Design of a GPS and Galileo Multi-Frequency Front-End

Cyril Botteron, Frédéric Chastellain, Pierre-André Farine, Enrique Rivera Parada, Youssef Tawk
Ieee Service Center, 445 Hoes Lane, Po Box 1331, Piscataway, Nj 08855-1331 Usa, 2009
Conference paper

Abstract

GNSS platforms such as the American Global Positioning System (GPS) or the Russian GLONASS system are being continuously updated with new satellites offering new signals, new frequencies and new functionalities. Moreover, new GNSS systems such as the European Union’s Galileo system or the Japan’s Quasi-Zenith Satellite System (QZSS) are currently being developed and planned to be in function within a couple of years. Taking advantage of these new signals requires the use of a multi-frequency Radio-Frequency (RF) Front-End (FE). In this paper, we highlight the design of such a FE based on a sub-sampling architecture. Indeed, with the technology advances in the Integrated Circuits (IC) industry, and more particularly the availability of GHz bandwidth analog-to-digital converters (ADC), this is one of the most attractive ways to achieve a multi-frequency FE. While a sub-sampling architecture has already been presented in some other publications [1], [2], we present a methodology that takes into account the effects of the filters characteristics and out-of-band noise. As a practical example, we apply our methodology to the design of a multi-frequency RF FE for the simultaneous acquisition of the GPS L1C; L2C; L5, and Galileo E1b;c; E5a;b signals.

Official source

https://infoscience.epfl.ch/record/148520?ln=en

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The Global Positioning System (GPS) is a trilateration system which allows to compute the position of a receiver from the time the signals need to propagate from the satellites down to the receiver. Since the Selective Availability (SA) was turned off in 2000, the most important source of error is due to the variable delay experienced by the signals when traveling through the ionosphere. Today, the majority of GPS receivers use the L1C/A signal, the only civil signal currently transmitted by a full constellation of satellites, to compute their positions. The United States' GPS is actually only one of several Global Navigation Satellite Systems (GNSS) under development, such as the european Galileo or the Japanese Quasi-Zenith Satellite System (QZSS). In the years to come, the constellations of these new GNSS will be fully deployed, providing new modernized signals. The GPS is actually also being modernized and will provide two new civil signals, the first in the L2 band (1227.6 MHz) and the second in the L5 band (1176.45 MHz), as well as an improved version of the L1C/A signal in the L1 band (1575.42 MHz). The first fully available new civil signal will certainly be the GPS civil signal in the L2 band called the L2C signal. The availability of two civil signals in two different bands will give the opportunity to correct the ionospheric error to a great extent! However, receiving two signals located in different bands will add complexity in the receiver, particularly in the radio-frequency (RF) front-end. This is a major issue since, for the mass market, improved performances do usually not justify a higher power consumption and cost. As a consequence, the first objective of this thesis was to design a low-power dual-frequency RF front-end architecture for the L1C/A and L2C signals that could be integrated using standard CMOS technology and which would have a power consumption and performances comparable with that of state-of-the-art single-frequency GPS RF front-ends. Dual-frequency correction of the ionospheric error will also allow to improve the performances of another application of GPS called GPS timing. Indeed, the GPS provides the most precise time reference globally available anywhere on earth! As a consequence, an attractive solution to synchronize telecommunication networks consists to use the time reference provided by the GPS. However, the accuracy provided by single-frequency GPS receiver will soon not be sufficient anymore to be compliant with upcoming telecommunication standards. For this reason, the second objective of this thesis was the development of a dual-frequency RF front-end for an L1C/A + L2C GPS receiver for timing applications.

EPFL2010

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Global positioning system (GPS) has been demonstrated to be a valid and efficient system for various space applications in low Earth orbit (LEO) and medium Earth orbit (MEO), such as for location determination and time synchronization. However, in highly elliptical and high Earth orbits (HEO), the number of existing space applications is much smaller because of the very weak power of the received signals and the bad geometric dilution of precision (GDOP). To counteract these problems, one method is to add an L5 processing module to the existing L1 C/A receiver module. Indeed, tracking the L5 signal brings several benefits: 1) a higher ranging precision; 2) a pilot channel allowing long integration times, which is helpful for both acquisition and tracking. But this also implies several drawbacks, especially in resource restricted conditions: 1) the length of the fast Fourier transforms (FFTs) and the amount of memory needed for the L5 acquisition module is huge; 2) the acquisition time is very long because of the secondary code and large frequency search space due to the long integration time. In this paper, a cross-band aided acquisition method for the L1&L5 signals is presented, which satisfy the requirements for extremely high sensitive environment without any further assistance. Compared to a traditional architecture that would acquire the L1 and L5 signals sequentially, this method acquires the L1 signal in the first place because its structure is simpler and there is no need to search the secondary code, then uses this information to reduce the code and frequency search space of the L5 signals. This brings huge benefits to the receiver: 1) the resources needed for the L5 acquisition are tremendously reduced; 2) the acquisition time for the L5 signal is considerably reduced. The implementation on an Altera Stratix III FPGA shows that about 7 % of the logic, 18 % of the multipliers and 47 % of the memory can be saved with the proposed method, while the acquisition time is reduced by 99 %.

International Astronautical Federation2014

Nowadays, civil Global Navigation Satellite System (GNSS) signals are available in both L1 and L5 bands. A receiver does not need to acquire independently the signals in both bands coming from a same satellite, since their carrier Doppler and code delay are closely related. Therefore, the question of which one to acquire first rises naturally. Although the common thought would tell the L1 band signals which are narrowband, an accurate comparison has never been done, and the decision is not as easy as it seems. Indeed, L5 band signals have several advantages such as stronger power, lower carrier Doppler, or a pilot channel, unlike the Global Positioning System (GPS) L1 C/A signal. The goal of this paper is therefore to compare the acquisition of L1 and L5 bands signals (GPS L1 C/A and L5, Galileo E1 and E5a/b) to determine which one is more complex and by which factor, in terms of processing time and memory, considering hardware receivers and the parallel code search. The results show that overall the L5 band signals are more complex to acquire, but it depends strongly on the conditions. The E5 signal is always more complex to acquire than E1, while the L5 signal can have a complexity close to the L1 C/A in some cases. Moreover, precise assistance providing accurate Doppler could significantly reduce the L5 complexity below the L1 complexity.

2018

EPFL2010

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International Astronautical Federation2014