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In this manuscript, a miniature high-temperature superconductor (HTS) bandpass filter (BPF) with multi-transmission zeros (TZs), high selectivity, and great attenuation of stopband is presented. A couple of dual-mode resonator (DMR) is employed to achieve the proposed BPF, which can be characterized by using the classical even-odd mode analysis technique. The presented cascaded DMR can excite four resonant modes, which can be individually managed. Plus, a pair of intrinsic transmission zeros can be yielded at both the lower and upper edges of the passband, which results in sharp shirt performance. As an example, the HTS BPF is designed, fabricated, and tested, in which the center frequency is centred at 3.95 GHz and the 3-dB fractional bandwidth (FBW) is 2.5%. The proposed HTS BPF is implemented by using Tl2Ba2CaCu2O8 (Tl-2212) thin films which are fabricated by two-step processing and the superconducting critical temperatures (Tc) of the HTS films can reach 103 K. The design methodology is confirmed since the experimental results are in good agreement with theoretical results, showing desired bandpass characteristics, high selectivity, and the attenuation of lower and upper stopbands above −50 dB. Further, the circuit size is only 0.4 cm2. [ABSTRACT FROM AUTHOR]

A compact and novel quad-element inset-fed octagonal-shaped multiple input multiple output patch (QIOMP) antenna with a hexagonal-shaped slot is designed for ultra-wideband applications. The proposed MIMO antenna comprises four identical octagonal-shaped radiating elements. To achieve better diversity performance and low mutual coupling, radiating elements are positioned at the ideal distance. The proposed octagonal-shaped MIMO antenna is prototyped on a Fr-4 substrate with the overall dimensions of 32 × 32 × 1.6 mm3. It achieves an ultra-wide bandwidth (S11 < − 10 dB) of 13.9 GHz, operating from 2.5 to 16.7 GHz, except for the band notch from 8.9 to 9.2 GHz. The proposed antenna has a gain of 3.50 dBi, 4.40 dBi, 6.67 dBi, and 5.22 dBi at 4.8 GHz, 8.1 GHz, 10.5 GHz, and 14.1 GHz, respectively. At the operating frequencies, surface current distribution and radiation patterns are examined. The diversity performance of the QIOMP antenna is evaluated by reviewing several MIMO parameters, including an envelope correlation coefficient < 0.03, a diversity gain > 9.8, the total active reflection coefficient, and channel capacity loss < 0.05 bits/sec/Hz. The simulated and experimentally obtained results are presented and exhibit a high degree of concurrence. [ABSTRACT FROM AUTHOR]

A compact dual-band quasi-elliptic filter with high selectivity is developed and investigated in this communication. It employs two hybrid-structure substrate integrated waveguide (SIW) triplets, which show completely inverse transfer responses under the same conditions of inductive cross coupling. The first meander-line-based triplet is able to produce a transmission zero (TZ) above the passband. Whereas the second SIW triplet,which is composed by a composite right/left-handed (CRLH) resonator, creates a TZ below the passband. By utilizing these features, a dual-band quasi-elliptic filter based on SIW dual-mode resonances (TE101 and TE201), whose operating frequencies are allocated at 8 GHz and 10 GHz, is designed for demonstration. The design process, principles, and experiments are carefully described in this communication. The measured and simulated results are in good agreement, indicating excellent electrical performance with low loss, compact device size and high selectivity. The most notable point is that a dual-band quasi-elliptic filter on SIW platforms is obtained with all inductive couplings for the first time, which shows a unique benefit in eliminating negative-coupling structures while permitting miniaturization for SIW dual-band filter design.

Abstract In this paper, a microstrip Wilkinson power divider (MWPD) based on particle swarm optimization (PSO) algorithm is designed, simulated, and fabricated using novel resonators. In addition, attenuators and open-ended stubs are incorporated to generate a broad cut-off band and reduce unwanted harmonics. The proposed power divider has a central frequency of 1 GHz. The performance of each used resonator is analyzed based on lumped-element circuit models.The L and C parameters of the equivalent circuit of the used resonators are predicted and optimized with the assistance of the PSO method. The subsequent phase was the fabrication of the proposed MWPD, after which its performance was evaluated in the light of the results obtained from the simulation. It was discovered that there was a high degree of concordance between the two. On the other hand, the fabricated circuit has several benefits, including a suitable S12 of − 3.15 dB, a high return loss of less than − 24 dB at the operating frequency, a compact size of 0.058 $${\varvec{\lambda}}_{{\varvec{g}}}$$ λ g × 0.064 $${\varvec{\lambda}}_{{\varvec{g}}}$$ λ g , and the ability to remove undesired harmonics. The results show a high level of suppression of the unwanted harmonics (up to the 16th harmonic) and a great responsiveness in the passband, while having very low ripple. As a result, the proposed circuit may be used in a wide variety of electronic devices, such as radar transmitter and receiver circuits, and many other high-frequency systems.

This paper presents the design and analysis of a compact circular microstrip patch antenna for 5G millimeter wave technology applications. The dimensions of the proposed patch are 5.959 mm × 5.959 mm × 1.400 mm. The antenna exhibits a resonant frequency of 28 GHz, a return loss of -45 dB, a bandwidth of 1.7638 GHz, and a gain of 0.1573. In order to meet the requirements of 5G applications at 28 GHz, a compact, high-gain, and large bandwidth antenna is necessary. The principal objective of this study is to enhance the performance of the antenna parameters, thereby achieving an optimal balance between size, gain, and bandwidth. A notable improvement in bandwidth and gain is achieved. The design, analysis, and optimization processes were conducted using the High Frequency Surface Structure (HFSS) software, which employs the Finite Element Method (FEM) numerical method. [ABSTRACT FROM AUTHOR]

In this paper, a microstrip Wilkinson power divider (MWPD) based on particle swarm optimization (PSO) algorithm is designed, simulated, and fabricated using novel resonators. In addition, attenuators and open-ended stubs are incorporated to generate a broad cut-off band and reduce unwanted harmonics. The proposed power divider has a central frequency of 1 GHz. The performance of each used resonator is analyzed based on lumped-element circuit models.The L and C parameters of the equivalent circuit of the used resonators are predicted and optimized with the assistance of the PSO method. The subsequent phase was the fabrication of the proposed MWPD, after which its performance was evaluated in the light of the results obtained from the simulation. It was discovered that there was a high degree of concordance between the two. On the other hand, the fabricated circuit has several benefits, including a suitable S12 of − 3.15 dB, a high return loss of less than − 24 dB at the operating frequency, a compact size of 0.058 λ g × 0.064 λ g , and the ability to remove undesired harmonics. The results show a high level of suppression of the unwanted harmonics (up to the 16th harmonic) and a great responsiveness in the passband, while having very low ripple. As a result, the proposed circuit may be used in a wide variety of electronic devices, such as radar transmitter and receiver circuits, and many other high-frequency systems. [ABSTRACT FROM AUTHOR]

An embedded series resonator for compact co‐polarized circular patch antenna pairs is presented in this paper. With a compact center spacing (CS) of 0.32λ0 and edge spacing (ES) of 0.03λ0 (λ0 is the free‐space wavelength at the center frequency), strong mutual coupling inevitably arises. However, by introducing a cross‐shaped fence and two quarter‐wavelength open‐ended slots onto a circular patch, port isolation of the first proposed antenna pair is significantly enhanced by 25.2 dB within a bandwidth of 6.2%. Moreover, the effectiveness of the embedded series resonator is demonstrated by achieving a wider 20‐dB decoupling bandwidth of 10.4% for the second proposed compact bandwidth‐enhanced antenna pair. For validation, both proposed prototypes are fabricated and measured, showing good agreement between measurements and simulations. To demonstrate the universality, a 1 × 8 patch array with an embedded series resonator can achieve a beam scanning angle of ±70◦ with a gain attenuation of 2.6 dB. Benefiting from compact size, high isolation, and enhanced decoupling bandwidth, the proposed designs hold promising potential for application in multiple‐input multiple‐output system and antenna array. [ABSTRACT FROM AUTHOR]

In this paper, stepped slot-type grooves are utilized to develop coplanar waveguide (CPW) spoof surface plasmon polariton (SSPP) transmission lines (TLs). The equivalent circuit model is developed to analyze the effect of the stepped slot-type grooves. And it is found that all the three proposed SSPP TLs exhibit lower asymptotic frequency and more compact size than conventional SSPP TLs based on uniform grooves. Moreover, the dispersion features can be controlled flexibly by changing the impedance ratio of the stepped slot-type grooves. And among the three proposed SSPP TLs (Type A, Type B, and Type C), Type C SSPP TL has the most compact size. Consequently, based on Type C SSPP TL, an ultra-compact plasmonic low-pass filter (LPF) is designed to validate the design theory. Good agreement is observed between the simulated and measured results for which reflection coefficient is lower than − 10 dB in passband from 0 to 1.73 GHz and good shape factor of 1.09 for the transition from the passband to the stopband. Besides, the proposed plasmonic low-pass filter occupies very compact size, indicating that the proposed plasmonic filter can find potential applications in compact plasmonic system design. [ABSTRACT FROM AUTHOR]

This paper proposes a microstrip filter with controllable transmission zeros based on the λ/4 stepped impedance resonator. This filter utilizes hybrid electric-magnetic coupling to generate transmission zeros, which can improve selectivity and stop-band performance. A fifth-order filter is designed and manufactured on a ceramic substrate with a center frequency of 26 GHz, bandwidth of 2 GHz and the signal suppression level is better than 42.51 dB from 10 to 22.8 GHz and 48.23 dB from 29.1 to 40 GHz. Furthermore, the proposed filter has a compact size of 2.074 × 1.071 mm (0.566λg × 0.292λg). [ABSTRACT FROM AUTHOR]

In this paper a very compact design of a dual-band band pass filter (D-BPF) using dual composite right-/left-handed (D-CRLH) and open-loop ring (OLR) resonators is presented. To overcome the frequency ratio limitations of D-CLRH resonators technique, the D-BPF design combines D-CRLH and OLR resonators to finally perform a D-BPF. The filter covers the 2.6 and 3.5 GHz spectrums for 4G and 5G applications, respectively. The reported D-BPF is designed and optimized using ADS software, and is implemented on a Rogers RO5880 substrate with a relative dielectric constant of 2.2 and thickness of 0.787 mm. The overall compact size is 8×8×0.787 mm^3. To our knowledge, this design is considered as the most compact and smallest size dual-bandpass filters.

In this paper, an ultrabroadband linear array in which horn‐reflector antennas are used as radiating elements by adding a central ridge to the rectangular waveguide, leading to an increased bandwidth of 3:1. With a reflector embedded in the H‐plane sectoral ridged horn, a desired narrow beam can be easily achieved. Moreover, due to the compact enclosed structure, the proposed reflector array can not only eliminate the illumination loss but also significantly reduce size compared with those of conventional array‐fed parabolic cylinder antennas. Good agreement between the calculated and measured results is obtained, showing that the proposed antenna array has a high aperture efficiency of about 80%, a ±45° scanning range in the E‐plane and 5° beam coverage with low side lobes in the H‐plane within the frequency range of 6–18 GHz. [ABSTRACT FROM AUTHOR]

This paper presents a new design approach of a compact wideband branch line coupler based on waveguide technique at 3.5 GHz. At the lower band of 5G technology, microwave devices such as hybrid couplers tend to be narrower in bandwidth and big in size, in addition to the phase difference error produced by using common planar technology. Therefore, waveguide technology aims to solve those challenges. This work aims to design a compact wideband coupler by implementing a direct coupling aperture between two waveguides with a cutting in the narrow wall of the structure. This technique helps in obtaining a wide bandwidth and reduces the size of the whole structure. The coupler is simulated using computer software technology and fabricated using CNC machining. The measured S-parameters of the coupler are observed to have low loss properties with return loss and isolation less than -10 dB. The coupling factor at the outputs are -3.21 dB with low loss of -0.2 dB. The measured phase error is about 2° at 3.5 GHz. A size reduction of 70% is observed compared to conventional waveguides and planar couplers. Overall, this coupler shows great performance that could be used for 5G beamforming applications. [ABSTRACT FROM AUTHOR]

In this paper a very compact design of a dualband band pass filter (D-BPF) using dual composite right- /left-handed (D-CRLH) and open-loop ring (OLR) resonators is presented. To overcome the frequency ratio limitations of D-CLRH resonators technique, the D-BPF design combines D-CRLH and OLR resonators to finally perform a D-BPF. The filter covers the 2.6 and 3.5 GHz spectrums for 4G and 5G applications, respectively. The reported D-BPF is designed and optimized using ADS software, and is implemented on a Rogers RO5880 substrate with a relative dielectric constant of 2.2 and thickness of 0.787 mm. The overall compact size is 8 × 8 × 0.787 mm³ . To our knowledge, this design is considered as the most compact and smallest size dual-bandpass filters. [ABSTRACT FROM AUTHOR]

A compact dual-band tripolarized antenna with simple structure and high isolation operating at 2.45 GHz and 3.5 GHz bands is presented. The design is composed of a slotted patch and a monopolar patch connected together by four vias. The antenna uses a double differential-fed scheme for x- and y-horizontally polarized broadside radiations and a single-ended port at the center for vertically-polarized omnidirectional radiation. The combination of slotted patch, monopolar patch, and vias yields several interesting features, which are exploited in the design to achieve dual-band tripolarized operation. Thank to the differential feed scheme and structural symmetry, the proposed antenna achieves a very high isolation among all ports. For verification, the final design is fabricated and measured. The double differential-fed scheme are realized by using two wideband out-of-phase power dividers, whose operational bandwidth covers both 2.45 and 3.5 GHz bands. The antenna with profile of $0.09\lambda _{2.45-{\mathrm { GHz}}}$ yields a measured 10-dB return loss bandwidth of $2.43-2$ .49 GHz and $3.23-3$ .66 GHz and isolation of $\ge $ 35 dB among all ports. Tripolarized radiation is verified with far-field measurement, showing highly symmetrical pattern and low cross-polarization in all three operational modes. The proposed design is a good candidate for dual-band communication systems which require polarization and pattern diversity antennas.

This article reports the Modified Microstrip Feed Hybrid Rectangular Dielectric Resonator Antenna (RDRA). The proposed structure has a ground plane with a plus-shaped slot on an FR4 substrate with a height of 1.6 mm and dimensions of 38 mm x 35 mm. The proposed Dielectric resonator antenna is made of a material with 10 as its dielectric constant, and the dimensions of the DR are 19 x 20 x 18 mm3. The DR is connected to a modified microstrip feed with an octagonal ring through the plus-shaped slot in the ground. The proposed structure operates in frequencies from 2.60 GHz - 2.74 GHz, 3.12 GHz - 3.37 GHz, and 4.25 GHz - 4.37 GHz. The resonant frequency of the final proposed RDRA is 2.68 GHz, 3.26 GHz, and 4.31 GHz, which covers WLAN, WIMAX and Wireless Avionics Intra-Communications (WAIC) applications, respectively. The entire structure was simulated using the CST microwave studio. The simulated results agree with the measured results and both are presented. The compact size, stable radiation pattern and reasonable gain make this antenna suitable for the proposed applications.

In this paper, a portable tri-band MIMO antenna with 1 × 1 and 2 × 2 inputs and outputs is developed for wireless applications. A decagon-shaped ring and two U-shaped radiating structures make up the proposed antenna, which can generate three resonance frequencies. Without utilizing any decoupling structures, the suggested antenna achieves improved isolation. The coplanar waveguide structure supplies all of the antennas, which are printed on the front side of the FR-4 substrate, which has a surface area of 18 × 18 mm. The suggested antenna serves a wide range of applications, including WLAN (5.2 GHz), Wi-max (5.5 GHz), and 5G n34 band, with an impedance bandwidth of − 10 dB over 1.98–2.03 GHz, 3.55–3.70 GHz, and 4.8–6.4 GHz (2 GHz). For tri-band MIMO antenna, the gain is (0.28 dB, 1.3 dB and 2.7 dB) and efficiency is (80%, 83%, and 91.5%). For MIMO, tri-band antennas are placed in rotational symmetry with respect to the adjacent ports. Distance between MIMO tri-band antenna is 20 mm. Isolation for tri-band MIMO antennas is (− 40 dB, − 28.5 dB and − 27 dB). ECC for tri-band MIMO antenna is 0.003. The fabricated antenna and simulated results agree quite well. As a result, the suggested antenna can be employed for WLAN and 5G applications. [ABSTRACT FROM AUTHOR]

In this study, the compact third‐order filter with wide stopband is proposed, and it is based on the folded substrate integrated waveguide (FSIW)‐patch resonator. The embedded semicircular patch with two etched slots is integrated into the closed dual‐mode FSIW, so the miniaturized single‐cavity triple‐mode resonator with electromagnetic (EM) shielding and high quality can be achieved. In addition, the slots can reduce transverse electricity (TE)101 and TE201 on FSIW, while the other higher‐order modes of FSIW remain unchanged, then the wide stopband can be realized, and the stopband can be further widened by designing the feeding position to suppress higher‐order modes. Then, this filter based on hybrid FSIW modes has compact size, wide stopband, and good EM shielding. Finally, a prototype with 3‐dB fractional bandwidth of 8.4% is designed at 5.87 GHz (f0), and its insertion loss is only 1.16 dB. The upper‐stopband attenuation is better than 23 dB extended to 3.08f0. It occupies only 0.18λg2, where λg is the guided wavelength at f0. [ABSTRACT FROM AUTHOR]

This paper presents a slow‐wave substrate integrated suspended parallel strip line (SW‐SISPSL) for the first time. The slow‐wave effect is produced by cascading high/low‐impedance SISPSL in the meander line configuration. Different from conventional single‐ended slow‐wave transmission lines, the proposed SW‐SISPSL supports differential signal transmission. The characteristic impedance and slow‐wave factor of the SW‐SISPSL are analyzed using equivalent circuit models. Using the proposed SW‐SISPSL and a SISPSL phase inverter, a very compact rat‐race coupler is implemented. The core circuit area of the slow‐wave rat‐race coupler is 0.083 λg × 0.089 λg, which is only 4.12% of the conventional topology. [ABSTRACT FROM AUTHOR]

In this paper, a new structure of the quadrature hybrid coupler (QHC) with compact size is proposed using capacitive composite lines and meandered open stubs. The proposed coupler works at 1.6 GHz with a 0.4 GHz bandwidth, which shows 25% fractional bandwidth (FBW). The proposed QHC occupies only 15 mm × 15 mm (0.12 λ × 0.12 λ), while the typical QHC size is 32 mm × 32 mm (0.25 λ × 25 λ) at the same working frequency. In the designed structure, two symmetric meandered stubs and two symmetric π-shaped composite networks including capacitors and microstrip lines are applied together. The designed QHC has a small size and occupies only 22% of the area of the conventional QHC, resulting in a 78% size reduction. The designed prototype has been analyzed, fabricated and tested, and the experimental results verify the simulated and analysis results. The results show a better than 27 dB return loss, more than 28 dB isolation between the output ports and less than 0.4 dB insertion loss at the working frequency of 1600 MHz. With the achieved desirable specifications, the fabricated QHC is a suitable choice for wireless microwave applications. [ABSTRACT FROM AUTHOR]

In this article, a compact super-wideband flexible textile antenna is proposed. It operates over an extremely broad frequency range from 3.16 to 50 GHz. The proposed design is characterized by its simple geometry, consisting of an offset rectangular patch, which is incorporated with three slots to enhance its performance, while a circular parasitic patch is positioned on the opposite side of the substrate. The proposed antenna prototype is fabricated on a footprint of 30 mm × 25 mm × 1 mm, which measures an electrical dimension of 0.31λ0 × 0.26λ0 × 0.012λ0 at 3.16 GHz. As per measurements, a wide bandwidth of 15.82:1 from 3.16 to 50 GHz is achieved with a peak gain of 7.70 dBi at 23.05 GHz. Furthermore, the ADS software is employed to create and analyze the equivalent circuit model of the designed antenna whose simulation studies are executed using CST software. The suggested antenna's overall performance is described by investigating the effects of structural bending and also proximity to the human body. Moreover, it provides acceptable values of specific absorption rate, ensuring lower absorption, which are under the safety standard limits for RF exposure. The measured results correlate with simulated results. Owing to its simple topology, compact size, super-wideband behavior, and high gain, endorse its suitability for low-power requirement applications in the real world. [ABSTRACT FROM AUTHOR]

This study presents a novel compact design of the Gysel topology and a filtering power divider (FPD) that utilizes a coupling structure. The proposed design replaces the traditional four-quarter wavelength transmission lines of the Gysel power divider with transmission lines and lumped components, resulting in a significantly reduced circuit size. Furthermore, the introduction of this coupling structure ensures the integration of the filtering and power division functions. Two transmission zeros are created near the passband to enhance the frequency selectivity of the responses. Theoretical analysis is carried out, and closed-form equations are derived based on the even–odd-mode method. To validate the theory, a three-port equal Gysel FPD operating at 2 GHz was designed and fabricated. The simulated and measured results demonstrate that this FPD has good power splitting and filtering capability with the size of 0.15 λ g × 0.25 λ g ( λ g is the medium wavelength of the central frequency), which is a significant reduction compared to the existing Gysel FPDs. The simulated and measured results are presented to verify the theoretical derivation, demonstrating good features, such as a return loss greater than 15 dB, isolation greater than 15 dB, and an insertion loss of about 4.02 dB (3 + 1.02 dB) in the passband. [ABSTRACT FROM AUTHOR]

This paper proposes a spoof surface plasmon polariton (SSPP) low-pass filter by etching butterfly-shaped cells on the middle line of a coplanar waveguide (CPW). The transmission and dispersion characteristics of the structure are analyzed. This design has a perfect low-pass transmission with tunable cutoff frequency. The angle and radius of the butterfly grooves are two variables that can adjust the cutoff frequency. The existence of two parameters is helpful to design a constant-width transition between the CPW and CPW-SSPP structures. It can be obtained by varying the angle of the butterfly grooves, while their radius is fixed. The introduced butterfly SSPP achieves a cutoff frequency reduction of 33% in comparison with its conventional rectangular counterpart with the same lateral size. It also has less phase velocity and more slow-wave effects than the rectangular SSPPs. Consequently, both transverse and longitudinal dimensions can be reduced by using the butterfly grooves. Moreover, the transition length is significantly reduced. The measured results show a 3-dB bandwidth from 0 to 10 GHz, a return loss of greater than 13.76 dB, an insertion loss of less than 1.6 dB, and an out-of-band rejection of higher than 15 dB from 10.2 to 14.5 GHz. The proposed circuit with the compact size, low loss, groundless structure, excellent slow-wave effect, and compact transition with excellent mode conversion can be applicable to the future communication systems. [ABSTRACT FROM AUTHOR]

In this paper, three super-compact equal/unequal filtering power dividers (FPDs) by combining the half-mode substrate integrated waveguide (HMSIW) platform and the metamaterial unit cell are proposed. To miniaturized the total dimension of the proposed equal/unequal FPDs, the evanescent mode technique, the half-mode technique, and the stepped-impedance resonator (SIR) technique have been utilized, simultaneously. In the modified metamaterial unit cell, which is called the complementary G-shaped resonator (CGR) unit cell, the quasi stepped-impedance slot line is replaced instead of the conventional slot line in the circular complementary split-ring resonator (CSRR) unit cell. Accordingly, the electrical size of the modified CGR unit cell is smaller than the conventional circular CSRR unit cell with the same physical sizes. Employing the introduced CGR unit cell and HMSIW structure, three equal/unequal FPDs with arbitrary power-dividing ratios have been designed and simulated. To illustration the performance of the proposed components, three HMSIW FPDs with different power division ratios of 1:1, 1:4, and 1:8 have been fabricated and measured. A reasonable agreement between simulated and measured results has been achieved. The results demonstrate that a miniaturization factor of about 0.64 is achieved. [ABSTRACT FROM AUTHOR]

This letter introduces a filtering magic‐T based on a hybrid microstrip‐cavity structure. TE011 and TE101 modes of the cavity are generated by the two perpendicular input microstrip lines to form the filtering responses. Because of the orthogonality of the feeding lines and the two resonant modes, in‐ and out‐of‐phase output currents and high port isolations are achieved. The measured filtering responses of the two input ports are in good agreement with each other and possess high‐frequency selectivity. The isolations of the input and output ports are below 41 and 22 dB, respectively. Moreover, benefiting from the hybrid microstrip‐cavity structure, only two cavity resonators are employed, which realizes compact size. [ABSTRACT FROM AUTHOR]

In this work a compact size capacitive load dual band planar inverted-F implant antenna is presented. The suggested antenna is modeled on RO3010 substrate that has a thickness of 2 mm, dielectric constant of 10.2, and tangent loss of 0.0023 to operate at both the Medical Implant Communications Services (MICS) and Industrial, Scientific, and Medical (ISM) bands. A capacitive load is inserted between the patch and the ground plane to get a dual band and compact size implant antenna. The idea behind the capacitive load is to support a simple structure with a dual band and compact size in addition to get a gain enhancement. The antenna size is 20 × 12 × 2 mm3. The antenna designed in this work operates at 402 MHz with a return loss of − 23.23 dB over a frequency band [397.15–409.4 MHz] for MICS band and operates at 2.42 GHz with a return loss of − 20 dB over a frequency band [2.37–3 GHz] for ISM band. The simulated gain is − 27.52dBi at 402 MHz for MICS band and − 1.85dBi at 2.42 GHz for ISM band. The proposed antenna has a good performance inside three-layered tissue model. The Computer Simulation Technologies (CST) Microwave studio is used to model and simulate the proposed antenna. [ABSTRACT FROM AUTHOR]

In this paper, a simple and compact monopole antenna with a high bandwidth ratio (BDR) of around is investigated for super wideband (SWB) applications. Using an F4B substrate with a dielectric constant of 2.65, loss tangent of 0.002, and connecting it to a triangular tapered 50‐Ohm line, the suggested antenna achieves its performance objectives. The proposed antenna has an electrical dimension of 0.14λ × 0.22λ and spans the SWB frequency range of 2.89–60 GHz with a 181.5% fractional bandwidth and reflection coefficient S11 < −10 dB. It has been revealed that the results of both experiments and simulations are remarkably similar to one another in terms of their conclusions. In comparison to other SWB antennas, the suggested antenna has a greater BDR, a larger bandwidth, and a more compact size. Apart from that, the antenna has good gain and good radiation characteristics over the whole operational frequency range. [ABSTRACT FROM AUTHOR]

A novel design approach for broadening 3-dB axial ratio beamwidth (ARBW) of circular polarization (CP) patch antenna is herein introduced. A patch structure consisting of three pairs of slots and four coupled strips is firstly proposed and examined. In such a compact size of $0.216\,\,\lambda _{0} \times 0.216\,\,\lambda _{0} \times 0.013\,\,\lambda _{0}$ ( $\lambda _{0}$ is the free-space wavelength at the 2.42 GHz). By carefully studying the evolution and related impact of the patch structure, the ARBW broadening mechanism is thoroughly revealed. The far-zone fields are further studied by the theory of equivalent magnetic currents (EMCs), and two polarized degenerate modes TM10 and TM01 are generated to excite CP radiation. To better understand the working mechanism of the proposed parasitic structures, an equivalent circuit consisting of three networks is given. Finally, to validate the performance, the proposed antenna is fabricated and measured, the simulated and measured results of impedance bandwidth for $\vert \text{S}_{11}\vert \le -10$ dB is from 2.36 GHz to 2.48 GHz, and the measured 3-dB ARBW is 244° at plane $\varphi $ = 0°. Both simulated and measured results show that the proposed antenna is very promising for high elevation angle wireless applications.

Rectangular Dielectric Resonator Antenna (RDRA) is utilized for the wireless communications system because of its miniaturized size and low profile. This paper presents a design and simulation of slotted RDRA for satellite communication. The major aim of the work is to attain a high gain and radiation efficiency. Hence, the parasitic patch is introduced in this work to achieve this requirement. In this work, the RDRA is designed with a compact size of 10 × 10 × 3 mm, which operates at 17.04 GHz for satellite communication applications. The design is evaluated on the substrate ROGERS RT DUROID 5880, and the antenna comprises Alumina (Al2O3) ceramic material. The slotted design provides better impedance bandwidth and gain. The entire work is simulated in Ansys HFSS software. The performance measures like gain, return loss, radiation pattern, VSWR and directivity are simulated and fabricated. The proposed design provides circularly polarized characteristics at 3 dB and better radiation efficiency of 100%. At last, the fabricated design prototype is analyzed and provides better performance. The simulated and fabricated outcomes proved that the proposed slotted RDRA is efficiently exploited for satellite communication. [ABSTRACT FROM AUTHOR]

In this paper, a wideband dielectric resonator antenna with compact size is presented. The proposed antenna is formed by four dielectrics. Non-adjacent dielectrics have same permittivity constant. A 50-ohm micro strip feed line is used to exciting the antenna through the coupling slot. By optimizing the dimensions and structure of the antenna, impedance bandwidth of 3.25 to 4.4 GHz is obtained. Impedance bandwidth of the proposed antenna is a very wide bandwidth compared to the previous dielectric antennas. The antenna gain is about 9.6 dB. [ABSTRACT FROM AUTHOR]

In this article, the compact, ultra-wideband and high-gain MIMO antenna is presented for future 5G devices operating over 28 GHz and 38 GHz. The presented antenna is designed over substrate material Roger RT/Duroid 6002 with a thickness of 1.52 mm. The suggested design has dimensions of 15 mm × 10 mm and consists of stubs with loaded rectangular patch. The various stubs are loaded to antenna to improve impedance bandwidth and obtain ultra-wideband. The resultant antenna operates over a broadband of 26.5–43.7 GHz, with a peak value of gain >8 dBi. A four-port MIMO configuration is achieved to present the proposed antenna for future high data rate devices. The MIMO antenna offers isolation <−30 dB with ECC of <0.0001. The antenna offers good results in terms of gain, radiation efficiency, envelop correlation coefficient (ECC), mean effective gain (MEG), diversity gain (DG), channel capacity loss (CCL), and isolation. The antenna hardware prototype is fabricated to validate the performance of the suggested design of the antenna achieved from software tools, and good correlation between measured and simulated results is observed. Moreover, the proposed work performance is also differentiated with literature work, which verifies that the suggested work is a potential applicant for future 5G compact devices operating over wideband and high gain. [ABSTRACT FROM AUTHOR]

In this paper, a new structure of the quadrature hybrid coupler (QHC) with compact size is proposed using capacitive composite lines and meandered open stubs. The proposed coupler works at 1.6 GHz with a 0.4 GHz bandwidth, which shows 25% fractional bandwidth (FBW). The proposed QHC occupies only 15 mm × 15 mm (0.12 λ × 0.12 λ), while the typical QHC size is 32 mm × 32 mm (0.25 λ × 25 λ) at the same working frequency. In the designed structure, two symmetric meandered stubs and two symmetric π-shaped composite networks including capacitors and microstrip lines are applied together. The designed QHC has a small size and occupies only 22% of the area of the conventional QHC, resulting in a 78% size reduction. The designed prototype has been analyzed, fabricated and tested, and the experimental results verify the simulated and analysis results. The results show a better than 27 dB return loss, more than 28 dB isolation between the output ports and less than 0.4 dB insertion loss at the working frequency of 1600 MHz. With the achieved desirable specifications, the fabricated QHC is a suitable choice for wireless microwave applications.

This article demonstrates a compact wideband four-port multiple-input-multiple-output (MIMO) antenna system integrated with a wideband metamaterial (MM) to reach high gain for sub-6 GHz new radio (NR) 5G communication. The four antennas of the proposed MIMO system are orthogonally positioned to the adjacent antennas with a short interelement edge-to-edge distance (0.19λmin at 3.25 GHz), confirming compact size and wideband characteristics 55.2% (3.25–5.6 GHz). Each MIMO system component consists of a fractal slotted unique patch with a transmission feed line and a metal post-encased defected ground structure (DGS). The designed MIMO system is realized on a low-cost FR-4 printed material with a miniature size of 0.65λmin × 0.65λmin × 0.02λmin. A 6 × 6 array of double U-shaped resonator-based unique mu-near-zero (MNZ) wideband metamaterial reflector (MMR) is employed below the MIMO antenna with a 0.14λmin air gap, improving the gain by 2.8 dBi and manipulating the MIMO beam direction by 60°. The designed petite MIMO system with a MM reflector proposes a high peak gain of 7.1 dBi in comparison to recent relevant antennas with high isolation of 35 dB in the n77/n78/n79 bands. In addition, the proposed wideband MMR improves the MIMO diversity and radiation characteristics with an average total efficiency of 68% over the desired bands. The stated MIMO antenna system has an outstanding envelope correlation coefficient (ECC) of <0.045, a greater diversity gain (DG) of near 10 dB (>9.96 dB), a low channel capacity loss (CCL) of <0.35 b/s/Hz and excellent multiplexing efficiency (ME) of higher than −1.4 dB. The proposed MIMO concept is confirmed by fabricating and testing the developed MIMO structure. In contrast to the recent relevant works, the proposed antenna is compact in size, while maintaining high gain and wideband characteristics, with strong MIMO performance. Thus, the proposed concept could be a potential approach to the 5G MIMO antenna system. [ABSTRACT FROM AUTHOR]

A novel ultra-wideband (UWB) KAYI-shaped and common KITE-shaped ground plane tri-port antenna is proposed. The proposed research work has a small size of (30 × 30 × 1.6 mm 3 ). The MIMO antenna elements are placed in a KAYI-shaped (Y-shaped) with a symmetric phase shift of 120 ∘ between the nearby MIMO antennas element improving the isolation. The antenna's gain is more than 5 dBi for the entire bands of WiMax, WLAN, and X-band satellite communication. The suggested work includes notches at 3.2 GHz, 5.2 GHz, and 8.9 GHz, respectively. The notching characteristics are made possible by L-shaped slits for the WiMax band, the inverted U-shaped slot for WLAN, while the third is created by the interaction between the L-shaped and U-shaped notching elements. Results were measured after making the prototype antenna on the FR-4 substrate. The proposed antenna has good impedance matching for 2–20 GHz and three notching characteristics with high isolation among the MIMO elements. Mean effective gain (MEG), envelope correlation coefficient (ECC), and total active reflection coefficient (TARC) are the diversity metrics of MIMO antennas which are in good comparison to the proposed antenna. The antenna is a good candidate for deployment in wireless communication and MIMO applications. [ABSTRACT FROM AUTHOR]

A broadband radiation dual‐polarized antenna is proposed for the application of 5G sub‐6 GHz base stations. The radiator of the antenna is consisted of a pair of crisscrossed sector dipoles, and is fed by microstrip stubs. By etching rectangular slots on the patches, the resonant modes of the antenna can increase to eight. Therefore, the broadband characteristic can be realized by effectively exciting the ideal modes. And the dual‐polarized characteristic is also achieved by exciting the ideal modes. The overall size of the proposed antenna is λ×λ×0.258λ (λ is the free‐space wavelength at 4.3 GHz) and it is fabricated and tested. The measured bandwidth can achieve 47.2% (3.19 ~ 5.22 GHz) for S11 <−10 dB and S21 < −26 dB, and the half‐power beam width (HPBW) is 55 ± 6° within the working band. The antenna gain attains 8.3 ± 1.6 dBi with a good stable radiation pattern. These features make the antenna more attractive for 5G sub‐6 GHz communication applications. [ABSTRACT FROM AUTHOR]

In this brief, compact multi-channel bandpass filters and diplexers are proposed based on dual-coaxial resonators. One coaxial resonator is embedded into the other to form a dual-mode resonator without increasing the size, where the resonant section of one resonator acts as the shielding cavity of the other one. In this way, the two modes of the dual-coaxial resonator are ideally isolated and can be controlled independently. By properly designing the feeding and coupling structures between resonators, the two modes in one dual-coaxial resonator can be excited and coupled to construct different filter channels without influencing each other. Accordingly, multi-channel filters are realized. For verification, a dual-channel and a triple-channel filters are presented. Moreover, the filter channels in a dual-channel filter can be applied to design the diplexer, resulting in a compact size. Experimental results are presented with good in-band responses and high isolation. [ABSTRACT FROM AUTHOR]

A new method for designing a compact microstrip lowpass filter (LPF) with wide stopband width (SBW) and sharp roll off (ROF) is presented. In proposed designing procedure, high impedance microstrip lines are bent to achieve an LPF with compact size. Then, to compensate for the effect of bending microstrip lines, the lengths of the lines are mathematically modified. Moreover, adding a suppressing cell composed of Radial stub resonator and a Butterfly stub resonator increases the SBW. Also, an elliptic filter structure is used to obtain sharp ROF. In this work, an LPF with 1.12 GHz cutoff frequency, 0.147 λg — 0.133 λg filter size; where λg is the guided wavelength at cutoff frequency, the SBW equal to 13.4 GHz, and the ROF more than 201 dB / GHz, is designed, simulated and fabricated to demonstrate efficiency of the proposed method. Also, the other conventional characteristics for the fabricated LPF such as 0.3 dB insertion loss, 14.4 dB return loss, and suppression factor equal to 2.2, are in the appropriate range of their amounts.

Magnetoelectric dipole antennas have attracted attention owing to their high performance, however, they are structurally complex and large. Attempts have been made to reduce their size, but the wideband properties and compact size are yet to be achieved simultaneously. This article proposes a dual‐polarized magnetoelectric dipole antenna to address these issues. The proposed antenna utilizes vertically oriented folded shorted patches to function as magnetic dipoles, which effectively enlarges the impedance bandwidth and stabilizes the antenna gain in the higher frequency. Additionally, it includes four L‐shaped metallic plates placed vertically on the reflector. Owing to the coupling with the adjacent electric dipoles, better impedance matching was obtained in the lower frequency, shifting the low limit of operating frequency to a lower frequency. This improvement enables the further enhancement of the impedance bandwidth and eventually a miniaturized structure is realized. A prototype was fabricated and measured with the results demonstrating that two ports both achieve 103% impedance bandwidth from 1.5 to 4.7 GHz, and the isolation was greater than 25 dB. Furthermore, stable radiation patterns with a gain of 7.1±1.1dBi was obtained. Moreover, the size of the antenna is very compact, which is only 0.37λL×0.37λL×0.11λL (λL denotes the wavelength at the lowest frequency). [ABSTRACT FROM AUTHOR]

In this brief, a triple-mode folded half mode substrate integrated waveguide (HMSIW) diplexer with wide stopband and high isolation based on embedded isolation network is proposed. The embedded isolation network of SIW diplexer is introduced to achieve miniaturization, low insertion loss and flexible design of high isolation between two channels for the first time. Triple-mode folded HMSIWs with loading different slots are utilized to design filtering responses in two channels, which can further reduce size and insertion loss of the diplexer. Besides, the wide stopband can be obtained for feeding technology in Channel 1 and harmonic mutual suppression technique in Channel 2. In final, a prototype with 3-dB fractional bandwidths of 14.6% (Channel 1) and 6.2% (Channel 2) is designed and fabricated at 5.05 GHz (Channel 1 @ $f_{1}$) and 7.46 GHz (Channel 2 @ $f_{2}$). The in-band isolations and upper-stopband attenuation are better than 55 dB / 49 dB (Channel 1 / Channel 2) and 20 dB extended to 12.3 GHz ($2.43f_{1}$). It occupies only $0.56~{\lambda }_{\mathrm{ g}}^{2}$ , where ${\lambda }_{\mathrm{ g}}$ is the guided wavelength at $f_{1}$. [ABSTRACT FROM AUTHOR]

The article presents a miniaturized monopole antenna dedicated to modern flexible electronic systems. The antenna combines three fundamental properties in a single structure. Firstly, it is characterized by a compact size compared to the state-of-the-art literature with an overall size of 18×18×0.254 mm3, secondly, the proposed antenna integrates the reconfigurability function of frequency, produced by means of a Positive-Intrinsic- Negative (PIN) diode introduced into the radiating element. Thus, the antenna is able to switch between different frequencies and different modes, making it suitable to meet the ever-changing demands of communication systems. third, the antenna is equipped by the property of flexibility. In fact, a conformability test is performed and has demonstrated the stability of the antenna performance under normal and bending conditions. Finally, in order to demonstrate the potential of the proposed antenna, a comparison between the simulated and measured results is made and turned out to be a strong agreement, making the antenna an excellent candidate for future miniaturized rigid and conformal devices. [ABSTRACT FROM AUTHOR]

In this letter, an efficient and compact tri-band rectifier with large frequency ratio is proposed, which adopts a novel low-cost direct current (dc)-pass filter structure in the design. Three large frequency ratio rectifiers are combined together by using diode arrays with a frequency-selective topology without additional impedance matching networks. The dc-pass filter is composed of microstrip line structures cascaded low-cost lumped components, which can effectively suppress the high-order harmonics at high- and low-frequency points while reducing the circuit size and costs of large frequency ratio. For validation, the proposed rectifier working at 0.915, 2.45, and 5.8 GHz is fabricated with the dimensions of 29.5 mm $\times21.3$ mm. The measured results show that the RF-dc power conversion efficiency (PCE) reaches 72.6%, 71.8%, and 73.5% at 0.915, 2.45, and 5.8 GHz, respectively, when the input power is 19 dBm. Compared with traditional multiband rectifiers, the proposed topology exhibits merits of compact size, high efficiency, and large frequency ratio. [ABSTRACT FROM AUTHOR]

This work proposes a new compact triple-band triangular patch antenna for RF energy harvesting applications in IoT devices. It is realized on Teflon glass substrate with a thickness of 0.67 mm and a relative permittivity of 2.1. Four versions of this antenna have been designed and realized with inclinations of 0°, 30°, 60° and 90° to study the impact of the tilting on their characteristics (S11 parameter, radiation pattern, gain) and to explore the possibilities of their implementation in the architectures of electronic equipment according to the available space. The antenna is also realized on waterproof paper with a thickness of 0.1 mm and a relative permittivity of 1.4 for biomedical domain. All the antennas (vertical antenna, tilted antennas and antenna realized on waterproof paper) have a size of 39 × 9 mm2 and cover the 2.45 GHz and 5.2 GHz Wi-Fi bands and the 8.2 GHz band. A good agreement is obtained between measured and simulated results. Radiation patterns show that all the antennas are omnidirectional for 2.45 GHz and pseudo-omnidirectional for 5.2 GHz and 8.2 GHz with maximum measured gains of 2.6 dBi, 4.55 dBi and 6 dBi, respectively. The maximum measured radiation efficiencies for the three antenna configurations are, respectively, of 75%, 70% and 72%. The Specific Absorption Rate (SAR) for the antenna bound on the human body is of 1.1 W/kg, 0.71 W/kg and 0.45 W/kg, respectively, for the three frequencies 2.45 GHz, 5.2 GHz and 8.2 GHz. All these antennas are then applied to realize RF energy harvesting systems. These systems are designed, realized and tested for the frequency 2.45 GHz, −20 dBm input power and 2 kΩ resistance load. The maximum measured output DC power is of 7.68 µW with a maximum RF-to-DC conversion efficiency of 77%. [ABSTRACT FROM AUTHOR]

In this article, a compact microstrip patch antenna (MPA) with enhanced bandwidth and filtering response is proposed and implemented solely by loading pairs of slots on the conventional square patch radiator. Initially, the dominant mode TM10 of the square patch radiator is theoretically investigated, revealing its broadside radiation pattern and its current flows in the consistent direction. After that, based on the regularities of field distribution, two pairs of slots are etched in the square patch so as to generate two extra modes without destroying both resonant and radiating properties of TM10 mode. By virtue of these two excited modes, two extra resonances are produced in proximity to its dominant one, so as to widen the bandwidth under triple resonant modes. Meanwhile, owing to the inverse equivalent magnetic currents (EMCs) along the radiation edges of the patch and the out-of-phase electric fields at the two sides of each slot under these two excited modes, radiation cancellation toward broadside direction and efficiency reduction occur simultaneously. Hence, radiation nulls are achieved in all direction, and particularly, the radiation null toward broadside direction is deeper than others. After our intensive investigation is done on the entire slots-loaded patch radiator, a wideband filtering MPA with three in-band resonances and two out-of-band radiation nulls has been finally constructed. For demonstration, a prototype antenna at a center frequency of 3.5 GHz is designed, fabricated, and measured. The measured results are found in good accordance with the simulated ones, demonstrating an impedance bandwidth of 9.14% with stable broadside realized gains as well as two radiation nulls at 3.12 and 3.83 GHz, respectively, in addition to its low profile of 0.029 free-space wavelength. Notably, the presented antenna has occupied the almost same area as the conventional square MPA, maintaining its good size compactness. [ABSTRACT FROM AUTHOR]

In this Letter, we investigate a wideband magnetoelectric dipole antenna miniaturized by folding. In the proposed design, a folded L‐shaped electric dipole is used instead of the conventional half‐wavelength horizontal electric dipole, and a pair of vertically folded shorted patches act as a magnetic dipole, producing a miniaturized radiator. Furthermore, a small‐size U‐shaped reflector replaces the traditional large‐size planar reflector, resulting in a decrease in the low end of the frequency band, while the high end of the frequency band remains almost unchanged. A better impedance matching is also obtained over the entire operating frequency band. Ultimately, a miniaturized overall structure and a wide bandwidth are obtained simultaneously. The overall size of the proposed antenna is only 0.25λL×0.25λL×0.12λL ${\boldsymbol{0}}{\boldsymbol{.}}{\boldsymbol{25}}{{\boldsymbol{\lambda }}}_{{\boldsymbol{L}}}{\boldsymbol{\times }}{\boldsymbol{0}}{\boldsymbol{.}}{\boldsymbol{25}}{{\boldsymbol{\lambda }}}_{{\boldsymbol{L}}}{\boldsymbol{\times }}{\boldsymbol{0}}{\boldsymbol{.}}{\boldsymbol{12}}{{\boldsymbol{\lambda }}}_{{\boldsymbol{L}}}$ (where λL ${{\boldsymbol{\lambda }}}_{{\boldsymbol{L}}}$ is the longest operating wavelength), which is 82% smaller than the size of the original design, but the proposed antenna can still obtain a large bandwidth of 120% (1–4 GHz) for VSWR < 2. Furthermore, stable radiation patterns are realized with an average gain of 5 dBi within the operating frequency band. [ABSTRACT FROM AUTHOR]