JOURNAL OF APPLIED ELECTROMAGNETIC
Year:2016 | Volume:3 | Issue:3 (8) |Papers Count:6

In this paper, a local positioning system based on LORAN positioning system is investigated. A radio foundation LORAN system accurately gains the position by measuring the difference in arrival times of vehicles which are far from each other and are moving from the transmitter station. LORAN transmitter station consists of power supply, antenna coupling network, and antenna damping network. Power supply in local positioning system is in charge of generating half sine wave through the current compression generator. In this paper, the principle of designing current compression generators (CCG) is proposed with the aim of transferring the maximum energy utilizing the least number of CCG modules. This approach is in contrast with the conventional ones in which the same CCG modules are employed. Accordingly, in the same number of CCGs, the proposed strategy is capable of transferring more energy to antennae circuit as well as higher quality in LORAN signal. The analytical design of CCGs is carried out to make the antenna current being the maximum of 175 amps at 62.5 microseconds. To this end, both strategies are examined and their results will be quantitatively and qualitatively compared with each other.

In bearing less permanent magnet synchronous motor, both torque winding and magnetic levitation winding are placed in common stator slots. When the rotor is not in the center of the stator, coupling is established between two windings. In most of the researches to be realized about control of this motor, coupling between two windings is neglected. In this paper, the impression of coupling between two windings on performance of suspension control system is studied. Simulation results show that coupling between two windings is not negligible and disturbances such as sudden changing of reference signals of radial displacement components and radial forces on shaft can displace the equilibrium point of rotor. Furthermore, in this paper with consideration of coupling between two windings, a proper controller has been designed in order to attain the desired performance of the motor against the sudden changing of reference signals of radial displacement components. Simulation results confirm the necessity of coupling effect modeling and correctness of the proposed method.

Weed control is one of the most important problems of agriculture industry due to the reduction of productivity of the fields. Traditional, chemical, and biological weed management alternatives have their own drawbacks such as environmental issues. This opens the doors for new technologies such as microwave treatment of weeds which directly target the weeds using electromagnetic heating. Due to their sensitivity, by increasing weed seeds temperature to about 60 degrees, they will lose their germination potential. The effects of microwave on a famous type of weed named Sisymbrium Irio have been investigated. Ready to germinate, buried weed seeds are exposed to microwave power in different exposure times. The results of our experiments and simulation show that the average electric field in the depth of 1cm in soil is around 5700 V/m and the amount of dissipated energy that is necessary for destroying Sisymbrium Irio seeds germination is around 200 J/cm3.

In this article a simple and compact frequency reconfigurable microstrip UWB Antenna with triple band notched is presented. The proposed antenna consists of an elliptic patch, and a micro-strip feed line. Three slots are used on the surface of patch to achieve notched bands. Each one of these slots is used in order to achieve notched band in WLAN (2.4-2.48GHz, 5.15-5.35GHz) and WiMAX (3.3-3.6GHz) bands. By changing the status of each slots Embedded on antenna by the high-frequency switches, notch bands can be controlled independently. The results of simulations and measurements show a proper impedance matching in the frequency range 2.2-11 GHz and achieving independent frequency notched bands. So, the antenna is capable of operating in one of the multiple modes which makes it an excellent candidate for UWB applications.

One of the applications of meta-materials is radiation attribute optimization in micro-strip antennas. In this research, a 7´7 cellular array of rectangular Split Ring Resonator (SRR) structures is considered. The structural parameters of the resultant meta-material including permeability (m) and permittivity (e) are extracted by using Nicolson- Rose method. A patch antenna is designed in 5.8 GHz frequency so that the meta-material array is used as superstrate. The results obtained from simulations done by CST software without the superstrate and the presence of it are presented. Consequently, aforementioned simulation results show that gain and bandwidth of the proposed antenna are improved by 114% and 116%, respectively. The meta-material and constructed antenna, the antenna's radiation pattern and return loss are operationally measured with and without the presence of a superstrate. Subsequently, the measurement results are properly compatible with simulations results; however, due to lack of standard SMA connectors that exist on the market, and also losses from wires and probes and also losses resulting from the measurement device, there are some differences between simulation results and the measurement (resonance frequency and return loss amplitude).

In this paper, the design and fabrication of a non-reciprocal phase shifter with high power handling capability is considered in the frequency of 9.4 GHz. In the design procedure, the effect of ferrite parameters such as location, width, and DC magnetic bias over phase shift value and insertion loss is outlined. By considering various parameters, the optimum design to obtain suitable phase shift is chosen. As regards impossibility of theoretical analysis of such structures, the HFSS simulator is used for calculation and optimization of the phase shifter. To ensure HFSS results, the structure is also simulated using the CST simulator and obtained results of two simulators are compared together. The final phase shifter consists of standard waveguide WR-112 and four ferrite slabs where connected to the wide wall of waveguide with dimension of 2mm×5mm×30mm. The measured results show that the 90° phase shift and insertion loss about 0.15 dB are obtained in frequency of 9.4 GHz. The measurement results have a very good agreement with simulation results.