L band

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

Design of phased array microwave scatterometer with digital beam forming technique in active and passive combining observation system for sea surface salinity

Abstract: Active and passive combining observation microwave instrument combines L band one dimension push-broom synthetic aperture radiometer and L band array mode microwave scatterometer to make accurate measurement for sea surface salinity. In this system, microwave scatterometer provides the information about the sea surface roughness, one of the main sources of error for salinity measurement. Phased array mode is adopted in scatterometer and the array elements are arranged between two elements with the largest baseline of radiometer. The number of array elements is set to 7 and digital beam forming technique is used to get scanning in cross azimuth direction. Then same footprints with radiometer can be obtained. Narrow band chirp signal is used to get range resolution. In this way, accurate backscattering information corresponds to observing area of radiometer can be achieved and then sea surface roughness can be derived. Finally, the error coming from surface roughness can be corrected.

System design of the MeerKAT L - band 3D radar for monitoring near earth objects

Abstract: This thesis investigates the current knowledge of small space debris (diameter less than 10 cm) and potentially hazardous asteroids (PHA) by the use of radar systems. It clearly identifies the challenges involved in detecting and tracking of small space debris and PHAs. The most significant challenges include: difficulty in tracking small space debris due to orbital instability and reduced radar cross-section (RCS), errors in some existing data sets, the lack of dedicated or contributing instruments in the Southern Hemisphere, and the large cost involved in building a high performance radar for this purpose. This thesis investigates the cooperative use of the KAT-7 (7 antennas) and MeerKAT (64 antennas) radio telescope receivers in a radar system to improve monitoring of small debris and PHAs was investigated using theory and simulations, as a cost effective solution. Parameters for a low cost and high performance radar were chosen, based on the receiver digital back-end. Data from such radars will be used to add to existing catalogues thereby creating a constantly updated database of near Earth objects and bridging the data gap that is currently being filled by mathematical models. Based on literature and system requirements, quasi-monostatic, bistatic, multistatic, single input multiple output (SIMO) radar configurations were proposed for radio telescope arrays in detecting, tracking and imaging small space debris in the low Earth orbit (LEO) and PHAs. The maximum dwell time possible for the radar geometry was found to be 30 seconds, with coherent integration limitations of 2 ms and 121 ms for accelerating and non-accelerating targets, respectively.

3 GS/s S-Band 10 Bit ADC and 12 Bit DAC 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) and DAC's (Digital to Analogue Converters) are key enabling components which open up new design opportunities for digital transceiver systems, including digital down and up-conversion closer to the antenna. In this regard, this paper describes new 10bit 3GS/s ADC and 12 Bit 3GS/s DAC, based on a 200 GHz SiGeC bipolar Technology, which enables direct digitizing or synthesing of 1GHz arbitrary broadband waveforms directly in the high IF region closer to the Antenna.

Improved coupled-line microstrip circuit for L and S band oscillators

Abstract: The coupled-bar microstrip circuit described here utilises a TRAPATT diode, and is ideally suited for systems applications such as i.f.f. transponder-transmitter sources and airborne altimeter sources. It is compact and rugged and allows high-efficiency operation. This circuit has delivered 150 W with 30% efficiency at L band, 150 W with 26% efficiency at 3.5 GHz, and 120 W with 19% efficiency at 3.85 GHz. The devices were operated with 0.5 μs pulses up to 1% duty cycle in a near jitterfree operation.