-frequency overlay GNSS receivers

Abstract

This paper presents a general overlay based front-end architecture that enables the joint reception of two signals broadcast in separate frequency bands, sharing just one common baseband stage. The consequences of this overlay in terms of signal quality are analyzed and it is shown that the noise floor superposition results in non-negligible signal degradations. However, it is also demonstrated that these degradations can be minimized by judiciously setting the relative gain between the two signal paths. As an illustration, the analytical optimal path- control expression to combine overlayed signals in an ionospheric- free pseudorange is derived for both Cramer-Rao Lower Bound and practical code tracking parameters

An integrated overlay architecture based multi-GNSS front-end

“…Using an appropriate power control before the overlay, the overlay noise can be controlled and at least partly mitigated as explained in [11]. Moreover, due to the overlay, jammers present in one frequency band also impact the other, previously undisturbed, frequency band.…”

“…This method was described in [11]. Moreover the SPI controller can be used to enable different power down features.…”

“…The digital core not only allows an effective debugging and testing of the chip, it also gives to the GNSS receiver the possibility to modify or control the front-end hardware according to its environment e.g. switching off one path if a severe interferer is detected or controlling the combiner gain values to minimize the overlay loss as described in [11].…”

Galileo E1 and E5a Link-level Performance for Dual Frequency Overlay Structure

“…This RFI is likely to affect only one of the two frequencies, thus receiving the signal through dual frequency may enhance the results. Indeed, the frequency diversity will provide better robustness against interference since one signal band may still be used while the other is jammed [2]. In addition, two frequencies can be used to correct the ionosphere error if the higher order effects are ignored, so that a higher positioning accuracy can be provided.…”

“…One well-known concept to reduce the complexity is to share the same front-end components and to use one common baseband stage [2] [4]. In this method, two signals will be combined before the common baseband stage as shown in [2].…”