Bandwidth enhancement of a circularly polarized tapered crossed slot antenna with corner parasitic directors

This paper presents a single‐feed wideband circularly polarized (CP) antenna with tapered crossed slots and corner directors. According to the multi‐mode resonance concept, the antenna uses two identical cross placed Vivaldi‐like tapered slots as the wideband radiating elements, and four rectangular parasitic patch directors are connected on each corner of the ground for further enhancing the bandwidth. A simple second‐order stepped microstrip line with a via on the other side of the substrate is used to feed the antenna. Two pairs of capacitors and inductors are placed on each slot to realize a 90° phase difference for CP operation. The proposed antenna is designed, fabricated and measured. Simulation results are in good agreement with the measured results that demonstrate a 10 dB impedance bandwidth (IMBW) from 1.98 to 5.71 GHz (3.73 GHz, 97.01%) and a 3 dB axial ratio bandwidth (ARBW) from 2.13 to 3.91 GHz (1.78 GHz, 58.94%). The antenna outperforms most of the reported cross slot antennas for its wide IMBW and ARBW.     

Planar UWB antenna with modified slotted ground plane

A compact coplanar waveguide‐fed (CPW) monopole antenna for ultra‐wideband wireless communication is presented. The proposed antenna comprises of a CPW‐fed beveled rectangular patch with a modified slotted ground. The overall size of the antenna is 30 mm × 27 mm × 1.6 mm. The lower edge of the band is attained by properly decoupling the resonant frequencies due to the extended ground plane and the beveled rectangular patch of the antenna. The upper edge of the radiating band is enhanced by beveling the ground plane corners near the feed point. Experimental results show that the designed antenna operates in the 2.7–12 GHz band, for S₁₁ ≤ ?10 dB with a gain of 2.7–5 dBi. Both the frequency domain and time domain characteristics of the antenna are investigated using antenna transfer function. It is observed that the antenna exhibits identical radiation patterns and reasonable transient characteristics over the entire operating band. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.     

Reconfigurable wide band circularly polarized antenna array for WiMAX,C‐Band,a and ITU‐R applications with enhanced sequentially rotated feed network

In this article, a wide‐band circularly polarized slot antenna array with reconfigurable feed‐network for WiMAX, C‐Band, and ITU‐R applications is proposed. Different novel methods are used in proposed array to improve antenna features such as impedance matching, 3 dB axial‐ratio bandwidth (ARBW), gain, and destructive coupling effects. Miniaturized dual‐feed square slot antenna, with one attached L‐shaped strip and a pair of T‐shaped strip at ground surface for improving impedance matching and circular polarization (CP) purity, is presented. For further enhancement of CP attributes, reconfigurable sequentially rotated feed network is utilized to obtain wider 3 dB ARBW. Furthermore reconfigurable property of network gives controlling Right and Left handed CPs, respectively. Finally, a special form of Electromagnetic Band gap structure is employed on top layer of substrate that provides high isolation between radiating elements and array feed network to enhance overall performance of antenna. The measured results depict 3 dB ARBW from 4.6 to 7.2 GHz, impedance bandwidth from 3.3 to 8.8 GHz for VWSR<2, and peak gain of 10 dBi at 6 GHz. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:825–833, 2015.     

Fork‐shaped patch printed ultra‐wideband slot antenna with dual band‐notched characteristics using metamaterial unit cells

In this article, a miniaturized fork‐shaped patch ultra‐wideband (UWB) planar wide‐slot antenna with dual band‐notched characteristics is proposed. With fork‐shaped patch, ultra‐wideband impedance matching from 3.1 to 13.2 GHz is easily achieved. Then, two novel and simple methods are applied to solve the difficulty for UWB slot antennas with fork‐shaped patch to realize band‐notched characteristics. By etching one pair of I‐shaped resonators on both branches of the fork‐shaped structure and adding a rectangular single split‐ring resonator in the rectangular openings of fork‐shaped patch, the wireless local area network (WLAN) band from 5.5 to 6.1 GHz and the International Telecommunication Union (ITU) 8 GHz band from 7.9 to 8.7 GHz are rejected, respectively. The coplanar waveguide‐fed UWB antenna is successfully designed, fabricated, and measured. The measured and simulated results show a good agreement. The antenna provides nearly stable radiation patterns, high gains and high radiation efficiency.     

A high gain wideband circularly polarized antenna with asymmetric metasurface

An asymmetric‐metasurface based wideband circularly polarized (CP) microstrip antenna using a coaxial probe is proposed for L‐band applications. The antenna involves a stacked asymmetric‐metasurface, a radiating rectangular‐patch and a coaxial feed. An asymmetric‐metasurface is designed using rectangular unit cells and smaller size unit cells along one of the diagonal lines. The asymmetric‐metasurface is placed above a radiating rectangular‐patch with support of foam layer to achieve a wideband CP radiation. The measured performance of the prototype antenna achieves an impedance bandwidth (?10 dB return loss bandwidth) of 15.7% (1.58‐1.85 GHz) with CP bandwidth (3‐dB axial ratio) of 13% (1.58‐1.80 GHz) and gain of ≥9 dBic.     

Low‐cost broadband microstrip antenna array for 24 GHz FMCW radar applications

Two designs of microstrip antenna arrays consisting of eight radiating elements and operating within a broad frequency range having the center frequency of 24 GHz are presented. One of the proposed antenna arrays uses a single laminate layer with a ground plane on one side and radiating elements on the other side, the other one is a double layer structure, where the radiating elements with beam‐forming network are placed on the top layer and are fed with the use of the slot coupler. The application of U‐slot radiating elements with enlarged inner parasitic patch allows us to achieve reflection coefficient better than 10 dB within the assumed bandwidth of currently developed FMCW radars, which is 23–25 GHz frequency range. The theoretical analysis as well as experimental results of the manufactured 2 × 4 antenna arrays is shown. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013.     

An off‐center‐fed compact wideband antenna with truncated corners and parasitic patches for circular polarization

A novel single‐fed circularly polarized wideband, compact and lightweight microstrip patch antenna (MPA) is proposed. The antenna is designed in a simple two‐phase procedure to achieve wideband and circular polarization. In the first phase, an off‐centered L‐shaped feeding arrangement is employed to obtain wideband (|S₁₁| < ?10 dB) over 10.6 GHz to 14.7 GHz with an improved peak gain of 5.25 dBi. In the second phase, the radiating patch is symmetrically truncated and two modified‐parasitic patches are added to ensure <3 dB axial ratio over 11.4 GHz to 12.8 GHz. A prototype has been fabricated and the measured results show close agreement with the simulation. The proposed antenna is suitable for fixed satellite and broadcast satellite communication in Ku‐band range.     

Wideband linear microstrip array antenna with high efficiency and low side lobe level

In this letter, the design and fabrication of the linear microstrip array antenna by series fed are presented. The array antenna consists of 16 reflector slot‐strip‐foam‐inverted patch (RSSFIP) antennas. The gain and efficiency of the linear array antenna is 16.6 dBi and 61% at 10 GHz, respectively. The antenna has a bandwidth (BW) of 45% from 8.1 to 12.8 GHz (S₁₁ < ?10 dB) and side lobe level (SLL) of ?25.6 dB across the BW of 19.2% from 9.4 to 10.4 GHz. These are achieved by using a microstrip series fed with defected ground structure (DGS) to feed the patch array antenna. Good agreement is achieved between measurement and simulation results.     

Reconfigurable ultra‐wideband monopole antenna with single‐, dual‐, and triple‐band notched functions

A miniaturized ultra‐wideband (UWB) monopole antenna with reconfigurable multiple‐band notched performance is demonstrated. By modifying the shape of the patch and the ground plane, the UWB operation is achieved. The first and second band‐notches are respectively generated by etching a rectangular slot with open ends and a U‐shaped slot in the patch, and the third band‐notch is produced by loading a C‐shaped parasitic element beneath the patch. To realize the reconfigurable band‐notched functions, four PIN diodes are inserted in three band‐rejected structures. The antenna has a compact dimension of 30 mm × 26 mm. It can switch between a UWB state and several band‐notch states by alternating the states of the diodes. Also, good radiation patterns are obtained.     

Low‐cost and wideband circularly polarized slot antenna array

A slot antenna with wideband circular polarization (CP) array, which operates on millimeter waves band, is proposed. A four‐direction sequential rotation technique is used in the feed network to feed the 2 × 2 slot element based on waveguide. The shot element resonates at both the fundamental mode and the high‐order mode. The slot element is studied in high order mode, and the radiation lobe can be redirected by changing the size of the slot element, thus improving the multi‐lobe problem. A strong single lobe is formed in the +z‐direction by using the ground edge diffraction characteristics of the slot element in the waveguide. The designed broadband characteristics are obtained through the appropriate combination of the feed network and CP antenna. The prototype of the antenna with an overall size of 137 mm × 137 mm × 0.6 mm³ is processed and verified by experiments. The prototype of the slot array is processed and examined. The test results display that the device has good performance of |S₁₁| < ?10 dB bandwidth of 3.72 to 6.56 GHz (2.84 GHZ, 55.25%), a 3 dB axial ratio bandwidth of approximately 4.39 to 5.43 GHz (21.18%).     

Miniaturized dual‐band metamaterial inspired antenna with modified SRR loading

A miniaturized dual‐band CPW‐fed Metamaterial antenna with modified split ring resonator (SRR) loading has been presented in this paper. Proposed antenna comprises a tapered rectangular patch with a slot in which an elliptically SRR has been loaded to achieve miniaturization. Proposed antenna shows dual band operations in the operating band 3.25‐3.42 and 3.83‐6.63 GHz, respectively. It has been observed that lower mode (at 3.36 GHz) is originated by means of modified SRR. SRR is being modified by small meandered line inductor which is placed instead of strip. This provides an extra inductance to SRR resulting miniaturization. Overall electrical size of the proposed antenna is 0.222 × 0.277 × 0.017 λ₀ at 3.36 GHz. Second band is due to coupling between feed and ground planes. The antenna offers an average peak gain of 1.72 and 3.41 dB throughout the first and second band respectively. In addition to that this antenna exhibits perfect omnidirectional and dipolar radiation patterns at xz‐ and yz‐ plane respectively. Due to consistent radiation pattern, ease of fabrication, and compact nature this antenna can be used for wireless applications such as worldwide interoperability for microwave access (WiMAX), industrial, scientific and medical (ISM) band, WLAN/Wi‐Fi bands.     

Compact broadband circularly polarized Hook‐shaped microstrip antenna with DGS plane

A new antenna structure comprises of defected ground structure with hook‐shaped radiating patch designed for broad impedance bandwidth and axial ratio bandwidth is presented. In the proposed design, hook shaped radiating patch is orthogonally connected with printed strip patch and excited with 50Ω feed line at the upper side of the substrate. At the bottom side, a small rectangular slit is removed from the ground plane just underneath of radiating patch for better impedance matching along with broader bandwidth. The ground plane is defected by etching 3 symmetrical narrow slots for antenna compactness. The optimized antenna prototype is simulated, fabricated, and experimentally tested for far field and axial ratio performances in anechoic chamber. The measured results clearly show that it can yield an impedance bandwidth of approximately 27.60% centered at 2.17 GHz frequency and a 3‐dB AR bandwidth of approximately 25.20%. The measured gain range from 3 to 4.3 dBic in entire 3‐dB AR bandwidth with maximum gain of 4.30 dBic. The cross polar suppression was witnessed better than 15 dB along with wide beamwidth of 85°     

Wafer level packaging compatible with millimeter-wave antenna

This paper presents a technological process compatible process compatible with an above integrated circuit (IC) to achieve a millimeter wave antenna structure that is well-suited for wafer level packaging technology. The radiating patch is introduced inside of the air cavity of packaging. This structure consists of two dielectric substrates and benzocyclobutene (BCB) sealing rings at the wafer level. The wafer level packaging that holds the radiating patch is made of Pyrex, a low permittivity substrate. The millimeter-wave antenna using the micromachining technology is excited by a coplanar waveguide fed aperture (CPWFA). This feeding mechanism is designed and realized on GaAs, a high permittivity substrate. The electromagnetic energy of the CPWFA to the radiating patch is made through a coupling slot. The fabricated antenna of 6 mm × 6 mm, including the ground plane, exhibits a 10 dB bandwidth of 3 GHz from 50.5 GHz to 53.5 GHz. The design has been driven by the interest of collective encapsulation of MEMS and MMICs devices.     

A wideband circularly polarized antenna using mutual coupling method

A novel wideband circularly polarized (CP) antenna is presented in this article. The proposed antenna consists of a four‐leaf clover patch, four L‐probes, and wideband networks. Based on the tightly coupled mechanism, the four L‐probes are formed as a ring with the adjacent ones kept close for strong mutual coupling. Consequently, the proposed antenna realizes a wideband impedance matching. Meanwhile, the four‐leaf clover patch is put closely inside of the ring for further improving the impedance bandwidth, which is proximity‐coupled fed by the four sequential‐rotation L‐probes with phase of 0°, 90°, 180°, and 270°. The four L‐probes are connected to the respective ports of a wideband feeding network by a two‐stage impedance transforming network. The measured results indicate that the proposed design has an impedance bandwidth of 66.7% from 1.0 to 2.0 GHz for VSWR ≤ 2 and a 3‐dB axial ratio bandwidth of 56.5% from 1.08 to 1.93 GHz. Furthermore, in the operating bandwidth, stable and symmetry radiation patterns and high gain are obtained. The design has a 3‐dB gain bandwidth of 38% from 1.3 to 1.9 GHz with a peak gain of 8.5 dBic.     

A 2 × 2 array antenna with circular polarization and conical beam radiation

A circular disk patch antenna loaded with a hemi‐circular slot is initially proposed for achieving circular polarization (CP). To exhibit broad CP bandwidth that can cover the WLAN 2.4 GHz operating band, the patch antenna is fed by an L‐shaped probe. To further attain conical beam radiation with peak gain of ～8 dBic at ±30 degrees theta angle (θ), a 2 × 2 array type is proposed in this study, in which four circular disk patch array elements are arranged in a sequentially rotated fashion via a corporate feed network. Here, desirable 3‐dB axial ratio (AR) bandwidth and 10‐dB impedance bandwidth of ～5% and 21% were measured. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:223–228, 2014.     

Compact substrate integrated waveguide mono‐pulse antenna array

A compact monopulse antenna array based on substrate integrated waveguide technology is presented through this article. The design is fabricated on Printed Circuit Board (PCB) technology consisting of a double‐layered 8‐cell array antenna with a slot in the middle‐ground metal used for aperture‐coupling excitation and reducing unwanted spurious emissions from feed network. The Impedance bandwidth and AR bandwidth are enhanced due to optimal feed network, including Rat‐Race coupler to generate sum and difference patterns for mono‐pulse applications operating at 10 GHz. The prototype of the proposed antenna with the size of 124*25 mm² is fabricated and tested. Measured results compared very well to simulation results obtained by CST microwave studio and show ?10‐dB impedance bandwidth of 4% and ?22 dB null‐depth in difference mode.     

A novel wideband circularly polarized modified square‐slot antenna with loaded strips

In this article, a novel inverted L‐shaped microstrip‐fed wideband circularly polarized (CP) modified square‐slot antenna is designed. By cutting a pair of triangle chamfers and introducing a pair of triangle patches at the square‐slot, the antenna achieves a wideband CP radiation. Moreover, CP performance of the antenna can also be remarkably enhanced by protruding an L‐shaped strip and embedding a tuning rectangle slot into the slot ground. The measured results demonstrate that the axial‐ratio bandwidth for AR < 3 is 75.1% (from 4.45 to 9.8 GHz) and the impedance bandwidth (|S₁₁| < ?10 dB) reaches 65.8% (from 4.95 to 9.8 GHz). In addition, surface current studies are performed to illustrate the operating mechanism of CP operation, and the antenna has bidirectional radiation characteristics with an average gain of ~4 dBic within the CP band.     

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.     

Low profile coupling feed circularly polarized antennas for WLAN applications

This article presents two designs of circularly polarized antenna with simple circular‐shaped radiator and circular slotted ground plane. An arc‐shaped microstrip line coupling feed mechanism is used to excite the circular radiating patch. The 3‐dB axial ratio bandwidth of the proposed antenna‐1 and proposed antenna‐2 are 3.33% and 18%, respectively. The proposed design has several advantages such as easy matching, fabrication simplicity, compact size, and wide axial ratio bandwidth. Both the antennas have been designed on FR‐4 substrate with dielectric constant 4.4 and thickness 1.59 mm. Simulated and measured results are presented to validate the working of the proposed antennas.     

A WiMAX circularly polarized antenna array using slot‐coupling feeding technique

In this letter, we present a circular polarization antenna array using the novel slot‐coupling feeding technique. This antenna includes eight elements which are installed in line, each array element is fed by means of two microstrip lines with equal amplitude and phase rotation of 90°. The feeding microstrip lines are coupled to a square patch through a square‐ring slot realized in the feeding network ground plane. With the presence of the slots, this antenna array is able to cover the range of frequency of 3 GHz to 4 GHz. The size of the proposed antenna array is 7λ × 1.8λ × 0.4λ. The measured gain is 15.2 dBi and the bandwidth of S11< ?10 dB is 1 GHz (3–4 GHz, 28%). The antenna array is suited for the WiMAX applications. With the use of slot‐coupling feeding technique, the measured bandwidth for axial ratio < 3 dB is about 24% in the WiMAX frequency band (3.3–3.8GHz). The measured HPBW of the y–z planes is larger than 62°. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:567–574, 2016.