Showing papers on "L band published in 2010"

An L-band coaxial relativistic backward wave oscillator with mechanical frequency tunability

Abstract: The initial experimental results of an L-band coaxial relativistic backward wave oscillator with mechanical frequency tunability are presented. The key effects of the inner-conductor contributing to the mechanical frequency tunability are investigated theoretically and experimentally. In the experiments, the L-band microwave with frequency of 1.58 GHz is radiated when the inner-conductor radius is 1.5 cm. Meanwhile, the S-band microwave with frequency of 2.31 GHz is generated after removing the inner-conductor. In addition, the frequency tuning within 4% is realized by mechanically altering the radius of the inner-conductor at a half power level.

The dual-band LP feed system for the Sardinia Radio Telescope prime focus

Abstract: We present the design of the passive feed system of the dual-band receiver for the prime focus of the Sardinia Radio Telescope (SRT), a new 64 m diameter radio telescope which is being built in Sardinia, Italy. The feed system operates simultaneously in P-band (305-410 MHz) and L-band (1300-1800 MHz). The room temperature illuminators are arranged in coaxial configuration with an inner circular waveguide for L-band (diameter of 19 cm) and an outer coaxial waveguide for P-band (diameter of 65 cm). Choke flanges are used outside the coaxial section to improve the crosspolarization performance and the back scattering of the P-band feed. The geometry was optimized for compactness and high antenna efficiency in both bands using commercial electromagnetic simulators. Four probes arranged in symmetrical configuration are used in both the P and the L-band feeds to extract dual-linearly polarized signals and to combine them, through phased-matched coaxial cables, into 180 deg hybrid couplers. A vacuum vessel encloses the two P-band hybrids and the two L-band hybrids which are cooled, respectively at 15 K and 77 K. For the P-Band, four low loss coaxial feedthroughs are used to cross the vacuum vessel, while for the L-Band a very low loss large window is employed. The P-band hybrids are based on a microstrip rat-race design with fractal geometry. The L-band hybrids are based on an innovative double-ridged waveguide design that also integrates a band-pass filter for Radio Frequency Interference (RFI) mitigation.

L-band phased array for maritime satcom

Abstract: In this paper a phased array antenna for maritime satellite communications is described. The antenna consists of 26 patch elements that are mounted on a soccer-like spherical aperture. The antenna allows full duplex communication via L-band satellite systems like Inmarsat BGAN or Thuraya. This design is an innovative and powerful alternative to current mechanically steered systems. A fully functional demonstrator has been built and measured. The measurement results are in perfect agreement with the simulations. An outdoor live test on a ship will take place in summer 2010. The prototyping phase is about to start.

An experiment and preliminary results for narrow-and wideband land mobile satellite propagation at K-band

Abstract: With increasing utilization of satellite mobile services capacity shortage in respectively common frequency bands (L band) is to be expected. To enhance understanding of propagation channel characteristics at higher frequency bands (Ku/Ka band) an experiment with a mobile receiver, using narrow- and wideband test signals has been carried out. An airborne test platform has allowed to consider real satellite incidence angles. A comprehensive database has been obtained on channel behaviour and — by means of auxiliary instruments -documenting the details of four typical scenarios measured. Preliminary results indicate excellent qualitative plausibility, such as recognition of electricity poles. Ongoing quantitative analyses include comparisons to literature, e.g. specific attenuation in vegetation. Focus is a statistical analysis to set up a channel simulator predicting the propagation channel characteristics under the measured scenarios' conditions. It is planned to submit results for standardization.

Broadband printed dipole antennas with shaped ground plane

Abstract: A printed dipole antenna, in spite of its numerous advantages in terms of size, weight, aerodynamic drag etc. suffers from the inherent disadvantage of incompatibility with wide band operation. Both microstrip dipoles and printed dipoles are resonant antennas but printed dipoles are often used to replace microstrip dipoles since they offer somewhat better band width. However, the maximum band width reported to be obtained is not sufficient for many present day high-speed data applications like streaming video, real time navigation and control links, as also applications like medical imaging, broad band EMI measurements etc. A novel yet simple design of printed dipole antenna without flared arms and with shaped ground plane is presented here using which −10 dB return loss band width as high as 41% in L band and below is achieved, a feat hitherto unachieved. By flaring its arms, the same antenna provides −10dB band width as high as 51% in the same band of frequency. Antennas are designed to operate in L band and below so that these can be used in GSM and CDMA wireless applications. Measured results of both antennas show good agreement with the simulated results.

Compact low loss L-band orthomode transducer

Abstract: The design of a wideband orthomode transducer (OMT) with an integrated directional coupler for radio astronomy applications in the frequency range 900 MHz to 1760 MHz is presented. The OMT has very low insertion and transmission losses, good isolation, and is of small size.

Studies of radio frequency interference at L-band using an airborne 2-D interferometric radiometer

Abstract: Potential radio frequency interference (RFI) sources at L-band include L-band radars; mobile, navigation and other satellite services; and various land services. We have collected data using our airborne L-band interferometric HUT-2D radiometer in order to support the ESA SMOS mission. We participated in April-May 2008 in ESA's rehearsal campaign for SMOS satellite validation activities in Germany and Spain. Additional data have been collected in Finland. Two basic categories of RFI have been observed: (1) Point-wise weak sources that do not saturate the HUT-2D instrument, and (2) strong sources that totally saturate the sensor over a large area.

3 GS/s S-Band 10 Bit ADC 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 ADC's (Analogue to Digital Converters) are key enabling components which open up new design opportunities for digital Receiver systems. In this regard, this paper describes a new 10bit 3GS/s ADC with 5 GHz Bandwidth, based on a 200 GHz SiGeC bipolar Technology, which enables the direct digitizing of 1GHz arbitrary broadband waveforms directly in the high IF region closer to the Antenna (L-Band or S-Band).

Slotted inverted patch - rectangular microstrip antenna for s and l - band frequency

Abstract: Light profile, low weight, low cost fabrication, enhanced patch area reduction with improved bandwidth and gain are the key characteristics for the antenna designed for wireless communication applications under S and L band frequency spectra. Microstrip patch antenna (MPA) suits the features mentioned except for its narrow bandwidth and low gain. This paper experimentally investigates an approach to achieve enhanced patch area reduction (of 23 %) without increasing the complexity of MSA too much with improved impedance bandwidth, gain for applications such as WiMax services, UK fixed satellite services, aeronautical mobile application, maritime mobile services covering the microwave frequency range from 3 - 4 GHz. Experimental results of return loss, impedance bandwidth, radiation pattern, Smith chart characteristics and gain are discussed and presented.

A compact L-band Ortho Mode Junction

Abstract: We describe the design construction and performance of a L-band (1300-1800 MHz) Ortho Mode Junction for the L-P dual-band receiver that will be installed on the 64 m Sardinia Radio Telescope (SRT), a new radio telescope which is being built in Sardinia, Italy. The Ortho Mode Junction (OMJ) separates two orthogonal linearly polarized signals propagating in a 172 mm diameter circular waveguide and couples them into four coaxial outputs. The OMJ is part of an OMT (Ortho Mode Transducer), which includes two 180

Radio frequency interferences investigation using the airborne L-band full polarimetric radiometer CAROLS

Abstract: In the present paper, different methods are proposed for the detection and mitigation of the undesirable effects of radio frequency interference (RFI) in microwave radiometry. The first of these makes use of kurtosis to detect the presence of non-Gaussian signals, whereas the second imposes a threshold on the standard deviation of brightness temperatures, in order to distinguish natural emission variations from RFI. Finally, the third approach is based on the use of a threshold applied to the third and fourth Stokes parameters. All of these methods have been applied and tested, with a CAROLS radiometer operating in the L-band, on data acquired during airborne campaigns made in spring 2009 over the South West of France. The performance of each, or of two combined approaches is analyzed with our database. We thus show that the kurtosis method is well adapted to pulsed RFI, whereas the method based on the second moment is well adapted to continuous-wave RFI.

A novel 180° hybrid power divider

Abstract: We describe the design, construction and performance of a novel 180° hybrid power divider for L-band (1.3-1.8 GHz). The hybrid is based on a double ridged waveguide cavity that also integrates a band pass filter. The device will operate at 77 K inside a cryogenically cooled receiver to be installed at the primary focus of the Sardinia Radio Telescope. The hybrid has three ports consisting of N-type coaxial connectors whose central pins are attached to launching probes located inside the double ridge waveguide structure. The signal is launched into the cavity from an input probe located on one cavity end and is extracted from two output probes on the opposite end. The output probes are arranged in balanced configuration, are axially symmetric, and aligned along the same axis. Both input and output probes are located in front of reactive loads consisting of shaped tunerless backshorts that provide broad band responses with low reflection coefficient. The band pass filter is located in the middle of the cavity, between the two input and output transitions. The dimensions of the device (excluding connectors) are 70 x 57.2 x 254.4 mm 3 . The design was optimized using a commercial electromagnetic simulator. From 1.3-1.8 GHz the measured output reflection coefficient was less than -17dB , the coupling and the phase difference between inputs and output was respectively, 3±0.25dB and 180 0 ±0.9 0 , over the full band. The amplitude and phase balance performances are much superior to that of commercially available devices.

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 and Realisation of L-band Frequency Scanning Radiometer

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Satellite radio interfaces compatible to 3GPP WCDMA system

Abstract: This paper provides an overview of a technical study on the satellite radio interfaces based on 3GPP WCDMA system. First, the outcome of the technical study is introduced, which has been carried out by the Mobile Satellite System Working Group of the ETSI Satellite Earth Satellite Technical Committee (ETSI TC SES MSS). The study dealt with the configurations and performance of the 3GPP WCDMA (UTRAN) radio interface over a satellite link. Second, as an evolution of satellite-specific radio interface, the study results are addressed on the possible adaptations of WCDMA to the satellite link in order to maximize the radio link performance. The resultant outcome of the study was reflected in a detail on the G and C families of the satellite radio interface of the ITU-R Recommendation M.1457, respectively. Copyright © 2010 John Wiley & Sons, Ltd.

Properties of the variation of the infrared emission of oh/ir stars ii. the l band light curves

Abstract: In order to study properties of the pulsation in the infrared emission for long period variables, we collect and analyze the infrared observational data at L band for 12 OR/IR. The observation data cover about three decades including recent data from the ISO and Spitzer. We use the Marquardt-Levenberg algorithm to determine the pulsation period and amplitude for each star and compare them with results of previous investigations at infrared and radio bands. We obtain the relationship between the pulsation periods and the amplitudes at L band. Contrary to the results at K band, there is no difference of the trends in the short and long period regions of the period-luminosity relation at L band. This may be due to the molecular absorption effect at K band. The correlations among the L band parameters, IRAS [12-25] colors, and K band parameters may be explained as results of the dust shell parameters affected by the stellar pulsation. The large scatter of the correlation could be due to the existence of a distribution of central stars with various masses and pulsation modes.

Solar Paddle Antenna on Pico-Satellite for Amateur Radio Communication

Abstract: This paper describes solar paddle antenna proposed in the development of Kagawa Satellite “KUKAI.” KUKAI is a mother-daughter pico-satellite for technical verification of a tethered space robot. The mother and the daughter satellites communicate respectively with the ground station by amateur radio frequencies. For the purpose of simple deployment system on orbit and antenna directivity suitable for KUKAI, solar paddle antenna mounted at the edge of a solar paddle is employed. After sufficient antenna adjustment on the ground, KUKAI was launched on 23 January 2009 by the H-IIA rocket from Tanegashima Space Center. The solar paddles were successfully deployed, and communication by the solar paddle antenna was successful.

Design of L band space-borne SAR digital receiver using direct RF sampling

Abstract: This paper presents a design of L band space-borne SAR digital receiver using direct RF sampling.Appropriate RF sampling frequency is selected and digital quadrature demodulation structure is improved.In order to reduce the volume of data that is stored onboard and later transmitted to ground station,a block adaptive quantization(BAQ) module with flexible compression ratio is developed.Simple electrical system design and advanced SAR system are achieved by using direct RF sampling.Feasibility and performance are verified by experimental results.

Experimental research of the dual-band array with cosecant-shape Far-field pattern

Abstract: Experimental investigation of the array with cosecant-shape Far-field pattern, working in L-band (1030-1090 MHz; 1450-1550 MHz) is presented. Comparison Results of the given date with the results of the computer simulation using Ansoft HFSS program are presented.

Development of Earthquake-induced Building Damage Estimation Model Based on Satellite L-band SAR and its Application to ALOS/PALSAR

Abstract: In order to expand the existing C-band SAR based damage estimation model into L-band SAR, this paper rebuilds a likelihood function for severe damage ratio on the basis of dataset from JERS-1/SAR (L-band SAR) images observed the 1995 Kobe earthquake and its detailed ground truth data. The model which integrates the fragility functions of building damage in terms of seismic intensity and proposed likelihood function is then applied to PALSAR (L-band SAR) images taken over the areas affected by the 2007 Pisco, Peru, and the 2008 Sichuan, China, earthquakes.