Open Access
Antenna mutual coupling suppression over wideband using embedded periphery slot for antenna arrays
(MDPI, 2018) Alibakhshikenari, Mohammad; Virdee, Bal S.; Shukla, Panchamkumar; See, Chan H.; Abd-Alhameed, Raed; Khalily, Mohsen; Falcone Lanas, Francisco; Limiti, Ernesto; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
This paper presents a new approach to suppress interference between neighbouring radiating elements resulting from surface wave currents. The proposed technique will enable the realization of low-profile implementation of highly dense antenna configuration necessary in SAR and MIMO communication systems. Unlike other conventional techniques of mutual coupling suppression where a decoupling slab is located between the radiating antennas the proposed technique is simpler and only requires embedding linear slots near the periphery of the patch. Attributes of this technique are (i) significant improvement in the maximum isolation between the adjacent antennas by 26.7 dB in X-band and >15 dB in Ku and K-bands; (ii) reduction in edge-to-edge gap between antennas to 10 mm (0.37 ); and (iii) improvement in gain by >40% over certain angular directions, which varies between 4.5 dBi and 8.2 dBi. The proposed technique is simple to implement at low cost.
Open Access
Meta-surface wall suppression of mutual coupling between microstrip patch antenna arrays for THz-band applications
(EMW Publishing, 2018) Alibakhshikenari, Mohammad; Virdee, Bal S.; Shukla, Panchamkumar; See, Chan H.; Falcone Lanas, Francisco; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
This paper presents a novel 2D meta-surface wall to increase the isolation between microstrip patch radiators in an antenna array that is operating in the teraherz (THz) band of 139-141 GHz for applications including communications, medical and security screening systems. The meta-surface unit-cell comprises conjoined twin 'Y-shape' microstrip structures, which are inter-digitally interleaved together to create the meta-surface wall. The proposed meta-surface wall is free of via holes and defected ground-plane hence easing its fabrication. The meta-surface wall is inserted tightly between the radiating elements to reduce surface wave mutual coupling. For best isolation performance the wall is oriented orthogonal to the patch antennas. The antenna array exhibits a gain of 9.0 dBi with high isolation level of less than -63 dB between transmit and receive antennas in the specified THz-band. The proposed technique achieves mutual coupling suppression of more than 10 dB over a much wider frequency bandwidth (2 GHz) than achieved to date. With the proposed technique the edge-to-edge gap between the transmit and receive patch antennas can be reduced to 2.5 mm. Dimensions of the transmit and receive patch antennas are 5×5 mm2 with ground-plane size of 9×4.25 mm2 when being constructed on a conventional lossy substrate with thickness of 1.6 mm.
Open Access
A new study to suppress mutual-coupling between waveguide slot array antennas based on metasurface bulkhead for MIMO systems
(IEEE, 2018) Alibakhshikenari, Mohammad; Virdee, Bal S.; Khalily, Mohsen; See, Chan H.; Abd-Alhameed, Raed; Falcone Lanas, Francisco; Limiti, Ernesto; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
In this paper, a new method is proposed to reduce mutual coupling between waveguide slot array (WSA) antennas based on metasurface technology. This is achieved by placing a metasurface bulkhead between the two WSA antennas. Performance of the dual-waveguide antenna structure is shown to substantially enhance when compared against an identical reference WSA antenna with no metasurface. WSA antennas used in the study has dimensions 40×20×5mm 3 and operates over 1.7-3.66 GHz, which corresponds to a fractional bandwidth of 73.13%. The average isolation of the reference WSA antennas is -20 dB; however, with a metasurface bulkhead the isolation is shown to increase to -36.5 dB. In addition, the bandwidth extends by ~10%, and the gain improves by 14.66%. The proposed method is should find application in MIMO systems where high isolation between neighbouring radiation elements is required to improve the antenna characteristics, and mimimise array phase errors, which is necessary to enhance the system performance.
Open Access
Wideband printed monopole antenna for application in wireless communication systems
(IET, 2018) Alibakhshikenari, Mohammad; Virdee, Bal S.; See, Chan H.; Abd-Alhameed, Raed; Falcone Lanas, Francisco; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
Empirical results of an electrically small printed monopole antenna are described with a fractional bandwidth of 185% (115 MHz to 2.90 GHz) for return-loss better than 10 dB, peak gain and radiation efficiency at 1.45 GHz of 2.35 dBi and 78.8%, respectively. The antenna geometry can be approximated to a back-to-back triangular shaped patch structure that is excited through a common feed-line with a meander-line T-shape divider. The truncated ground-plane includes a central stub located underneath the feed-line. The impedance bandwidth of the antenna is enhanced with the inclusion of meander-line slots in the patch and four double split-ring resonators on the underside of the radiating patches. The antenna radiates approximately omni-directionally to provide coverage over a large part of very high frequency, the whole of ultrahigh frequency, the whole of L-band and some parts of S-band. The antenna has dimensions of 48.32 × 43.72 × 0.8 mm 3 , which is corresponding to the electrical size of 0.235 λ 0 × 0.211 λ 0 × 0.003 λ 0 , where λ 0 is the free-space wavelength at 1.45 GHz. The proposed low-profile low-cost antenna is suitable for application in wideband wireless communications systems.
Open Access
Interaction between closely packed array antenna elements using meta-surface for applications such as MIMO systems and synthetic aperture radars
(Wiley, 2018) Alibakhshikenari, Mohammad; Virdee, Bal S.; Shukla, Panchamkumar; See, Chan H.; Abd-Alhameed, Raed; Khalily, Mohsen; Falcone Lanas, Francisco; Limiti, Ernesto; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
The paper presents a technique to enhance the isolation between adjacent radiating elements that is common in densely packed antenna arrays. Such antennas provide frequency beam-scanning capability needed in multiple-input multiple-output (MIMO) systems and synthetic aperture radars. The method proposed here uses a metamaterial decoupling slab (MTM-DS), which is located between radiating elements, to suppress mutual coupling between the elements that would otherwise degrade the antenna efficiency and performance in both the transmit and receive mode. The proposed MTM-DS consists of mirror imaged E-shaped slits engraved on a microstrip patch with inductive stub. Measured results confirm over 9–11 GHz with no MTM-DS the average isolation (S12) is −27 dB; however, with MTM-DS the average isolation improves to −38 dB. With this technique the separation between the radiating element can be reduced to 0.66λ0, where λ0 is free space wavelength at 10 GHz. In addition, with this technique there is 15% improvement in operating bandwidth. At frequencies of high impedance match of 9.95 and 10.63 GHz the gain is 4.52 and 5.40 dBi, respectively. Furthermore, the technique eliminates poor front-to-back ratio encountered in other decoupling methods. MTM-DS is also relatively simple to implement. Assuming adequate space is available between adjacent radiators the MTM-DS can be fixed retrospectively on existing antenna arrays, which makes the proposed method versatile. ©2018. American Geophysical Union. All Rights Reserved.
Open Access
Mutual-coupling reduction in metamaterial substrate integrated waveguide slotted antenna arrays using metal fence isolators for SAR and MIMO applications
(IEEE, 2018) Alibakhshikenari, Mohammad; Virdee, Bal S.; See, Chan H.; Abd-Alhameed, Raed; Falcone Lanas, Francisco; Limiti, Ernesto; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
A new type of mutual coupling reduction technique is applied to metamaterial substrate integrated waveguide (SIW) slotted antenna array. The circular shaped reference SIW antenna array is constructed from Alumina substrate with dimensions of 40×5×1.5 mm3. Embedded in the reference antenna are 38 slots with dimensions of 2×1×1.5mm3. The reference SIW antenna operates over X-to Ku-bands with average isolation between the radiation slots of approximately-10Db. Isolation was increased by inserting metal fence isolators (MFIs) between the radiation slots, which increased the isolation by an average of 13dB. In addition, the antenna's impedance matching bandwidth is improved with no degradation in the radiation patterns. With MFIs the maximum gain achieved improves by ~10%. The technique is simple to implement and proposed for synthetic aperture radar (SAR) and multiple input multiple output (MIMO) applications.
Open Access
Study on antenna mutual coupling suppression using integrated metasurface isolator for SAR and MIMO applications
(IEEE, 2018) Alibakhshikenari, Mohammad; Virdee, Bal S.; See, Chan H.; Abd-Alhameed, Raed; Falcone Lanas, Francisco; Andujar, A.; Anguera, J.; Limiti, Ernesto; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
A metasurface based decoupling structure that is composed of a square-wave slot pattern with exaggerated corners that is implemented on a rectangular microstrip provides high-isolation between adjacent patch antennas for Synthetic Aperture Radar (SAR) and Multi-Input-Multi-Output (MIMO) systems. The proposed 1-2 symmetric array antenna integrated with the proposed decoupling isolation structure is designed to operate at ISM bands of X, Ku, K, and Ka. With the proposed mutual coupling suppression technique (i) the average isolation in the respective ISM bands listed above is 7 dB, 10 dB, 5 dB, and 10 dB; and (ii) edge-to-edge gap between adjacent radiation elements is reduced to 10 mm (0.28λ). The average antenna gain improvement with the metasurface isolator is 2 dBi. © 2018 European Microwave Association.
Open Access
Study on isolation improvement between closely-packed patch antenna arrays based on fractal metamaterial electromagnetic bandgap structures
(Institution of Engineering and Technology, 2018) Alibakhshikenari, Mohammad; Virdee, Bal S.; See, Chan H.; Abd-Alhameed, Raed; Ali, Abdul; Hussein Ali, Ammar; Falcone Lanas, Francisco; Limiti, Ernesto; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
A decoupling metamaterial (MTM) configuration based on fractal electromagnetic-bandgap (EMBG) structure is shown to significantly enhance isolation between transmitting and receiving antenna elements in a closely-packed patch antenna array. The MTM-EMBG structure is cross-shaped assembly with fractal-shaped slots etched in each arm of the cross. The fractals are composed of four interconnected-'Y-shaped' slots that are separated with an inverted-'T-shaped' slot. The MTM-EMBG structure is placed between the individual patch antennas in a 2 × 2 antenna array. Measured results show the average inter-element isolation improvement in the frequency band of interest is 17, 37 and 17 dB between radiation elements #1 & #2, #1 & #3, and #1 & #4, respectively. With the proposed method there is no need for using metallic-via-holes. The proposed array covers the frequency range of 8-9.25 GHz for X-band applications, which corresponds to a fractional-bandwidth of 14.5%. With the proposed method the edge-to-edge gap between adjacent antenna elements can be reduced to 0.5λ0 with no degradation in the antenna array's radiation gain pattern. Across the array's operating band, the measured gain varies between 4 and 7 dBi, and the radiation efficiency varies from 74.22 and 88.71%. The proposed method is applicable in the implementation of closely-packed patch antenna arrays used in SAR and MIMO systems. © 2018, The Institution of Engineering and Technology.
Embargo
A new waveguide slot array antenna with high isolation and high antenna bandwidth operation on Ku- and K- Bands for radar and MIMO systems
(IEEE, 2018) Alibakhshikenari, Mohammad; Virdee, Bal S.; See, Chan H.; Abd-Alhameed, Raed; Limiti, Ernesto; Falcone Lanas, Francisco; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
In this paper a novel technique is proposed to reduce the mutual coupling between the radiating elements of a waveguide slot array antenna. This is achieved by inserting slots between the waveguide oval shaped slots. The reference waveguide array antenna used in the study was implemented with an arrangement of 3×5 oval shaped slots. By incorporating linear slots between the radiating oval shaped slots in both horizontal and vertical directions significant reduction in mutual coupling is achieved of 24 dB, 20 dB, and 32 dB in the frequency bands of 12.95-13.75 GHz (Ku-band), 15.45-16.85 GHz (Ku-band), and 18.85-23.0 GHz (K-band), respectively. Edge-to-edge distance between the slot radiators is 0.2λ, which is at least twofold smaller than conventional array antennas. With the slot isolators the antenna's minimum and maximum gains improve by 53.5% and 25.5%, respectively. In addition, the radiation patterns are unaffected. The proposed method is simple to implement, low cost solution mass production. © 2018 European Microwave Association.