High Performance Receiver Front-End for Multiple Galileo Frequencies

Frank Förster, Alfonso Carrera, Nestor Lucas and Gunther Rohmer

Abstract:	This paper describes a multi-frequency very high bandwidth receiver front-end combined with a single quadrifilar helix antenna. It has the capability to receive the Galileo bands namely E6, E5a,b and L1 with full bandwidth. The presentation focuses on the implementation of the receiver chain from the antenna to the digital base-band signal. For the receiver antenna an approach is made to use one single antenna for all three bands. The challenge is to design an antenna with such a high bandwidth characteristic combined with a very good noise matching to the first LNA (low noise amplifier). A splitter separates the received, pre-amplified signal into three the parts E5, E6 and L1 of which each is processed by a different receiver. Every receiver consists of the front-end and the acquisition-board. A PC-card serves as the navigation processor and user interface to the GATE system. All cards permit modular assembly and are plugged into a PXI framework. The front-end architecture chosen for the reception is low- IF. The starting point of the receiver design is the frequency band with the largest bandwidth. The E5 band of 71.61 MHz bandwidth is therefore the crucial factor for the receiver design. One major advantage over a superhet architecture is that no band-pass filtering in the IF domain is required. One important constraint of the low-IF architecture, which has to be taken into account, is the image band. A method to minimize the effect is to use an I/Q-downconverter in conjunction with a poly-phase filter. Simulations show that an image rejection of more than 20 dB is achievable via a cascaded implementation. For the subsequent A/D-converter jitter is a major concern. While sampling at a comparatively high frequency the clock has to exhibit ultra low jitter in order to prevent degradation of the received signal. The digitized signal is converted to base band. The sample rate is adapted before delivering the data to the acquisition-board where the despreading is performed. The front-end for each band is divided into two PCB-boards, which are attached to the acquisition-board.
Published in:	Proceedings of the 18th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2005) September 13 - 16, 2005 Long Beach Convention Center Long Beach, CA
Pages:	935 - 940
Cite this article:	Förster, Frank, Carrera, Alfonso, Lucas, Nestor, Rohmer, Gunther, "High Performance Receiver Front-End for Multiple Galileo Frequencies," Proceedings of the 18th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2005), Long Beach, CA, September 2005, pp. 935-940.
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