High gain cavity backed UWB antenna with and without band notch feature

High directivity antennas are often used in communication systems to meet specific coverage requirements. This paper presents a unidirectional, high gain UWB antenna. A reference UWB antenna is considered and a metallic cavity is built around it, this arrangement along with a stacked parasitic patch shows a maximum increase of 8.5 dB in the gain of the UWB antenna. A maximum increase of 8.43 dB in the gain is seen for the UWB antenna having band rejection feature

Experimental validation of bulk-graphene as a thermoelectric generator

Quest for alternate energy sources is the core of most of the research activities these days. No matter how small or large amount of energy can be produced by utilizing the non-conventional techniques and sources, every bit of innovation can reshape the future of energy. In this work, experimental analysis of the thermoelectric (TE) properties of bulk-graphene in the temperature range of (303 to 363) K is presented. Graphene powder was pressed to form a pellet which was used to fabricate the TE device. The effects of temperature on the Seebeck coefficient, electrical and thermal conductivities, and the dimensionless figure of merit (FOM) were measured. The increasing value of the Seebeck coefficient (thermopower) with temperature is indicant of the metallic behavior. Additionally, the observed thermopower (TEP) is positive, which shows that the majority charge carriers are holes and peaked to a value of 56 μV K-1 at 363 K. The thermopower of the pellet is four times larger than the previously reported values for single layer graphene (SLG) and few layer graphene (FLG). In addition to this, low values of the thermal conductivity were observed for the pellet which is one of the requirements of a good TE material. Besides this, an upward trend is observed with increasing temperature for FOM, which attains a peak value of 0.0016 at 363 K, which is almost ten times that of the previously reported values

UWB Antenna with Enhanced Directivity for Applications in Microwave Medical Imaging

Microwave medical imaging (MMI) is experiencing a surge in research interest, with antenna performance emerging as a key area for improvement. This work addresses this need by enhancing the directivity of a compact UWB antenna using a Yagi-Uda-inspired reflector antenna. The proposed reflector-loaded antenna (RLA) exhibited significant gain and directivity improvements compared to a non-directional reference antenna. When analyzed for MMI applications, the RLA showed a maximum increase of 4 dBi in the realized gain and of 14.26 dB in the transmitted field strength within a human breast model. Moreover, it preserved the shape of time-domain input signals with a high correlation factor of 94.86%. To further validate our approach, another non-directional antenna with proven head imaging capabilities was modified with a reflector, achieving similar directivity enhancements. The combined results demonstrate the feasibility of RLAs for improved performance in MMI systems

Behavioral Modeling Paradigm for DC Nanogrid Based Distributed Energy Systems

The remarkable progress of power electronic converters (PEC) technology has led to their increased penetration in distributed energy systems (DES). Particularly, the direct current (dc) nanogrid-based DES embody a variety of sources and loads, connected through a central dc bus. Therefore, PECs are required to be employed as an interface. It would facilitate incorporation of the renewable energy sources and battery storage system into dc nanogrids. However, it is more challenging as the integration of multiple modules may cause instabilities in the overall system dynamics. Future dc nanogrids are envisioned to deploy ready-to-use commercial PEC, for which designers have no insight into their dynamic behavior. Furthermore, the high variability of the operating conditions constitute a new paradigm in dc nanogrids. It exacerbates the dynamic analysis using traditional techniques. Therefore, the current work proposes behavioral modeling to perform system level analysis of a dc nanogrid-based DES. It relies only on the data acquired via measurements performed at the input–output terminals only. To verify the accuracy of the model, large signal disturbances are applied. The matching of results for the switch model and its behavioral model verifies the effectiveness of the proposed model