Port Isolation Research Articles

Dual-Polarized Millimeter-Wave Endfire Array Based on Substrate Integrated Mode-Composite Transmission Line

A dual-polarized endfire array is presented in this article for millimeter application. The substrate integrated mode-composite transmission line is introduced to exciting the dual-polarized radiation. Specially, the horizontal polarization is excited by the transverse electromagnetic (TEM) mode, whereas the vertical polarization is based on the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> mode. Two metal blocks sandwich the substrates to form a sandwich structure, and an open-ended slot is designed on the block edge to construed complementary sources radiation. Benefiting from the wideband feature of complementary sources, the proposed dual-polarized endfire array achieved a considerable bandwidth performance of 26.9% (24.8–32.5 GHz) based on the standard that both the voltage standing wave ratios of the two ports are less than 2. In terms of the key factor of dual-polarized antenna and isolation, measured results show a high port isolation of over 36 dB and a cross-polarization discrimination rate of over 30 dB. The excellent dual-polarized performance gives the proposed endfire array the potential of application in millimeter-wave mobile communications.

Conjoined Yet Decoupled Wideband Multiantenna MIMO Linear Patch Array

A conjoined yet decoupled wideband multi-antenna MIMO linear patch array (LPA) based on using a wideband patch antenna with dual slanted (±45°) shorting metal walls as a building antenna unit (BAU) is presented. The BAU alone can have a very wide operating band of larger than 4 GHz (about 3.25-7.40 GHz, a fractional bandwidth of about 78%). Owing to the antenna’s dual shorting metal walls, it allows arbitrary antenna units to be directly connected in series into a linear patch array with high port isolation (>20 dB) over the very wide band, with no additional decoupling elements required. A four-antenna LPA constructed by using four BAUs is demonstrated. In addition to the high port isolation, the four-antenna LPA can generate four uncorrelated waves with their measured envelope correlation coefficients (ECCs) less than 0.03 over the very wide band almost same as that of the BAU alone. In addition, the proposed MIMO LPA has an all-metal structure, with no substrate materials required. The obtained results make it promising for MIMO access-point application to cover the 5G band of 3.3-5.0 GHz and the unlicensed or mobile band of 5.925-7.125 GHz. Details of the BAU-based wideband multi-antenna MIMO LPA and the experimental results of the four-antenna LPA are presented.

Low-Profile Six-Port Circular Patch Antenna With Six Triple-Shorted Dual-Resonant 60°-Disk Sectors to Generate Six Uncorrelated Waves for Wideband Mobile MIMO Antennas

A low-profile six-port circular patch antenna generating six uncorrelated waves in a wide band of about 5.8-7.5 GHz (based on 3:1 VSWR, fractional bandwidth about 25%) is presented. The antenna thickness is 1.4 mm (about 0.027&#x03BB; at 5.8 GHz), which includes a 0.4 mm thick FR4 substrate with the circular patch printed thereon and an additional 1.0 mm thick air layer to achieve a low-permittivity antenna substrate. The circular patch with a diameter of 40 mm (about 0.77&#x03BB; at 5.8 GHz) is separated into six 60&#x00B0;-disk sectors by using three linear slots across the patch center and sequentially rotated by 60&#x00B0;. Each disk sector is short-circuited to the ground plane through three properly located shorting pins. It thus makes the 0.5-wavelngth and 0.25-wavelength resonant modes excited at nearby frequencies to form a dual-resonant wide band for each port. Additionally, the six ports in the proposed antenna have their port isolation larger than 10 dB and the corresponding six radiating waves have very low envelope correlation coefficients (less than about 0.02) over the wide band. That is, six uncorrelated waves suitable for MIMO (multi-input-multi-output) operation are obtained. The proposed antenna can find applications for wideband mobile MIMO antennas to cover 6.425-7.125 GHz of the possible new mobile communication band or 5.925-7.125 GHz for the new unlicensed WiFi-6E band.

Very-Wide-Band Six-Port Single-Patch Antenna With Six Uncorrelated Waves for MIMO Access Points

A very-wide-band six-port circular patch antenna for MIMO access-point application is presented. The six-port patch antenna can radiate six uncorrelated waves (envelope correlation coefficients &#x003C; 0.01) in a very wide band of about 3.1-7.2 GHz (fractional bandwidth about 80%), which can be applied to cover 3.3-5.0 GHz for 5G communication and 6.425-7.125 GHz for possible new mobile band. The six uncorrelated waves are generated by using six coupling L-strip feeds to respectively excite six 60&#x00B0;-resonant sectors isolated by six radial shorting metal walls connecting the circular patch to the ground plane. Enhanced port isolation (&#x003E; 20 dB) is obtained by embedding six decoupling radial slots along the centerlines of the six 60&#x00B0;-resonant sectors, with very small effects on the excited resonant modes. Details of the proposed six-port six-uncorrelated-wave single-patch MIMO antenna are addressed. Experimental results of the fabricated prototype are presented.

Compact Interlaced Dual Circularly Polarized Sequentially Rotated Dielectric-Resonator Antenna Array

In this study, a compact 2 × 2 interlaced sequentially rotated dual-polarized dielectric-resonator antenna array is proposed for 5.8 GHz applications. The array is composed of a novel unit elements that are made of rectangular dielectric resonator (RDR) coupled to an eye slot for generating the orthogonal modes, and to acquire circular polarization (CP) radiation. For the purpose of miniaturization and achieving dual polarized resonance, the array is fed by two interlaced ports and each port excites two radiating elements. The first port feeds horizontal elements to obtain left hand circular polarization (LHCP). The second port feeds vertical elements to obtain right hand circular polarization (RHCP). A quarter-wave length transformer is employed to reduce the attenuation and consequently increase the array gain performance. The 35 × 35 mm2 () gains were 8.4 and 8.2 dBi for port 1 and port 2, respectively, with port isolations of −33.51 dB. The design achieves a voltage standing-wave ratio (VSWR) < −10 dB and an axial ratio (AR) ˂ − 3 dB bandwidth of 2.48% (5.766 to 5.911 GHz) for LHCP at port 1 and a VSWR < −10 dB and AR ˂ −3 dB bandwidth of 2.28% (5.788 to 5.922 GHz) for RHCP at port 2. The findings of the proposed design validate its use for ISM band applications.

A Novel Cross-Band Decoupled Shared-Aperture Base Station Antenna Array Unit for 5G Mobile Communications

In this paper, a novel compact, dual-polarized, dual-broadband shared-aperture antenna array unit consisting of a lower band (LB) element and 4 upper band (UB) elements underneath is proposed for 5G mobile communications. L-shaped parasitic branches are introduced in the LB to expand the bandwidth and suppress the mutual coupling between the LB element and UB elements. Compared with the traditional lower-band dipole, the proposed LB element has far less influence on the electric field of the UB array, thus preserving their radiation patterns. To verify the performance, the antenna was fabricated and experimentally demonstrated to achieve the bandwidth of 32.7% (0.69-0.96 GHz) in the LB and 45.5% (1.7-2.7 GHz) in the UB with VSWR < 1.5. High port isolation and stable radiation pattern have been attained in both the LB and UB as required for dual-band base station antennas.

Rigorous Analysis and Investigation of the Bandwidth Broadening Mechanism in a Compact Power Divider With Physical Port Isolation

This paper proposes a compact power divider with simultaneous physical port isolation and wideband operation based on the simple Wilkinson power divider (WPD) configuration. Rigorous analysis based on the even- and odd-mode bisected networks has been performed to investigate the relationship between the design parameters and the overall performance. Theoretical analysis revealed that the impedance and isolation bandwidth are directly related to the reflection coefficients of the even- (Γ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e</sub> ) and odd-mode (Γ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> ) bisected networks. Simultaneous broadening of the impedance and isolation bandwidth is possible through the optimum choice of design parameters which confines the trajectories of the Γ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e</sub> and Γ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> in the low constant-Q region on the Smith Chart. Experimental verification by the prototype designed at 1 GHz exhibited the widest overall system bandwidth (43.2%) and the lowest total electrical length (140.8°) as compared to the previous state-of-the-art WPD’s with physical port isolation.

Orthogonal Printed Microstrip Antenna Arrays for 5G Millimeter-Wave Applications.

This article presents the design of a planar MIMO (Multiple Inputs Multiple Outputs) antenna comprised of two sets orthogonally placed 1 × 12 linear antenna arrays for 5G millimeter wave (mmWave) applications. The arrays are made of probe-fed microstrip patch antenna elements on a 90 × 160 mm2 Rogers RT/Duroid 5880 grounded dielectric substrate. The antenna demonstrates S11 = −10 dB impedance bandwidth in the following 5G frequency band: 24.25–27.50 GHz. The scattering parameters of the antenna were computed by electromagnetic simulation tools, Ansys HFSS and CST Microwave Studio, and were further verified by the measured results of a fabricated prototype. To achieve a gain of 12 dBi or better over a scanning range of +/−45° from broadside, the Dolph-Tschebyscheff excitation weighting and optimum spacing are used. Different antenna parameters, such as correlation coefficient, port isolation, and 2D and 3D radiation patterns, are investigated to determine the effectiveness of this antenna for MIMO operation, which will be very useful for mmWave cellphone applications in 5G bands.

Design of improved compact decoupler based on adjustable capacitor for EAST-ICRF antenna

The Ion Cyclotron Radio Frequency (ICRF) heating antenna on EAST adopts a decoupling device to constrain power coupling among the radiation straps, which was discovered shortcomings such as long size, poor contact, and etc. In order to improve these weak points, a new type decoupler with terminal-loaded tunable capacitor is designed to replace the previous design. Besides the capability of the tunable admittance parameters of decoupler, the withstand voltage of the capacitor is the most significant consideration for working under high power. Therefore, the theoretical analysis carefully elaborates the capacitor withstand voltage, and the detailed analytical equations and criteria for design are given. After the comparative analysis of theoretical calculation and 3D simulation results, the decoupler design scheme is finalized. The capacitor-loaded decoupler has been successfully adopted for ICRF antenna at port N on EAST, and achieved the optimization of adjacent port isolation from −22 to −58 dB at 37 MHz without plasma to restrict mutual coupling. The new design of the decoupler has greatly improved its compactness and automatic adjustment performance, and could be good solution for the decoupling network of ICRF antennas.

A four port circularly polarized printed multiple‐input multiple‐output antenna with enhanced isolation

SummaryIn this article, a four‐port circularly polarized printed multiple‐input multiple‐output (MIMO) antenna is designed to cover Wi‐Fi/WLAN (5 GHz), Wi‐MAX (3.4–3.6), and C band applications, which consists of four trapezoidal shaped patches with microstrip feed. To achieve high isolation between the ports, the antenna elements are located orthogonally to each other. The antenna elements are separated by placing diagonal lines to further enhance the port isolation. Circular polarization is achieved by modifying the ground plane and trimming the edges of the trapezoidal patch. The proposed MIMO antenna works between 3.2 and 6.2 GHz and has a 63.83% impedance bandwidth (IBW) for S11 ≤ −10 dB. It also offers a good diversity performance with envelope correlation coefficient (ECC) &lt; 0.04 and diversity gain of ≈10 dB. The antenna is fabricated on a low‐cost FR4 material with 1.6 mm thickness and has dimensions of 50 mm × 50 mm. This article also clarifies some of the prior literature's misconceptions about MIMO antenna metrics. The measured results show that the proposed MIMO antenna is circularly polarized, has a similar IBW, and axial ratio bandwidth (ARBW) to the simulated results, and has &gt;25‐dB isolation.

A Hybrid Antenna with Equal Beamwidth in Two Frequency Bands for Radar Applications

This paper presents a novel hybrid antenna with equal beamwidth in two frequency bands for short-range radar applications. The proposed design consists of a 2 × 2 patch array and a SIW-fed dielectric rod antenna. The two kinds of radiators are responsible for the 5.8 GHz and 24 GHz ISM bands, respectively. Pencil beams are obtained in both lower and upper bands. The beamwidth generated by the dielectric rod can be flexibly tuned to coincide with that of the patch array. Magneto-electric (ME) dipole, composed of a slot and two parasitic monopoles, is constructed to replace the conventional 3-D waveguide feeder, which can excite the dielectric rod effectively. The complementary structure is helpful to obtain a pencil beam. The 2 × 2 patch array has the size of 70 × 70 mm2 and is fed by a four-way power divider. Due to no overlapping radiating aperture, the two radiators can work independently with high port isolation. The measured peak gain in the two bands is 12.5 dBi and 12.7 dBi. The measured 3-dB beamwidth at 5.8 GHz and 24 GHz is 42° and 39° in x-z plane, and 43° and 42° in the y-z plane. The proposed antenna features a small beamwidth difference in two frequency bands, thus being attractive for dual-band radar systems.

Planar Millimeter-Wave Shared-Aperture Self-Diplexing Antenna With Small Frequency Ratio and High Isolation

This communication proposes a shared-aperture self-diplexing antenna using the composite parallel-plate waveguide (PPW). The long-straight slots (LSSs) etched on the top surface of the PPW are utilized as the common radiation aperture for two operating bands. At the high frequency band, the proposed antenna, excited by the alternative-phase TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> -mode wave, operates as a leaky-wave antenna (LWA). Meanwhile, it serves as a continuous transverse stub (CTS) array antenna when excited by the TEM wave at the low-frequency band. Two kinds of feeding networks are adopted to generate the alternative-phase TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> -mode wave and TEM wave, respectively. To verify the proposed method, a millimeter-wave prototype is designed, fabricated, and measured. The measured results show that −10 dB fractional bandwidths (FBWs) are 3.42% (76.25–78.9 GHz) and 14.5% (83.2–96.2 GHz), respectively, and the port isolation is higher than 40 dB. Additionally, the peak gains are 27.1 dBi at 78.5 GHz and 25.3 dBi at 90 GHz, respectively. The proposed antenna can be used to develop compact frequency-division system without using duplexers and multiband wireless systems.

새로운 6-단자 급전 회로망을 이용한 이중 직교 원형 편파를 갖는 소형 고이득 GPS 안테나

In this study, the design, fabrication, and performance of a small high-gain global positioning system (GPS) antenna that generates dual orthogonal circular polarization using a novel six-terminal feeding network is presented. The proposed six-terminal feeding network has two input quadrature terminals and four output terminals having the same amplitude and 0° or 180° phase. Therefore, it is suitable for feeding the four radiating elements with linear polarization characteristics. To realize a dual orthogonal circular polarization antenna with miniaturization and high gain characteristics, the six-terminal power supply network is positioned in the center of the antenna, and the four radiating elements are arranged on the outside. The radiating element selected after considering the limited space is a three-dimensional printed dipole element with linear polarization characteristics which is rotated by 90°. The antenna size designed optimally in the GPS L1 band (1,575.42±12 MHz) is less than 130 mm (0.68 λ0) in diameter (D) and 40 mm (0.21 λ0) in height. The antenna’s input return loss and port isolation characteristics measured with a vector network analyzer are excellent within the band at 17.1 dB and 18.0 dB or more, respectively. In addition, the antenna gain, and efficiency measured in the anechoic chamber are 8.69 dBi (@bore-sight) or more and 83 % or more, respectively. Furthermore, it can be seen that the axial ratio characteristics of the dual orthogonal circular polarization wave are very good, with less than 0.2 dB (@bore-sight) and less than 1.8 dB (@ 3 dB beam width).

Decoupling of 2 × 2 MIMO Antenna by Using Mixed Radiation Modes and Novel Patch Element Design

This article presents a novel and simple method for the decoupling of a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\times 2$ </tex-math></inline-formula> MIMO antenna array. Two distinct radiation modes, with different patterns and polarizations, are created by a novel patch element design. This new configuration enables the excitation of additional coupling paths between antennas, and ultimately the neutralization of mutual coupling. Since the two radiating modes are generated by the same patch element, the proposed MIMO antenna also features simple structure and compact size. For verification, a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\times 2$ </tex-math></inline-formula> MIMO antenna with center-to-center spacing of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.475\lambda _{0}$ </tex-math></inline-formula> is prototyped and characterized. Simulation and experimental results reveal that the proposed design can offer enhanced port isolation, antenna efficiency, and pattern diversity.

Shared-Radiator Design of Dual-Band Coplanar Base Station Antenna Array Using Cavity-Backed Slots

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.

Design of a co‐planar waveguide‐fed flexible ultra‐wideband ‐ multiple‐input multiple‐output antenna with dual band‐notched characteristics for wireless body area network

In this article, a co-planar waveguide-fed ultra-wideband (UWB) multiple-input multiple-output flexible antenna with dual band-notched characteristics on liquid crystal polymer substrate with high isolation for wireless body area network application is designed and fabricated. Two fan-shaped monopole UWB antenna elements are designed and placed vertically, with tampered feeder, asymmetrical ground plane and two C-shaped slots on the radiation patch. The measured working bandwidth can reach 2.63–11.6 GHz and the rejection bands are 3.25–4.36 and 5.41–6 GHz. The port isolation (S21) is better than −22 dB. When the bending radius is 35 and 45 mm, the antenna is measured for flexibility. In addition, the antenna is placed on human tissue to test its performance. All the results show that it has good radiation, high isolation and flexibility, and has broad application prospects in the wearable field.

Low‐profile wideband dual‐polarized microstrip antenna element for 5G communication

AbstractA low‐profile wideband dual‐polarized microstrip antenna is presented for 5G communication. Using a periodical diamond structure, both low profile and wideband performance have been achieved with high port isolation. Relative bandwidths of 53.4% and 54.0% are obtained for two polarizations with a low profile of 0.047λ0, where λ0 is the free space wavelength at the center frequency of 4.18 GHz. The dual aperture coupling method is adopted for each polarization direction and high‐order modes are stimulated across the passband. The measured port isolation of more than 30 dB is obtained. Unidirectional radiation patterns have been achieved with low cross‐polarization levels. The proposed dual‐polarized microstrip antenna can offer a low‐profile structure and wideband performance, which can be another potential candidate for the 5G communication.

Performance analysis of a sub-Rayleigh resolution distance spaced MIMO for 5G/WLAN applications

In this article, a two element mutiple-input multiple-output (MIMO) antenna is designed to operate in 4.98 GHz to 6.04 GHz. The antenna has inter-element edge to edge spacing of 0.4 mm (≈0.013λg/0.00664 λ0, where λg and λ0 are the guided and free space wavelength respectively at the lowest resonant frequency 4.98 GHz) which is extremely smaller than Rayleigh resolution distance. In spite of this, an acceptable port isolation is achieved by employing a stub in the common ground. Each radiating element comprises of etched rectangular patch having largest dimension ≈0.6 λg fed with 50 Ω microstrip line. The proposed MIMO has overall size of 40 × 26 × 1.67 (≈1.34 λg × 0.87 λg × 0.056 λg) mm3. Furthermore, the diversity parameters such as envelope correlation coefficient, diversity gain and mean effective gain have been studied in non-uniform medium. The total active reflection coefficient (TARC) and loss in channel capacity are found to be remain within the acceptable limit to exhibit the desired performances. The proposed antenna can be applied in 5G (below 6 GHz), WLAN and Wi-Fi bands.

Analysis and Control of a Four-Port Megawatt-Level High-Frequency-Bus-Based Power Electronic Transformer

Aiming for mutual isolation between ports, this article proposes a four-port high-frequency-bus-based power electronic transformer (HFB-PET), the core of which is the modular multiactive bridge (MMAB). In addition to port isolation, it also has the advantages of modularity, scalability, and reduced power conversion stages. First, the configuration of the proposed PET is introduced and compared with the existing solutions. Then, based on the mathematical model, a power coordinated control scheme is presented, including the power decoupling control for the cascaded H-bridge converter of the medium-voltage ac port to handle unbalanced grid voltages and active loads, the cell-power balance control for the medium-voltage dc port to achieve dc-link voltage equalization, and the power cross-coupling suppression control employed to improve the dynamic performance of the MMAB. On top of that, a hierarchical control framework with the global synchronous clock is constructed. Besides, a soft startup scheme considering the power balance between cells is introduced. Finally, the effectiveness of the proposed control scheme under the bidirectional power flow for the dc ports and the four-quadrant power flow for the ac ports is verified by experiments conducted on the laboratory scale-down prototype and the 10 kV/2 MVA industrial prototype.

Three‐line microstrip directional coupler with high directivity

AbstractThis article proposes a novel microstrip directional coupler with high directivity. The proposed coupler was configured using three coupled transmission lines and two reflectors to cancel the leakage components in the isolation ports. To demonstrate the validity of the proposed coupler, we designed and fabricated the microstrip directional coupler with 15 dB coupling at 5.8 GHz. The measurement showed the directivity of 50.0 dB at 5.83 GHz, which was improved by 35.9 dB compared with that of conventional one.