Showing papers on "L band published in 2005"

Signal excited-state absorption in the L-band EDFA: Simulation and measurements

Abstract: Signal excited-state absorption (ESA) influences the performance of erbium-doped fiber amplifier (EDFA) in the L band. The influence is twofold: 1) ESA is responsible for signal absorption, and thus for noise figure increase in the long wavelength range of the L band and 2) ESA decreases inversion of erbium ions, and as a result, amplifier gain is decreased. Two methods of signal ESA measurement are discussed. It is shown that reliable data can be obtained through measurement and later used for accurate simulation of amplifier performance.

Watt-level L band superfluorescent fiber source.

Abstract: An L band superfluorescent fiber source (SFS) with output power of 0.94W is presented, under 4.4W 976nm pump power. The optical conversion efficiency is about 21%. The spectrum covers the broad wavelength range from 1560nm to 1615nm. The high power L band SFS is constructed by a low power L band amplified spontaneous emission (ASE) seed source and a high power erbium-ytterbium co-doped fiber (EYDF) amplifier in double pass forward pumping configuration.

Monitoring of mining induced surface deformation using L-band SAR interferometry

Abstract: In the mining context there is a specific interest in monitoring temporally non-uniform high deformation rates with high spatial gradients. In recent years land surface deformation monitoring with SAR data reached some maturity. Mainly C-band SAR data were used. Nevertheless, there remain important limitations to the availability of the interferometry based deformation information. Reasons include incomplete spatial coverage with information gaps for low coherence areas, problems in resolving high deformation gradients, and problems in resolving temporally non-uniform deformation. The objective of our contribution is to demonstrate that these limitations are significantly reduced at L-band. In vegetated areas and for fast deformations a good applicability of Lband INSAR was found.

Comparison of model prediction with measurements of galactic background noise at L-band

Abstract: The spectral window at L-band (1.413 GHz) is important for passive remote sensing of surface parameters such as soil moisture and sea surface salinity that are needed to understand the hydrological cycle and ocean circulation. Radiation from celestial sources (mostly galactic) is strong in this window, and an accurate accounting of this background radiation is often needed for calibration. This paper presents a comparison of the background radiation predicted by a model developed from modern radio astronomy measurements with measurements made with several modern L-band remote sensing radiometers. The comparison validates the model and illustrates the magnitude of the correction necessary in remote sensing applications.

A superconducting microstrip bandstop filter for an L-band radio telescope receiver

Abstract: A seven-pole high temperature superconducting (HTS) microstrip bandstop filter at L band is presented in this paper. The filter has application in a radio astronomy receiver. The zig-zag loop resonator and the zig-zag phase line are developed to reduce the parasitic effect of the direct resonator-to-resonator coupling. The measured results match the simulated results very well.

L-band radio interferences observed by the JERS-1 SAR and its global distribution

Abstract: This paper describes characteristics of the L band radio interferences appeared in the JERS-1 SAR images, which were acquired world widely during six years and a half. It also describes a filtering method that mitigates the radio interference. This filtering method replaces the interfered component of SAR raw data by zero padding from the statistical power spectrum analysis. The corrected SAR raw data is well correlated with the SAR imaging reference signal and the output image is shown to be useful.

Design of high performance narrow band hts filter for l-band radar system

Abstract: An ultra selective narrow bandpass HTS filter in L band has been designed and fabricated. This cascaded quadruplet (CQ) filter consists of 10 resonators and two cross coupling structures that produce two transmission zeros near the band edges. The coupling matrix Mand the external quality factors Q_ e1 , Q_ e2 are obtained by an analytical gradient-based optimization technique. The exact filter layout was simulated and optimized by full-wave EM simulation using Sonnet software. The filter was fabricated on a double-sided YBCO film epitaxially grown on a two-inch diameter MgO wafer. The measured filter response showed a bandwidth of 5 MHz (FBW0.4%). The insertion loss at the passband center was only 0.3dB including two SMA connectors. Steep rejection slopes were obtained at the band edges and the measured skirt slope has exceeded 100 dB/MHz, resulting in an excellent out of band rejection very close to the band-edge.

A L/X dual-frequency co-aperture microstrip array design

Abstract: A new dual-frequency co-aperture microstrip antenna array is proposed and studied, which operates at L and X band simultaneously. The new antenna model has good characteristics, such as low cross polarization, wide bandwidth (X-band) and so on. Details of the design and results are presented

Sky observations at L-band with an interference suppressing microwave radiometer

Abstract: Radio Frequency Interference (RFI) can adversely impact microwave passive remote sensing measurements, and prohibits passive observations outside protected portions of the radio frequency spectrum. A microwave radiometer including a digital backend with real-time RFI mitigation has been developed to address this issue. In this paper, we describe the radiometer design and its pulse blanking strategy. We also demonstrate the system using the sky as a target of observation.

Efficiency at L-Band on the Expanded Very Large Array Synthesis Telescope

Abstract: A primary goal of the Very Large Array Expansion (EVLA – Phase 1) Project is to provide continuous frequency coverage with increased sensitivity from 1 to 50 GHz from the secondary focus. Eight receiver bands were chosen to cover the above range. The lower three bands cover the 1-8 GHz range, with each receiver covering an octave band (1-2, 2-4 and 4-8 GHz). A new feed cone has been designed for the EVLA antenna to accommodate the eight receivers and feeds. The feeds for the lower three bands use the compact feed design [1], [2], which is relatively small compared to the linear taper design for the same illumination taper. The design of the L-band feed was critical as its size dictated the layout of the feeds on the feed cone. The feed layout was driven by two factors: (i) the phase center of the feed at mid-band needs to be at or near the secondary focus and (ii) the larger feeds do not cause blockage for the adjacent feeds. In order to achieve these goals, a compromise was made on the size of the L-band feed, resulting in a small loss in efficiency. The calculated aperture efficiency varied between 0.46 and 0.62. Spillover temperatures at 1.4 GHz and 2.0 GHz were 12.3 K and 12 K, respectively. However, measurements on the antenna gave lower efficiencies and spillover temperatures. The cause of this discrepancy has been analyzed and is presented here.

The New Solution of the Model of L-band Erbium-doped Amplifiers

Abstract: The L band EDFA were calculated by using Giles model. The ASE spectrum of L-band EDFA and the relationship between the optimum length of L-band EDF and input pump power were numerically simulated.

Design and Operation of an L-Band MBK for TESLA

Abstract: Summary form only given. The design and operation of a 1.3 GHz higher-order-mode multiple beam klystron (MBK) that has been developed for the TESLA facility will be described. The klystron contains six off-axis electron beams set on a 26.7 cm bolt circle diameter that interact with a combination of TM02 and TM01 mode cavities to efficiently produce high power RF. The off-axis electron beams are the salient feature of the device which results in a low cathode current density loading and a long product lifetime. Extensive two and three dimensional simulations were conducted to design the novel magnetic focusing and RF circuits. Initial testing proved the basic design concepts and has validated the simulation techniques used. However, an arcing problem developed in one of the windows due to a poor contact in a high RF current carrying joint. This necessitated a repair and re-processing of the klystron. New test results show improved performance. The goals of producing 10 MW of peak power and 150 kW of average power have been achieved, although at a lower efficiency of 59% than had been originally expected. The klystron has also demonstrated stability into a 1.2:1 VSWR mismatch at six equally varying phases over 180 electrical degrees. Approximately 11 MW of power was generated, corresponding to an efficiency of 64.5%, at the mismatch phase corresponding to the highest interaction impedance in the output cavity gaps. Additional refinements to the RF circuit will be implemented in a future klystron to reach the 65% efficiency goal level while maintaining stability into the 1.2:1 mismatch

Effect of wavelength, building blockage and terminal antenna pattern upon LEO satellite coverage in urban and suburban environments

Abstract: While land mobile satellite systems operating at VHF (150 MHz) should provide better coverage in urban and suburban environments than similar systems that operate at L-band (1 GHz and above), previous work has not quantified the improvement. Here, we fill that gap by presenting results obtained with a 3D-satellite signal propagation simulation tool that we have developed around the NEC-BSC UTD code. Results obtained using a representative street geometry show that the mean signal at VHF may be as much as 6 dB stronger than that at L-band with a standard deviation that is almost 2 dB less. Results also show that an antenna with a hemispherical pattern can provide much more effective coverage than the λ/4 monopole antenna which has traditionally been the most popular antenna for ORBCOMM applications. I. INTRODUCTION Parametric models such as Loo Model and Lutz Model are based on measurements at UHF and L band and no parameter set is available for VHF band. A few exceptions, e.g., (2), only characterize building penetration at VHF band for indoor propagation. Therefore, little quantitative information exists to support LMSS system planning and performance prediction at VHF where propagation is expected to be somewhat easier. This study seeks to fill a gap in previous work by determin- ing the manner in which the coverage of LMSSs operating in urban and suburban environments are affected by both wavelength and building blockage. In particular, we compare the coverage obtained at both 138 MHz and 1.3 GHz under different degrees of buildup and using a realistic satellite con- stellation. We also consider the manner in which changing the pattern of the terminal antenna affects system coverage. Our Uniform Theory of Diffraction (UTD) based 3-D propagation simulation tool is based upon the NEC-BSC code developed at Ohio State University. We have validated the results with respect to measured data using the Feature Selective Validation method. Details of the effect of wavelength and building blockage on system coverage are presented.