RF Front-End Transmitting System for Agricultural Applications

In this paper, a design of an RF front-end transmitter for actuating greenhouse plant leaves with electromagnetic wave is proposed. The proposed RF front-end transmitter consists of a phase-locked loop (PLL), variable attenuator, power amplifier (PA), protector and detector circuits, and antenna. The overall circuit is designed for ISM band application with a center frequency of 2.45 GHz. The attenuation range of the variable attenuator is 20 dB. This variable attenuator is connected between PLL and driver PA to control the radiated electromagnetic wave power level for the optimum plant growing condition. The RF power higher than 20 W can be obtained at the output port of PA. The protector and detector circuits consist of the isolator, dual directional coupler, and RF detecting circuits. The isolator is used to protect the PA from the reflected power when the antenna is disconnected from the system. The RF detecting circuits are connected to the couple ports of the dual directional coupler to check long time operation. The designed PAs have been operated very well on humid operating conditions for 14 days.