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.     

Metasurface‐based low‐profile high‐gain substrate‐integrated Fabry‐Pérot cavity antenna

A metasurface‐based substrate integrated Fabry‐Pérot cavity (FPC) antenna is presented for improved radiation performance associated with the low profile. A novel partially reflective planar (PRS) artificial magnetic conductor (AMC) structure is proposed as the upper reflector of the substrate integrated FP resonant cavity. A microstrip patch antenna is embedded inside the cavity as a feed. The proposed antenna is designed to operate at 9.35 GHz with the maximum realized gain of 14.2 dBi and the overall profile of λ₀/10 (λ₀ is the operating wavelength in free space). The low‐profile performance of the proposed design outperforms any previous substrate‐integrated FPC antenna design with this gain performance. The influences of the FP cavity on the reduction of the antenna profile and the enhancement of the antenna gain are also investigated. Good agreement between the measured and simulated results validates the feasibility of the analysis and design approach.     

Metasurface cavity antenna for broadband high‐gain circularly polarized radiation

The article presents a microstrip patch (MSA) fed high gain circularly polarized metasurface cavity (CP‐MSC) antenna using a planar progressively‐phased‐reflector and a transmissive linear to circular polarization conversion metascreen. The bottom metasurface reflector consists of a remodeled Jerusalem cross to obtain 2π reflection phase variation. Linear to circular polarization conversion is achieved by a hexagonal ring based meta‐element with high transmission and bellow 3 dB axial ratio from 9.5 to 10.5 GHz. Simulated and measured results of assembled CP‐MSC antenna with MSA are in good agreement. The gain of the proposed cavity antenna with 10 and 10.5 GHz MSA are 14.9 and 16.3 dBi, respectively. Below 3 dB AR throughout the operating band denotes significant circular polarization performance of the proposed antenna.     

A novel wideband high‐gain modified biquad dipole antenna

This article thoroughly investigates a novel modified biquad dipole antenna with a simple structure, wideband, high‐gain and linear polarization key features for wireless communication systems fabricated on FR4 substrate. The proposed antenna is investigated using circular wire loop antenna designing and is, then, extended to a strip structure antenna. Here, a circular reflector is employed to achieve maximum gain, while a coax line feeds the dipole element. Additionally, the presence of a balun, or lack thereof, is examined. The bazooka balun balances the coaxial cable and increases the bandwidth. Consequently, a wide bandwidth and a triple bandwidth are achieved. The resulting parameters demonstrate that the entire S, partial L and C IEEE radio bands comprise the bandwidth of the proposed antenna. The simulated current distribution, experimented and simulated efficiency, radiation pattern, reflection coefficient and gain of the designed antenna are also examined. The simulation and experimentation results exhibit an impedance bandwidth of 105.4% (1.3‐4.2 GHz) for (S₁₁ < ?10 dB). The broadside radiation pattern fills the entire band with maximum simulated and measured gains of 11.8 and 11.02 dBi, respectively. The simulated and measured results tie in closely with each other.     

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.     

Broadband T‐bar fed slot antenna array with stable horizontally polarized omnidirectional radiation

A broadband horizontally polarized omnidirectional antenna array is proposed, which consists of a circular array of four identical broadband T‐bar fed cavity‐backed slot antenna elements and a 1‐to‐4 power divider. The proposed omnidirectional antenna array has a compact diameter of only 0.44λ₀, a broad bandwidth of 75.9% (450‐1000 MHz) and a favorable omnidirectional radiation pattern in the azimuth plane with a gain variation below 3 dB in the operating band. Moreover, the cavity‐backed structure makes the proposed antenna array hardly affected by metal environment and the all metal construction allows for high‐power applications, and the reserved cable channel behind the cavities of the antenna elements ensures the extensionality and stability of the proposed array when longitudinal array expansion is needed. Design procedures of the proposed antenna array have been described in detail, simulations and measurements of the proposed antenna array have also been carried out to validate its performance in this article.     

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.     

Matched feeds for offset reflector antenna using circular microstrip patch antenna

This article presents two designs of matched feed for an offset fed reflector. Circular microstrip patch antennas are used in the proposed designs. Both the matched feeds achieve conjugate field matching by generating TM₂₁ mode at an appropriate ratio to the fundamental TM₁₁ mode. The first matched feed generates the required dual mode field distributions using a dual layer stacked patch antenna. The second matched feed is a novel design using centered circular array with the central element generating the required TM₂₁ mode and the surrounding circular ring antenna elements operating in the TM₁₁ mode. Both the designs are studied analytically using cavity model and are implemented in High frequency System Simulator (HFSS) and Computer Simulation Technology (CST). The matched feed designs are investigated for an offset reflector with the projected diameter, D = 50λ, focal length, F = 30λ and clearance height, H = 5λ operating at 20 GHz. The secondary field patterns of the offset reflector fed by the matched feeds are evaluated numerically using a MATLAB code based on geometrical optics technique and verified by HFSS‐PO results. Offset reflector performance such as cross‐polarization, ?30 dB cross‐polar bandwidth, gain, and first side‐lobe level are investigated for the both matched feeds.     

A wideband patch antenna with a pair of antisymmetric balun as differentially fed network

A novel singly differentially‐fed microstrip patch antenna (DFMA) is proposed, which is composed of a radiating patch, a differentially‐fed network with a twin antisymmetric miniaturized baluns and a ground plane for unidirectional radiation. In the differentially‐fed network, the signal is coupled to the two feedlines on both sides by the two miniaturized baluns. The radiating patch is excited by the coupling feed sheet located below the radiating patch, and the coupling feed sheet is connected to the upper end of the feedline. The lower end of the feedlines is connected to the ground plane, and there is a slot on the ground of the feeding network. Due to the existence of coupling feed sheet and slot, a second nonradiating resonant is achieved, and a wideband property is obtained. Finally, the prototype of the antenna is fabricated and studied experimentally. Simulated and measured results show that the impedance bandwidth of the antenna is 30.3% (1.71‐2.32 GHz) for S₁₁ < ?10 dB. Besides, a stable symmetric radiation pattern is obtained with gain around 9.6 dB and cross‐polarization less than ?21 dB, which demonstrates the designed antenna has the property of wideband, high gain and low cross polarization.     

A K/Ka‐band dielectric and metallic 3D printed aperture shared multibeam parabolic reflector antenna for satellite communication

A K/Ka‐band (22‐33 GHz) high‐gain aperture shared multibeam parabolic reflector antenna is proposed. It performs a two‐dimensional beam scanning from a shared single parabolic reflector by introducing off‐focal feeds. The feed array is placed on and off the focal of the parabolic reflector. Traditionally, the feed blockage has a great impact on the performance of the antenna, which reduces the gain and increases the sidelobe level. The purpose of this paper is to suppress the negative effects of feed blockage by using hybrid material processing method. Both dielectric and metallic 3D printing technologies are used for antenna fabrication. The parabolic reflector antenna is printed by selective laser melting using aluminum alloy. The feed array and the supporting structures are printed by stereolithography apparatus in resin to control the blockage. The method helps to suppress the sidelobe level from ?10 to ?15 dB and to enhance gain by up to 2.3 dBi. The reflection coefficient is less than ?10 dB, while the coupling coefficient between the ports is less than ?20 dB over the entire designed band. At 31.5 GHz, the simulated maximum gain of the antenna are 30.7, 29.1, and 29.7 dBi, when different port separately excites. Multiple beams at ±15° and 0° are observed on both E‐ and H‐planes. Besides, it also verifies the possibility to use dielectric and metallic 3D printing technologies in hybrid for microwave device fabrication.     

A new modified CPW‐fed wideband circularly polarized half‐split cylindrical dielectric resonator antenna with different permittivity of two layers in radial direction

In this article, a wideband circularly polarized half‐split cylindrical dielectric resonator antenna (HS‐CDRA) having two layers with different permittivity in radial direction is investigated. Designed antenna is excited by a new modified CPW fed which consists of signal line, helps to realization of circular polarization, half‐split cylindrical dielectric resonator (HS‐CDR), to confirm that circular polarization in proposed antenna. HS‐CDR is made of two different materials which can supports to enhance the input impedance bandwidth and 3‐dB axial ratio bandwidth. From the distributions of E‐fields in HS‐CDRA, it is observed that TM_11δ mode has been excited. To confirmed the circular polarization in proposed antenna, E‐field distribution on different phases (φ = 0º, 90º, 180º, and 270º) have been plotted. This antenna provides measured ?10 dB input impedance bandwidth of 25.94% (centered on 4.70 GHz) and 3‐dB axial ratio bandwidth in broadside direction of 17.34% (centered on 4.90 GHz). The average gain and radiation efficiency in working band are 1.56 dBi and 93.43% in broadside direction, respectively. CP radiation pattern shows that the proposed antenna has left hand circular polarization and this developed antenna could be useful for wireless applications like WLAN/Wi‐MAX bands.     

Design of a 16‐beam pattern‐reconfigurable antenna for vehicular environment

This article presents the design of a multipattern antenna with pattern switching for vehicular communications. The proposed antenna has four triangular patches integrated onto a split square ring (SR) resonator to operate at two distinct frequencies, viz. 2.4 and 3.5 GHz. The proposed antenna is designed with a view to enhancing the link reliability of Wireless Local Area Network (WLAN), WiMax, and vehicle to vehicle communication frequencies. Each triangular patch is separately excited using a microstrip line feed to enable beam steering. The ground plane of the antenna is embedded with two SR slots to improve the bandwidth and radiation performance. Further gain enhancement is achieved by loading the antenna with a plane reflector located at a distance of 20 mm from the antenna's ground surface. In reality, this reflector is realized using the vehicle's roof which provides gain enhancement up to 5.2 dBi at 2.4 GHz and 4 dBi at 3.5 GHz. By exciting single to multiple ports sequentially 16 different radiation patterns are obtained, which provides high‐gain omnidirectional coverage. The prototype antenna is fabricated and the simulation results are verified using experimental measurements. From the results, it is evident that the proposed antenna is suitable for vehicular communication applications.     

Ultrawideband high‐gain dual‐polarized antenna with anti‐interference capability

In this article, a high‐gain dual‐polarized antenna with band‐rejection capability for ultrawideband (UWB) applications is proposed. Tapered dipoles are chosen as a primary radiator to achieve UWB operation and it is reflected by a metallic cavity reflector for high gain radiation. A notch at WLAN band is realized by etching a set of four bent slots in the radiating elements. The measured results demonstrate that the proposed design with overall dimensions of 0.69λ _L × 0.69λ _L × 0.16λ _L (λ _L is free‐space wavelength at the lowest operating frequency) has operating bandwidth of 95.1% (3.2‐9.0 GHz) and the rejected frequency band from 5.0 to 5.9 GHz. Additionally, good unidirectional radiation patterns with a broadside gain from 8.1 to 11.5 dBi and radiation efficiency of better than 90% are also achieved.     

Enhancing characteristics of dual‐polarized BTS element antenna using metal director

This article proposes a dual‐polarized antenna with enhanced characteristics using metal director for base transceiver station applications. The proposed antenna consists of a main radiation element, ±45^? dual‐polarized feed structure, a reflector and a metal director. The metal director improves the impedance matching and increases the gain and front to back ratio. A prototype of the antenna is fabricated and the measured results show the wide frequency bandwidths of 63% for port 1 with frequency range 1.6 to 3.1 GHz and 60% for port 2 with frequency range 1.6 to 3 GHz. The obtained experimental isolation between ports is greater than 28 dB. The measured results also represent a gain of >8.4 dBi and the stable radiation patterns with half‐power beam width wider than of 65°. According to mentioned experimental results, the presented antenna can be used in the microcell base stations for Global System for Mobile, Code Division Multiple Access, and Long‐Term Evolution services.     

Design and implementation of a low profile polarization‐reconfigurable transmitarray with linear polarized feed

A novel polarization‐reconfigurable transmitarray with linear polarized feed is presented in this letter. Each element in the proposed transmitarray consists of two cascaded cross dipoles to achieve more than 310° of linear phase with transmission magnitude equal to or better than 0.8 dB. The proposed unit cell has a thickness of 0.22λ₀, which leads to a low profile transmitarray compared with those conventional designs. The element behavior of low transmission loss has resulted in higher antenna efficiency. By properly rotating the feed antenna around the center and selecting the x‐ and y‐dimension of each element, the proposed transmitarray can generate radiation patterns with different polarization states, including left‐handed circular polarization (LHCP), right‐handed circular polarization (RHCP), and linear polarization(LP). For the purpose of validation, a double‐layer center‐fed 11 × 11‐element transmitarray prototype is manufactured and tested at X‐band. Measurement results demonstrate the designed transmitarray realize both high gain performance and multiple polarization operation.     

Circularly polarized rectangular DRA coupled through orthogonal slot excited with microstrip circular ring feeding structure for Wi‐MAX applications

In this article, a wideband circularly polarized rectangular dielectric resonator antenna (RDRA) coupled through orthogonal slots and excited with a new microstrip circular ring has been investigated. Circular polarization has been achieved by using plus shaped (+) slot on the ground plane and excited through a new microstrip circular ring feed. TE_11δ mode has been excited in the RDRA which has been confirmed through the distribution of E ‐field and dielectric waveguide model (DWM) method of RDRA. Circularly polarized (CP) RDRA offering measured ?10 dB input impedance bandwidth of 20.79% (centered at 3.27 GHz) and 3 dB axial ratio bandwidth in broadside direction of 12.09% (centered at 3.39 GHz), respectively. From the CP radiation pattern, proposed design confirms that right ‐ handed CP (RHCP) in broadside direction. The difference between RHCP field and left ‐ handed CP (LHCP) field are above ?26 dB in operational band. In addition, the proposed CP antenna offers stable gain and radiation efficiency in working bands and it is suitable for IEEE 802.16e/d Wi‐MAX (3.3‐3.7 GHz) band.     

Dual ISM band printed antenna with omnidirectional radiation pattern and better radiation efficiency

Designing a high gain planar antenna on the low‐cost FR4 substrate is one of the major challenging tasks for the researchers. The omnidirectional radiation pattern is desired for 360° coverage. Both of these requirements have been addressed in this article. This article presents a dual band printed antenna designed on an FR4 substrate of 1.6 mm thickness. The proposed antenna operates in the ISM band of 2.4 and 5.8 GHz for the application of dual‐band WLAN/WIFI. The proposed antenna consists of a circular patch and ring‐shaped ground plane. The overall dimension of the antenna is 66 × 66 × 1.6 mm³. Excellent impedance matching and radiation efficiency for both the bands have been achieved. The proposed antenna shows omnidirectional radiation pattern at 2.4 GHz ISM band and nearly omnidirectional pattern along with high gain of 4.7 dBi at 5.8 GHz ISM band.     

A modified split ring resonator based printed compact monopole UWB antenna with spiked elliptical radiator having five band rejection features

A coplanar waveguide (CPW) fed printed compact monopole antenna with five band rejection features is presented. Wide bandwidth was achieved by beveling the lower part and adding a modified ellipse on the upper portion of the patch. An inverted circular arc, single circular split ring resonator (SRR) with wide opening and two symmetrical circular single SRRs were embedded for obtaining three stop‐band characteristics. Two symmetrical slits were inculcated in the ground forming defected ground structure (DGS) to get another stop‐band characteristic. Two concentric rectangular modified SRRs were etched to obtain a higher frequency stop‐band feature. The proposed antenna was designed, fabricated, and experimentally tested for the validation of results. The overall dimensions of the proposed antenna were 29 mm × 24 mm × 1.6 mm. The measured impedance bandwidth of the antenna was 2.87 to 13.3 GHz at | S₁₁ |< ? 10 dB. The measured results show that the proposed antenna has five band notches centred at 3.96, 4.35, 5.7, 8.54, and 9.95 GHz to reject WiMAX band (3.65‐4.04 GHz), ARN band (4.29‐5.18 GHz), WLAN band (5.5‐6.9GHz), ITU‐8 band (7.37‐8.87), and amateur radio band (9.2‐10.3 GHz) respectively. The proposed antenna maintains omnidirectional radiation pattern in H‐Plane and dumbbell‐shape radiation pattern in E‐plane. Further, stable gain over the whole UWB except at notched frequency bands was reported.     

Compact high gain half‐mode substrate integrated waveguide cavity antenna using hybrid mode

In this article, a compact fully planar high gain antenna based on half‐mode substrate integrated waveguide (HMSIW) cavity is presented. The design uses a novel configuration of HMSIW cavity with high length to width ratio along with tapered open edge and a pair of slot stub. The high length to width ratio of the cavity helps to excite closely spaced multiple TE^y_m10 cavity modes within comparatively smaller footprint due to use of the HMSIW cavity. These modes combine to give hybrid mode resonance in the cavity which helps to generate a narrow beam high gain radiation pattern of the antenna. The size of the proposed antenna is further reduced and a pair of slot stub is put along the sidewall of the cavity which helps to sustain similar hybrid mode field distribution within much smaller dimension. A size reduction of 76.7% is achieved in the proposed design configuration without degrading much of the gain performance. The proposed antenna resonates at 9.8 GHz with a gain of 7.9 dBi which is much higher than other reported HMSIW cavity antenna. The proposed antenna may find application in point to point communication, short range radar in X band.     

Dual polarized triple band hybrid MIMO cylindrical dielectric resonator antenna for LTE2500/WLAN/WiMAX applications

In this communication, triple band hybrid multi‐input–multi‐output (MIMO) cylindrical dielectric resonator antenna (CDRA) with high isolation is examined. The proposed MIMO antenna includes two symmetric folded microstrip line feeding structures along with CDRA at two different ends of substrate. Two inverted L‐shaped strips on the ground plane are used to enhance the isolation (S₁₂ < ?15 dB) as well as to generates 2.7 GHz frequency band. Metallic strip on the ground plane act as an electromagnetic reflector and also enhance the isolation between two antennas (S₁₂ < ?20 dB). Archetype of proposed MIMO antenna design has been fabricated and tested to validate the simulated results. The proposed antenna operates at three different frequency bands 2.24–2.38 GHz, 2.5–3.26 GHz, and 4.88–7.0 GHz (S₁₁ < ?6 dB) with the fractional bandwidth 6.06%, 26.4%, and 35.7%, respectively. Folded microstrip lines generate path delay between the electric field lines and originate circular polarization characteristics in the frequency range 5.55–5.75 GHz with the fractional bandwidth of 3.55%. In order to satisfy the different performance requirement of MIMO antenna such as envelop correlation coefficient, mean effective gain, effective diversity gain, peak gain are also examined. The proposed antenna is found suitable for LTE2500, WLAN, and WiMAX applications. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2016.