Viabilidade da ampliação do alcance de rádio-enlaces entre uma central e sensores de nível de água em lavouras de arroz

Abstract

In this work, different topologies of rectangular microstrip antennas are studied, which are fed in different ways so as to increase the maximum allowed distance between the trans-mitter and a receiver of data transmission system used to supervise a rice crop. The antennas were designed based on the specifications of the data transmission system, whose operating frequency is 2,4𝐺Hz. Initially, a monopole antenna is analyzed to assess its radiation characteristics. This mo-nopole antenna is part of the data transmitting system that is being employed in a rice crop located in Uruguaiana, in South Brazil. Based on these analyses, an assessment on possible modifications in the communication system will be proposed so as to improve the perfor-mance of the radio links. The main characteristics of simple microstrip radiators are described next. Four different models antennas are proposed and discussed. Among these models, one antenna has been manufactured. The initial design of each antenna has been performed using the transmission line method. Further optimizations have been then carried out employing commercial elec-tromagnetic simulators such as Ansoft Designer and HFSS. The designed probe-fed antenna has been measured. After comparison between experi-mental and theoretical results, a frequency shift between the reflection coefficient curves has been verified. By means of simulations, it could be demonstrated that the frequency shift was due to the use of a wrong value for the dielectric constant. Finally, it has been verified that the distance between the transmitter to the receiver of the data transmitting system currently in used can be nearly doubled, if the monopole is replaced by the microstrip antenna with the best performance, which was designed in the present work.