Navigare după Autor "CRIȘAN Nicolae"

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DESIGN AND IMPLEMENTATION OF A FULL-DUPLEX GROUND STATION FOR THE QO-100 SATELLITE SYSTEM BASED ON SDR AND RASPBERRY PI
(Technical University of Cluj-Napoca, 2024) CRIȘAN Nicolae
Abstract: This paper proposes an approach based on the Adalm-Pluto SDR and Raspberry PI to design a ground station for geostationary satellite communications. The system is designed from modules to be versatile, agile, and scalable. In this case, the usage of modules is mandatory due to the complexity of the communications system, which simultaneously operates two radio channels at 2.4 GHz for uplink and 10 GHz for downlink. Such a combination with SDR (Software Defined Radio) and classic down and up converters benefits from using a Raspberry PI 4 with a powerful processor running under Linux. The proposed system allows the usage of GNU Radio with its powerful graphical interface written in Python. User interface UI has been undertaken by the Raspberry PI’s most versatile display with a touch screen of 7 inches. Another topic the paper addresses is using the helical antenna in front of the Horn antenna at the same focus point established by the dish reflector. The ground station proposed here has been successfully tested to transmit short radio packages containing data about temperature, atmospheric conditions, and voice.
UHF-RFID ANTENNA FOR SEMI-ACTIVE ASSISTED TAGS
(Technical University of Cluj-Napoca – Romania, 2023-12-09) CRIȘAN Nicolae
This paper proposes a new concept of using RFID tag antennas more actively in the identification process. This innovative concept is based on antenna native properties that allow RF harvesting for DC biasing, either from the reader or from other proximity RF sources at the same time. Nevertheless, for now, RFID identification tags without a self-DC power supply have become more popular and are referred to as passive. Eventually, both RF and light harvesting processes could be addressed as a foreseeable solution for identification range extension. Soon this trend will lead to the cheapest (printable) RFID tags at competitive prices closely shifted to those of the already mass-produced barcode tags, mainly in use today. The proposed semi-passive tag antenna is working by replacing the IMPINJ-MONZA chip with the EM4325 chip which can be DC supplied by a PV panel. This tag can work as RF energy harvester and can be DC biased as well, being the most capable for the proposed concept. The antenna is printed on paper using a metal powder ink printer and the tag is interrogated using a UHF-RFID reader. The harvesting for tag DC biasing is extended through a very small solar panel, which acts also as a substrate for the RFID antenna. Thus, the extended concept of the semi-active tag could increase the coverage and the sensing range of the reader significantly. This happens especially in daylight or when other nearby RF sources are available, otherwise, the tag will work as an ordinary one. This approach will allow the antenna to be shrunk even further near the Chu-Harrington limit.