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A novel design concept of multiple‐input and multiple‐output (MIMO) antenna with aiming to improve matching and port isolation at the same time is proposed. As the only additional component, a cross resonator is connected between the two patch antennas. The equivalent circuit model and calculation formula of resonant frequency of cross resonator in differential mode (DM) and common mode (CM) state are given, respectively. The same resonant frequency in the two states is the goal to want, and which is proved to be achievable by the relevant expression. Then, the two port antenna system can obtain good matching and high isolation. The coincidence between simulation and measured results brings the possibility of practical implementation. [ABSTRACT FROM AUTHOR]

In this article, a wideband base station antenna is designed. A new resonant mode is introduced into the antenna. Finally, four U‐shaped slots are added to the dipole of the antenna, and the antenna's third resonant mode is close to the first two resonant modes, which makes the antenna achieve wideband performance. The antenna is fabricated, and its performance is measured. The results show that the antenna has stable gain and radiation patterns. At the same time, the antenna works at 1.6–3.85 GHz with an impedance matching of −14 dB, and the relative bandwidth is 82%, the polarization isolation of the proposed antenna is better than −40 dB. [ABSTRACT FROM AUTHOR]

A novel concept of simultaneous matching, decoupling and miniaturization in multiple input multiple output (MIMO) antenna is proposed. Firstly, the integration of matching and decoupling can be achieved by making the resonant frequency of common mode (CM) and differential mode (DM) consistent. Then, the same resonant frequency of CM and DM will move to lower frequency through changing parameters value of the folded cross resonator. The MIMO antenna will operate normally at lower frequency with low mutual coupling without increase the volume. The operating frequency of antenna is reduced from 3 to 2.5 GHz of achieving 16.7% miniaturization, and the isolation is increased from 20 to 45 dB at 2.5 GHz at the same time. The measurement and simulation results are in good agreement, which verifies the correctness of the design. The goal of matching, decoupling and miniaturization for MIMO antenna will be completed without too much software optimization and other complex structures. [ABSTRACT FROM AUTHOR]

In this article, a simple dual wideband antenna with a novel feeding structure is designed based on two folded dipoles. Because of the particular antenna structure, the feeding structure of the antenna works as an impedance transformer. Then, four resonance modes are excited to achieve dual wideband performance, which brings a wide impedance bandwidth to the two pairs of dipoles. A prototype of the proposed antenna is fabricated and measured. Results show that the proposed antenna successfully supports the dual wideband operation of 1.4–2.7 GHz (63%) and 3.4–5.2 GHz (41%). [ABSTRACT FROM AUTHOR]

In this article, the realization method and operation mechanism of suppressing cross‐band scattering is introduced, firstly. And then, a SSRs‐loaded electromagnetic transparent antenna (ETA) is designed to suppress the scattering interference existing in the proposed dual‐band shared‐aperture antenna (P‐DBSA). The P‐DBSA is composed of the proposed ETA operating in the lower‐band (LB: 1.7–2.2 GHz) and a 2 × 2 array antenna operating in the higher‐band (HB: 3.4–3.6 GHz). The proposed ETA is obtained by etching folded split‐slot resonators (F‐SSRs) on the entire radiating arms of the LB antenna. In this way, the scattered field formed by the HB‐induced current distributed on the LB radiating arms can be self‐canceled, thereby HB radiation pattern restoration can be achieved. In addition, etching F‐SSRs will not cause the ETA to be difficult to match. The proposed decoupling method has the advantages of simple in structure, high integration, and easy to manufacture, and has important reference value for suppressing cross‐band scattering existing in DBSAs. [ABSTRACT FROM AUTHOR]

A low‐profile dual‐band dual‐polarized base station antenna array is proposed. The dual‐band array is backed by an artificial magnetic conductor (AMC) surface. The AMC achieves profile reduction to 0.159 λL0 in the low band (LB), but it acts as a bandpass metasurface in the high band (HB). The nested design of AMC unit cell creates two out‐of‐phase induced currents with lower intensities, enabling suppression and cancelation of HB scattered fields. The back cavities establish clear and independent radiating environments for the LB and HB antennas. They aid in further radiation pattern restoration and antenna profile reduction. The proposed antenna array was fabricated and experimentally measured. The simulated and measured results are presented. The operating principles of the proposed AMC and back cavities are also investigated. [ABSTRACT FROM AUTHOR]

A novel electromagnetic transparent high-band (HB) antenna can be achieved by loading dumbbell-like slots, U-shaped slots, square-loop slots, and straight slots on the patch dipoles. The HB antenna operates in the band of 1.71–2.69 GHz (VSWR < 1.5), and the dipoles achieve low-scattering property in the band of 3.4–3.8 GHz. In the design, the impedance matching of HB antenna is very good even scattering suppression technique is applied on the dipoles. The loading of U-shaped slots introduces an additional resonance point, which can alleviate the impedance problem caused by the technique. Besides, a dual-band antenna array has been designed and fabricated for validation. Both simulated and measured results show that the HB antenna has a good performance on electromagnetic transparency. [ABSTRACT FROM AUTHOR]

An antenna decoupling method based on modal control is proposed in this paper. Different from the previous characteristic mode decoupling methods, which excite one of the characteristic modes from each port, a pair of decoupling modes is excited simultaneously at each port. To validate our method, a head‐to‐head antenna pair is analyzed and designed. According to the characteristic mode analysis, an inductor‐loaded coupled sheet is introduced for the head‐to‐head antenna pair. Thus, the resonant frequencies of decoupling modes can be tuned individually. To further demonstrate the flexibility of our design, an eight‐element multiple‐input multiple‐output (MIMO) antenna composed of two integrated four‐element blocks is designed, fabricated, and measured. The proposed antennas show good impedance matching, isolation, and diversity performance varying from 3.35 to 3.71 GHz. Both simulated and measured results show the 8 × 8 MIMO system can achieve isolations of better than 11.5 dB and envelope correlation coefficients of less than 0.2 of each port. [ABSTRACT FROM AUTHOR]

A novel electromagnetic transparent low-band (LB) antenna is given in this article, with a good impedance matching in the band of 0.69–0.96 GHz (VSWR < 1.5). The key feature lies in its great patch dipoles with low-scattering properties. The transparent performance is achieved by loading slots on the dipoles, instead of inserting chokes. Dagger-like slot plays an important role in both impedance matching improvement and scattering suppression. An extra resonance point can be introduced to the reflection coefficient curve in the operating band, so the impedance matching problems can be alleviated. Besides, a dual-band shared-aperture array was designed and fabricated for validation. Both simulated and measured results have proved that the LB antenna has satisfactory impedance characteristics within the operating band and achieves an electromagnetic transparency in the band of 1.7–2.4 GHz. [ABSTRACT FROM AUTHOR]

In this article, a height‐reduction dual‐polarized antenna suitable for base station applications with a simple structure is proposed. By adopting the form of bilateral coupling feed, the height of the antenna has been significantly reduced. The working mechanism of height‐reduction of the antenna is given. The experimental results show that the antenna operates at 0.698–0.96 GHz for reflection coefficient <−12 dB with isolation (ISO) of more than 30 dB. It has a stable gain of 8.4 ± 0.6 dBi and a half‐power beamwidth (HPBW) of 66.8 ± 6.8° in the working band, and the height of the proposed antenna is only 0.115λ0, which is much smaller than the traditional 0.25λ0 (λ0 denotes the free wavelength corresponding to the center frequency). [ABSTRACT FROM AUTHOR]

A tri‐band dual‐polarized antenna array for base station applications is presented. The proposed tri‐band antenna array is devised by stacking the 1 middle‐band (MB) + 4 high‐band (HB) interleaved array above the low‐band (LB) patch antenna. The MB antenna yields partial reflection to the HB subarrays, enabling cross‐band and in‐band decoupling abilities without introducing additional decoupling layer. With the aid of spatial cancelation and partition, transmission nulls are successfully generated in the in‐band mutual coupling curves. Measured results show that good impedance matchings and polarization isolations are acquired in the operating bandwidths. The measured co‐ and cross‐polarized in‐band isolations in the HB are improved to >22.4 dB and >29.1 dB, respectively. The HB radiation patterns are well restored. [ABSTRACT FROM AUTHOR]

A new decoupling concept for dual-band shared-aperture base station antenna arrays is proposed. By loading arrow-shaped decoupling structures in the hollowed regions of the low-band (LB) loop dipole arms, the LB antenna can yield partial reflection to the high-band (HB) antennas, canceling the HB-coupled wave. A dual-band base station antenna array is designed, fabricated, and measured based on this decoupling concept. With decoupling, the HB radiation patterns are restored. The copolarized in-band couplings between the HB antennas are reduced by about 9 dB, reaching >26.9 dB. The proposed antenna array possesses both cross-band and in-band decoupling abilities, without extra decoupling layer. [ABSTRACT FROM AUTHOR]

A triband shared aperture (TBSA) antenna is proposed to meet the new requirements of base station antennas for multiband antennas fusion. The proposed TBSA (P-TBSA) antenna is composed of a lower band (LB, 790–960 MHz) antenna, two columns of middle band (MB, 1710–2170 MHz) subarrays, and a $4\times 8$ array antenna operating at N78 band (higher band (HB): 3.4–3.6 GHz). The LB antenna is located in the center of a shared reflector. The MB subarrays are located around the LB antenna with a side-by-side scheme. The HB array antenna is located below the MB and LB antennas for multi-input–multioutput (MIMO) application. The cross-band coupling interference existing in the P-TBSA antenna can be divided into scattering interference and common-mode interference, which will seriously deteriorate its performance. To suppress the scattering interference, an LB crossed dipole antenna with low radar cross Section (RCS) at both MB and HB and an MB crossed dipole antenna with low RCS at HB are designed. In addition, the method of “path extension” is used to suppress the common-mode interference. By taking the above measures, the distorted radiation pattern of the P-TBSA antenna is significantly recovered. [ABSTRACT FROM AUTHOR]

A high‐isolation dual‐band base station antenna array is proposed. At first, a 5‐element high‐band (HB) dipole antenna array with inter‐element distance of 0.4 λH0 (the free‐space wavelength at the center frequency of the HB) is decoupled. With the main antenna decoupling surface (ADS), metal baffles and auxiliary ADS, the E‐plane and H‐plane couplings can be reduced to <−23.1 dB (<−11.4 dB without decoupling) and <−22.6 dB (<−14.8 dB without decoupling), respectively. The dual‐layer ADS design successfully resolves the contradiction between decoupling performance and matching. The ground plane of the 5‐element array is then exploited as the low‐band patch radiator, forming the proposed dual‐band antenna array. Measured results show that satisfactory cross‐band isolation (>33.1 dB), in‐band isolation (>22.2 dB) and polarization isolation (>30 dB) are obtained. Stable unidirectional radiation patterns are also acquired. [ABSTRACT FROM AUTHOR]

A wide‐band circularly polarized reconfigurable antenna based on a pure water dielectric patch antenna is proposed. By changing the shape of pure water in the plexiglass container symmetrically, the circularly polarized states of the antenna can be switched. And the available bandwidth of right‐hand circular polarization and left‐hand circular polarization remain unchanged. The interface between pure water and air with a great difference in relative dielectric constant is equivalent to an electrical wall. When feed with an L‐shaped metallic probe, the axial ratio of a wide band can be formed, and the impedance bandwidth of antenna can be fully utilized. Under the two circularly polarized states of the antenna, the measured results show that the 3‐dB axial ratio bandwidth is above 24.4% for |S11| < −10 dB, the radiation efficiency is concentrated at 58%–71%, and the maximum gain reaches 3.5 dBi. [ABSTRACT FROM AUTHOR]

In this communication, we propose a shared-radiator design concept for dual-band base station antenna arrays. To realize the concept, novel differentially fed dual-polarized slot antenna is devised to be the high-band (HB, 3.4–3.6 GHz) radiator, while the large slot ground can be reused as the radiating arm of the low-band (LB, 0.69–0.96 GHz) crossed dipole. Reflective cavities are introduced to back the HB antennas, building clear and independent radiating environments for the two operating bands. A dual-band base station antenna array with one LB dipole antenna and four HB slot antennas is designed, by adopting the proposed integration concept. Good impedance matching (voltage standing wave ratio <1.5) and high port isolation (>29.5 dB in the LB and >26.6 dB in the HB) are obtained. Stable radiation patterns are also achieved in the two bands. [ABSTRACT FROM AUTHOR]

In this article, we propose a novel reflector-back cavity-low-band (LB)/high-band (HB) configuration for the dual-band dual-polarized base station antenna array design. The HB antennas are embedded in the opening sections of the loop radiating arms of the LB antennas. Clear and independent radiating environments are fulfilled by using two different types of reflectors (large planar reflector and back cavity). The mutual effects between the LB and HB antennas help to acquire good impedance matching and stable radiation patterns. Loop-like LB radiators work as directors in the HB, thereby effectively suppressing the side and back radiations of the HB antennas. Dual-function open slots are loaded on the ground stubs of the LB baluns, serving as impedance transformer in the LB but filtering structures in the HB. The experimental results validate that the proposed antenna array successfully covers bandwidths of 0.69–0.96 and 3.3–3.8 GHz (VSWR < 1.5) for 4G/5G applications. The port isolations are higher than 38 and 25 dB in the LB and HB, respectively. With the two independent radiating environments formed in the two bands, both LB and HB antennas exhibit stable unidirectional radiation patterns. The antenna gains and HPBWs are also satisfactory in both bands. [ABSTRACT FROM AUTHOR]

A dual-band dual-polarized antenna array is considered to analyze the operating mechanism of the resonant coupling in multiband multiarray antennas, firstly. The considered antenna is composed of a lower band (LB) antenna operating from 690 to 960 MHz and two columns of higher band (HB) subarrays operating from 1690 to 2690 MHz. Then, a novel method of suppressing the resonant coupling interference by using ferrite cores is proposed. It is implemented by loading ferrite cores on the feed cables of the HB elements. The resonant coupling interference is caused by the LB common-mode currents distributed on the HB feed cables. It will seriously distort the LB radiation patterns. With the ferrite cores, the LB common-mode currents are eliminated, and then, the distorted LB radiation patterns are completely restored. Furthermore, the loaded ferrite cores hardly affect the performance of the HB elements. [ABSTRACT FROM AUTHOR]

A compact differentially fed dual‐polarized patch antenna with filtering performance is proposed for 5G applications. By utilizing the half‐wavelength standing current along the open‐ended microstrip line, the out‐of‐phase output signals are obtained. Utilizing the E‐shaped coupled resonator in series with the open‐ended microstrip line, balanced differential feeding with filtering property are realized, as excitation for the patch. The filtering patch antenna was fabricated for demonstration. Measured results show that the antenna has −15 dB impedance bandwidths of 13.7% (3.26–3.74 GHz) and 14.2% (3.25–3.75 GHz) for two polarizations, respectively, covering the 5G band (3.3–3.6 GHz). The patch antenna achieves good port isolation and cross‐polarization discrimination. In addition, the measured gain is higher than 6.8 dBi within operating band. Out of the operating band, the gain drops sharply, exhibiting a bandpass response. The out‐of‐band radiation suppression level of the proposed filtering patch antenna is larger than 16 dB. [ABSTRACT FROM AUTHOR]

In this communication, a ±45° dual-polarized antenna for 690–960 MHz base station applications is proposed. The proposed antenna has a crisscross-shaped radiator which is fed by four triangular-shaped couplers. The ±45° dual polarization is achieved by vector synthesis of the currents on the radiator. To further broaden the impedance bandwidth (IBW), a miniaturized lowpass filter is designed and integrated with the baluns of the proposed antenna. With the lowpass filter, a new resonance is introduced and harmonic suppression is also realized. The experimental results which agree with the simulations show that wide harmonic suppression bandwidth which can cover the interference bands (1.69–2.69 GHz and 3.3–3.8 GHz) is obtained. In the operating frequency band (690–960 MHz), a voltage standing-wave ratio (VSWR) of less than 1.5, a polarization isolation (ISO) of more than 35 dB, a half-power beamwidth (HPBW) of 66.8° ± 1.5°, and the gains of 8.3 dBi ± 0.2 dBi are obtained by the proposed antenna. [ABSTRACT FROM AUTHOR]

In this article, dielectric loading is introduced as a method for miniaturizing dual‐polarized crossed dipole antenna. Specifically, the size, thickness, and relative permittivity of dielectric slab are considered as three critical parameters for antenna miniaturization. It is found that the three parameters have different loading effects on a crossed dipole, due to distinct modal current and field distributions. Furthermore, an antenna configuration loaded by 3‐layer dielectric slabs is proposed. Utilizing the slow‐wave property of dielectric loading, two miniaturized crossed dipole antennas with size of 40 mm × 40 mm (0.29 λ0 × 0.29 λ0) are devised, exhibiting an at least 21% size reduction over the previous dual‐linearly‐polarized crossed dipole antennas. Simulated and measured results demonstrate that the proposed antennas have wide bandwidth (1.71‐2.69 GHz), desirable impedance matching (VSWR <1.5), stable radiation pattern, and low gain loss. [ABSTRACT FROM AUTHOR]

Different from the traditional reconfigurable antennas, in which PIN diodes are just used as switches, a novel method for achieving the reactance tuning is proposed, in which the impedance characteristics of the PIN diode in different working states are used to realize elements sharing. The mechanism of element sharing is explained by mathematical analysis, firstly. Then, the novel method of realizing element sharing based on the impedance characteristics of PIN diode is explained. By this way, reactance tuning can be easily achieved using PIN diode. Finally, a 360° beam switchable dipole antenna array is designed to illustrate the feasibility of the proposed method. The results show that gains of 7.8 dBi, and FBRs (front‐to‐back ratios) of greater than 19 dB are achieved by the proposed antenna. In particular, the maximum gain drop of the proposed antenna is less than 0.72 dB when switching between different working modes. [ABSTRACT FROM AUTHOR]

A dual‐polarized filtering antenna (DPFA) with high‐order harmonics suppression for 690‐960 MHz based station applications is proposed in this letter. The proposed DPFA is obtained by integrating a miniaturized lowpass filter with a ±45° dual‐polarized antenna (DPA) which made by two crossed dipoles. With the miniaturized lowpass filter, harmonic suppression is easily achieved by the proposed DPFA without increase its size. The experimental results which agree with the computer simulations show that wide impedance bandwidth (|S11| < −15 dB) of 43.2% (690‐1070 MHz) and harmonic suppression frequency up to 4.5 GHz are realized. In the operating frequency band (690‐960 MHz), port‐to‐port isolation of more than 35 dB, cross‐polarization discrimination of more than 27 dB, 3‐dB beamwidth of 68.8° ± 2.1°, efficiency of more than 82%, and stable gain of 8.2 ± 0.5 dBi are obtained by the proposed DPFA. In addition, radiation suppression of more than 18 dB in the interference bands (1690‐2690 MHz and 3300‐3800 MHz) is obtained. [ABSTRACT FROM AUTHOR]

Considering the defects of particle swarm optimization (PSO) and multi-objective evolutionary algorithm (EA) based on decomposition (MOEA/D), this article proposes an improved multi-objective EA MOEA/D-GPSO for compact log-periodic dipole array (LPDA) design. MOEA/D-GPSO decomposes multiple objectives into a number of single-objective optimization problems. Each particle deals with one sub-problem. All the particles are divided into a few groups, and each particle has several neighboring particles. During the search, a new solution is constructed by learning information from the random non-dominated solutions found by its own neighbors and group. ZDT instances have been introduced to verify the effectiveness of MOEA/D-GPSO with respect to other outstanding multi-objective EAs. Further, two miniaturized LPDA designs for the application of digital video broadcasting-terrestrial (DVB-T) (470–790 MHz), a tri-objective compact LPDA, and a novel LTE800-refused compact LPDA, respectively, are presented, showing their good performance over other similar designs and promising prospect of the proposed algorithm for high-dimensional and multi-functional LPDA design. [ABSTRACT FROM AUTHOR]

This paper proposes that ring slot antennas, loaded with shorting strips, can achieve broadside gain enhancement while maintaining a low profile and bidirectional radiation. Both circularly polarized (CP) and linearly polarized (LP) ring slot antennas are used to demonstrate this method. With infinite ground plane (GP), CP and LP ring slot antennas are observed to increase by at least 0.8 and 1.7 dBi in realized gains, respectively. Combined characteristic modes (CMs) are used to analyze and explain the working mechanisms of these antennas. It is shown that shorting strips could help to enlarge the radiation apertures of ring slots, while the center frequency remains constant; hence, broadside gains are enhanced successfully. It is also discussed that by replacing the infinite GP with a finite one of about $1.5\lambda \times 1.5\lambda $ , gains of both CP and LP ring slot antennas change little at center frequencies. Prototypes of these two antennas are then fabricated and measured to experimentally validate the analysis and designing approach. [ABSTRACT FROM AUTHOR]

A compact, dual-polarized multiband array is proposed and developed for 2G/3G/4G base station applications. The antenna is formed by two-element lower band array, five-element higher band array, bowl-shaped reflectors, bended baffles, and rectangular baffles, which are coexisting over one reflector. Miniaturized higher band element covering 2G/3G/4G bands and new square-shaped aperture lower band element covering LTE700/GSM850/GSM900 have been proposed. The higher band elements are placed upon the bowl-shaped reflector and composed of two pairs of loop dipoles with chamfers and vertical stubs for miniaturization. The bowl-shaped reflector is of great significance to the stable beamwidth, while the rectangular and bended baffles are designed further to improve the beamwidth. Moreover, the five-element higher band array is designed with electric downtilt from 0° to 10°. The measured results determined by VSWR <1.7 are with the whole broadband coverage from 0.698 to 0.96 and 1.7 to 2.7 GHz, which can cover the whole 2G/3G/4G bands. Furthermore, the stable half-power beamwidth of 65.9 ± 4.3° at the horizontal plane (H-plane) as well as stable gain and enhanced cross-polarization discrimination (XPD) are achieved within both higher and lower frequency bands. [ABSTRACT FROM AUTHOR]

This paper proposes an accurate and general method to calculate and characterize the couplings of patch antennas. It is found that the coupling effects of open-/short-circuited patches can be represented by J/K inverters. Unlike traditional ones, these J/K inverters should be with complex- and frequency-dependent values. Three different patch antennas are used to exemplify how to characterize couplings with J/K inverters. Once the values of J/K inverters are successfully extracted, the total equivalent circuits of these patch antennas can be easily given in a unified way. J/K inverters can also help us see how the couplings affect antenna bandwidth. To present advantages of the proposed method, comparison with traditional coupling calculation approach based on characteristic modes is conducted. Technical limitations and potential applications of the proposed method are also discussed. [ABSTRACT FROM AUTHOR]

This paper proposes a new modal approach for evaluating $Q$ -factors of antennas based on newly introduced XeR/XmR modes rather than characteristic modes (CMs). In our new approach, $Q$ -factors could be represented as direct linear superpositions of eigenvalues of XeR and XmR modes. We validate the accuracy of the new formula for $Q$ -factors by studying two canonical wire antennas. Moreover, the relations between XeR/XmR, TE/TM, and Xe/Xm modes are presented, which show interesting properties. It is found that eigenvalues of XeR/XmR modes reveal useful information about minimum $Q$ -factors. Compared with the CMs, some disadvantages of the proposed modes are also discussed. [ABSTRACT FROM AUTHOR]

This communication finds that it is the combined characteristic modes (CMs), rather than the purely magnetic ones, that are always associated with low-resistance resonances of slot antenna. Thus, combined CMs could help control its bandwidth. A ring slot antenna with loaded stubs is proposed and analyzed to show how to use combined CMs to explain and achieve wideband characteristic. It is shown that by loading stubs, a new combined CM is introduced. A prototype antenna is then fabricated to experimentally validate the analysis and designing approach. The fractional bandwidth of the proposed ring slot antenna could be effectively increased from 12.5% to 18.2%. [ABSTRACT FROM AUTHOR]

A helical resonator with two-sectional different pitches is proposed in this paper. The frequency ratios of the first two resonant modes of the helical resonator can be tuned to desirable values in a certain range by adjusting the pitches. The proposed resonator is applied to design dual-band bandpass helical filters. To achieve control over dual-band filtering characteristics, a feeding structure with step-rectangular plate and a coupling window with three apertures are also proposed to realize the expected external quality factors and coupling coefficients in the two bands. To validate the design, a second order and a fourth order dual-band helical filters are fabricated and measured. The measured results show good agreement with simulation ones. [ABSTRACT FROM AUTHOR]

A wideband dual-polarized antenna loaded resonator is proposed in this article. A new resonant mode is induced while loaded with L-shaped resonator beside the dipole. This mode can be moved by adjusting the size and position of the resonator. And the main resonant mode is decided by the size of the dipole. In this way, a wide bandwidth of 33.7% from 0.67 to 0.97 GHz for | S11|<−15 dB is achieved with two resonant modes in the desired band. Moreover, stable radiation pattern gain, and low cross polarization are obtained over the entire operating band. [ABSTRACT FROM AUTHOR]

A novel radiation pattern reconfigurable multiple-input multiple-output (MIMO) antenna based on the loading of water is presented. By altering the situation of loading and unloading the distilled water on the surface of the parasitic element, the function of the parasitic element can be switched between a director and a reflector. According to the Yagi-Uda principle, the antenna creates a directional radiation pattern in the azimuth plane through the electromagnetically coupled parasitic elements. A good direction is achieved with the front-to-back of 13 dBi. The MIMO antenna consists of 2 identical elements lying orthogonally to each other. As a result, high-isolation (>35 dB) and low-envelop correlation coefficient (ρe < 0.0001) between MIMO elements are obtained by orthogonal dual-polarization antenna element. Good agreement is achieved between the measured results and the simulated results. [ABSTRACT FROM AUTHOR]

A single-layer circularly polarized (CP) antenna with omnidirectional radiation in the azimuth plane has been designed and evaluated. The concept is the combination of multiple identical endfire CP antenna elements in a circular array configuration. The design of each element is based on the superposition of two closely spaced complementary current sources, which are, respectively, realized by a sectorial parallel-plate cavity and arc-shaped strip arms. A meandered double-sided parallel strip line is introduced to adjust the phase relationship between two orthogonal linear polarized components. All antenna elements can be simultaneously excited by adopting a single coaxial probe in the center of the overall structure. Take 5.8-GHz Industrial Scientific Medical (ISM) band applications (5.725–5.875 GHz), for example, a prototype with a diameter of 0.62\lambda 0 and a low profile of 0.029\lambda 0 was fabricated. Experimental results show that the designed antenna has a usable bandwidth from 5.68 to 5.91 GHz (the common overlapped bandwidth limited by the −10 dB \vert S11\vert and the 3-dB axial ratio). Within the operation band, good omnidirectivity and a wide coverage can be obtained. [ABSTRACT FROM PUBLISHER]

ABSTRACT A wideband dual-polarized antenna is proposed. With chamfers in cross loop dipoles, the two resonating modes can be controlled, the first resonating mode can move lower and the second resonating mode can move higher by changing the size of the chamfer. Therefore, the radiator size is reduced to 48 mm × 48 mm (0.35 λ × 0.35 λ, λ is the wavelength at 2.2 GHz) and a wider bandwidth is achieved. Measured results show that the proposed antenna has a bandwidth of 48.8% from 1.7 to 2.8 GHz for VSWR < 1.5. Stable radiation pattern and stable gain are also obtained over the operating band. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:631-635, 2017 [ABSTRACT FROM AUTHOR]

ABSTRACT A printed-circuit differential-fed Yagi-Uda antenna is presented that features enhanced bandwidth by employing a parasitic quarter-wavelength coplanar stripline (CPS) resonator which adds one more resonant mode within the operating bandwidth. The proposed antenna is designed, fabricated and measured. Experimental results are in good agreement with simulations. In the band of 2.27-2.58 GHz, the return loss is better than 10 dB and the gain better than 6 dBi. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:156-159, 2017 [ABSTRACT FROM AUTHOR]

ABSTRACT This paper presents a reconfigurable bandpass filter (BPF) with constant absolute bandwidth (ABW). The structure is composed of a pair of novel half wavelength (λ/2) resonators with two center-tapped var actors. Frequency tuning is made possible by modifying the electrical length of the resonators with four varactors. Following the traditional synthesis approach, the internal coupling is analyzed and designed properly to meet the requirement of constant ABW. At last, the proposed filter exhibits a 49% fractional tuning range from 500 to 825 MHz, and a near constant 3-dB bandwidth of 56 ± 5 MHz. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1401-1404, 2016 [ABSTRACT FROM AUTHOR]

A novel method of enhancing cross-polarization discrimination (XPD) of a \pm 45^\circ dual-polarized base-station antenna, by addition of four parasitic elements placed in a square contour, is presented. First, it was established that high XPD at the broadside can be obtained by addition of four parasitic elements around a simple \pm 45^\circ dual-polarized base-station antenna. Second, we investigated the principle of wide beamwidth high XPD after studying magnitude currents on parasitic element, spacing between parasitic elements and length of parasitic elements. Finally, a \pm 45^\circ dual-polarized base-station antenna was designed, fabricated and measured. Measurement results are in good agreement with the results of simulation in terms of radiation pattern, gain, and Voltage Standing Wave Ratio (VSWR). In particular, the enhanced XPD is more than 20 dB at the boresight and more than 10 dB within \pm 60^\circ of the main lobe at the horizontal plane. [ABSTRACT FROM AUTHOR]

This paper proposes a triple-mode dielectric-loaded cylindrical cavity diplexer by using a novel packaging technique for long term evolution (LTE) base station applications. Four metal cavities, loaded by a triple-mode dielectric resonator (DR), are designed to resonate at two different frequencies for the diplexer operation. In this context, three resonant modes of a single cavity are classified as a TM mode and a pair of hybrid degenerate modes (HE modes). The two degenerate modes in the same cavity are properly excited by employing an off-centered DR instead of a traditional corner-cut structure as a perturbation element. Finally, such a diplexer is designed and fabricated, and good agreement between measurement and simulation is achieved. [ABSTRACT FROM AUTHOR]

A Ka-band isolated radial power divider via circular waveguide TE01-mode converter is presented in this paper. By redesigning and using the circular waveguide TE01-mode transducer to feed the 20-way radial power divider–combiner, the overall structure is miniaturized. Moreover, the resistive septum is inserted into the waveguide to improve the return loss and the isolation of the output ports. A measured return loss at the output port has improved by around 15 dB, while the worst case isolation is more than 12 dB over 28–36 GHz after using the resistive septum. [ABSTRACT FROM PUBLISHER]

A differentially fed dual-polarized multidipole antenna is proposed in this paper. Two pairs of long dipoles and two pairs of short dipoles are printed on an oriental crown-shaped substrate. Through a rational design of positions of dipoles, stable radiation patterns are achieved at the horizontal plane within a relative bandwidth of 45%. Because of the symmetry of the antenna, its differential port-to-port isolation is theoretically infinite. The antenna is designed, fabricated, and measured. The measurement results are in good agreement with the simulated ones in terms of gain, radiation patterns, and voltage standing wave ratio. Wideband impedance matching and stable radiation patterns are achieved by the proposed antenna. In particular, the half power beamwidth (HPBW) at the horizontal plane maintains a mean value 65° with only 4° variations across the desired band, which is suitable for the requirement of a three-sector base-station antenna. Interestingly, the proposed antenna looks like the famous building: the Oriental Crown-China Pavilion in the World Expo held in Shanghai. [ABSTRACT FROM PUBLISHER]

Modified coupled feed-lines (MCFLs) and coupled-line stubs (CLSs)/coupled-line stub-loaded resonators are proposed and applied to design wideband balanced filters to obtain high selectivity and common-mode suppression. MCFLs are implemented by loading short- and open-circuited stubs at the end of the traditional parallel-coupled feed-lines to perform bandpass and bandstop response, respectively. Impedance matching and additional transmission poles guarantee that the filters have wideband differential-mode (DM) passband. Transmission zeros can be allocated to suppress the common mode through different electrical length of stubs. Moreover, the CLSs and its stub-loaded resonators have the property of dual transmission zeros outside the passband, which improves the selectivity of the DM passband. Specifically, two prototypes based on CLSs with second harmonic suppression and CLS-loaded resonators with sharp rejection (\Delta f{{3dB}} / \Delta f{{20dB}}=0.97) are designed and fabricated for demonstration. The simulation and measurement results are in good agreement. [ABSTRACT FROM PUBLISHER]

A circularly polarized (CP) antenna with a wide axial-ratio (AR) beamwidth is presented by placing the two pairs of folded dipoles in a square contour. First, our study demonstrates that the CP radiation can be achieved at the broadside by setting a 90° phase difference between the vertical- and horizontal-paired folded dipole radiators. Second, a radiation pattern subtraction approach is presented to explain how the radiation beamwidth of the paired folded dipoles could be appropriately widened or narrowed according to the radiation pattern subtraction of two opposite electric current densities in the folded dipoles. Using this approach, the E-plane beamwidth of a pair of folded dipoles is made certainly widened, whereas its H-plane counterpart becomes narrowed. On this basis, the E- and H-plane radiation patterns can still be made approximately identical with each other over a wide range of polar angle, even though the distance between dipoles is deliberately shortened. As such, the desired CP antenna with shortened dipole-to-dipole distance and unaffected wide AR beamwidth can be achieved using two pairs of parallel folded dipoles with shortened distance between them instead of linear dipoles in [24]. Finally, a CP printed antenna is designed and fabricated on a single dielectric substrate. Experimental results are found in good agreement with the simulated ones in terms of radiation patterns, gain, AR, efficiency, and reflection coefficient. In particular, the 3-dB AR beamwidth at the central frequency of 1.6 GHz is extended to 135° at XZ-plane and 142° at YZ-plane. Moreover, the overall size of the constituted CP antenna with folded dipoles is decreased to \mathbf0.\mathbf43\;\boldsymbol\lambda _\mathbf0 \times 0.43\;\boldsymbol\lambda _\mathbf0 (\mathbf\lambda _\mathbf0 is the wavelength in free space). [ABSTRACT FROM PUBLISHER]

A broadband dual‐polarised antenna for 2G/3G/LTE/5G wireless communication is proposed. A new resonant mode is induced with parasitic resonator loaded inside the loop radiator. Wide impedance bandwidth of 72.2% for VSWR<2 (1.69–3.6 GHz) is achieved with three controllable resonant modes. Stable gain and radiation patterns are obtained over the whole band. [ABSTRACT FROM AUTHOR]

A circularly polarized antenna with wide axial-ratio beamwidth is presented by placing two pairs of parallel dipoles in a square contour. Firstly, our study demonstrates that circular polarization can be achieved at the broadside by setting a 90^\circ phase difference between the vertical and horizontal paired-dipoles. Secondly, the principle of wide-beamwidth circularly-polarized radiation is described under the similarity in polar and azimuthal radiation pattern for a pair of parallel dipoles. After the spacing between two parallel dipoles is studied, the similar radiation patterns in these two orthogonal planes are derived. As such, a wide-beamwidth circular polarization can be achieved by placing the two pairs of parallel dipoles vertically and horizontally while setting a 90^\circ phase difference between them. In final, a circularly-polarized printed antenna is designed and fabricated on a single dielectric substrate. The two arms of its four dipoles are formed on the lower and upper interfaces of the substrate, and they are excited by a 1-to-4 probe-to-microstrip feeding network. Experimental results show good agreement with simulated ones in terms of radiation pattern/gain, axial ratio and returned loss. In particular, the 3-dB axial ratio beamwidth at the central frequency of 1.6 GHz has extended to 126^\circ in an angular range from -63^\circ to +63^\circ. The fabricated antenna exhibits a low-profile property with the height of 0.0043 free-space wavelength. [ABSTRACT FROM PUBLISHER]

ABSTRACT A sharp-rejection dual-band bandstop filter using transversal signal-interaction with three paths, consisting of a transmission line path and two coupled paths, is proposed. By tuning the coupling coefficient and odd-mode impedance of the coupled lines, the center frequency ratio and bandwidth can be controlled, respectively, and the transmission line impedance is used to allocate the transmission poles to sharp the attenuation rate. A compact dual-band bandstop filter prototype is designed and fabricated. The simulation and measurement results agree well. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:657-660, 2015 [ABSTRACT FROM AUTHOR]

A broadband \pm 45^\circ dual-polarized base station antenna is proposed for 2G/3G/LTE bands. The proposed antenna has Y-shaped feeding lines to impart a wide impedance bandwidth to it, and a rectangular box-shaped reflector to enhance its stability in radiation patterns over the operating frequencies. A prototype of the proposed antenna is designed, fabricated, and tested. The measured results show achievement of impedance bandwidth of 45% for \ SWR<1.5 at both ports, port-to-port isolation >25 dB , a stable radiation pattern with 3-dB beamwidth 68^\circ\pm 2^\circ at H-plane and V-plane, and a stable antenna gain of 8.2 \pm 0.6 dBi from 1.7 to 2.7 GHz. A broadband dual-polarized antenna array with five elements for the band is developed for base station application. Measurements show achievement of array gain of 14.8 \pm 1.4 dBi, 3-dB beamwidth 66.56^\circ\pm 2.22^\circ at H-plane at port 1 and 64.85^\circ\pm 4.96^\circ at port 2 with \ SWR<1.5 over the operating frequency band. Simulation results have a good agreement with measurement ones. [ABSTRACT FROM PUBLISHER]

ABSTRACT This article presents a quad-band bandpass filter (QB-BPF) using a set of stub-loaded half-wavelength step impedance resonators operated at the second and third passbands (2.4/3.5 GHz) and a set of stub-loaded quarter-wavelength step impedance resonators operated at the first and fourth passbands (1.3/5.8 GHz), and the frequency ratio is 4.46 times. Furthermore, all the frequencies and bandwidths can be adjusted. Finally, the proposed filter is designed and fabricated. The measured results are in good agreement with the full-wave simulation results. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2845-2848, 2014 [ABSTRACT FROM AUTHOR]

In this paper, an E-plane waveguide power divider and a waveguide-to-microstrip transition are used to form a waveguide magic-T with four arms in the same E-plane. The input port of the original E-plane waveguide power divider acts as the difference port of the magic-T, and a waveguide-to-microstrip transition is utilized to realize the sum port. The four arms are in the same plane, and traditional matching elements, such as cones, wedges, pins, and irises are not needed. The proposed magic-T features easy connection, fabrication, and assembly. The principle and design procedure are described in detail. A Ka-band E-plane waveguide magic-T is designed, fabricated, and measured. A fractional bandwidth of 21% is achieved. The measured and simulated results show good amplitude, phase, and isolation characteristics validating the proposed magic-T. [ABSTRACT FROM AUTHOR]

Two compact coradiator multiple-input–multiple-out (MIMO) antennas operating in the UWB frequency band with dual polarization are proposed. Different from traditional MIMO antennas, the radiator is shared by two antenna elements, which greatly reduce the overall size of the MIMO system. High isolation between the two antenna elements is achieved by etching a T-shaped slot in the radiator and extending a stub on the ground. Dual polarization can be realized by exciting the pentagonal radiator with perpendicular feeding structure. The simulated results of current and electric-field distribution show the dual-polarization characteristics of the diversity system. Besides, a four units UWB MIMO antenna is also proposed. Furthermore, the diversity characteristics of mean effective gains (MEGs) and diversity gain (DG) are also studied. The simulated and measured results demonstrate that the UWB-MIMO antenna has good impedance matching, isolation and dual polarization characteristics. [ABSTRACT FROM PUBLISHER]

ABSTRACT Wideband bandpass filter with high-selectivity is presented in this article. An initial circuit model, which is composed of quarter-wave coupled lines, is given and analyzed that sharp passband selectivity can be obtained by the two transmission zeros, which are generated by the short-ended parallel-coupled lines. Then, the quarter-wave impedance transformers are added to improve the passband transmission and reflection characteristics. The filter is analyzed, designed, fabricated, and measured. Simulated and measured results are well-agreed. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1418-1421, 2014 [ABSTRACT FROM AUTHOR]