The importance of UAVs (Unmanned Aerial Vehicle), also called drones, in the society has been increasing over last years. Today, UAVs are used in different situations, for example on emergency conditions for locating people after an earthquake or transporting medicines to not accessible places.A major drawback of drone's communications is the short distance that can be reached. In this paper, the perform of LoRa (Long-Range) protocol is studied with the purpose of implementing it in these kinds of communications. Also, a system is proposed with the goal of increasing coverage area in UAVs communications.Furthermore, some tests were developed equipping two UAVs with the necessary hardware and transmitting information between two far points to analyze the performance of the system developed. Some of these values were the distance, power of transmission, the Signal to Noise ratio (SNR) and the Received Signal Strength Indicator (RSSI). Finally, the developed system was tested and gave a successful result for a distance of 10 km.
A new technique is presented to obtain reduced-order models of microwave oscillators from experimental measurements. The models can then be applied to the analysis and design of single-oscillator or multioscillator configurations such as coupled-oscillator systems. The first-order model is given by the derivatives of the oscillator admittance function with respect to the amplitude and frequency. The experimental technique presented here is based on the extraction of these derivatives from the injection-locked response of the oscillator, synchronized to a small-signal source. The new approach to obtain the derivatives has been validated through comparison with the standard method using commercial harmonic-balance software. The experimental setup and all the key aspects related to calibration and equipment requirements are explained in detail. Finally, the proposed technique is applied to characterize a voltage-controlled oscillator at 4.97 GHz. Excellent agreement has been obtained between measurements and simulations.Index Terms-Auxiliary generator (AG) technique, free-running voltage-controlled oscillator (VCO), synchronized VCO, VCO derivatives.
The Automatic Identification System (AIS) standard is encompassed within the Global Maritime Distress and Safety System (GMDSS), in force since 1999. The GMDSS is a set of procedures, equipment, and communication protocols designed with the aim of increasing the safety of sea crossings, facilitating navigation, and the rescue of vessels in danger. The use of this system not only is increasingly attractive to security issues but also potentially creates intelligence products throughout the added-value information that this network can transmit from ships on real time (identification, position, course, speed, dimensions, flag, among others). Within the marine electronics market, commercial receivers implement this standard and allow users to access vessel-broadcasted information if in the range of coverage. In addition to satellite services, users may request actionable information from private or public AIS terrestrial networks where real-time feed or historical data can be accessed from its nodes. This paper describes the configuration of an AIS receiver based on a modular design. This modular design facilitates the evaluation of specific modules and also a better understanding of the standard and the possibility of changing hardware modules to improve the performance of the prototype. Thus, the aim of this paper is to describe the system's specifications, its main hardware components, and to present educational didactics on the setup and use of a modular and terrestrial AIS receiver. The latter is for academic purposes and in undergraduate studies such as electrical engineering, telecommunications, and maritime studies.
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