Volume 77, Issue 1-2

In this article, a compact microstrip low-pass filter (LPF) with low in-band insertion loss and a wide attenuation band is recommended. The structure is modeled using two rectangular-shaped open resonators (ORs) loaded with multiple sections of the interdigital capacitor. The proposed LPF has a cut-off frequency of 1.5 GHz, a passband insertion loss of 0.35 dB, and an electrical circuit size of 0.02  λ g 2 . In the ground plane, two dissimilar defected ground structures (DGSs) are introduced to generate additional attenuation poles for enriching the stopband performance of the LPF. The harmonics suppression is achieved up to 15 GHz with tenth harmonic suppression and relative stopband rejection of almost 165%. The EM simulated results show a well-matched behavior with the experimental ones. The proposed LPF can be used for global positioning systems (1500 MHz), telecommunications (1600 MHz), and audio broadcasting (1400 MHz) applications.

The manuscript presents a broadside coupled ultra-wideband (UWB) bandpass filter with quasi-elliptic response having multiple transmission zeros (TZs) in/out of the UWB spectrum. Developed on a low cost substrate (FR4), the basic geometry consists of a short-circuited co-planar waveguide (CPW) in ground coupled to the back-to-back arranged microstrip lines on the top. This broadband balun architecture leads to a 3rd order bandpass filter (BPF) with good quasi-elliptic frequency characteristics. Later, split ring resonators (SRRs) and folded SRRs (FSRRs) are placed adjacent to the input/output (I/O) feeding lines to develop the multiple in/out band TZs. The proposed structure is fabricated and measured for its frequency characteristics. The notched-BPF occupies an area of 21.6 × 16 mm 2 .

A novel compact S-band band-pass filter (BPF) with ultra-wide stopband is presented. The proposed filter mainly consists of three parts, a novel crossed resonator, parallel-coupled microstrip lines, and defect ground structures (DGSs). The resonator is constructed by three capacitive open stubs, while a defect is etched in the center stub to eliminate high frequency harmonics. The parallel-coupled microstrip lines are mainly used to improve the passband and the roll-off rate (the ratio of height to width of the filter transition band). And the DGSs are utilized to improve the stopband performances. The proposed BPF has the merits of compactness, good insertion loss and good stopband characteristic. The measured 3 dB operating band is 1.80–4.03 GHz (76.5% at f 0  = 2.92 GHz), The upper out-of-band suppression was better than 20 dB for the frequency up to 20 GHz (6.33 f 0 ), and the upper roll-off rate reaches 75.59 dB/GHz.

In this paper, a new design of Gysel power divider with good performance and very compact size is presented. In this design, rectangular resonators and U shaped transmission lines are used. Operating frequency that is considered is 580 MHZ. The proposed power divider only takes 15.83% of the area of the corresponding conventional Gysel power divider. Proposed equal low pass filters are replaced with transmission lines and the harmonics suppression is also improved. In this design, 10 harmonics are suppressed. Finally, the proposed power divider is fabricated and a good match is found between the simulation and measurement results.

A dual band reconfigurable active frequency selective surface is designed which resonates at 2.5 and 3.6 GHz as transmission pole frequencies. Lower and upper pass bands have −3 dB bandwidths of 0.4 and 0.5 GHz, respectively. Two notch frequencies are configured from 4.71 to 3.5 GHz and from 2.78 to 2.45 GHz. Dimensions of the unit cell are optimized to λ 0 /10 calculated at the lowest resonance. The proposed design exhibits insignificant variation at oblique excitation angles until 75° of dual polarized plane wave. An equivalent circuit model is developed for optimization and vivid understanding of the structure behaviour. A prototype of the designed structure is fabricated and the measured response is in satisfactory agreement with the simulated transmission response. High angle stability, low insertion loss at both the transmission pole frequencies, dual band pass/stop tuning for single and dual polarized wave with use of only two varactor diodes are eminent features of the design.

In this manuscript, an antenna design configured for dual-band circularly polarized (DBCP) characteristics is presented. The proposed design is quite compact (0.63 λ g  × 0.63 λ g  × 0.04 λ g ) and comprises a mushroom-shaped monopole with a modified ground structure (MGS). In the proposed antenna structure, dual-band CP behavior is generated through a tunable side stub joined orthogonally with the feed patch and reshaping the wide square slot. The impedance bandwidth is measured as 2900 MHz ranging from 1.32 to 4.22 GHz in the lower frequency band (Band 1); however, 980 MHz from 4.78 to 5.76 GHz in the higher frequency band (Band 2). The 3-dB AR bandwidth is measured as 370 MHz (from 3.54 to 3.91 GHz)in the lower frequency band; whereas, it is measured as 650 MHz (from 5.07 to 5.72 GHz) in the higher frequency band. The measured gains spread from 2.5 to 8.3 dBi with a maximum gain of 8.3 dBi in the lower frequency band, whereas 4.8 to 7.05 dBi with a 7.05 dBi maximum gain in the higher frequency band, respectively. The cross-polar rejection is observed greater than 14 dB. Besides, 3-dB half-power beamwidths are seen as 86° & 84°, and 87° & 86° in the x - z and y - z planes for the lower and higher frequency bands, respectively.

In this paper, a 2×2 multi-layer array antenna based on the metamaterial concept is proposed at 28 GHz for 5-Generation (5G) applications. The feed network is designed in the first layer. This network feeds the rectangular patch located in the first layer using four shorted-pins (SPs). To realize the metamaterial environment, a novel unit-cell was designed. In the first layer between the two dielectrics, 2 unit-cell rows are used. In the second layer and adjacent to the patches, 4 rows of metamaterial unit-cells are loaded. Each of the metamaterial rows contains 6 unit-cells. As such, the antenna gain has increased more than 10 dB from the prototype without any metamaterial structures. The final dimensions of the proposed array antenna are 30×35.2×0.508 mm 3 . To prove the design, the proposed antenna was fabricated. The simulated and measured maximum gain at 28 GHz are 18.28 and 17.91 dB, respectively.

In this paper, a quadband MIMO diamond-shaped antenna with two highly isolated elements is proposed and discussed. A novel metamaterial cell-inspired decoupling parasitic structure is deployed between the two antenna elements to achieve high isolation greater than 20 dB in the frequency bands of interest. Moreover, the design adopts a defected ground structure and open-ended multiple diamond-shaped branches for multiband characteristics, enabling the proposed MIMO to cover several modern wireless applications. The performance metrics of the proposed MIMO antenna are validated by evaluating various diversity parameters such as envelope correlation coefficient (ECC), diversity gain (DG), total active reflection coefficient (TARC), and channel capacity loss (CCL). This antenna is fabricated on an FR4 substrate with a compact size of 12 × 30 × 1.524 mm (0.082 λ 0  × 0.204 λ 0  × 0.001 λ 0 , λ 0 is the wavelength at 2.04 GHz). With the edge-to-edge separation distance of 0.053 λ 0 between the antenna elements, its prototype is experimentally measured using a two-port Rohde & Schwarz ZVA50 Vector Network Analyzer. The port-to-port isolation is about −20.87 dB, −23 dB, −25.93 dB, and −25.22 dB for 2.3 GHz, 3.18 GHz, 4.08 GHz, and 5.42 GHz frequency bands, respectively. Also, the proposed MIMO antenna exhibits good diversity performances with the ECC < 0.005, DG > 9.99, and TARC<−10 dB making it an outstanding candidate covering 4G/LTE, 5G NR sub-6 GHz n40/n41/n77/n78, Wi-Fi, WiMAX, ISM, WBAN, Bluetooth, MBAN, WiBro, C-V2X, and UWB applications.

In this paper, a novel, compact and high gain H-plane horn antenna with Substrate Integrated Waveguide (SIW) technology is examined for X-band applications. To increase the gain, an array of metamaterials is used by cutting the gap in the aperture area of the antenna in high metallization. After examining the size and position of the metamaterial unit cell and several array elements, which act as a focusing structure, and in addition, by reducing the electric permittivity coefficient of the substrate and consequently reducing the losses, an increase in gain is achieved. The performance of the proposed SIW horn antenna with metamaterials has been compared with the SIW conventional horn antenna without metamaterials. To highlight this point, the proposed antenna was designed with CST software. Then, it was fabricated and measured. Measurements show that the gain of the modified antenna is 9.2 dBi, which is 6.2 dBi higher than a conventional antenna.

This paper demonstrates a novel form of substrate integrated waveguide SIW antenna array based on Fourier Series Equations. An optimized SIW power divider feeds the proposed structure where a micro-strip transition is used for impedance matching at 50 Ohm. The proposed antenna is traveling wave antenna type, in conventional methods the curve of antenna is of a linear or exponential form. In our method, we used the FSE to modify the contour of the antenna. The method is based on optimization of the Fourier series coefficients in order to maximize the gain for φ  =  π /2 and θ  =  π /2. The results of the return loss, the field’s distribution, the radiation pattern and the realized gain were analysed. Furthermore, the antenna is designed in HFSS and CST with a comparison between them. The simulated return loss was compared with experimental measurements. The return loss of the proposed 1 × 4 antenna array is less than −10  dB at 5.5–6.8 GHz with an average gain about of 6 dBi and a peak gain about of 7.2 dBi. The proposed 1 × 4 antenna array is optimized with HFSS and designed using FR4 substrate, and considered in C-band for centimeters waves applications.

Dual polarization is achieved by putting a rectangular or circular patch in between two orthogonal gaps. At the beginning a single-polarized patch is considered. Then by using anequivalent circuit, the impedance matching property of the gap is being configured. After optimization of the length of the patch and width of the gap, a dual polarized antenna is being considered. Here in this article we projected a new technique to design dual polarized microstrip antenna for WLAN, WiMAX, wireless applications using circular patch. By combining all resonant modes we have finally achieved a wide operating bandwidth. Experimental result of the projected antenna shows the operating bandwidth of 21.56% (5.24–6.37 GHz) for (differential mode S-parameter) S dd11  ≤ −10 dB with a high port isolation of 40 dB and a relative gain of 13.5 dBi is achieved. From the result analysis this antenna finds its applications for various WLAN and Wi-MAX frequency band.

In the proposed work, a miniaturised ultra-wideband tapered slot planar antenna with the aim of gain enhancement, working bandwidth containing lower frequency range, and improving antenna efficiency is presented. The proposed antenna consists of a slotted patch printed on the top layer of FR4 substrate with three 50-Ω resistors connected in the slotted arms and bottom layer consists of an optimized ground plane with a non-uniform parasitic patch which is used to achieve circular polarization in the frequency range of 2.4–2.6 GHz. The measured impedance bandwidth of the proposed antenna is 0.3–4 GHz with a peak gain of 3.2 dBi. The overall antenna efficiency is 83% and radiation patterns of the proposed design on different frequencies are shown to confirm the proposed antenna result, especially at lower frequencies. The proposed antenna can be used for the detection of artifacts in the deeper ground known as ground-penetrating radar applications.

Free Space Optics (FSO) is one the most in-demand technology, and is used indoors, on the ground, in space, and even underwater. It is used to broaden communication access to places where bandwidth is insufficient or where difficult topography prevents the use of cable communications. One of the foremost communication challenges that contribute to the degradation of FSO performance is the environmental condition. Hilly regions experience heavy rainfall and have rough terrain which may demean the FSO link communication. In this work, for real-time rain rate analysis of the Meghalaya region two unique rain attenuation models are investigated for monsoon months from the years 2014 to 2020. Considering Marshall and Palmer’s model and by employing 8, 16 and 32-quadrature amplitude modulation (QAM) schemes, radio-over-free space optical (RoFSO) system has been evaluated by varying FSO channel range, power and bit rate.