A dual‐polarized low‐profile microstrip patch antenna with U‐ or M‐shaped feed network

In this article, a dual‐polarized low‐profile microstrip patch antenna with U‐ or M‐shaped feed network is presented. The U‐ or M‐shaped feed network is printed on the same layer, which can achieve dual bands (5.3 and 5.8 GHz) and low profile (0.06 λ_g). Dual polarizations and high isolation are realized by making use of a quasi‐cross‐shaped slot feeding. Moreover, the port isolation is better than 25 dB, and the antenna gain is above 8.4 dBi for the two ports. And the cross‐polarization levels in both E and H planes are better than ‐30 dB for the two polarization ports, respectively. The design is suitable for array application in MIMO system. Details of the proposed design and experimental results are presented and well agreed.     

Substrate integrated waveguide dual‐frequency dual‐sense circularly polarized cavity‐backed slot antenna

A novel design of dual‐frequency dual‐sense circularly polarized (CP) substrate integrated waveguide (SIW) cavity‐backed slot antenna is presented for dual‐band wireless communication systems. The proposed antenna consists of square SIW cavity, asymmetrical bow‐tie‐shaped cross slot and probe feed. Due to use of asymmetrical bow‐tie‐shaped cross slot, circularly polarized wave radiates at two different frequencies with opposite sense of polarizations. The RHCP radiation occurs at (10.45‐10.54) GHz (Lower band) and LHCP occurs at (11.26‐11.34) GHz (Upper band). Moreover, in each band, sense of polarization can be change by changing the feed position. The front to back radiation ratio (FTBRR) is more than 10.5 dB and cross polarization level is lower than ?20 dB in both the bands.     

Design of a compact orthogonal fed self‐diplexing bowtie‐ring slot antenna based on substrate integrated waveguide

In this article, a novel design of compact cavity‐backed slot antenna based on substrate integrated waveguide (SIW) technology is presented for dual‐frequency communication services. A single layer printed circuit board is applied to implement the proposed antenna. The bowtie‐ring slot engraved on the SIW square cavity is excited using two orthogonal microstrip feed lines to operate at two distinct frequencies (6.62 GHz and 11.18 GHz). The proposed antenna allows each of these frequencies to be designed independently. A prototype of the proposed cavity‐backed antenna that radiates at both 6.62 GHz and 11.18 GHz is fabricated and measured. The port isolation better than 29.3 dB is achieved by utilizing the transmission zeros (TZs), which are produced due to the orthogonal feed lines, TE₁₁₀ mode and coupling between the TE₁₂₀ and TE₂₁₀ modes. The measured peak gains of the proposed diplexing antenna are 5.77 dBi and 5.81 dBi at lower and upper resonating frequencies, respectively. The proposed dual‐frequency antenna exhibits the front‐to‐back‐ratio (FTBR) and cross‐polarization level greater than 26 dB and 21 dB, respectively, at both resonating frequencies.     

Novel dual‐band asymmetric U‐shaped slot antenna for dual‐circular polarization

A novel dual‐band, dual‐circularly polarized antenna is proposed and fabricated. The proposed antenna consists of an asymmetric U‐shaped slot and an inverted L‐shaped slot which are designed to excite two orthogonal E vectors with equal amplitude and 90° phase difference (PD), in addition, fed by a coplanar waveguide (CPW) Furthermore, a left‐hand circular polarization in the direction of z > 0 and a right‐hand circular polarization instead of the opposite direction both at the lower and upper bands are exhibited by the radiations of the antenna. Good agreement is achieved between the measurement and simulation, which indicates that a 10‐dB bandwidth of 38.75% from 2.56 to 3.8 GHz and 21.8% from 10.01 to 12.53 GHz, while a 3‐dB axial‐ratio bandwidth (ARBW) of 13.4% from 2.77 to 3.2 GHz and 9.23% from 10.25 to 11.25 GHz at two operation bands, respectively, are covered in the designed antenna. To explain the mechanism of dual‐band dual‐circular polarization, the analysis of magnetic fields distributions and a parametric study of the design are given. Meanwhile, compared to other recent works, a single layer structure, wider axial ratio and impedance bandwidths and a more compact size are the key features of the proposed antenna.     

Integrated circular polarized microstrip antenna with dual‐mode‐polarization insensitive characteristics

A dual‐mode circularly polarized compact antenna with integrated left‐hand and right‐hand circular polarization (LHCP and RHCP) is presented in this work. A multilayer arrangement of a square patch and square ring structure with an irregular transmission line is analyzed for dual‐band, dual‐CP operation. To realize dual mode propagation the proposed structure is excited using electromagnetic coupling technique. Succeeding proximity feeding with T‐stub match is analyzed, which conveys impedance bandwidth of 180 and 300 MHz within |S₁₁| < ?10 dB at 3.5 and 5.5 GHz. The designed CP elements is suitably arranged with feed line for generating two orthogonal polarization of equal amplitude and a 90° phase difference at both the resonant modes (TM₁₀ and TM₀₁). Alterable LHCP and RHCP performance is realized by altering the compensated position and peculiar angle. Having both LHCP and RHCP polarization this design shows polarization insensitive characteristic. Each LHCP and RHCP antenna element accomplished a 3‐dB AR of 70 and 120 MHz with a gain up to 6 dBi. With a low profile of 0.27λ₀ × 0.27λ₀ × 0.04λ₀, the CP antenna is fabricated, and the performance is validated through experimental analysis. With all the viable characteristics, the antenna is proposed for Wi‐MAX/WLAN communication.     

A low‐profile wideband dual‐polarized antenna with gain enhancement,low gain variations,and low cross polarization for 5G indoor communications

A low‐profile wideband dual‐polarized antenna with high gain, low gain variations, and low cross‐polarization for the fifth generation (5G) indoor distribution system is proposed. By using circular‐thread vase‐shaped structure, a low profile of 0.23λ₀ (λ₀ is the free‐space wavelength at the starting frequency) as well as low gain variation feature can be achieved by the vertically polarized (VP) radiating element. An eight‐way power divider network is employed to feed the horizontally polarized (HP) dipoles so that wideband performance is obtained. Here, eight pairs of arc‐shaped parasitic strips are used to broaden the bandwidth, and eight pairs of director elements are introduced to enhance the gain and reduce the gain variations. In addition, the protruded stubs that are extended from the circular ground plane will help to reduce the cross polarization in the VP direction. Measured results show that a bandwidth of 46.5% (3.3‐5.3 GHz) (S₁₁ < ?10 dB) with a gain of 0.85 ± 0.35 dBi, and another bandwidth of 85.0% (2.5‐6.2 GHz) with a gain of 4.75 ± 1.75 dBi can be realized in the HP and VP directions, respectively. Furthermore, high isolation (>27 dB) and low cross polarization (<?24 dB) can also be attained. Therefore, the proposed antenna is a good candidate for 5G indoor distributed system.     

A cavity‐backed quad‐slot antenna with novel aperture‐coupled feed for circular polarization

This article describes a novel aperture‐coupled feed, for the excitation of a cavity‐backed quad‐slot antenna with circular polarization. Firstly, a quad‐slot cavity‐backed antenna with linear polarization (LP) is proposed. Then, a novel aperture‐coupled feed, which is composed of a cross‐shaped coupling aperture and a T‐shaped feeding microstrip line, will be applied to this LP antenna. By differing the lengths of the four radiation slots together with the novel aperture‐coupled feed, 90° phase difference and equal magnitude between the radiations from the two pairs of slots can be generated. As a result, a good performance of axial ratio will be achieved for the proposed antenna. A prototype is fabricated at Ka band for a demonstration. Investigations show that the antenna can present a minimum axial ratio (AR) of only about 0.37 dB, as well as a fractional AR bandwidth of about 0.94%. A relative high gain of 6.9 dBic at 32.1 GHz is also achieved for the prototype. The proposed substrate integrated cavity backed antenna with circularly polarization has great potential to be integrated into millimeter‐wave transceiver modules. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:588–594, 2016.     

Dual‐band CPW fed MIMO antenna with polarization diversity and improved gain

A dual‐band MIMO slot antenna with polarization diversity and improved gain is proposed in this article. The antenna is composed of two C‐type back‐to‐back connected slot resonators and offers resonances at 3.5 and 5.2 GHz. This antenna element is further used to design a MIMO antenna. By introducing one U‐shaped slot between two antenna elements, isolation between the ports of this MIMO antenna is improved further. Finally, an artificial magnetic conductor (AMC) is placed below the MIMO antenna to enhance its gain. Gain enhancement of 1.5 and 2.2 dB is achieved at lower and upper band, respectively. S‐parameters, radiation patterns, gain, envelope correlation coefficient, and channel capacity loss are investigated to conclude about its performances in MIMO applications. Dual band dual polarization (circular and linear), improved isolation, polarization diversity (right‐hand circular polarization and left‐hand circular polarization), gain enhancement all are presented in a simple design represents the novelty of the proposed MIMO antenna.     

Design of a novel metasurface for dual‐band Fabry‐Pérot cavity antenna

A novel reflective metasurface which presents different reflection phases to different polarization waves is designed in this article. The metasurface is used as the ground plane of a Fabry‐Pérot cavity (FPC) antenna. The radiator of the FPC antenna is a dual‐band patch antenna which has different polarizations in different bands, so by tuning the reflection phase of the metasurface correctly, the FPC antenna can work in two frequency bands. A prototype antenna is fabricated and measured. The measured results show that the antenna can operate at 8.35‐8.56 GHz (2.5%) in x‐polarization and 9.5‐10.1 GHz (6.1%) in y‐polarization. The maximum realized gains of the antenna in two bands are 17.6 dB at 8.75 GHz and 19 dB at 9.8 GHz. The measured results agree well with the simulated results which confirm the correctness of the design.     

Compact planar frequency reconfigurable multiple‐input‐multiple‐output antenna with pattern and polarization diversity characteristics for WiFi and WiMAX standards

A compact planar frequency reconfigurable dual‐band multiple‐input‐multiple‐output (MIMO) antenna with high isolation and pattern/polarization diversity characteristics is presented in this article for WiFi and WiMAX standards. The MIMO configuration incorporates two symmetrically placed identical antenna elements and covers overall size of 24 mm × 24 mm × 0.762 mm. Reconfiguration of each antenna element is achieved by using a PIN diode which allows antennas to switch from state‐1 (2.3‐2.4 GHz and 4.6‐5.5 GHz) to state‐2 (3.3‐3.5 GHz and 4.6‐5.5 GHz). In state‐1, the configuration offers isolation ≥18 dB and 20 dB in lower band (LB) and upper band (UB) respectively; whereas, in state‐2, isolation ≥21 dB and 20 dB in LB and UB respectively is achieved. The same decoupling circuit provides high isolation in dual‐band of two states, which makes overall size of the proposed design further compact. The antennas are characterized in terms of envelope correlation coefficient, radiation pattern, gain, and efficiency. From measured and simulated results, it is verified that the proposed frequency reconfigurable dual‐band multi‐standard MIMO antenna design shows desirable performance in both operating bands of each state and compact size of the design makes it suitable for small form factor devices used in future wireless communication systems.     

Microstrip patch antenna feed for offset reflector antenna for dual band application

In this article, details of a dual band microstrip patch antenna (MPA) array feed for an offset reflector antenna is presented. The main objective of the proposed structure is to achieve low cross‐polarization at Φ = 90° plane in the reflector pattern. Low cross‐polar levels in the reflector pattern are achieved by illuminating the reflector with fields of the proposed dual band feed structure. A centered circular array as the dual band feed structure is proposed in which the central radiating element is a dual mode circular MPA operating at 6 GHz and the surrounding circular ring of eight circular MPA elements operating at 4 GHz in the dominant mode. The dual mode central antenna uses the concept of conjugate field matching for cross‐polarization reduction. TM₂₁ mode is excited at an appropriate ratio with the TM₁₁ mode to achieve the proper field matching at 6 GHz. The radius of the surrounding circular array is varied to obtain cross‐polarization better than ?30 dB at both the resonant frequencies. The offset reflector gain is found to be better than 37 dB with a 2.5 m parabolic reflector and F/D = 0.8 at both the operating frequencies.     

A dual‐band dual‐polarized end‐loaded quasi‐open‐sleeve dipole antenna with stable pattern for wireless local area network applications

This article presents a dual‐band dual‐polarized end‐loaded quasi‐open‐sleeve dipole antenna (ELQOSDA) with stable radiation patterns for WLAN applications. The ELQOSDA consists of an end‐loaded planar dipole and two parasitic strips. Dual polarization is obtained by two ELQOSDAs perpendicularly crossing, with some parts overlapped. The unidirectional stable radiation patterns are achieved by adding a square resonance ring between the ground plane and antenna. The ring has little influence on antenna performance at the lower frequency, but improves the coupling currents between the ground and antenna at the upper frequency. As a result, satisfactory dual band and broadside radiation performance is obtained. For demonstration, the proposed antenna is implemented. Measured dual‐band 10‐dB impedance bandwidths are 9.4% (2.33‐2.56 GHz) and 33.5% (4.23‐5.93 GHz) in the lower and upper bands, covering the entire WLAN 2.4/5.2/5.8‐GHz bands. Moreover, the measured antenna has a 6.7‐8.1 dBi broadside gain and stable radiation patterns over the whole operating band.     

Circular polarized dual‐band antenna for WLAN/Wi‐MAX application

A novel square ring printed antenna has been suggested for dual‐band circular polarization (CP). The geometry contains a square patch and a square ring structure for dual‐band operation. Circular polarization is achieved using triangular cut at the boundary and right angle bend with inner perturbation. The suggested antenna is excited from the lower layer through electromagnetic (EM) coupling technique. The antenna shows good impedance bandwidths of 90 MHz (2.43‐2.52 GHz) and 800 MHz (5.7‐6.5 GHz, respectively. The antenna shows 3 dB axial ratio bandwidth of 20 MHz at lower band and 120 MHz at upper band with improved gain > 6 dBi. The simulated and measured results are well agreed with each other. The antenna is promising wideband operation at the upper band. This antenna was implemented on fiberglass reinforcement laminated Arlon substrate with dielectric constant (?_r = 2.55), and the overall physical dimension of 30 × 30 × 3.048 mm³. The designed antenna can be extensibly applicable in WLAN/Wi‐MAX communication. The presented antenna is designed using hyperlynx IE3D and the simulated results are presented.     

Design of a cavity‐based filtering antenna with dual‐polarization operating at Ka‐band

The contribution of this work is to propose a cavity‐based antenna with both dual‐polarization and bandpass filter characteristics. Proper cavity resonators and antenna based on the substrate integrated waveguide (SIW) technology are designed utilizing the low temperature co‐fired ceramics (LTCC) for demonstration. By properly arranging and coupling the cavities, a shaping of filter‐like response for the antenna gain and input return loss can be obtained. Measures for achieving a good isolation and a low cross‐polarization level have also been taken into account during the design procedure. A 4th‐order prototype working in the Ka‐band is designed and fabricated. Investigations show that the antenna presents a good isolation below ‐29 dB across the operating bandwidth, together with a cross‐polarization level lower than ‐25 dB at the center working frequency. The performance of the prototype has been verified in the measurement.     

Miniaturized dual‐band slot antenna design for GPS,amateur radio and WLAN applications

In this article, miniaturization of dual‐band slot antenna design for GPS, WLAN and amateur radio applications is presented. The proposed dual‐band miniaturized antenna is achieved using slits, rectangular split ring and metallic strips fed by 50 Ω microstrip feed. The first resonant frequency is achieved by loading reference antenna with eight slits that is antenna 1 and the second resonant frequency is achieved by loading with one center slits and rectangular split ring that is antenna 2. Dual‐band antenna is achieved by loading reference slot antenna with nine slits and rectangular split ring which resonates at frequency of 1.52 and 3.03 GHz respectively. As a result, it is achieved 53.79% reduction in first band resonant frequency with 76.07% improvement in ?10 dB bandwidth and 7.90% reduction in second band resonant frequency compared to reference slot antenna. Further, this dual‐band antenna is miniaturized by metallic strips which are placed on the bottom of the substrate. This results in 61.39% reduction in first band resonant frequency with 32.07% improvement in ?10 dB bandwidth and 26.13% reduction in second band resonant frequency in comparison with reference slot antenna topology.     

High gain transmitarray antenna based on ultra‐thin metasurface

This article presents a bandwidth enhanced transmitarray (TA) antenna based on ultra‐thin metasurface (MS) for high gain operating at X‐band. The antenna consists of a three layers continuous flat structure and an aperture coupled microstrip antenna as the feed source. The relative phase shift of 360° is achieved by the unit cell design based on ultra‐thin MS, and the quasi‐spherical wave could be focused as plane wave when the wave goes through TA. The aperture coupled microstrip feed is designed with a bandwidth of 20.6%, and the bandwidth enhanced property of feed source will reduce the negative effect of elements mutual coupling on TA and increase the bandwidth of the TA antenna. The TA antenna gain increases from 8.25 to 18.98 dB and with a side lobe level of ?14.3 dB. Owing to the low‐profile and easy configuration, this kind of TA antenna has great potential, wireless communication.     

Dual‐band circularly polarized aperture‐coupled stack antenna with fractal patch for WLAN and WiMAX applications

This article presents a novel circular polarized (CP) aperture coupled stack antenna for wireless local area network and worldwide interoperability for microwave access dual‐band systems. The compact stack antenna consisted of square fractal patch, aperture couple, feed line and the perturbation. The square patch is constructed with the complementary Minkowski‐island‐based fractal geometry. By way of adjusting the relevant parameters, we can obtain the dual‐band responses at 3.5 and 5.25 GHz respectively. The CP of each band are presented. The measured 10 dB return loss impedance bandwidth are 270 MHz (7.5%) for 3.5 GHz band and 450 MHz (8.6%) for 5.25 GHz band. The 3 dB axial ratio bandwidths for each bands are 1.4 and 0.76%, the polarization of radiation patterns are both left‐hand CP, and the antenna power gain are 2.84–3.1 and 0.16–2.2, dBic respectively. The proposed antenna is successfully simulated and measured with frequency responses, radiation patterns and current distributions. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:130–138, 2014.     

High isolation,proximity‐fed monostatic patch antennas with integrated self‐interference cancellation‐taps for ISM band full duplex applications

This work presents two dual polarized proximity‐fed monostatic patch antennas with improved interport isolation for 2.4 GHz industrial, scientific and medical band same frequency full duplex wireless applications. The presented antennas achieves the high interport decoupling through intrinsic isolation of the polarization diversity in conjunction with a simple single‐tap and two‐taps self‐interference cancellation (SIC) topologies. The polarization diversity isolation is achieved through two perpendicular microstrip feeds for proximity feeding to excite orthogonal polarization mode for transmit (T_x) and receive (R_x) modes. The prototype for proposed antenna with integrated single‐tap and two‐taps SIC circuit is tested to record its interport isolation, impedance bandwidths and gains for both T_x and R_x ports. The implemented antenna with single‐tap SIC circuit demonstrates 10 dB return‐loss bandwidth of ≥100 MHz for both T_x and R_x ports. The measured isolation exceeds 40 dB over the 40 MHz bandwidth. Moreover, the recorded peak isolation is better than 74 dB for implemented antenna prototype. Furthermore, the 40 MHz bandwidth with 40 dB isolation can be tuned with the help of SIC‐tap as demonstrated through the experimental results. The measured gain levels are around 4.6 dBi for both T_x and R_x port. The same antenna structure with integrated two‐taps SIC topology features better than 55 dB isolation within 10 dB return loss bandwidth of 100 MHz. The peak isolation exceeds 97 dB and isolation levels are better than 60 and 80 dB over 50 and 20 MHz bandwidths, respectively, for presented antenna with two‐taps SIC configuration. The compact antenna offers comparatively wider impedance and isolation bandwidth with improved SIC levels compared to previous designs.     

A low‐profile,dual‐polarized,and wideband square cavity‐backed antenna

A cavity‐backed antenna with low‐profile, dual‐polarization, and wide operating bandwidth characteristics is proposed. In this design, two orthogonally positioned triangular bowtie antennas printed on a low‐cost substrate are loaded onto a square cavity, so that two orthogonal linear polarizations can be excited. By further introducing four extended ground stubs from each side of the square cavity, the proposed antenna can also acquire low‐profile characteristic of approximately 0.1λ (15 mm). To achieve good impedance matching, additional circular slots are introduced into each bowtie design. The measured results show that the proposed antenna can cover a wide operating bandwidth of 62% (2.0–3.8 GHz) with a VSWR of 2:1. Besides exhibiting good isolation (>20 dB) between the two feeding ports, desirable realized gains (6.0–10.5 dBi) over the wide operation band are also demonstrated. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:724–730, 2016.     

High‐gain dual‐polarized antenna for ultrawideband applications

In this article, a high‐gain and dual‐polarized antenna with UWB operation is proposed. The antenna is composed of two tapered dipoles as radiating elements, which are arranged orthogonally and fed perpendicularly to achieve polarization diversity. A metallic cavity reflector is placed behind the radiator for high gain radiation entire the operating bandwidth. To validate the design method, an antenna prototype is designed, fabricated, and measured. The measured results demonstrate that the proposed design has good performance with |S₁₁| ≤ ?10 dB and isolation ≥20 dB over a frequency band 3.2‐8.8 GHz, equivalently to about 93.3%. In addition, unidirectional radiation pattern and broadside gain of from 8.1 to 11.8 dBi are obtained across the operating bandwidth.