This paper presents the design of a novel lowpass–bandpass diplexer with compact size and good performance using microstrip cells. For this purpose, two microstrip lowpass and bandpass filters are separately designed and mathematically analyzed. The proposed microstrip diplexer has a novel and simple structure. It occupies a compact area of 0.037 λg2 (722 mm2), and its insertion loss and S11 at both channels are low. The insertion loss at the lower and upper channels is only 0.047 and 0.16 dB, respectively. Meanwhile, both channels are flat with the maximum group delay of 1.68 ns which is the lowest compared to the previously reported diplexers mentioned in this paper. To design the proposed diplexer, first, a lowpass diplexer with good performance is designed which has low losses and a good figure of merit. It has a flat passband with a sharp roll-off. Then, to achieve the proposed diplexer, a bandpass resonator is added to the lowpass filter without any extra matching circuit, which saves the overall size. The proposed diplexer is designed, simulated, and fabricated, where the simulation and measurement results are close.

In this paper, a new design configuration has been proposed in which a prototype of resonant inductive power transfer-based contactless power transfer to wound rotor has been developed which provides field power to brushless alternating current (BLAC) or brushless direct current (BLDC) motors without the use of permanent magnets in the rotor. Further, wound field in the rotor of DC motor can be powered without carbon brushes. The proposed design facilitates motor performance improvement by adding an extra dimension of field flux control, while the armature circuit is conventionally fed from position detection and commutation schemes. It contains a primary multilayer concentrated coil fed with high-frequency resonating AC supply or switched mode supply. A single layer helical secondary coil coaxially fixed on the shaft receives high frequency wireless AC power transmitted from primary coil. Fast rectifier inside the hollow shaft and DC filter provides the transferred DC power to field terminals in the rotor. It has been verified that rotor power can be varied linearly with linear variation in input DC power with the highest efficiency at the resonant frequency. Available power to the rotor remains invariable with rotational speed and angle, which is a necessary requirement for rotor field. DC voltage on the rotor terminals can be effectively controlled during standstill as well as during rotation at any speed.

An experiment was carried out to assess the performance of an automatic irrigation system based on remotely-sensed soil moisture measurements in blueberries grown in sandy soil under plastic tunnels. The system uses the information provided by soil moisture sensors installed at three soil depths (10, 20 and 30 cm) and user-defined irrigation set-points to trigger automatic irrigation events. An Optimized irrigation treatment in which irrigation set-points and duration of irrigation have been determined from soil hydraulic properties analysis and soil water modelling is compared to the irrigation scheduling criteria established by the grower (Control treatment). The results showed that the Optimized treatment applied 30% of the water applied by the Control treatment, led to mild to moderate crop water stress conditions and had no impact on berry yield and quality.

This paper describes the design, realization, and application of a custom temperature sensor devoted to the monitoring of the temperature differential between the leaf and the air. This difference is strictly related to the plant water stress and can be used as an input information for an intelligent and flexible irrigation system. A wireless temperature sensor network can be thought as a decision support system used to start irrigation when effectively needed by the cultivation, thus saving water, pump fuel oil, and preventing plant illness caused by over-watering.

Here we demonstrate wireless energy transfer that exploits the conductivity and permittivity of soil to create a potential gradient on the surface around an earthed electrode, distributing electrical energy over the area. This generated surface potential can be amplified using a special standing-wave receiver for harnessing the distributed energy. We have experimentally mapped the surface potential around the electrode and plotted the received energy covering an area of 1200 m2. Key operating parameters are determined with a discussion on optimizing the system efficiency. This technique could address the challenge of distributing electrical energy to many low power devices over large outdoor areas without the use of wires.

Wireless network has been emerged as one of the most promising technologies for sensor-integrated applications so far. The ever-increasing demand in long-term chronic monitoring of vital or essential signals is driving a technology revolution in dealing with critical issues of clinical, healthcare, fitness, and wellness, creating multidisciplinary collaborations to benefit mankind. The voltage-controlled oscillator has been one of the important building blocks in this regard. In this paper, we report on study concerning the design and implementation of such a key circuit, with particular emphasis on a μW-level low-power design. All the aspects regarding the oscillator are detailed. The proposed circuit structure and experimental results justifying our work are given as proof of concept.

Many scientists and engineers contributed – more or less successfully – to the development of radio and wireless. This historical survey describes briefly the projects realized more than a century ago by some of them, at the early beginnings of wireless. It is hoped, in this manner, to draw attention to the unknown or forgotten researchers who built up the considerable body of knowledge that led to Marconi's remarkable achievements.