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Wireless communication networks could become quicker and more dependable as sixth generation (6G) antennas develop. One difficult development in the field of wearable technology is wearable textile antennas. Wearable textile antennas require flexible building materials, primarily textiles with planar structures. This study will concentrate on the design and specification of microstrip rectangular patch antennas that use a variety of fabrics as the substrate, such as lycra, polyester, and washed cotton. Using two-dimensional (2D) materials in the terahertz (THz) range, the study presented here will help in the construction of appropriate wearable antennas. This work may significantly improve materials science and engineering by investigating and using 2D materials, such as tungsten disulfide, in antenna design. The suggested antennas’ resonance frequencies are 1.1254 THz for polyester substrates, 4.4019 THz for washed cotton, and 2.9861 THz for lycra substrates. For substrate materials such as lycra, polyester, and washed cotton, the measured return loss was -44.92 dB, -38.17 dB, and -20.75 dB. This study could lead to the creation of new technologies and materials, such tungsten disulfide, which would have far-reaching uses outside of wearable electronics and provide significant advantages for society. [ABSTRACT FROM AUTHOR]

A wideband end‐fire stepped slot antenna with gain enhancement and filtering capability is proposed. On one hand, a parasitic dipole serving as a director is introduced in the stepped slot to improve the radiation gain of the slot antenna without increasing its physical size. It is found that a gain enhancement of about 2 dB can be achieved after adopting such approach. On the other hand, an absorptive branch possessing a nearly complementary frequency response with regard to the one of the slot antenna is in‐parallel loaded at the microstrip feedline. It allows the partial dissipation of the out‐of‐band/non‐radiated RF‐signal power of the antenna to attain both an RF‐quasi‐absorptive behaviour and filtering capability. It is found that after loading the dissipative branch, the out‐of‐band radiation efficiency of the slot antenna is reduced to less than 20%. The measured results of a fabricated proof‐of‐concept antenna prototype show a reasonable agreement with the simulated ones and verify the RF performance merits of the proposed stepped slot antenna, such as wide RF operating band covering the 3.39−4.73‐GHz range, end‐fire radiation with a front‐to‐back ratio (FBR) above 10 dB, flat radiation gain, and co‐integrated filtering functionality with RF‐quasi‐absorptive capability. [ABSTRACT FROM AUTHOR]

The authors extend the resonant modal theory (RMT) developed previously for a metal object to an arbitrary source region consisting of metals, dielectrics, or a combination of both. The influences of dielectrics on the fields are replaced by equivalent volume sources through the use of the compensation theorem in electromagnetic theory. The resonant frequencies can be determined by finding the roots of the determinant of the matrix resulted from the discretisation of the real homogeneous volume–surface integral equation derived from the requirement that the difference of stored field energies in the source region vanishes. As applications of the extended RMT, three examples have been investigated. The first example is a dielectric resonator antenna and is designed by exciting the first resonant mode of the composite structure in which the dielectric cylinder is combined with a conformal metallic strip. The second example is a dual‐band dielectric‐coated metallic wire antenna. The third example studies the resonant modes of a rectangular patch antenna. [ABSTRACT FROM AUTHOR]

This article proposes a novel fixed-frequency beam scanning leakage antenna based on a liquid crystal metamaterial (LCM) and adopting a metal column embedded microstrip line (MCML) transmission structure. Based on the microstrip line (ML) transmission structure, it was observed that by adding two rows of metal columns in the dielectric substrate, electromagnetic waves can be more effectively transmitted to reduce dissipation, and attenuation loss can be lowered to improve energy radiation efficiency. This antenna couples TEM mode electromagnetic waves into free space by periodically arranging 72 complementary split ring resonators (CSRRs). The LC layer is encapsulated in the transmission medium between the ML and the metal grounding plate. The simulation results show that the antenna can achieve a 106° continuous beam turning from reverse −52° to forward 54° at a frequency of 38 GHz with the holographic principle. In practical applications, beam scanning is achieved by applying a DC bias voltage to the LC layer to adjust the LC dielectric constant. We designed a sector-blocking bias feeder structure to minimize the impact of RF signals on the DC source and avoid the effect of DC bias on antenna radiation. Further comparative experiments revealed that the bias feeder can significantly diminish the influence between the two sources, thereby reducing the impact of bias voltage introduced by LC layer feeding on antenna performance. Compared with existing approaches, the antenna array simultaneously combines the advantages of high frequency band, high gain, wide beam scanning range, and low loss. [ABSTRACT FROM AUTHOR]

This paper introduces a novel metasurface (MS)-based circularly polarized (CP) microstrip patch antenna. Utilizing a square microstrip patch with plus- and diagonal-shaped slots on a 1.6 mm thick FR-4 substrate as the host antenna, the design incorporates a 4 × 4 square array MS on another 1.6 mm thick FR-4 substrate, separated by a 3.4 mm thick Teflon layer. The antenna offers a −10-dB impedance bandwidth from 5.45 to 7.55 GHz and an axial ratio (AR) bandwidth between 6.02 and 6.35 GHz, achieving a maximum realized gain of 6.3 dBic at 6.25 GHz, exhibiting right-handed circular polarization (RHCP). An equivalent circuit model is developed to validate impedance response, and the fabricated antenna closely matches simulated results. With a low profile of $ 0.42\lambda\, {\rm o} \times 0.42\lambda\, {\rm o} \times 0.033\lambda\, {\rm o} $ 0.42 λ o × 0.42 λ o × 0.033 λ o at 6.25 GHz, this CP antenna is suitable for applications like satellite communication for their uplinks and WLAN application. [ABSTRACT FROM AUTHOR]

It is necessary to have a reconfigurable antenna for multi-function radar. The same antenna can be used for search, tracking, and imaging applications across a wide range of frequencies. The monopole antenna is suitably etched in its patch to achieve ultra-wideband (UWB) performance, while the modification of the partial ground to have an electromagnetic band gap (EBG) structure and rectangle slots improves the operational bandwidth that extends between 2.7 GHz and 12 GHz. The inclusion of a stub in the microstrip feed along with partial ground brings size miniaturization up to 63%. The perturbation of "L"-shaped slots at the corners of the rectangular patch and loading of left-hand metamaterial (LHM) into the monopole antenna realize circular polarization and also increase the gain of the antenna to 5.68 dBi. The inclusion of a filter across the feedline of the proposed antenna modifies the antenna's frequency/bandwidth in some desirable fashion, which provides bandwidth reconfiguration. The proposed antenna uses a step feed that offers better impedance matching over the wide operating bandwidth. [ABSTRACT FROM AUTHOR]

This study presents a planar dual-band multiple-input multiple-output (MIMO) antenna design for the prospective fifth-generation (5G) frequency bands of 28 and 38 GHz. The antenna element is designed by utilizing a rectangular patch with an offset microstrip feeding technique. A dual-band response is achieved by placing semi-circular slots on each side of the patch element. To tune the frequency response and improve impedance matching, vertical rectangular slits are etched in the rectangular patch and the ground plane, respectively. The results show that the single antenna element offers an impedance bandwidth of 2.52 GHz (26.32–28.84 GHz) and 7.5 GHz (34–41.5 GHz). In addition, a MIMO configuration based on pattern diversity using four antenna elements is designed and fabricated. The designed MIMO configuration achieves an impedance bandwidth of 3 GHz (27–30 GHz) and 5.46 GHz (35.54–41 GHz) at operating bands of 28 and 38 GHz. The peak realized gain for the single element at 28 and 38 GHz is noted to be 7.4 dBi and 7.5 dBi, respectively. Furthermore, the polarization diversity configuration illustrates an isolation of > 15 dB and > 25 dB for the 28 and 38 GHz frequency bands, respectively. Moreover, the MIMO configuration attains appropriate values for the envelope correlation coefficient (ECC) and diversity gain (DG), Total Active Reflection Co-efficient (TARC), Channel Capacity Loss (CCL) and Mean Effective Gain (MEG) for the operating frequency bands. The proposed MIMO system based on results seems to be potential choice for mmwave Ka Band Applications. [ABSTRACT FROM AUTHOR]

In this paper, a radar cross-section (RCS) reduction of a microstrip antenna is investigated both experimentally and numerically. A traditional metal ground plane antenna and a bandstop frequency selective surface (FSS) filter are designed at 5.4 GHz. In order to reduce RCS and reflectivity of the reference antenna, the bandstop filter structure is set up instead of the full metal ground plane. The study observed a wide frequency range between 3 GHz and 14 GHz. The maximum RCS reductions between the reference antenna and the low RCS antenna in-band and out of band are obtained at 9.2 dBsm and 28 dBsm, respectively. The antennas are analysed under different θ – and φ – polarised incidence conditions. Low RCS antenna shows satisfactory results especially at X band in terms of reflectivity and RCS under these angular conditions. [ABSTRACT FROM AUTHOR]

Maintaining acceptable radiation performance over the entire operation bandwidth is a significant challenge in development of a miniaturised reconfigurable antenna. To address this issue, a new Substrate Integrated Waveguide (SIW) based reconfigurable antenna using slow wave structure is presented in this study. The proposed SIW antenna is based on a layered construction with metallic blind vias connecting to ground plane of SIW. The multi-layer structure of SIW with blind vias helps to separate magnetic and electric fields in the SIW cavity. Thus, a slow wave effect is also utilised and it leads to 36% reduction in the antenna size as compared to conventional SIW cavity. To attain the polarisation and frequency reconfiguration, a cross slot is introduced in the top metallic layer of the SIW cavity and four PIN diodes are connected into the cross-slot arms. Experimental results exhibit frequency reconfigurability in different operating regions with resonant frequencies 4.35, 5, 5.8, 6.4, and 9.6 GHz. The polarisation reconfigurability of the proposed antenna is achieved at 5 GHz with LP/RHCP/LHCP. The proposed antenna exhibits 3-dB axial ratio bandwidth of 4.8 to 5.2 GHz with peak gain of 4.2 dBi. [ABSTRACT FROM AUTHOR]

A 4x4 Isotropic Homogeneous Metasurface (IHM) backed, rectangular slotted dual-layered triband microstrip patch antenna (MPA) is proposed in this article. A detailed mathematical way to analyze the tensor surface impedance matrix (TSIM) of the proposed 4x4 IHM and slotted patch is demonstrated. The proposed IHM-backed MPA has a triband even-mode resonance at fr0 = 2.45 GHz, 2fr0 = 5.4 GHz, and 4fr0 = 7.7 GHz. A better and more accurate estimation of bio-superstrate loading effect for triband resonance is employed using the human skin (εr = 52.79, σs = 139) and blood (εr = 52.8, σs = 123) layer on the top of dual-layered metasurface-backed slotted MPA. TSIM characterization is observed for both blood- and skin layer-loaded dual-layered metasurface-backed slotted MPA. Chicken breast (εr = 55.2, as = 149, and tan σs = 0.325) with blood (εr = 58.2, as = 2.59, and tan σs = 0.364) is loaded onto fabricated dual-layered structure to verify numerically modeled estimation. A closed form triband, even-order resonance mode (i.e., fr0, 2fr0, and 4fr0) estimation based on dielectric superstrate thickness (Hs) is numerically established using MATLAB solver. Complete measurement setup with simulated vs. measured results is compared in this article. [ABSTRACT FROM AUTHOR]

This paper presents the design of a performance-improved 4-port multiple-input–multiple-output (MIMO) antenna proposed for millimeter-wave applications, especially for short-range communication systems. The antenna exhibits compact size, simplified geometry, and low profile along with wide bandwidth, high gain, low coupling, and a low Envelope Correlation Coefficient (ECC). Initially, a single-element antenna was designed by the integration of rectangular and circular patch antennas with slots. The antenna is superimposed on a Roger RT/Duroid 6002 with total dimensions of 17 × 12 × 1.52 mm3. Afterward, a MIMO configuration is formed along with a novel decoupling structure comprising a parasitic patch and a Defected Ground Structure (DGS). The parasitic patch is made up of strip lines with a rectangular box in the center, which is filled with circular rings. On the other side, the DGS is made by a combination of etched slots, resulting in separate ground areas behind each MIMO element. The proposed structure not only reduces coupling from −17.25 to −44 dB but also improves gain from 9.25 to 11.9 dBi while improving the bandwidth from 26.5–30.5 GHz to 25.5–30.5 GHz. Moreover, the MIMO antenna offers good performance while offering strong MIMO performance parameters, including ECC, diversity gain (DG), channel capacity loss (CCL), and mean effective gain (MEG). Furthermore, a state-of-the-art comparison is provided that results in the overperforming results of the proposed antenna system as compared to already published work. The antenna prototype is also fabricated and tested to verify software-generated results obtained from the electromagnetic (EM) tool HFSS. [ABSTRACT FROM AUTHOR]

Recently, there has been an increasing fascination for employing radio frequency (RF) energy harvesting techniques to energize various low-power devices by harnessing the ambient RF energy in the surroundings. This work outlines a novel advancement in RF energy harvesting (RFEH) technology, intending to power portable gadgets with minimal operating power demands. A high-gain receiver microstrip patch antenna was designed and tested to capture ambient RF residue, operating at 2450 MHz. Similarly, a two-stage Dickson voltage booster was developed and employed with the RFEH to transform the received RF signals into useful DC voltage signals. Additionally, an LC series circuit was utilized to ensure impedance matching between the antenna and rectifier, facilitating the extraction of maximum power from the developed prototype. The findings indicate that the developed rectifier attained a peak power conversion efficiency (PCE) of 64% when operating at an input power level of 0 dBm. During experimentation, the voltage booster demonstrated its capability to rectify a minimum input AC signal of only 50 mV, yielding a corresponding 180 mV output DC signal. Moreover, the maximum power of 4.60 µW was achieved when subjected to an input AC signal of 1500 mV with a load resistance of 470 kΩ. Finally, the devised RFEH was also tested in an open environment, receiving signals from Wi-Fi modems positioned at varying distances for evaluation. [ABSTRACT FROM AUTHOR]

Summary: A novel antenna system that utilizes multiple‐input and multiple‐output (MIMO) technology to suit the requirements of 5G applications is proposed in this article. The antenna has a wide operating bandwidth and high isolation in n257/n258/n261 5G bands. The suggested arc‐shaped MIMO antenna is composed of four similar patch units with modified ground planes arranged in a four‐port configuration and is made on a Rogers RT/duroid 5880 substrate, which measures 31.891 × 37.5885 × 0.508 mm3. The prototype of the suggested MIMO antenna is realized to confirm the obtained simulated results and validate the proposed design. The four‐port MIMO antenna features a broad frequency range of 7.3 GHz from 21.8 to 29.1 GHz, a peak gain of 5.76 dBi at 29 GHz, and a good isolation less than −18 dB. The proposed antenna's MIMO performance is evaluated by analyzing several diversity parameters. The findings of the evaluation demonstrate an envelope correlation coefficient (ECC) value of less than 0.001, a diversity gain (DG) value exceeding 9.995 dB, and an average mean effective gain (MEG) of −3 dB within the operational frequency band. The suggested MIMO antenna's compact size and impressive performance make it a suitable choice for intended n257/n258/n261 5G NR networks. [ABSTRACT FROM AUTHOR]

Summary: This article introduces Crystal Structure Algorithm (CryStAl), a novel metaheuristic optimization algorithm, for fine‐tuning microstrip patch antennas (MPA) in C‐band applications, which utilizes CryStAl with dielectric constant and resonant frequency inputs to optimize MPA dimensions, addressing limited bandwidth and gain issues. Achieves superior antenna performance with 32.71 dB return loss, 5.09 dB gain, and 1.2 VSWR, demonstrating improved convergence speed, radiation pattern, and suitability for diverse C‐band conditions. [ABSTRACT FROM AUTHOR]

Summary: A dual‐band, wearable coplanar microstrip patch antenna (CPW) integrated with electromagnetic bandgap structure (EBG) to operate dual wireless bands at 2.48 GHz industrial, scientific, and medical band (ISM) and 5.2 GHz WLAN. The proposed textile wearable antenna and EBG structure are screen‐printed using silver conductive ink on the cotton polyester substrate (εr = 1.6) for flexible wearable applications. A 3 × 3 EBG array is realized by a concentric square patch surrounded by the annular square ring to reduce back radiation and increase the forward gain and front‐back ratio. The proposed EBG‐backed antenna, compared with the conventional CPW‐fed antenna, improves forward gain from 2.18 to 6.59 dB at 2.48 GHz and 3.5 to 7.03 dB at 5.2 GHz. Moreover, the EBG array is used to isolate the human body from the antenna and reduces the specific absorption rate (SAR). The antenna is performed with a human phantom tissue model, which exhibits a specific absorption rate of 0.12 W/kg, and 0.260 W/kg for 1 g tissue at 2.48 GHz and 5.2 GHz, respectively. [ABSTRACT FROM AUTHOR]

• Microwave techniques used as a dual-purpose tool for: i) the elimination of moisture and ii) the moisture infiltration measurement in a monument's masonry. • Important pieces of cultural heritage architecture or art could be treated with non-destructive microwave techniques for moisture elimination and assessment. • Measurement of electrical permittivity for the extraction of volumetric water content in tuff bricks. • Electrical characterisation with a vector network analyser for measuring the phase shift of scattering parameters and calculating electrical permittivity. • A complete two-step methodology for controllable moisture elimination. In this paper, we present our experimental methodology, which was developed to assess and eliminate the excess moisture levels in the masonry of a Roman archeological monument, namely the Mensa Ponderaria of Tivoli, which is an important landmark dating back to the first century A.D. The need to keep interventions to a minimum were crucial factors for choosing microwave techniques as a non-destructive method for removal and moisture infiltration measurements in the walls. We used a microwave generator connected to a horn antenna to increase the temperature locally at the point of treatment and achieve the elimination of moisture. Additionally, to quantify the amount of eliminated water, we used a free space transmission measurement by two patch micro-strip fed antennas with a resonance at 2.62 GHz connected to a vector network analyser (VNA). S-parameters were measured at a frequency range 2–3 GHz. The phase shift method was used to extract the effective dielectric permittivity by the phase of the transmission S 21 parameter. In the final step, we derived the volumetric water content of the wall θ (%) based on the dielectric permittivity of the wall material (tuff). Measurements were performed at several points of the masonry, which were previously treated with microwaves or remained without treatment for comparison. We report an average of 139 gr in water extraction from the treated areas of the masonry with the mild treatment protocol we used, with the possibility of further increase with longer or higher-power drying cycles. [ABSTRACT FROM AUTHOR]

A modified slotted microstrip patch sensor antenna has been developed for sensitivity enhancement to measure the moisture content of leaves. The design incorporates a rectangular slot positioned above the feed of a rectangular patch antenna. The antenna achieves resonant frequency at a lower range than the operating frequency of a traditional patch antenna without slot while maintaining a miniaturized form factor. To evaluate the sensitivity of the proposed modified slotted patch antenna, the variation in the resonant frequency and the reflection coefficient (S11) is observed with the sample under test (SUT), i.e., leaf is placed above the patch. A comparative analysis with regard to sensitivity and shift in frequency is performed between the designed antenna structures. The designed antenna is fabricated on a 0.8 mm F4B substrate in order to resonate within the 2.40–2.80 GHz range under unloaded conditions. The antenna's sensitivity is tested by performing parametric analysis with respect to the permittivity of the leaf ranging from 20 to 30. The experimental results reveal that the sensitivity of the proposed patch antenna is enhanced by a factor of 1.67 as compared to traditional patch antenna for the four levels of SUT, demonstrating an enhanced sensitivity in detecting the moisture content of leaves. [ABSTRACT FROM AUTHOR]

This paper presents a compact portable patch antenna for 6G wireless communications at terahertz (THz) applications. The asymmetric co-planer waveguide (CPW) fed curved slits are proposed on rectangular microstrip patch antenna to resonate at THz applications. The asymmetric CPW-fed antenna is designed to be 50 μm thick on FR-4 substrate with 500 × 500 µm2 rectangular substrate with gold plating patch (thickness is 0.02 μm). The designed antenna is offers dual bands and resonates 0.813 THz, 1.254 THz frequencies. The first resonating frequency has a return loss of -16.86 dB is observed with the impedance bandwidth of 92 GHz (0.761 THz-0.853 THz) and gain is 6.14 dBi. The return loss of -28.52dB is observed over the impedance bandwidth of 295 GHz (1.117 THz-1.413 THz) with a realized gain of 7.31dBi at a second resonating frequency of 1.254 THz. The results obtained for the proposed design antenna have wider impedance bandwidth and more gain with a low reflection coefficient for high-speed wireless data communication systems. The proposed compact terahertz antenna is used in 6G applications for ultra-high-speed wireless communications with support to connect massive devices. [ABSTRACT FROM AUTHOR]

This paper presents a modified rectangular microstrip patch antenna (MRMPA) array conforming to the hemisphere for wide-angle beam scanning. Two different conformal antenna array designs are presented in this work. The first of these designs, a 13-element MRMPA array conformal to the surface of a circular arc, and the second one, a 9-element array conformal to the surface of a hemisphere, are designed and optimized. The geometrical approach of calculating the phase value is used to calculate the phase value of each antenna. The simulated results show that the 13-element conformal MRMPA array is achieving a beam scanning angle of ±84° with a gain of 13.89 dBi with low side lobe levels, and further, the gain of the array is enhanced by a dielectric superstrate that improved the gain by ∼2 dBi at all the scanning angles. Second, an MRMPA array conformal to a hemisphere with nine elements is designed with beam scanning ability from φ = 0°−360° and θ = ±30° with a gain of 15.69 dBi, and further, the gain is enhanced by ∼3 dBi with the dielectric superstrate. Full-wave simulations have proven both designs to be accurate and aligned with theoretical calculations. [ABSTRACT FROM AUTHOR]

In this article, a design of two-layered, dual circular-polarization (CP) and dual-band path antenna is presented for BeiDou navigation satellite (BDS) system applications. A single 50-Ω Co-axial probe feeding arrangement is employed to achieve dual-band operation and it feeds both the antennas simultaneously. This mode introduces the CP radiation on both upper (RHCP) and lower (LHCP) operation bands. The impedance bandwidth is further widened by accommodating two semi-circular stubs on the top patch. The fabricated and experimentally validated prototype radiates at 1.82 and 3.45 GHz (center frequency). The upper and lower operating band exhibits right and left-handed CP radiations, which constructs dual-band operation. The fabricated prototype has a physical size of πr2 × 0.024 λg with an antenna profile of 2.38 mm (0.024 λg). The experimentally validated upper and lower bands impedance bandwidth with |S11| < −10 dB are 21.1% and 11.1%, respectively. The fabricated prototype is a good candidate to use in BDS applications. [Q2 [ABSTRACT FROM AUTHOR]

A circularly polarized patch array antenna with a metasurface having a polarization conversion feature at 4.975 THz frequency is proposed. The structure consists of a fully metalized grounded patch array with a metasurface on top of the antenna and separated from the array antenna by a silicon dioxide layer. The modified antenna is placed between a symmetrical surface of 11 rows of 25 fishbone-shaped gold metasurface and a ground plane. The optimal antenna structure dimensions have been examined and provided for the designed array. The performance of an array antenna has been investigated from various aspects including gain, bandwidths of impedance, and axial ratio. Placing the metasurface on the microstrip antenna array causes the radiation waves of the antenna source to be converted from the linearly polarized form to circularly polarized waves, which improves the impedance and bandwidth of the axial ratio. In addition, a transmission line model is provided to show how to achieve a suitable axial ratio, which provides a high gain as well. The overall size of the final antenna is 400 × 400 × 3.3 μm3 and provides a gain of 16 dB in the operating bandwidth of 4.71–5.2 THz (i.e., 10%). [ABSTRACT FROM AUTHOR]

In this study, we introduce a unique geometrical design of a rectangular patch antenna for sub-6 GHz 5G applications. The proposed antenna is designed at 5.2 GHz, and design criteria and performance characteristics have been investigated through numerical simulations and verified using measured data. A composite structure is suggested to overcome the restrictive parameters of conventional antennas. Two different materials, Rogers RT5880, and RT5870, are utilized, achieving a maximum gain of 6.210 dB, and a 90.2% radiation efficiency was attained. Four layers of superstrates are placed above the antenna to enhance the antenna's radiation performance further. The fabricated antenna is evaluated by measuring its radiation characteristics and return loss. The final antenna prototype offers a maximum bandwidth of about 896 MHz at a −10 dB reflection coefficient with a maximum gain of 9 dB. The proposed model achieved ultimate efficiency as high as 89% by employing four superstrates. The results showed good impedance matching (S11, VSWR), high efficiency, and appropriate radiation patterns. The outcomes from simulation and measurement are well aligned, making this antenna suitable for high-performance 5G applications. [ABSTRACT FROM AUTHOR]

The latest developments in communication systems require an economical, light‐weight, compact size, and excellent performance in microstrip patch antennas in order to meet the requirements of the upcoming implementation. The optical, electrical, and physical properties of different materials have an impact on the design of antennas. An innovative composite photonic crystal microstrip patch antenna with outstanding gain has been developed. For composites of fumed silica embedded in RT‐Duroid dielectric material, the effective permittivity is calculated using the Maxwell‐Garnett model. The performance of composite antennas for different volume fractions and various dielectric substrate thicknesses is studied. The resonance frequencies of composites also shift from the X‐band to the C‐band with an increase in volume concentration, which is suitable for wireless communication systems. This investigation provides a perspective on how composite substrates can represent a communication revolution by providing an alternative to substrates that are readily accessible commercially in situations when the material qualities are insufficient. The photonic crystal composite antenna records the highest gain of 13.89 dB with the coverage of C‐band, X‐band, and Ku‐band, whereas the composite antenna reaches the best gain of 10 dB with the coverage of C‐band and X‐band. [ABSTRACT FROM AUTHOR]

Designing and fabricating antennas that exhibit low losses and are compact, lightweight, and highly radiation efficient are challenging in the wireless‐communication field. In this study, we simulated and fabricated microstrip patch antennas using β‐CaSiO3 low‐temperature co‐fired ceramic (LTCC) as dielectric resonator substrate. Compact ceramics that show good microwave dielectric properties (a relative dielectric constant [εr] of 6.57, high‐quality factor [Q × f] of 35 086 GHz [@14.85 GHz], and temperature coefficient of frequency [τf] of −33.56 ppm °C−1 for the optimal composition) were obtained when Li2O–CaO–B2O3–CuO glass was added to β‐CaSiO3 and sintered at 950°C. The high‐frequency properties of these composite ceramics reveal that the dielectric constant and dielectric loss are stable in the 38−58 and 70−90 GHz ranges, respectively. Furthermore, a circularly polarized antenna fabricated using a CaSiO3‐based ceramic shows a high radiation efficiency (92.04%) and gain (3.35 dBi) at a center frequency of 2.5 GHz. These β‐CaSiO3 composite ceramics offer promising prospects for high‐frequency use as well as in mobile communication applications. This study provides insight for the development of innovative antennas with new LTCC materials. [ABSTRACT FROM AUTHOR]

In this paper, a new approach to analyzing graphene-based antennas in the terahertz frequency range using the characteristic mode analysis method is presented. By the proposed method, graphene antenna parameters are obtained with simpler analysis and better physical visibility compared to numerical methods. In this regard, two structures of a graphene-based rectangular microstrip patch antenna for resonance in the terahertz frequency range are considered. The first structure consists of a metal ground plane and a substrate on which a layer of graphene is placed instead of a 10 μm × 7 μm metal patch. The second structure includes a metal ground plane with dimensions 19 μm × 16 μm, a substrate, a graphene layer on the substrate and a 10 μm × 7 μm metal patch placed on a graphene layer. Characteristic mode analysis method has been applied to the mentioned structure with different substrates, and the effect of graphene chemical potential on the modal behavior of the structure has been analyzed. For the first structure, there are two modes in the frequency range of 1–3 THz, but they do not have good resonance and they can be considered as non-resonant mode. Due to the conductivity of graphene in low frequency range of terahertz, which causes graphene to be a dielectric in this area. For the second structure, the 7.6 THz resonant frequency corresponds to the first mode of the structure and the 10 THz resonant frequency corresponds to the second mode of the structure, respectively, in the vertically and horizontally feeding stimulated. [ABSTRACT FROM AUTHOR]

A wideband planar microstrip antenna with good horizontally polarized omnidirectional radiation performance is presented. Using tightly coupled structures, six planar dipole elements are deployed in a circular pattern, and radiation is synthesized into a horizontal omnidirectional radiation pattern by superposing the far‐field pattern of the six dipoles. Owing to the tight coupling between radiating elements, the proposed antenna has a wide operating band. The radiating elements are printed on a printed circuit board and excited by a balun with uniform magnitude and synchronized current. A prototype is manufactured and measured. The measurement results show that the impedance bandwidth of the proposed antenna is 102% $ \% $. The gain variation of the horizontal omnidirectional pattern is less than 1.2 dB in the 1.27–3.89 GHz band. Within the operating frequency band, the total efficiency and radiation efficiency are greater than 82% and 88%, respectively. The diameter of the antenna is 0.48λL ${\lambda }_{L}$, where λL ${\lambda }_{L}$ is the wavelength corresponding to the lowest frequency in the operating band. [ABSTRACT FROM AUTHOR]

An antenna‐filter‐antenna (AFA) based frequency selective surface (FSS) with excellent spatial filtering performance is proposed. This FSS design incorporates two back‐to‐back microstrip patch antennas, which not only ensures a high roll‐off rate at the passband edge and excellent flatness within the passband, but also achieves an ultra‐low profile. Significantly, the upper and lower band edges demonstrate a substantial drop from −3 to −10 dB within the 0.006 and 0.02 GHz ranges, respectively, resulting in a sharp roll‐off skirt. Furthermore, the frequency of radiation null can be controlled by manipulating the length of the quarter‐wavelength open‐ended stub, thereby possessing exceptional out‐of‐band suppression. A prototype of the proposed FSS with low profile is fabricated and measured. The simulations and measurements of the AFA‐based FSS show that a quasi‐elliptical bandpass filtering response with superior performance is achieved. [ABSTRACT FROM AUTHOR]

In this paper, a single‐layer filtering antenna based on half‐mode patches is proposed. It consists of a main driven patch and a parasitic patch. A U‐shaped slot is first etched on the main driven patch to generate a new resonant mode and a radiation null simultaneously. Four pairs of shorting pins are introduced on the main driven patch to raise its operating frequency to near that of the U‐shaped slot, thus broadening the impedance bandwidth (IBW). Additionally, a parasitic patch is introduced near the driven patch to introduce an extra half‐TM10 mode and an extra radiation null, significantly enhancing the IBW and the upper‐edge selectivity of the antenna. A prototype was fabricated and tested for validation. It achieves a peak realized gain of 6.55 dBi and −10‐dB IBW of 8.8%, and exhibits good out‐of‐band rejection performance while maintaining a low profile of 0.017 λ0 and a compact transverse size of 0.29 λ02. [ABSTRACT FROM AUTHOR]

This letter presents a novel analysis of the input impedances of differential feed microstrip antennas using the bi‐characteristic‐impedance transmission line (BCITL) model instead of the conventional two‐port parameters. The expressions of associated input impedances using the novel BCITL model are found to be simple, compact, and robust with better physical insights. In addition, measured results are also provided to validate the accuracy of the BCITL model. [ABSTRACT FROM AUTHOR]

Summary A band‐notched super wideband (SWB) planar monopole antenna with improved notch characteristics is proposed in this article. A hexagonal SWB antenna operating in the frequency range from 3.04 to 36 GHz is initially designed on Arlon substrate. The hexagonal patch is then loaded with optimum sized U‐shaped slot to eliminate WLAN band (5.15–5.85 GHz). The notch band's characteristics are further improved by incorporating a frequency selective surface (FSS) of a square array at a specific distance below the antenna to introduce a phase delay of 180° between the back radiation reflected by the FSS with the front radiation at the notched frequency. Improvement of notch band gain, efficiency, and antenna front‐to‐back ratio (FBR) are studied. The antenna without embedding an FSS exhibits working spectrum from 3.1 to 33.6 GHz with notch frequency gain of −2.6 dBi and efficiency 53%. The inclusion of an FSS layer at 25.2 mm behind the antenna results in notch frequency gain of −7.6 dBi with an efficiency of 23%. FBR improvement of about 16 dB is achieved at 8 GHz, and FBR is reduced by about 5 dB at the notch frequency. 169% fractional bandwidth with bandwidth dimension ratio (BDR) of 1622 is achieved in this proposed FSS integrated antenna. The inclusion of FSS to improve the band elimination performance represents the novelty of this proposal. The data are validated by electromagnetic simulation and physical measurement techniques. [ABSTRACT FROM AUTHOR]