A Comparative Study of the Effects of Substrate Composite Materials on External and Internal Handset Antenna EM Absorption

Cellular phones are used in the vicinity of a human head, which absorbs power from antenna radiation. This investigation analyzes the effects of antenna substrate materials on electromagnetic (EM) absorption in a human head. Antennas are used in analysis with four different dielectric substrate materials, which are Bakelite, FR4 glass epoxy, Rogers R04003, and Taconic TLC. Moreover, two different thicknesses of each substrate are considered in the experimental setup. The EM absorption associated with two types of cell phone antennas is evaluated in the closed vicinity of the human head model. One of them is planar inverted-F antenna (PIFA), which is used as the internal handset antenna and another one is helical antenna, which is used as external handset antenna. This investigation consists of two different operating frequency bands, GSM 900 MHz and DCS 1800 MHz. The EM absorption in the human head is presented using the peak specific absorption rate (SAR) and total absorbed power (TAP) by the user. The finite-difference time-domain (FDTD) method based on Computer Simulation Technology (CST) Microwave studio is utilized in this investigation. The obtained results show that the substrate materials do not effect SAR and TAP values considerably for both antennas, but substrate thickness affects the SAR and TAP values significantly. In addition, the substrate thickness affects the SAR and TAP values significantly in most of the cases Moreover, PIFA produces lower SAR than that of a helical antenna significantly for both GSM and DCS frequency band

Treatment Options of Temporomandibular Joint Ankylosis at a Tertiary Level Hospital in Bangladesh: A Two-Year Retrospective Analysis

Introduction: The study compares the surgical treatment options utilized to treat temporomandibular joint ankylosis at a tertiary level hospital in Bangladesh from 2016 to 2017. Materials and Methods: In this retrospective analysis, 18 patients (28 joints) were studied. History, radiological and physical examinations, and mouth opening were all part of the preoperative and postoperative evaluation. Age, sex, underlying cause, affected joint (s), surgery modality, complications, and follow-up durations were all taken into consideration. The data was analyzed using the SPSS 22.0 statistical software. The degree of mouth opening before and after different surgical techniques in different patient categories was compared using a one-way ANOVA followed by Tuky's HSD test. Results: Temporomandibular joint ankylosis was found to be in several forms (fibrous, fibro-osseous, and osseous), with trauma (61.11%) being the most common cause. The patients ranged in age from 5 to 30 years old, with females accounting for 55.55% of the total. The mean mouth opening significantly increased from 3.11 mm pre-operatively to 31.17 mm in the first month following surgery (p = 0.00001). In 55.55% of the instances, temporary facial nerve paresis occurred. Conclusions: Temporomandibular joint ankylosis can be successfully managed with early excision of the ankylotic mass, restoration of the ramus height by bone grafting, interpositional arthroplasty, and intensive physiotherapy

Calibrated parallel-plate waveguide technique for low-frequency and broadband absorptivity measurement

A broadband measurement technique for the normal-incidence absorptivity based on parallel-plate waveguide (PPW) is proposed. The method is well-suited for frequency selective surface (FSS)-based absorbers. By employing the PPW structure, only a small sample size, i.e. 1D array of FSS, is required for the measurement. The Thru-Reflect-Line (TRL) calibration is implemented to remove the time-gating ambiguity in the conventional PPW-based method. A measurement system working up to 6 GHz is designed such that its length is adjustable to ensure all three calibration standards (Thru, Reflect, and Line) can be carried out in a single device. Moreover, the height of the PPW is also adjustable to allow the measurement of absorbers with a different periodicity of FSSs. Two single-layer FSS-based absorbers with different periodicity are fabricated and measured. The results agree well with the conventional free-space measurement system, which validates the proposed method

A comparative study of the PIFA and printed monopole antenna EM absorption

This paper represents a comparative study on electromagnetic (EM) absorption in the human head between a printed monopole antenna and a planar inverted-F antenna (PIFA). The specific absorption rate (SAR) values and total absorbed power in the human head phantom are used to evaluate EM absorption for both antennae. Moreover, antenna performances in terms of return loss, radiation efficiency, and gain are also investigated in this study. The finite integration technique (FIT) based on CST Microwave studio and SAM head phantom are used in this study. The antenna performances are measured in an anechoic chamber and the SAR is tested using COMOSAR measurement system. The obtained results indicate that the printed monopole antenna lead to higher EM absorption in the human head as compared to PIFA for both GSM frequencies

Low specific absorption rate microstrip patch antenna for cellular phone applications

The aim of this study is to design a new microstrip-fed patch antenna for cell phone applications. The antenna design is composed of slots and Flame Retardant 4 dielectric substrate fed by a partial ground plane and a microstrip line. The user's effects on antenna performances are also analysed using standard specific anthropomorphic mannequin head phantom. The specific absorption rate (SAR) values of the proposed antenna are evaluated for different frequency bands considering cheek position of talk mode. The proposed antenna has an impedance bandwidth of 230.4 MHz (0.725-0.95 GHz, lower band), and 522.24 MHz (1.74-2.25 GHz, upper band), which can cover global system for mobile (GSM) 900 MHz, digital communication system 1800 MHz, personal communications service 1900 MHz, GSM 1900 MHz, and universal mobile telecommunications service 2100 MHz bands. Moreover, the proposed antenna produces lower SAR values in the human head than that of a dipole antenna, helical antenna, and planar inverted-F antenna

A metamaterial-embedded wide-band antenna for the microwave C-band

In this paper a metamaterial-embedded, compact microstrip-fed patch antenna is introduced for microwave C-band applications. The proposed antenna is composed of a rectangular metamaterial-embedded patch, microstrip-fed line and a partial ground plane. The finite-integration technique (FIT) based on Computer Simulation Technology (CST) Microwave Studio is utilized in this study. The measurements of antenna performances are conducted in a near-field measurement laboratory. The antenna performance parameters comprising the reflection coefficient, radiation efficiency, gain, and radiation pattern are studied to validate the antenna performance. The measured results show that the proposed metamaterial-embedded antenna exhibits a wide impedance bandwidth over the C band (from 3.77 GHz to 6.58 GHz). The results also indicate good radiation efficiency and antenna gain with a nearly omni-directional radiation pattern at the frequencies of interest

A new wide-band double-negative metamaterial for C- and S-band applications

A new design and analysis of a wide-band double-negative metamaterial, considering a frequency range of 0.5 to 7 GHz, is presented in this paper. Four different unit cells with varying design parameters are analyzed to evaluate the effects of the unit-cell size on the resonance frequencies of the metamaterial. Moreover, open and interconnected 2 x 2 array structures of unit cells are analyzed. The finite-difference time-domain (FDTD) method, based on the Computer Simulation Technology (CST) Microwave Studio, is utilized in the majority of this investigation. The experimental portion of the study was performed in a semi-anechoic chamber. Good agreement is observed between the simulated and measured S parameters of the developed unit cell and array. The designed unit cell exhibits negative permittivity and permeability simultaneously at S-band (2.95 GHz to 4.00 GHz) microwave frequencies. In addition, the designed unit cell can also operate as a double-negative medium throughout the C band (4.00 GHz to 4.95 GHz and 5.00 GHz to 5.57 GHz). At a number of other frequencies, it exhibits a single negative value. The two array configurations cause a slight shift in the resonance frequencies of the metamaterial and hence lead to a slight shift of the single-and double-negative frequency ranges of the metamaterial