Ramón Gerardo López La Valle

A practical RF front-end for high performance GNSS receivers

We present the design and implementation of a GNSS front-end intended for receiving the L1/E1 band of GPS/Galileo and GLONASS signals. The proposed scheme consists of a radio frequency (RF) stage, with a low noise amplifier which has a noise figure of 1.1dB. Then, the RF signals are down-converted to an intermediate frequency, where the GPS/Galileo and GLONASS bands are separated. Thanks to this separation, a considerable reduction of the necessary sampling rate for the digitalization stage is achieved. This simplifies and reduces the power consumption of this stage of the complete GNSS receiver. The present design is versatile since it can be used to receive signals from the L2 band by replacing only a few components, without the necessity of modifying the printed circuit board. Measurements realized to an implemented prototype that validate the proposed design are presented.

An Experimental L1/L2 GNSS Receiver for High Precision Applications

In this work we present the design and implementation of a GNSS receiver that can work with the civil signals of the L1 and L2 bands of GPS and GLONASS, and the E1 Open Service signal of Galileo. The developed prototype has two RF front-ends, one for the L1 band and another for the L2 band. The signals from each band are amplified and then down-converted to an intermediate frequency. The two local oscillator tones used for the mixing, and the clock signals for the next digitalization and processing stages are generated by a frequency synthesizer board, from a common reference. The digitalization and posterior processing of the signals can be carried out using generic devices, like an acquisition board and an FPGA, according to the Software Defined Radio (SDR) concept. In this way a programmable receiver is obtained. These kinds of receivers are versatile since they can be used for testing acquisition, tracking, and navigation algorithms for research and develop purposes. Commercial receivers do not have that capability, because their digital processing stages cannot be modified by the user. Moreover, a multi-band and multi-constellation receiver allows to greatly increase the performance in relation to mass market GNSS receivers which relay on only one navigation system and one carrier frequency. Measurements realized to the implemented prototype that validate the proposed design are presented.

New Design of a Variable Impedance Based on Polarized Diodes at Microwave Frequency

In this letter, we present a new variable impedance termination consisting of two polarized diodes. To generate a complex-valued impedance, two controlled current sources polarize the diodes, which are interconnected with a Wilkinson power divider through transmission lines of different electric lengths. Because of the reduced number of diodes, this structure presents low power consumption and simple control. We validated the proposed design by implementing a prototype at the operating frequency of 1575.42 MHz. Mapping the measured results in the Smith chart, the impedance can produce reflection coefficients with full-phase coverage within the circle of magnitude 0.35 over a frequency range of 1.5–1.6 GHz.

Plataforma de adquisición de señales GNSS con conexión USB

This paper presents a GPS and GLONASS L1 band acquisition system with an USB interface. This system has been conceived as an intrument capable of sampling L1 band GPS/GLONASS signals and transfering the samples to a PC through a USB connection, where they can be processed in real-time or stored for later processing. This tool enables the user to test new types of GNSS signal processing algorithms on a personal computer, therefore taking advange of the flexibility and the processing power of such platform. The quality of the GNSS samples obtained through this platform was verified by proccesing them in a PC, obtaining satisfatory results in the acquisition of both GPS and GLONASS signals.

Design of a dual-antenna and dual-band GPS receiver for CubeSats

During the last few years, there has been a rise in the use of nanosatellites because they offer a low cost and short development time alternative to larger satellites intended for long-duration missions. The use of commercial components (COTS) instead of the expensive space-grade components required for long missions is one of the main reasons of the popularity of the nanosatellites. This paper presents the hardware design of a GPS receiver compatible with the CubeSat standard. The receiver has two antenna inputs and is capable of operating on the L1 and L2 bands. Since the proposed design is based on non-space qualified components, a tolerance and fault mitigation scheme for SEU and SEL events produced by the effect of radiation is implemented.

Dual-band bandpass filter with wide stopband and low insertion loss for GNSS signals

We present the design of a dual-band bandpass filter for GNSS signals based on microstrip open-loop resonators. The filter has two frequency bands intended for the L1 and L2 signals of GPS and GLONASS, and the Galileo open service signal E1. The low insertion loss and the wide stopband achieved make this filter suitable for rejecting out of band interferences in GNSS receivers as a first stage in the RF chain. The filter was implemented and the measurements carried out validate the proposed design, which has only 1.5 dB of insertion loss and about 30 dB out of band attenuation in a wide frequency range.