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Transmission Module with Frequency Hopping for Wireless Sensor Mesh Networks Used in Plant Stress Monitoring Systems

This paper present the results regarding the simulation and the practical implementation of a transmission module based on the principles of frequency hopping spread spectrum technique (FHSS). The module is dedicated for high speed, spectral efficient wireless sensor mesh networks used in plant stress monitoring systems. The proposed design relies on a circuit architecture that uses a set of frequencies that are periodically switched according to a three bit code produced by a pseudorandom generator. The switched frequencies are used as carrier signals for transferring data blocks between the nodes of the mesh network. A critical problem in this approach is represented by the generation and quickly switching, without significant distortions, of a large set of carrier signals, but this problem was alleviated by using a high performance PLL based frequency synthesizer. Compared with other similar implementations the presented solution ensures a communication with increased immunity against noise. Another advantage of the proposed design is represented by the improved energetic efficiency which allows lowering the power consumption of the module due to the operation using the frequency hopping spread spectrum transmission technique.