In this study, factorial experiments were conducted in two different scenarios to design a Wireless Sensor Network for monitoring a cocoa crop in a rural area in Colombia. Node sensors measured temperature, relative humidity, soil moisture, Ultra-Violet light, and visible light intensity. The factors considered in the experiments were distance between node sensors, height from the ground, and type of antenna; in turn, Received Signal Strength Indicator and data transfer time were the outputs. The wireless sensor network was deployed in the crop, covering approximately 3 % of the area and using 7 different nodes in a cluster tree topology. First, an open field scenario with line of sight was used to determine the appropriate height of the node sensors. Second, a scenario in the actual cocoa crop was utilized to find the appropriate distance between modules and type of antenna. We found, based on our calculations and experimental data, that a height of 1.25 m was required to avoid the Fresnel zone and improve the RSSI of the network. Furthermore, we determined that a distance below 35 m was needed to guarantee signal reception and avoid long data transfer times. The wire antenna exhibited a better performance. Finally, the proposed methodology and monitoring system can be used for agronomic applications in rural areas in Colombia to increase crop yield.

Radio-over-fiber is a cost-effective support for the forthcoming 5G developments aimed to fulfill the ever-increasing demand for information. However, such systems are limited by transmission impairments that reduce the quality of communication. To enhance the system performance, an adaptive decision-feedback equalizer based on the least mean square algorithm is proposed in this work to compensate for frequency mismatch in the transmitter and receiver local oscillators in a radio-over-fiber transmission scenario when considering the latest 5G New radio standard. Simulation results in MATLAB exhibit a major impact from the equalization technique in improving the system performance in the presence of such a frequency offset, allowing the optical link to be extended from ∼100 km with no equalizer up to ∼690 km after equalization. Thus, it was demonstrated that the proposed adaptive equalization technique is a promising contender to enhance 5G-based Radio-over-Fiber data transmissions.

The following article presents computer-aided design software for multi-stage amplifiers with bipolar transistors and field effect. It is composed of two units: a design and analysis unit that allows for step-by-step introduction of polarization and small signal values, the type of transistor to be used (bipolar or field effect) with their respective characterization values: current gain, thermal voltage, activation voltage, and saturation current, to result in the configurations and values of the resistors; and a theoretical unit that contains complete information on multi-stage amplifiers. A n-stage amplifier design method was developed, represented through a flowchart, and coded using a freely usable programming language. With the software, designs were made and simulated in a computational tool for academic use endorsed by the scientific community. The result for all variables evaluated was an average error of less than 2%. The research concludes that this software allows an effective design process of multi-stage amplifiers with bipolar transistors and field effect in a short time, it also allows changing the resistance values obtained for commercial values and calculating the error when implementing the circuit being a useful tool in the experimental area.