Showing papers on "L band published in 2007"

Galileo System Navigation Antenna for Global Positioning

Abstract: Within the frame of Galileo project, EADS CASA ESPACIO has been developing the navigation antenna for the space segment of the future European Global Positioning System. The main antenna requirements are the isoflux corrected pattern in the earth coverage (12.67° semi-cone angle), circular polarisation, (around 1 dB axial ratio in the coverage), two independent self-diplexed L band (1.15-1.6 GHz) transmit bands operation (two channels E5 and E6 in Low Band 2 x 50 W and one channel LI in High Band 75W) and high parameters stability (including phase centre location and group delay). The selected design is a 1.4 m diameter flat array of 45 stacked patches with hexagonal lattice and less than 14 kg weight, manufactured in suspended substrate multi-layer printed technology developed by EADS CASA ESPACIO in previous projects. The design includes array design, beam forming networks, structural design and thermal control. One electrical model has been manufactured and qualified along with the two flight models of the demonstrator GSTB-V2 (Galileo System Test Bed-Version 2) [1], one of them to be launched at the end of 2007, on-board GIOVE-B satellite (see figure 1). The design description and test results are presented. (6 pages)

A Novel Wide Beam Dual-band Dual-Polarization Stacked Microstrip - Dielectric Antenna

Abstract: A novel dual-band dual-polarization stacked microstrip -dielectric antenna is analyzed and designed. It transmits left-hand circularly polarized (LHCP) signals in L band and receives right-hand circularly polarized (RHCP) signals in S band. The antenna has been realized by two stacked square patches which are fed by four quadrature pins placed symmetrically on the two main axis. The amplitude and phase relationship between the four pins to maintain circular polarization is obtained by two wide band 90deg hybrid couplers. It can easily realize matching by changing the position of feed points. In the experiment results, high isolation between transmission port and receiving port, wide 3-dB beamwidth and perfect circular polarization characteristics in the dual-band are obtained.

Wide-band dual polarized probes for near field antenna measurements

Abstract: Wide-band, dual polarized probes based on an innovative self-balanced feeding scheme has been developed for high accuracy near field measurements. The innovative self-balanced feeding gives a reduction in cost and complexity while maintaining high performance standards. The overall simplicity makes the new technology attractive for probe designs in the L to Ka band range.

A Triple-band Circular Polarization Stacked Microstrip Antenna

Abstract: A novel triple-band circular polarization stacked microstrip antenna is presented. The proposed antenna operates at L band when transmitting left-hand circular polarization signal, and L2 band of GPS and S band when receiving right-hand circular polarization signals. Stacked structure carries out compactness of the antenna and special dual-feed structure has guaranteed good circular polarization performance, what' s more, the extra cone-pedestal greatly enhances gain at low elevation angle.

Combination of X, C, and L band SAR images for retrieval of surface parameters

Abstract: The main aim of this paper is the investigation of the potential of different radar frequencies for surface parameters estimation. Two case studies have been analyzed. The first is devoted to obtain soil moisture and roughness of bare soils from a combination of X, C and L band SAR images acquired during the SIRC/XSAR mission. The results indicate that the combination of the three bands is particularly useful when roughness parameter estimation is performed. Also the use of the cross-polarization VH has been exploited. The second case study is focused on vegetation water content estimates by using a combination of C and L band data acquired during the SMEX'02 experiment on densely vegetated fields. The errors on estimates are reduced when both C and L band data and a correction for roughness are used.

L-band Superfluorescent Fiber Source

Abstract: An L band superfluorescent fiber source (SFS) is presented. The spectrum covers wavelengths from 1560 nm to 1615 nm. The L band SFS is constructed by a low power L band amplified spontaneous emission (L-ASE) seed source and a high power erbium-ytterbium co-doped fiber (EYDF) amplifier in double pass configuration. The output power of 0.72 W is obtained under 5.0 W, 980 nm pump power.

Novel textured, small aperture, thin patch for L-band satellite communications

Abstract: An L-band circularly polarized antenna is designed using genetic algorithms. The design has an impedance bandwidth of 12.5% at 1.6 GHz with a remarkably constant 4.2 dBi gain. Further, it is very thin (

New Travelling Wave Tubes for L-Band and S-Band in Orbit Applications

Abstract: The ongoing development in satellite application requires more and more high power travelling wave tubes (TWT) to relieve the requirements for end user terminals and to improve the quality and channel capacity of the satellite down link. Also more types of TWTs are demanded by the customers to obtain a higher flexibility in satellite design with respect to output power, weight and thermal requirements. Thales Electron Devices (TED) therefore has filled up its portfolio of different TWTs for L-Band and S-Band. This paper will present some technical details and illustrate the performance of state- of-the-art tubes.

Fast Determination of Phase Advance, Path Delay and Ray Path Curvature between Satellites Through a 3D Ionosphere for L-band Transmissions

Abstract: A fast and accurate method of determining path delay and phase advance and range error between any two satellites for L-band frequencies has been determined. The method takes into account the bending of the ray path due to refraction by both vertical and horizontal gradients as well as the effect of the geomagnetic field and the actual profile of the electron density and its gradients along the path. The method has been validated against both analytical and precise numerical calculations. Results are presented of first and higher order ionosphere errors and path displacements from the LOS for satellite to ground and satellite to satellite paths. (5 pages)

Transmission 32 C and L Band DWDM System at 40 Gbit/s over 257 km of Dispersion Compensation Structure

Abstract: We propose and demonstrate experiment transport of 32x40Gbit/s DWDM system structure in C band and L band wavelength range which use the combination of Single Mode Fiber (SMF) and Reverse Dispersion Fiber (RDF) as dispersion compensation device [1, 2]. C band wavelength range 1529.55 nm ∼ 1560.61 nm, L band wavelength range 1570.42 nm∼1603.17 nm channel spacing 100 GHz combine Erbium Doped Fiber Amplifier (EDFA) and Distributed Raman Amplifier (DRA) which use the combination of SMF and RDF as dispersion compensation device is proposed and demonstrated [3]. The system structure transmission length of 257 km consisted of 50 km SMF and 14.25 km RDF for four fiber spans. This proposed system is suitable for DWDM systems in long distance transmission [4].

Design considerations for L band erbium-doped hole-assisted lightguide fiber amplifiers

Abstract: The finite element method is applied for solving the modal field of erbium-doped hole-assisted lightguide fiber (EDHALF). The modified average population inversion iteration method is proposed for simulating the gain coefficients of EDHALF amplifiers. The relation between the structural parameters of EDHALFs and the gain coefficient of L band EDHALF amplifiers is investigated by means of the finite element method combined with the modified average population inversion method. Four structural parameters of EDHALF-core diameter, the refractive index difference between the core and silica cladding, the relative hole-to-core spacing and the relative size of air holes are optimized in terms of the design criteria of L band erbium-doped fiber, which take into account the cutoff wavelengths, the gain coefficients of L band fiber amplifiers and the splice loss between the EDHALF and the conventional single-mode fiber. At last, the comparisons between the EDHALF and the conventional erbium-doped fiber for L band applications are made.

Experimental demonstration of L-Band to S-Band wavelength conversion

Abstract: 50-nm optical wavelength conversion based on the potentially noise-free Bragg scattering process in an optical fiber is demonstrated experimentally. 2.5-Gb/s output waveforms and eye diagrams for the initial and converted signal are presented.

Attenuation Characteristic of Satellite Communication Signal Associated with Asian Dust in the Frequency Range L-band to Ka -band

Abstract: [] This paper present s attenuation characte ristics of the satellite communication signals operating in the range 1 to 20GHz associated with Asian Dust (the so -called Yellow Dust). The signal level values for L -, S -, C -, Ku -, and Ka -band frequencies of the satellite communication downlink were measu red in a clear weather and in Asian Dust weather by the Satellite Signal Monitoring Center. For three years, from 2004 to 2006 year, the measured signal level values were compared to the total number concentration and Asian Dust size distribution that were measured by the Korea Meteorological Administration/Korea Meteorological Research Institute and the possible correlation between these sets data were analyzed. The results demonstrate that the average variation width (dB) of signal level for 3 years from 2004 to 2006 in Asian Dust days were about 1. 23 dB, 2.3dB, 1.0dB, 1. 85 dB and 4.9dB to L -band, S -band, C -band, Ku -band and Ka -band, respectively . Hitherto, merger information has been reported as to the influence of Asian Dust on satellite communications ope rating in regions affected by Asian Dust .

On the Characteristics of L- Band Persistent Scatterers

Abstract: The characteristics of L-band persistent scatterers (PS) are investigated for their size and brightness variation. The seasonal deformation of an urban area was assessed using the PSInSAR (Persistent Scatterer SAR Interferometry) technique first. L-band HH-polarization images of JERS-1 were utilized. The seasonal deformation was monitored and the thermal expansion and contraction is likely to be the cause of the periodic motion. The mean size of the PSs was estimated to be 6.7 m from the relation of the normal baseline and the ensemble phase coherence. This result is larger than that of the C-band result (Ferretti et al., 2001). The PSs can be considered as point scatterers as they are much smaller than the resolution cell. According to the result of polarimetric analysis of coherent scatterers (CR), many CRs are dihedral scatterer [6]. L-band PSs are also inferred to be dihedral scatterers. In order to confirm this idea, its seasonal brightness variation was estimated. The L-band signal suffers from Faraday rotation during its propagation through the ionosphere and the polarization plane of the incident wave changes according to the prevailing conditions of the ionosphere. The brightness of some PSs, of which undulation amplitudes are large, was plotted as a function of the season. The variations in the brightness of PSs appear to display a smooth decrease during summer, when the Faraday rotation becomes stronger. Such a decrease in brightness is expected when small dihedral scatterer suffers from Faraday rotation effects. However, most of scatterers lost their brightness under Faraday rotation [8]. It is insufficient to say that L-band PSs are dihedral scatterers.