Coupling Feed Research Articles

Compact multi‐band eight‐element MIMO antenna with decoupled antenna pairs for 5G mobile terminal applications

AbstractThis paper presents a novel design method for a tri‐band multiple in multiple out (MIMO) antenna. The antenna consists of four sets of identical antenna pairs arranged on the two side frames. Three resonant modes can be obtained using a microstrip coupling feed structure by employing different branches in antenna unit design. The working frequencies of the modes can be adjusted independently. Moreover, in each pair of antennas, two antenna units were closely arranged and a decoupling grounding branch was employed between the adjacent antennas to ensure good isolation. The tri‐band eight‐element MIMO antenna operates at 3.5, 4.9, and 5.6 GHz and the isolations were better than 14 dB. The proposed antenna had a low profile of 0.06 and good isolation so it has potential applications in 5G mobile terminals.

A Dual-Band 8-Antenna Array Design for 5G/WiFi 5 Metal-Frame Smartphone Applications.

This paper presents a dual-band 8-port multiple-input multiple-output (MIMO) antenna specifically designed for fifth-generation (5G) smartphones, featuring two open-slot metal frames. To enhance impedance matching and improve isolation between adjacent antenna elements, each antenna element employed a coupling feed. All simulation results in this paper come from Ansys HFSS. The operational frequency bands of the proposed antenna spanned 3.36-4.2 GHz for the lower band and 4.37-5.95 GHz for the higher band, covering 5G New Radio (NR) bands N78 (3.4-3.6 GHz) and N79 (4.4-4.9 GHz), as well as WiFi 5 (5.15-5.85 GHz). Notably, the antenna demonstrated outstanding isolation exceeding 16.5 dB within the specified operating bands. The exceptional performance positions the proposed antenna as a promising candidate for integration into 5G metal-frame smartphones.

Wideband, Dual-Polarized Patch Antenna Array Fed by Novel, Differentially Fed Structure

In this article, a 1 × 4 wideband, dual-polarized patch antenna array fed by a novel, differentially fed structure is proposed. The differentially fed structure of the antenna was realized by a parallel line structure that was printed on a PCB and connected with the inner and outer conductors of a coaxial cable. This method elaborately solved the problem of the narrow bandwidth of conventional microstrip differential feeding. By using a relatively thick air substrate (thickness = 0.19 λ0), stacked patches, a coupling feeding structure, and a differential feeding structure with the novel design, the element of the patch antenna array introduced below operated from 0.415 GHz to 0.707 GHz (achieving the 52.0% bandwidth) with a VSWR < 2.0, yielding a high port isolation less than −28 dB. For the array, an active VSWR less than 2.0 was also obtained with a port isolation of less than −25 dB, ranging from 0.405 GHz to 0.696 GHz. In the desired bandwidth, the array had an azimuth 3 dB beamwidth of about 19° for both horizontal polarization and vertical polarization. The antenna array also had good performance in scanning (stable gain and 3 dB beamwidth) and circular polarization (a 3 dB axial ratio bandwidth better than 54.5%).

An SIW Quasi-Pyramid Horn Antenna Based on Patch Coupling Feed for Automotive Radar Sensors

An SIW quasi-pyramidal horn antenna based on patch coupling feed with reduced machining difficulty and facilitated integration with the radar chip is proposed in this paper. Compared with the metal pyramid horn antenna, the Rogers 5880 dielectric substrate based on the SIW structure is used to form the horn structure and waveguide structure, which effectively reduces the difficulty of machining the antenna. The patch coupling feed structure provides a solution for integrating the SIW quasi-pyramid horn antenna with the radar chip. The proposed SIW quasi-pyramid horn antenna element achieves approximately 9 dBi realized gain, about 95% radiation efficiency and 8.2 GHz bandwidth (74.1–82.3 GHz). A four-port inverting power divider was designed to verify the feasibility of forming an array with antenna elements. The designed antenna array achieves approximately 14.5 dBi realized gain, about 80% radiation efficiency and 7.2 GHz bandwidth (74.3–81.5 GHz). Simulation and measurement results maintain good agreement for the antenna array. To further assess the impact of errors on the performance of the proposed antenna array, we have implemented a corresponding error analysis. The proposed antenna element and antenna array show promising potential for application in automotive radar systems.

Dual‐mode dielectric resonator antenna design with stub‐loaded feeding slot

AbstractA dual‐mode dielectric resonator antenna based on a microstrip line‐slot coupling feed, operating in both the GMS‐900 and GMS‐1800 frequency bands, is presented. The antenna structure consists of a rectangular dielectric substrate and a cylindrical dielectric resonator, which is fed by a microstrip line‐slot coupling. The cylindrical resonant cavity and the dual‐stub coupling slot are designed so that the HEM111 and HEM311 modes are excited simultaneously, resulting in resonance at the two desired frequency points. The gain of the antenna is 3.74 and 7.63 dBi at 0.9 and 1.8 GHz respectively, and the efficiency of the antenna is greater than 70% in both operating bands.

A Dual-Polarization Broadband Coupling Feed Dipole Antenna Based on Artificial Magnetic Conductor

A dual-polarized broadband coupled feed dipole antenna loaded with artificial magnetic conductor (AMC) structure is proposed. The proposed AMC structure with 4×4 elements shown in this paper consists of four perfect electrical conductor (PEC) rectangular strips and a ring to reduce the profile height of the dual-polarized dipole antenna. In addition, the dual-polarization antenna adopts coupling feed microstrip to excite two pairs of bow-tie patch. The overall size of the coupling feed dipole antenna is 1.1λ0×1.1λ0×0.09λ0 at 5.5 GHz. Measured results shows that the proposed dual-polarization antenna loaded AMC exhibit a 25.2% common working bandwidth (4.75-6.12 GHz). The isolation is less than -14 dB, and the peak gain is 10.6 dBi. This dipole antenna with AMC structure has the virtues of low profile, wide band, and good radiation performance and it has the potential to be used in C-band communication.

A Compact Broad Circularly Polarized Cross-Dipole Antenna with Grounded Parasitic Elements

A new wideband cross-dipole antenna (CDA) with a circularly polarized (CP) characteristic is proposed in this article. The antenna consists of four L-shaped patches, two modified trapezoid-microstrip lines as an impedance tuner, a pair of vacant-quarter feeding loops as a continuous-phase feeding network, and four grounded inverted L-shaped strips as parasitic elements. It is noticed that the grounded inverted L-shaped strips are inserted directly below the L-shaped patches to increase the CP bandwidth and enhance the gains of the antenna, which is different from the conventional parasitic elements. First, a pair of vacant-quarter feeding loops is used as a feeding structure to provide a sequential phase characteristic. Second, four L-shaped patches as driven elements are connected to the feeding structure to excite two CP resonant modes. Third, two modified trapezoid-microstrip lines are inserted into the feeding structure to adjust the impedance match. Moreover, four grounded inverted L-shaped strips are introduced into the square reflector to achieve wider CP operation by utilizing a gap capacitive coupling feeding way. Finally, the proposed antenna is simulated, manufactured, and measured to verify the design rationality. The measured results indicate the proposed antenna has a broad 3-dB ARBW of 82.5% (1.38–3.32 GHz, 2.35 GHz) and a wide −10-dB IBW of 81.2% (1.18–3.04 GHz, 2.29 GHz). Furthermore, the measured and simulated CP bandwidths are 75.1% (1.38–3.04 GHz, 2.21 GHz) and 74.7% (1.36–2.98 GHz, 2.17 GHz), which is suitable for CP applications in WiBro (2.3–2.39 GHz) and GPS (L1 1.575 GHz) bands.

Wide stopband QMSIW diplexer with large frequency ratio and flexible specification

AbstractIn this letter, a wide stopband quarter‐mode substrate‐integrated waveguide (QMSIW) diplexer is proposed. By using coupling feeding lines and QMSIW cavities, the two passbands of the diplexer can be controlled independently by their respective QMSIW bandpass filters. In comparison to other counterparts, the proposed diplexer provides flexible passband specification, compact size, and high isolation. The design exhibits a wide 20‐dB stopband up to 3.2f0, a frequency ratio of 1.6, and a high isolation level larger than 42.2 dB across the passbands.

Enrichment strategies for mixed cultures in valorisation of crude glycerol into polyhydroxyalkanoate bioplastics

This study investigated two different strategies for enrichment using crude glycerol and mixed culture. Coupled feeding allowed simultaneous supplies of glycerol and nutrients at start of feast, whereas uncoupled feeding postponed nutrient supply until start of famine. Adaptation of culture enriched by the uncoupled feeding strategy was faster with higher operational stability. This however resulted in low PHB content of 20% and yield of 0.137 mg PHB/mg glycerol in feast phase, cell growth at yield of 0.298 mgX/mg PHB in famine. With more abundance (29.2%) of PHA storing bacteria in culture enriched by the coupled feeding strategy as revealed from 16 S rRNA analysis, results showed that polymer storage was dominated in feast phase (max. PHB content of 68%, yield of 0.563 mg PHB/mg glycerol), leading to high cell growth yield of 0.745 mg X/mg PHB. PHB accumulation by the enriched culture from coupled feeding has achieved 82% PHB content with 1094 mg PHB/L.h volumetric productivity. Thus, the coupled feeding was more effective to enrich PHA storing culture for PHA production using crude glycerol via two-step process.

Millimeter-Wave Wideband ±45° Dual-Polarized Phased Array Antenna Based on Compact Wideband Widebeam Dipole Element Antenna

To meet the requirements of a millimeter-wave (mmWave) communication system prototype complying with 5G (24.25-29.5GHz) and B5G/6G (30-33GHz) standards, this letter presents a compact wideband widebeam ±45° dual-polarized dipole element antenna to form a wideband phased array antenna (PAA) covering the entire 24-33GHz (∼31.6%) band. First, by placing two orthogonal coupling feeding baluns over a dual-polarized dipole to excite the dipole's two pairs of orthogonal arms and employing four parasitic patches, a ±45° dual-polarized dipole element antenna is developed, showing a compact size (0.34λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ×0.34λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> @24GHz), wide -14-dB impedance bandwidth (24-33GHz, 31.6%), wide 3-dB beamwidth (>100°), high polarization isolation (>25dB), and high cross-polarization discrimination (XPD) (>25dB) within the -14-dB impedance bandwidth. Then, based on the element antenna, a 4×4-element ±45° dual-polarized PAA is designed, fabricated using the LTCC process, and measured. The measurements show that, within the entire 24-33GHz band, the broadside scanning gain of the PAA is up to 14dBi, and the 3-dB gain variation scanning range is >±41° with a peak up to ±60º.

Low‐profile and broadband microstrip antenna with pattern diversity

AbstractThis paper presents a low‐profile and broadband pattern diversity microstrip antenna with quasiperiodic radiating patches fed by two slots. The thickness of the whole design is only 0.044λ0 (λ0 is the free‐space wavelength of the center frequency), showing great potential in applications. The broadband property is realized by efficiently exciting TM10 mode and antiphase TM20 mode and forming two resonant frequencies in the target band. The antenna can generate a broadside or difference pattern by switching the input port of the broadband 180° hybrid coupling feed network. The measured results show that the coincident impedance bandwidth of the antenna working in the two pattern modes is 20.5% (3.20–3.93 GHz), and the maximum gain values are 6.85 dBi for the directional pattern and 5.80 dBi for the difference pattern.

An S‐band wide beam miniaturized omnidirectional circularly polarized antenna

AbstractA wide beam miniaturized broadband omnidirectional circularly polarized antenna operating at S‐band is proposed. It is composed of a hub‐shaped circular horizontally polarized radiator, a vertically polarized radiator consisting of a monopole and eight shorting‐circuited pins, and a coupling feed device. The measured results indicate that the impedance matching band of |S11| &lt; −10 dB is from 2.15 to 2.75 GHz (24.4%), and the band of the axial ratio &lt;3 dB is from 2.2 to 2.7 GHz (20.4%). The gain of the antenna is about 1 dB, and the noncircularity in the azimuth plane is &lt;1.2 dB. In addition, the antenna has the characteristics of wide axis ratio beam in the pitch plane with sizes of 0.68 λ0 × 0.68 λ0 × 0.14 λ0. The antenna is very suitable for satellite receiving system and short‐range wireless communication system.

Low-Profile Wideband Dual-Polarized Patch Antenna Based on Differential-Paired Multi-Mode Arms

This paper presents a low-profile wideband, dual-polarized patch antenna using differential-paired, multi-mode arms. By employing the arrow-shaped, differential-paired arms, three modes of them are excited simultaneously, leading to a broad bandwidth. The shorting pins are uniquely inserted at the wings of the arms to obtain stable radiation patterns. Then, two pairs of arms are structured like the dipoles and a dual-polarized antenna is designed. In addition, by employing coplanar coupling feeding structures, a good wideband impedance matching is also achieved without increasing the height. For demonstration, a wideband dual-polarized patch antenna is designed and measured. Benefitting from the advantages of the multi-mode patch and symmetrical structure as a dipole antenna, the proposed dual-polarized antenna operates between 2.10–3.95 GHz, possessing a 10-dB impedance bandwidth of 61%, a profile of 0.1λ0, an average gain of 7.31 dBi, and stable radiation patterns.

A Compact Fourth-Order Tunable Bandpass Filter Based on Varactor-Loaded Step-Impedance Resonators

In this paper, a compact high-selectivity frequency tunable bandpass filter (BPF) with constant absolute bandwidth (ABW) based on varactor-loaded step-impedance resonators (SIRs) is presented. By introducing cross coupling between resonators, a pair of transmission zeros (TZs) close to the passband are produced and the selectivity of the filter is enhanced significantly. Another pair of TZs are generated to improve the out-of-band rejection by using source-load coupling. The varactor-loaded SIRs are utilized to design the compact fourth-order tunable BPF in order to realize wide tuning range and compact size. In addition, the frequency-dependent coupling feeding structures are employed instead of lumped capacitors used in conventional feeding structures, as a result, the insertion-loss performance is improved. The simulated and measured results are presented and show good agreement. The measured results exhibit a tuning range from 0.8 to 1.14 GHz with a 3 dB constant ABW of about 47 ± 5 MHz, the return loss of the filter is greater than 13.9 dB, and the insertion loss is about 2.7–3.1 dB. Moreover, four TZs are generated, and the proposed tunable filter shows high selectivity with a rectangular coefficient of 2.3–3.1.

Combined Open-Slot and Monopole 8 × 8 High-Isolation Broadband MIMO Antenna System for Sub-6 GHz Terminals

In this article, an 8 × 8 MIMO antenna system with multidecoupling structures is proposed for the fifth-generation (5G) terminal applications. First, an antenna element consisting of an L-shaped open slot with dimensions of 5.6 × 5 mm2 and two bent-L-shaped monopoles with dimensions of 12.7 × 6.1 mm2 is introduced. Due to coupling feed technology, the initial open slot owns a wide bandwidth from 3.62 GHz to 4.82 GHz. For broadening the bandwidth of the initial antenna element, two bent-L-shaped monopoles are added to the open slot to adjust the input impedance. By optimizing the parameters of monopoles, the proposed antenna element has been finally determined and the bandwidth of the antenna element has been broadened (2.82 GHz to 5.23 GHz). Second, a dual antenna pair is constructed by placing the two antenna elements with an edge-to-edge distance of 27 mm in a mirror image placement; the 8 × 8 MIMO antenna system is brought about by symmetrically disposing four such antenna pairs with an edge-to-edge distance of 47 mm. Moreover, the isolation of two closely placed antenna elements is achieved by the parasitic strip-loading technique and defective ground techniques. Due to the decoupling techniques used in the 8 × 8 MIMO antenna system, the average isolation has been optimized from 13.2 dB to 21.9 dB and the total efficiency of each antenna element has been improved from a worst 20% to over 45%. Besides, the calculated mean efficiency gain is less than 1 dB, and the calculated envelop correlation coefficient (ECC) is lower than 0.01 for desired frequency bands. Furthermore, the proposed 8 × 8 MIMO antenna system has the measured broadband bandwidth from 3.28 GHz to 5.05 GHz (covering N77, N78, and N79 bands) and a compatible dimension for ultra-thin mobile phones. The simulated results of this work are all obtained from EM software CST STUDIO SUITE 2019. In general, the proposed 8 × 8 MIMO antenna system with a high-isolation property provides a hopeful solution to 5G ultra-thin mobile phones.

Metal Crack Detection Sensor Based on Microstrip Antenna

A metal crack detection sensor based on a microstrip antenna is presented in this paper to detect cracks hidden under the coating. Since the frequency offset of the microstrip antenna is caused by the disturbance of the current path by the metal surface crack, the crack width, depth, and length can be characterized by the frequency offset of the microstrip antenna. Firstly, a dual-band microstrip antenna based on a transmission line coupling feed is employed to detect metal cracks. The simulation and measurement results verify that the sensor can detect the crack width, length, and depth. Secondly, the sensor has good scalability and can detect multiple cracks. Taking the triple-band sensor as a sample, it is verified that the sensor can be easily expanded to multi-band for crack detection. This feature significantly improves detection efficiency. Finally, experimental results confirm that the sensor can detect large-area metal surface cracks, broadening its application scope.

A simple decoupling method applied in gain improvement of a planar array antenna

AbstractA 4 × 4 patch array antenna based on loading shorting vias is proposed in this letter. The excitation method of the array antenna adopts stripline coupling feed, leading to a strong mutual coupling between the adjacent elements. The realized gain and impedance match are deteriorated seriously. Then, eight groups of metallic vias are introduced to the array antenna. By adjusting their number and spacing, the radiation performance of the array antenna can be improved significantly. Finally, the experiment results show that the proposed array antenna resonates at 5.4 GHz. Compared with the antenna without shorting vias, one resonance point caused by the mutual coupling can be removed within 5.34 GHz to 5.46 GHz. The gain drops unexpectedly, which is improved as well.

Design of MIMO Antenna with Double L-Shaped Structure for 5G NR

To satisfy the demand for 5G communication to smartphone terminal antennas in element quantity and isolation, an eight-element wideband MIMO antenna set of high isolation level is proposed. Each antenna element in the array is a double-L antenna consisting of an L-shaped slot and an L-shaped 50 Ω microstrip line. The L slot is formed by adding an I-shaped open circuit directly to the side of the rectangular slot. In addition, the antenna arrays are located on the long bezels on both sides of the mobile phone motherboard, and the coupling feed is made in the frequency range of 3.6–4.7 GHz through the L-shaped microstrip line, so as to cover the 5G NR band (N77/N78/N79). Finally, the four element pairs (8 components) achieve isolation of greater than 11 dB, the performance frequency range is 3.6–4.7GHz, the return loss is −6 dB, the total efficiency is greater than 85%, and the envelope correlation coefficient is less than 0.08. Other MIMO performances are also calculated, the design process is discussed in detail, and one-handed grip mode and two-handed grip mode are discussed to demonstrate their stabilities in real-world applications.

CMA-Based Quadruple-Cluster Leaf-Shaped Metasurface-Based Wideband Circularly-Polarized Stacked-Patch Antenna Array for Sub-6 GHz 5G Applications

This research proposes a quadruple-cluster leaf-shaped metasurface (MTS)-based circularly-polarized (CP) stacked-patch antenna array with hybrid coupler feed network for sub-6 GHz 5G applications. In the study, the leaf-shaped MTS-based CP stacked-patch antenna is characterized by characteristic mode analysis (CMA). In the antenna design, one cluster of the quadruple-cluster leaf-shaped MTS-based antenna array consists of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4\times4$ </tex-math></inline-formula> leaf-shaped MTS elements; and the hybrid coupler feed network is used to enhance impedance bandwidth (IBW), axial ratio bandwidth (ARBW), and antenna gain. Simulations are carried out and an antenna prototype is fabricated and experiments undertaken. The measured IBW, ARBW, and maximum gain at the center frequency (4 GHz) are 62.5% (3.4– 5.9 GHz), 21% (3.8– 4.54 GHz), and 9.04 dBic at 3.9 GHz. The novelty of this research lies in the use of: (i) the CMA concept to design and develop the leaf-shaped wideband MTS-based stacked-patch antenna with CP radiation pattern; and (ii) a low-complexity hybrid coupler feed network to enhance the IBW, ARBW and gain.

Circularly Polarized Conformal Antenna with Dual V-shaped Coupling Feed Lines

Circularly Polarized Conformal Antenna with Dual V-shaped Coupling Feed Lines