L band

About: L band is a research topic. Over the lifetime, 674 publications have been published within this topic receiving 4570 citations.

3 GS/s S-Band 12 bit MuxDAC on SiGeC technology

Abstract: In advanced applications such as digital radar, Ultra Wide Bandwidth communications and software defined radio, the need for instantaneous bandwidth often drives system design decisions. Access to high speed data converters enabling up and down conversion directly in the L Band and S Band removes the limit imposed by bandwidth scarcity and allows the design of flexible and simplified system architectures. Broadband DAC's (Digital to Analogue Converters) are key enabling components which open up new design opportunities for digital Synthesizer systems. In this regard, this paper describes a new 12 Bit 3GS/s DAC, based on a 200 GHz SiGeC bipolar Technology, which enables direct synthesing of 1GHz arbitrary waveforms directly in the high IF (S_Band) region closer to the Antenna.

Design of Inset Feed Tri-Band Microstrip Patch Antenna for GPS and IRNSS Application

Abstract: A low profile tri-band microstrip patch antenna is designed and fabricated for GPS and IRNSS application. The design involves Inset feeding technique and substrate FR_4 which is dielectric in nature. The slotted patch is designed using Keysight Technologies, Advanced Design System© where considerable antenna parameters were obtained for the simulated design and for the prototype when measured using Keysight N9917A Vector Network Analyser. Simulated results show that the patch resonates in L1 Band (1.575 GHz), L5 Band (1.176 GHz) and S-Band (2.49 GHz) with reasonable antenna parameter values.

Correcting and Measuring Ionospheric Scintillation Amplitude Stripes in L-Band SAR Images

Abstract: The amplitude stripes induced by the ionospheric scintillation have been frequently observed in spaceborne L-band synthetic aperture radar (SAR) images, such as ALOS PALSAR, which may impede SAR applications. From another perspective, the presence of ionospheric stripes implies a reverse guidance for ionospheric sounding. In this paper, a methodology for correcting and measuring ionospheric stripes from SAR images is proposed. Firstly, based on prior information of the stripes’ orientation, the stripe components are automatically detected and extracted using a band-rejection spectral filter. Secondly, the extracted amplitude errors are further applied to measure ionospheric scintillation parameters by fitting the power spectrum. The methodology is tested on several PALSAR acquisitions. The results indicate that the methodology can automatically corrects the stripes and has a great potential of measuring ionospheric scintillation from the SAR images with amplitude stripes.

Thickness retrieval and emissivity modeling of thin sea ice at L-band for SMOS satellite observations

Abstract: In this study we have developed an empirical retrieval for thickness of young and first-year ice during the freeze up period for the L-band passive microwave radiometer Microwave Imaging Radiometer with Aperture Synthesis (MIRAS) on the Soil Moisture and Ocean Salinity (SMOS) satellite. The retrieval is based on intensity and polarization difference using the incidence angle range of 40◦ to 50◦ and is validated using data from airborne EM-Bird, Moderate-resolution Imaging Spectroradiometer (MODIS) thermal imagery, and self consistency checks for ice thicknesses up to 50 cm with an error of 30% on average. In addition, we modeled the microwave emission for Arctic first-year ice using the sea ice version of the Microwave Emission Model of Layered Snowpacks (MEMLS). The sea ice conditions used as input for MEMLS were generated using a thermodynamic energy balance model (based on the Crocus model) driven by reanalysis data from European Centre for Medium-Range Weather Forecasts (ECMWF). From unexpected features in the modeled microwave emission and disagreements with the empirically trained SMOS retrieval several shortcomings of the energy balance model and MEMLS were identified and corrected. The corrections include a treatment of mismatch of layer definition between the energy balance model and MEMLS, an adaptation of the reflection coefficient for lossy media in MEMLS, and several smaller corrections. For comparison, two simple models ignoring volume scattering, one incoherent and one coherent, were set up and were found to be able to reproduce the results of the more complex MEMLS model on average. With the simple models, the effects of thin coherent layers, the snow cover, the interface roughness and three different dielectric mixture models for sea ice were explored. It was found that the choice of the mixture model is essential for the relation of sea ice thickness to brightness temperatures in L-band, suggesting sea ice thickness sensitivities from few centimeters to several meters for salinity conditions of the global oceans. The interface properties, especially at the sea ice bottom, were found to be a major uncertainty source when modeling the microwave emission of thin sea ice. In addition, the variability in snow depth, the interface roughness, and the ice surface salinity and temperature were found to have a similar influence on the resulting brightness temperatures, with a strong effect on horizontally (up to 30K) and weak effect on vertically polarized radiation (up to 10K) for temperatures below 260K. A model for simulating coherent microwave emission for thickness distributions of ice and snow was prepared to overcome weaknesses from the single thickness coherent and incoherent models. Comparison to the incoherent model showed that for realistic snow depth distributions obtained from Operation IceBridge (OIB) coherence effects can change the brightness temperatures on the scale of a SMOS footprint up to 10K in horizontal polarization. These findings suggest that the retrieval for the thickness of thin sea ice with satellite based L-band sensors yield higher uncertainties than expected from earlier studies.