Ajay Krishno Sarkar

An investigation of SAR inside human heart for antenna directivity, surface current variations and effect on antenna frequency in presence of heart

In this work, the impact of human heart on an 800 MHz inset fed rectangular microstrip patch antenna characteristics were investigated using CST Microwave Studio. The antenna was simulated over a mimic human heart muscle and the distance between them was varied to analyze the changes in Specific Absorption Rate (SAR) upon antenna performance parameters (specifically, directivity & surface current) for discreet and waveguide port feeding. The results exhibited that the center frequency of the antenna was shifted to lower value and an increase in SAR values when the antenna was closer to heart for both the feeding techniques. However, the discrete port had more values of SAR than the waveguide port but for both cases SAR decreased with the increment of antenna distance from heart. SAR values for up to 4 mm distance in between the antenna and human heart did not satisfy IEEE and ICNIRP standards. For increasing surface current, the SAR values decreases due to less penetration of flux inside the tissue for both feeding techniques. Increasing directivity resulted decrement of SAR values due to the fact that more reflection of the wave from the tissue happened for more directivity. This work demonstrates how mobile phone antennas of GSM band affect human heart and how human heart affects antenna resonance frequency when mobile phones are kept in chest pocket.

Total efficiency comparison of different shaped microstrip patch antennas having Defected Ground Structure

In this paper, 15 different shaped (E, F, inverted F, G, H, I, L, inverted L, S, T, inverted T, U, inverted U, W and inverted W) conventional microstrip patch antennas along with a dumbbell (H) shaped Defected Ground Structure (DGS) in each are designed and simulated at 2.4 GHz operating frequency using CST Microwave Studio Suite. The efficiency of microstrip patch antennas are compared in terms of surface wave concept and the antenna with H shaped patch exhibiting total efficiency of -2.546 dB is found most efficient. The implementation of this work is highly anticipated to be employed for designing hybrid shaped patches for WLAN, wireless network (Wi-Fi and Bluetooth), nonstandard RF remote, ISM band applications.

Effect of human body on an 800 MHz inset fed rectangular microstrip patch antenna characteristics

This work demonstrates the impact of human body on an 800 MHz inset fed rectangular microstrip patch antenna characteristics. The antenna was simulated over a human phantom model consisting human thigh muscle using CST Microwave Studio. The distance between the antenna and human thigh muscle was varied to analyze the changes in antenna performance for waveguide port feeding. The results exhibited significant changes in antenna characteristics, especially the shifting of center frequency to a lower value due to the human body. Specific Absorption Rate (SAR) was studied as well to illustrate how on-body communication or mobile phone antennas of GSM band might affect human body when mobile phones are kept in pants pocket.

RF absorption in biological tissue at varying distances and angles and rapport to tissue impedance

Exposure of the general public to low-level RF fields causes direct or indirect coupling of the fields in the human body. Due to this coupling, there is an induction of the fields inside the body tissue that causes currents in the tissue while the tissue absorbs RF power. In this work, the RF absorption by a biological tissue was measured by using an antenna trainer in a laboratory set up by varying distances and angles of RF radiation source. Using the detector current, the absorbed power by the tissue as well as the incident component of Electric field upon the receiving antenna was calculated with and without the tissue. From calculating rms value of the field, the voltage inside the tissue was estimated. Using the absorbed power and voltage inside the tissue, the impedance inside the tissue was calculated. Results indicated that the more impedance values inside the tissue incur more absorption of RF power. The more dominant effects for angles than the distances were obtained for absorbed power by the tissue.

Modeling of graphene conductivity using FDTD in the near infrared frequency

This paper investigates the modeling of graphene interband conductivity in near infared frequency range. First, the interband graphene conductivity is incorporated in surface boundary condition (SBC). Then, SBC is applied in finite-difference time domain (FDTD) method for modeling graphene sheet. Moreover, auxiliary differential equation (ADE) is used to characterize frequency dependent graphene conductivity in FDTD method. Advantages, accuracy, applicability and stability of the proposed method are analyzed by numerical examples. The method is validated by comparing the existing analytical results. This method can be easily implemented to model the graphene interband conductivity for optical device applications.