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Thin-film oxide superconductor materials and advanced processing techniques have been used to fabricate high-performance filters for cellular communications base, stations. Quasi-elliptic bandpass and band reject filters were designed and realized using microstrips to approximate lumped elements. These quasi-lumped resonators have achieved unloaded Q's of more than 40,000. Precise system control allows for high operating temperature (77 K), using either Yttrium or Thallium high T, compounds, compensating €or temperature dependence. Such filters have been successfully integrated into a permanently evacuated dewar and cooIed by a miniature Stirling cycle cooler. The cooler and dewar were integrated with control electronics which run off standard cellular base station +27V power sources. The system consumes less than lOOW in operation, making it one of the most efficient WTSG subsystems demonstrated to date.
This paper presents the integration and channel characterization of a highly integrated dual-band digital beamforming space-borne synthetic aperture radar (SAR) receiver. The proposed SAR sensor is a low-cost, lightweight, low-power consumption, and dual-band (X/Ka) dual-polarized module ready for the next-generation space-borne SAR missions. In previous works, by the authors, the design and experimental characterization of each sub-system was already presented and discussed. This work expands upon the previous characterization by providing an exhaustive experimental assessment of the fully integrated system. As it will be shown, the proposed tests were used to validate all the instrument channels in a set-up where the SAR sensor was illuminated by an external source minim the ground reflected waves. Test results demonstrate how the system channels are properly operating allowing the reception of the input signals and their processing in the digital domain. The possibility to easily implement a calibration procedure has also been validated to equalize, in the digital domain, the unavoidable amplitude differences between the different channels.
A 60-Channels ADC (Analog to Digital Converter) board for space borne Digital Beam Forming (DBF) Synthetic Aperture Radar (SAR) applications is described. The purpose of the board is to digitize analog signals detected by a dual band SAR receiving array operating at X and Ka band. It contains 48 high speed ADCs, which sample synchronously the incoming data of the antenna front end at Ka band. Other 12 ADCs are used to sample the coming data from the X band antennas. The board is composed by an analog section, a digital section and a clock distribution network used to synchronize the ADCs. Output digital signals from the board are routed to digital boards were are processed in the Digital Beamforming Network (DBFN).
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