In this study, a crop health monitoring system is developed by using state of the art technologies including wireless sensors and Unmanned Aerial Vehicles (UAVs). Conventionally data is collected from sensor nodes either by fixed base stations or mobile sinks. Mobile sinks are considered a better choice nowadays due to their improved network coverage and energy utilization. Usually, the mobile sink is used in two ways: either it goes for random walk to find the scattered nodes and collect data, or follows a pre-defined path established by the ground network/clusters. Neither of these options is suitable in our scenario due to the factors like dynamic data collection, the strict targeted area required to be scanned, unavailability of a large number of nodes, dynamic path of the UAV, and most importantly, none of these are known in advance. The contribution of this paper is the formation of dynamic runtime clusters of field sensors by considering the above mentioned factors. Furthermore a mechanism (Bayesian classifier) is defined to select best node as cluster head. The proposed system is validated through simulation results, lab and infield experiments using concept devices. The obtained results are encouraging, especially in terms of deployment time, energy, efficiency, throughput and ease of use.

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A novel tunable channelized two-branches passive bandstop filter using a reconfigurable parallel-coupled-line-based Phase Shifter (PS) is presented. The filter topology uses the signal destructive principle and aims to protect the receiver against an unwanted interference signal received by the antenna. The global filter topology contains two branches, each of which has a different function. The bandpass tunable branch selects the frequency to be rejected while the reconfigurable PS plays the signal invertor role. The simultaneous tunability of both bandpass and PS branches is ensured by using identical varactor diodes and features 550-700 MHz tuning range. In addition of having a constant and relatively high rejection level over all the tuning range and low insertion loss in the passband area, the filter guaranties ultra-low power consumption. Moreover, synthesis equations are proposed and used to illustrate the operating principle, and finally validated by comparing simulations results to measurements.