In this paper, a novel circularly polarized rectenna, with a harmonic suppression, capable of harvesting low-power RF energy with wide operating output loads is presented. The proposed rectenna is composed of a circularly polarized CPW-fed antenna based on a split ring resonator (SRR) and a wideband rectifying circuit. The circular polarization characteristic is achieved by breaking the symmetry of the SRR. The designed topology is fabricated and measured. Simulated and measured results show that the rectenna's efficiency is more than 45% at 2.45 GHz with an input power of -15 dBm under different polarizations. Importantly, the measured results show that the proposed configuration can maintain the same efficiency over wide ranges of loads (from 1 to 5 kΩ). The measured output dc voltage of the rectifier with a load resistance of 3-kΩ is 0.21 V and 1.22 V at -15 dBm and 0 dBm, respectively. The proposed design concept is very suitable for the 2.45 GHz ISM band (Wi-Fi, Bluetooth, RFID, etc.).
Seawater is generally considered as an electrical conductor with rather weak electrical conductivity. As a moving electrical conductor in an electromagnetic field, seawater motions induce weak electromagnetic field in surrounding environment. The movement of vessels in seawater leads to the variations of electromagnetic field pattern, called as magnetic wake. In order to detect a moving object through the induced magnetic wake, a magnetometer can be placed under the seawater surface. In this paper, we present a mathematical model through which we can study the magnetic wake in water of finite depth and, explore its behavior with respect to environmental parameters and geometric characteristics of the moving object. More specifically, we show through mathematical expressions and numerical results that there always exists an optimal depth under the sea surface wherein if amagnetometer isplaced, maximum amplitude of magnetic wake can be captured. Several key properties are verified for the optimal magnetic wake detection through numerical results. Firstly, the optimal depth is increased by increasing the speed of the moving vessel. Secondly, the optimal depth is not influenced considerably by the variation of sea depth, and thirdly, in the case wherethe Froude number of the vessel is lower than 0.5, the optimal depth is below 15 m.
The magnetic-geared generator integrates the magnetic gear and the generator by using the magnetic field modulation technology. It has the characteristics of high power density, high material utilization, and has a wide application prospect. However, compared with the general generator, its structure is relatively complex which makes its design and optimization become more complex. Therefore, a new structure and an optimization method based on orthogonal regression statistics is proposed. The experimental results fully prove the effectiveness of the proposed structure and optimization method.
In this paper, half-mode substrate integrated waveguide (HMSIW) bandpass filters with modified complementary split-ring resonators (CSRRs) for the reduction of machining tolerance sensitivity are presented. Profiting from the evanescent-mode resonance operation, the conventional CSRR and its modified versions have been successfully utilized to miniaturize the physical sizes of SIW components. However, few investigations have focused on the fabrication tolerance. Performance of most CSRR-loaded SIW components, as well as their modified versions, is significantly sensitive to the fabrication tolerance. Hence, as the conventional machining process is with large fabrication tolerance, the CSRR-loaded SIW components suffer from limited performance and restrained application practicability. To decrease the influence from the machining tolerance on the components' performance, the slots-embedded CSRR (SECSRR) is proposed and loaded into HMSIW to design evanescent-mode filters. Numerical simulations exhibit that the proposed SECSRR can help to decrease the machining tolerance sensitivity effectively as the fractional frequency offset resulting from the fabrication error is reduced from ±8.11% to ±4.95%, which indicates that the proposed SECSRR is able to improve the suitability of SIW/HMSIW components and circuits for practical radio frequency (RF) and microwave applications.