A dual parallel Mach–Zehnder modulator linearization scheme based on 90° phase shifters

In this paper, a dual-drive dual-parallel Mach–Zehnder Modulator based linearization scheme is implemented by utilizing only two phase shifters and comprehensively demonstrated for a photonic transmission link. Third order intermodulation distortion is suppressed by adjusting angles of electrical phase shifters i.e. π/2 and−π/2 and a non-linear distortion immune system can be proposed for microwave photonic link. A complete suppression in intermodulation terms and 20.8 dB enhancements are found in spurious free dynamic range (SFDR). SFDR reaches 135.6 dB Hz4/5 by suppressing major spurious contributors of third order intermodulation distortions in optical domain only which ensures the improvement in performance of link against non-linear terms.

Reconfigurable bandstop filter using active frequency selective surface, design and fabrication

In this paper a novel FSS array is proposed, that provides dynamic band-gap in C-band. Inside the band-gap, the FSS acts as a bandstop filter. Outside the band-gap the amplitude of the reflected wave from the FSS array decreases. Therefore, the outside band is very useful in radar cross section (RCS) reduction. In this paper, at first a new FSS unit cell is designed, then in order to achieve the maximum bandwidth (1.2 GHz), dimensions of the cell are optimized. In the next step, the FSS cell is equipped with PIN diodes. Turning the diodes ON or OFF, shifts the resonant frequency of the band-gap electronically. When diodes are OFF, the resonant frequency and −10 dB bandwidth of the FSS are 5.23 and 0.9 GHz respectively. When the diodes turn ON, the resonant frequency shifts to 4.75 GHz over a bandwidth of about 1 GHz. While the band-gap is shifted dynamically, the bandwidth is kept wide, which is the novelty of this paper. In order to validate the design process, an array of active cells consisting of 128 pin diodes was designed, fabricated and then tested. Finally, the simulation and measurement results are compared with each other and a good agreement is observed between them.

A compact simple microstrip lowpass filter based on elliptical analyzed resonator

In this article, a compact microstrip lowpass filter (LPF) using elliptical shaped resonators with ultra-wide stopband is rendered. In this respect, LC equal structures of the elliptical shaped resonators are calculated based on the formula of circumference. In addition, to calculate transmission zeros of the presented elliptical shaped resonator, the LC equal structure and its output to input ratio are employed. The proposed LPF has a −3 dB cut-off frequency at 1.50 GHz and the stopband bandwidth of the designed filter is about 13fc, which refers to its ultra-wide stopband. The occupied circuit size of the presented filter is 0.151λ g × 0.044λ g (λ g is the guided wavelength at 1.50 GHz). The designed filter is fabricated on RT/Duroid 5880 substrate. The results of the fabricated and designed filter have clearly demonstrated that not only has the proposed LPF shown a suitable agreement between measured and simulated S-parameters, but also an appropriate stopband bandwidth.

Design of miniaturized dual-polarized dipole antenna for 4G & sub-6 GHz 5G applications

Dual-polarization, enhanced gain and compact size is the basic need of the base station antennas whereas a modern communication system needs a wideband antenna which can cover both the LTE & 5G applications. In the present work, a cross dipole antenna is proposed for LTE & sub 6 GHz 5G frequency band for Base Station Antenna Applications. By introducing asymmetrically shaped pentagon slots in the dipole and open-loop dipole patches, wide impedance bandwidth of 1.65–4.05 GHz at a return loss of −14 dB are achieved for 4G & 5G applications. Two symmetric feeding lines orthogonal to each other have been used to obtain the dual-polarization. Also, a high stable gain of 7 ± 1 dBi & HPBW of 80 ± 5° was achieved over the entire operating band at both the ports due to the symmetric structure. The proposed antenna is compared for size and bandwidth with the structures already proposed in the literature and significant enhancement is observed to be used for Base station antennas.

Dependence of specific absorption rate and its distribution inside a homogeneous fruit model on frequency, angle of incidence, and wave polarization

Electromagnetic regulatory guidelines prescribed by the international and national organizations are in effect worldwide to protect humans from immediate health effects. For restricting human exposure to electromagnetic radiation in near field, a quantitative term ‘specific absorption rate (SAR) limit’ has been coined and well established in literature. In addition, reference power density limit has also been prescribed in far field for human safety. At the same time, plants and fruits also absorb reasonable amount of electromagnetic energy due to high permittivity and electrical conductivity. Unfortunately, there is not much concern regarding electromagnetic energy absorption in plants and fruits, and no prescribed SAR limit in spite of recent reports in literature. Unlike humans, plants and fruits are of asymmetric shapes and sizes; therefore even at a particular frequency and fixed reference power density, electromagnetic energy absorption rate i.e., SAR in plants and fruits is expected to differ depending upon angle of incidence and wave polarization. To address these issues in detail, a typical bunch of three single layered water apples has been prototyped and exposed to plane wave irradiation at five different frequency bands as per the existing Indian electromagnetic regulatory guidelines. Broadband dielectric properties of water apples have been measured using open ended coaxial probe technique; thereafter, measured dielectric properties have been fed into the designed model. At a particular frequency, reasonable variations in magnitude and position of maximum local point (MLP) SAR, 1 g averaged SAR, and 10 g averaged SAR data have been noted for six different combinations of angle of incidence and wave polarization. This whole course of action is repeated over five different frequency bands. Moreover, variations in observed SAR data are also compared with previously reported variations in SAR data for a multilayer fruit structure. Observations indicate different order of changes in SAR for different fruit structures due to similar combinations of frequency, power density, angle of incidence, and wave polarization. Hence, direct definition of SAR limits for plant and fruit structures should be adopted even in far field in conjunction with reference power density.

Compact circular polarized CPW antenna for WLAN and biomedical applications

A compact, circularly polarized, CPW-fed antenna is proposed for wearable applications in ISM Band (5.8 GHz). The antenna is based on DGS, where the ground plane is responsible for impedance matching. The 10 dB impedance of the proposed antenna varies from 5.39 GHz to 5.94 GHz. The circular stub introduced in the ground plane mitigates the surface current and enriches the 3 dB axial ratio from 5.73 GHz to 5.92 GHz. Proposed antenna exhibits the LHCP and RHCP pattern of circular polarization, the antenna can effectively work for biomedical and wearable applications. The antenna is analyzed on the skin phantom model and the SAR value obtained is 1.218 W/kg, which is below the maximum permissible level. The proposed antenna is also used for the detection of breast tumors.

Design and Experimental Validation of Miniaturized Self-Triplexing Antenna Employing HMSIW

The design and experimental verification of miniaturized cavity-backed self-triplexing antenna (STA) with high-isolation employing half-mode substrate integrated waveguide (HMSIW) are presented in this work. The proposed STA is constructed by using HMSIW, an Y-shaped slot and three 50Ω feed lines. Three unequal radiating patches are generated by engraving an Y-shaped slot on the top surface of the HMSIW cavity to operate at 3.7/5.0/5.8 GHz for WiMAX/WLAN applications. The proposed STA allows to realize one of the operating band independently by keeping other operating band unaltered and vice-versa. The circuit area of STA is highly miniaturized due to the use of HMSIW cavity and loading of Y-shaped slot. The isolations between three ports are greater than 31 dB. The fabricated STA provides 5.5, 5.92 and 5.93 dBi peak gains at 3.7, 5.0 and 5.8 GHz, respectively. The efficiency of the STA is greater than 92% at all the frequency bands. The constructed STA has a front-to-back ratio of more than 23 dB and a separation of more than 21 dB between co-to-cross polarization levels. Fabrication and measurement are used to validate the intended STA.

Effect of moisture content on dielectric properties of banana leaves and peels in frequency range of 1–20 GHz

The quality of agricultural products can be remotely sensed and enhanced by determining the dielectric properties. This paper studies the dielectric properties of banana leaf and banana peel over the frequency range 1–20 GHz using the open-ended coaxial probe (OCP) method. A new curve fitting model is proposed to characterize the dielectric properties of banana leaf and banana peel. The different moisture content (MC) levels are considered for both banana leaf and banana peel samples and, their dielectric properties are characterized. Further, the banana leaf and banana peel’s measurement data are compared with the data obtained using the proposed model. In addition, Root Mean Square Error (RMSE) and R-squared (R 2) are calculated to validate the performance of the proposed model. In case of banana leaf at 68.26% MC, the dielectric constant achieves the value of R 2 and RMSE of 0.98 and 0.0648, respectively. Similarly, dielectric loss achieves the value of R 2 and RMSE of 0.88 and 0.0795, respectively. Further, for banana peel at 80.89% MC, the dielectric constant achieves the value of R 2 and RMSE of 0.99 and 0.2989, respectively. Similarly, dielectric loss achieves the value of R 2 and RMSE of 0.96 and 0.6132, respectively.

Circularly polarized CPW fed MIMO/Diversity antenna for Wi-Fi and WLAN applications

In this paper, circular polarized two-element and eight-element CPW fed MIMO/Diversity antenna with defected ground is presented. The dimension of the two-port antenna is 30 mm × 30 mm whereas the edge-to-edge gap between radiating elements is 5.65 mm. The |S11| in dB varies from 4.95 to 5.95 GHz with a gain up to 4.1 dB and efficiency is more than 90%. The isolation of two-element CPW antenna is more than 20 dB with open and diagonal stub in the ground whereas more than 18.7 dB for eight-element antenna without decoupling network. The circular and rectangular stub perturbs the surface current in the ground and is responsible for RHCP and LHCP in two-elements and eight-elements antenna where it covers the complete operating band. The acceptable ECC, TARC, DG, and CCL values of the antenna are determined which represents the diversity characteristics of the antenna. The Wi-Fi/WLAN applications can be fulfilled with the proposed two and eight-element antenna.