SAR reduction and gain enhancement of compact wideband stub loaded monopole antenna backed with electromagnetic band gap array

Abstract

This article discusses a design of compact wideband stub loaded monopole antenna (CWSLMA) backed with 3 Â 3 array of hexagonal shaped electromagnetic band gap (EBG) cell operating at 2.45 GHz with enhanced gain and low specific absorption rate (SAR) for wireless body area network (WBAN) applications. The split ring rectangular shaped radiator is designed with protruding stub to miniaturize the antenna size of monopole antenna (34 Â 18 Â 1.6 mm 3 ) at resonance frequency 2.45 GHz. The proposed CWSLMA is fabricated on glass epoxy FR4 substrate supported with 3 Â 3 array of hexagonal shaped EBG cell over Kapton polyimide flexible substrate.The proposed antenna consists of simulated 10 dB return loss (RL) bandwidth (BW) of 16.7% (2.3-2.72 GHz). The proposed 3 Â 3 array of hexagonal shaped EBG cell enhances the realized gain of proposed CWSLMA to 7 dBi by reducing the back-lobe radiation. The EBG array also increased the isolation between fabricated wearable antenna and human body and thus, reduced SAR to 0.44 W/kg (tested over 10 g of human tissues) at frequency 2.45 GHz. The fabricated proposed CWSLMA with EBG achieved a measured 10 dB RL bandwidth of 17.3% (2.27-2.7 GHz) and a measured group delay below than 1 ns in entire operational band with measured gain of 6.8 dBi. The proposed CWSLMA with EBG is designed, fabricated, and tested. The measured results of fabricated antenna prototype are verified and validated with simulated ones.

A compact fully fabric I‐shaped antenna supported with textile‐based AMC for low SAR 2.45 GHz wearable applications

“…Traditional antennas are rigid and present uncomfortable feeling; however, body-worn antennas need certain properties such as flexibility; hence, this type of antenna is designed on substrates, which are based on soft materials. Substrates like polyethylene, polycarbonate and polyester sheets, 2,3 textile, [4][5][6][7][8][9][10][11] polydimethylsiloxanes (PDMS), 12,13 and thin polyimides [14][15][16] are flexible and robust. These substrates made flexible electronics more attractive than conventional electronics technology.…”

“…The SAR value can be decreased by widening the void space between the antenna and human body, 16 designing reflectors in the form of arrays, [2][3][4][5][6][7][8][9]11,12,[14][15][16][17] that are relatively large in size, or having a full ground plane separator. 13 These structures are usually placed in the void space between the antenna and human body; therefore, reflecting the back radiations to a normal direction from the human body.…”

“…The first is the American one, where its threshold level is 1.6 W/kg averaging over 1 g of tissue, while the second is the European one, which has a threshold limit of 2 W/kg averaging over 10 g of tissue. The SAR value can be decreased by widening the void space between the antenna and human body, 16 designing reflectors in the form of arrays, 2–9,11,12,14–17 that are relatively large in size, or having a full ground plane separator 13 . These structures are usually placed in the void space between the antenna and human body; therefore, reflecting the back radiations to a normal direction from the human body.…”

A novel wearable monopole antenna with controlled SAR using metamaterial

“…Meta-surfaces have been effective for enhancing gain by either absorbing energy in a certain direction or reflecting energy due to their unique properties. A number of attempts have been made in recent years to incorporate these metasurface (MS) based structures, such as artificial magnetic conductors, electromagnetic band gap structures, partial reflecting surfaces, and frequency-selective surfaces to redirect backward radiation of antennas [14][15][16][17][18][19][20][21][22][23][24][25][26][27]. The metamaterial acts as a filter at the designed frequency.…”

Design of an Analog RFID-Based Tag Antenna with Opened Circuited L-Shaped Stubs for Applications in Localization

“…In addition to the gap method, the performance of the system depends greatly on the chip's dimensions. In [12], a parametric study on stubs and load sizes was performed to enhance the characteristics of the proposed antenna [13].…”