Showing papers on "L band published in 2008"

Correction of the Sea State Impact in the L-Band Brightness Temperature by Means of Delay-Doppler Maps of Global Navigation Satellite Signals Reflected Over the Sea Surface

Abstract: This paper presents an efficient procedure based on 2-D convolutions to obtain delay-Doppler maps (DDMs) of Global Navigation Satellite Signals reflected (GNSS-R) over the sea surface and collected by a spaceborne receiver. Two DDM-derived observables (area and volume) are proposed to link the sea-state-induced brightness temperature to the measured normalized DDM. Finally, the requirements to use Global Positioning System reflectometry to accurately correct for the sea state impact on the L-band brightness temperature (quantization levels, decimation, truncation, and noise impact) are analyzed in view of its implementation in the Passive Advanced Unit instrument of the Spanish Earth Observation Satellite (SeoSAT/INGENIO) project.

Correction of the Sea State Impact in the L-Band Brightness Temperature by Means of Delay-Doppler Maps of Global Navigation Satellite Signals Reflected Over the Sea Surface

Abstract: -This paper presents an efficient procedure based on 2-D convolutions to obtain delay-Doppler maps (DDMs) of Global Navigation Satellite Signals reflected (GNSS-R) over the sea surface and collected by a spaceborne receiver. Two DDM-derived observables (area and volume) are proposed to link the sea-state-induced brightness temperature to the measured normalized DDM. Finally, the requirements to use Global Positioning System reflectometry to accurately correct for the sea state impact on the L-band brightness temperature (quantization levels, decimation, truncation, and noise impact) are analyzed in view of its implementation in the Passive Advanced Unit instrument of the Spanish Earth Observation Satellite (SeoSAT/INGENIO) project.

A diplexer for gigawatt class high power microwaves

Abstract: With the rapid development of high power microwave (HPM) technologies, HPM devices with several output frequencies are becoming more and more attractive. Diplexer is a microwave device with two output frequencies, here, an L/X band diplexer with novel structure is tried to be employed in the HPM system. In order to obtain the same radiation direction for the L and X band microwaves in the diplexer, the reflection of L band microwaves and transmission of X band microwaves are realized by an array of irises. To obtain the required performance, the width and thickness of the irises and the distance between them should be well chosen. The diplexer is investigated through theoretical analysis and numerical computation, and the final design described in this work, is the result of an overall optimization process. In simulation, both the reflectivities of L-band microwaves and the transmissivities of X band microwaves reach 99.5%, and the power handling capacity of the diplexer is higher than 5.6 gigawatt (GW). Then, the L/X band diplexer is designed and fabricated according to the optimized results. After that, a series of experiments are carried out to test the diplexer. The cold test results show that the reflectivities of L band microwaves are as high as 97.5%, and the transmissivities of X band microwaves are up to 98.8%, and the acquired radiation patterns show that the designed diplexer is suitable for the diplexing of L/X band microwaves, in a word, the cold test results of the diplexer are in good agreement with the simulational results. In the end, the diplexer is tested with GW class HPMs. The radiated HPMs have little change in the pulse duration and magnitude with the diplexer applied, that is to say, there is no microwave breakdown during the HPM reflection and transmission.

L-Band Circularly Polarized Small Aperture Thin Textured Patch Antenna

Abstract: An ultra thin L-band textured patch antenna is proposed with a 12.5% impedance bandwidth centered at 1.6 GHz. The antenna can cover several bands, including two satellite L bands at 1.525-1.560 GHz (uplink) and 1.625-1.660 GHz (downlink). It employs quadrature feeding for circular polarization and its textured design on the thin substrate (

Detection of Ionospheric Structures with L-Band Synthetic Aperture Radars

Abstract: Numerical simulations of low-latitude ionospheric instabilities show the formation of plasma density structures can be detected by synthetic aperture radar (SAR) radio signals. At L-band, the phase front distortions produced by propagation through plasma "bubbles" should provide measurable changes in both the complex-amplitude and polarization waves from orbiting satellite radars. The diffraction pattern from scattered ground SAR signals can be detected by orbiting receivers. Based on reciprocity, ground radars at Kwajalein Atoll are being used to determine the feasibility of space-based detection of ionospheric density structures. This new measurement technique can provide a global data base of ionospheric data for space-weather models that predict the effects of the ionosphere on radio systems.

Characteristics of the dual-forward pumped L-band ASE fiber source - art no 683809

Abstract: We present a two-stage dual-forward pumped configuration to achieve a wavelength stable L-band amplified spontaneous emission (ASE) source. The effects of EDF length and pump power arrangements on the characteristics of L-band ASE spectrum, output power, and mean wavelength are investigated. The results show that not only the pumping conversion efficiency can be improved largely but also the pump power independent mean wavelength operation can be achieved by optimizing the fiber length ratio and pump ratio of the dual-forward pumped configuration as comparing to that of the conventional double-pass forward configuration.

L-band reflection-type RF-MEMS tunable BPF

Abstract: This paper proposes the reflection-type tunable band pass filter (BPF) for the L band. The filter is composed of two identical MEMS tunable BRFs, which are connected to a 90-degree hybrid circuit. The trial fabrication validates the configuration by showing the low loss in seven bands from 0.8 GHz to 2.4 GHz.

Analysis of Internal Wave SAR Image with Multi-frequency

Abstract: The relationship between the frequency and SAR image of internal wave is discussed based on the SIR-C/X-SAR multi-frequency data.For both elevation internal waves and depression internal waves,the feature of internal wave is significantly distinct in both X band and C band,while L band is the least.Also,the reason for the similarity between C band and L band but above both bands different from L band is explained by Bragg resonant scattering theory.Subsequently,we give the simulated SAR image of internal wave under the given program of M4S,and the result is also coincident with the analysis.

Design of a novel triple-band antenna with spiral ring shaped parasitic patches for T-DMB (Band-III) / DVB-H / DAB (L-Band) applications

Abstract: A novel triple-band antenna for the terrestrial digital multimedia broadcasting (T-DMB), digital video broadcasting handheld (DVB-H) and digital audio broadcasting (DAB) services are presented. By using the simple structure of two bar-shaped radiators with spiral ring shaped parasitic patches, meandered structures and lumped elements on FR4 substrate, triple-band performance and compact size are achieved. The designed antenna has good impedance matching and radiation characteristics for T-DMB band-III (174 MHz~216 MHz) band, DAB L-band (1.45 GHz~1.48 GHz) band and DVB-H band (470 MHz~870 MHz). Details of the antenna design as well as antenna characteristics are presented.

RFI Measurement Database Assembled During the Square Kilometre Array Site Qualification Campaigns

Abstract: The Radio Astronomy and Remote Sensing communities are linked both formally and informally. The objective of this paper is to bring to the attention of the wider RF sensor remote sensing community some of the recent work undertaken while qualifying potential sites around the world for siting of the Square Kilometre Array (SKA). The construction of this SKA telescope is planned for some time after 2015, in a number of phases. At present, demonstrator systems are being assembled and tested at a number of locations around the world. Although remote sensing RF sensors are mostly directed from space to the earth, and the SKA candidate sites have been selected for radio quietness, it will be seen that SKA qualification measurements do provide a good assessment of the broad spectrum of radio frequency signals measured close to the surface of the earth, almost with global coverage. The SKA project adopted an approach of measuring average RF occupancy over a wide band (70 MHz to 26 GHz) and true RFI only in the L Band. The latter uses time domain sampling and FFT spectral analysis of the whole L Band.

Single-mode LiNbO3-based waveguides for L-band interferometry

Abstract: We present three different techniques for single-mode waveguide realization in Lithium Niobate at the 3.39μm atmospheric transmission band, named L-band. These methods include Titanium diffusion, Ion Beam Implantation and Photo-inscription. After describing the fabrication process and waveguide characterization, we will present an integrated interferometer based on the Young's double slit experiment. From the recorded interferogram we recover information about the source, namely, its peak emission lines.

Development of a microstrip array antenna for L-band radiometer

Abstract: This paper deals with the design, realization and measurement of a planar low-profile microstrip array antenna for aircraft remote-sensing applications, operating in the dedicated L-band (1.400 - 1.427 GHz) for passive radiometry. Design strategies, manufacturing solutions and measured results are provided.