Zeeshan Zahid

A neutralization‐line (NL) decoupling method with a dipole‐patch‐antenna (DPA)‐oriented design rule is proposed for high‐density arrays. The NLs are directly connected between adjacent patches near their open ends, where the voltage is maximum, and the current is minimum. An equivalent‐circuit model and parametric analysis demonstrate that the connection position and NL impedance jointly control the compensating coupling. The design rule is validated in dual‐, tri‐, and twelve‐element MIMO configurations as well as 1‐D and 2‐D linear arrays. A fabricated twelve‐element prototype achieves a 200 MHz impedance bandwidth from 3.4 to 3.6 GHz, isolation exceeding 16 dB, a measured peak broadside gain of 6.3 dBi, and far‐field envelope correlation coefficients below 0.1. These results demonstrate the method's applicability to high‐density multi‐element DPA arrays.

This letter introduces a novel dual-band decoupling concept using capacitor-loaded shorting posts (CLSPs) as modal tuners to align the resonances of TM₀₂ and TM₁₂ with TM₀₁ and TM₁₁, respectively. Leveraging modal superposition of two pairs of anti-phase current modes, a dual-band, dual-port single-patch antenna is developed, operating in the 3.5 GHz and 5.5 GHz frequency bands. Measurements confirm the design's effectiveness, improving the isolation from 3.5 dBi to over 12 dB, with peak gains of 6.5 dBi and 7.1 dBi in the respective bands.

This paper proposes a wideband four-element multiple-input multiple-output (MIMO) antenna operating in the millimeter-wave frequency band for 5G communications from 24.37–39.44 and 45.09–50.62 GHz. The antenna design has been realized using Rogers 5880 substrate and consists of a T-shaped strip that is attached to the top of a 50 Ω feeding line. Two microstrip lines are affixed at the terminal points of T-shaped strip and bent toward the feeding structure. These bent strip lines are then extended by joining two additional L-shaped microstrip lines. On the back, there is a partial defective ground plane featuring a rectangular slot and a thin strip line located at its center. The dimensions of the proposed single element and MIMO antenna are 0.933λ × 0.933λ × 0.024λ and 1.865λ × 1.865λ × 0.024λ, respectively (at 28 GHz), while the edge-to-edge distance between the radiation elements of the MIMO antenna is 4.0 mm. The design incorporates an efficient passive fan-shaped decoupling structure to decrease coupling between antenna elements. Simulations and experimental results show good agreement with each other. For all resonant frequencies the measured peak gain is greater than 4.85 dBi, radiation efficiency is over 90%, diversity gain is greater than 9.5, ECC is less than 0.025, TARC is less than -10 dB and CCL is below 0.4 bits/s/Hz. The proposed MIMO antenna, with its wide bandwidth, high gain, high inter-port isolation, and high efficiency characteristics, can be used for 5G wireless communication applications.

This letter presents a wideband bezel coupled T‐type isolator, decoupling two antenna elements for smartwatch multiple‐input multiple‐out applications. The antenna elements consist of PIFA antennas operating at 2.45 GHz, covering Bluetooth and Wi‐Fi bands. The proposed T‐type isolator has been installed between the antenna elements made by inserting two slits in the bezel separated by 21 mm. The separated segment of the bezel is connected with the circular ground plane by a conducting strip and an inductor. In this way, the slits offer stray capacitance, and the capacitive coupling between the T‐type isolator has been utilized to achieve a wide isolation bandwidth. Meanwhile, the isolation can also be tuned using the gaps of the slits and the inductor. The design performance has been validated in simulations and measurement. The measured impedance bandwidth is higher than 120 MHz whereas the isolation bandwidth is 790 MHz with a maximum isolation higher than 22 dB. The measured envelop correlation coefficient is below 0.01. The proposed design is a good candidate for smartwatch applications.

This paper presents a novel decoupling technique for two-element multiple-in multiple-out (MIMO) antennas for smartwatch applications with floating metallic bezel. The radiating elements consist of embedded loop-type ground-radiation antennas and operate at the 2.45 GHz Bluetooth/Wi-Fi bands. An isolator, consisting of a loop-type structure with a lumped capacitor, is attached externally to the ground plane such that wideband isolation between the antennas has been achieved. It is demonstrated that the small-sized isolator is coupled with the large-sized bezel surrounding the ground plane, where the bezel operates as a low-Q decoupler between the antenna elements producing wideband isolation property. Accordingly, optimized results can be obtained by controlling the location of the isolator, the gap between the isolator and the bezel, and the loaded capacitor. Simulation and measured results have been presented to validate the design performance. The measured −10 dB impedance bandwidth of both antenna elements is more than 210 MHz, whereas the isolation bandwidth is 770 MHz with reference to 20 dB. The envelop correlation coefficient is <0.1 in the operating band. Furthermore, the proposed technique is versatile regardless of the angular separation of the antenna elements on the circular ground plane, which makes it a good candidate for smartwatch MIMO applications in practical scenarios.

In this letter, a novel colocated 2 × 2 multiple‐input multiple‐output (MIMO) antenna pair has been proposed. The pair consists of a monopole antenna (J‐source) and a slot antenna (M‐source) integrated at the same location on the terminal ground plane. The inherent orthogonality between the electric source (J) and magnetic source (M) has been exploited to isolate the antenna elements from each other without deploying any additional decoupling component. The proposed 2 × 2 MIMO antenna pair is extended to an 8 × 8 MIMO antenna design for terminal applications. The measured peak isolation between the antenna elements is 25 dB and the impedance bandwidth of the antennas is above 200 MHz with a 3 dBi peak gain, and the envelope correlation coefficient is less than 0.1. The design is proposed for 5G applications operating at the 3.5 GHz band and is a strong candidate for modern smartphone applications.

In this investigation, a circularly polarized (CP) dual-loop ground-radiation antenna has been proposed for GPS applications using a transverse loop and a longitudinal loop. The transverse loop is designed within an 8 mm × 4.5 mm (0.042λ × 0.024λ) clearance, installed at the horizontal edge of the ground plane for excitation of the ground mode along the y-axis, whereas a 1 mm × 10 mm (0.005λ × 0.053λ) longitudinal loop is etched at the vertical edge of the ground plane for excitation of the ground mode along the x-axis. In this way, the magnitudes and phases of the orthogonal components of the radiated electric field have been controlled independently, satisfying the CP conditions. The proposed antenna produced right-hand circular polarization towards the + z-axis, which has been verified using rectangular and square-shaped ground planes. Both simulation and measurement were conducted, and the measured axial ratio bandwidth with reference to 3 dB was 20 MHz (1.27%) while the impedance bandwidth with reference to −6 dB was 141 MHz (8.95%).

This paper presents a novel two-element multiple input multiple output (MIMO) reconfigurable antenna that can be switched among 600 MHz, 1.8, 2.4, 3.5, and 5.5 GHz bands. The proposed antenna consists of two semi-circular ring-shaped strip-lines and a rectangular slot on the top conducting layer of the substrate and a U-shaped slot, etched on the bottom side of the substrate. Frequency reconfigurable characteristics have been achieved using single pole four throw radio frequency micro-electro-mechanical system switch. The switch has been installed in the ground slot. The dimensions of the proposed MIMO antenna are 32 × 98 × 1 mm³. Measured isolation greater than 15 dB has been achieved in the operating bands. The calculated envelop correlation coefficient is less than 0.04 and the diversity gain in the operating bands is greater than 9.8 dB.