Compact ultra‐wideband slot antenna with three notched‐band characteristics

A very compact ultra‐wideband (UWB) slot antenna with three L‐shaped slots for notched‐band characteristics is presented in this article. The antenna is designed and fabricated using a new stepped slot with different size, integrated in the ground plane, and excited by a 50 Ω microstrip transmission line. The stepped slot is used to minimize the dimensions of the antenna and to achieve an impedance bandwidth between 2.65 and 11.05 GHz with voltage standing wave ratio (VSWR) less than 2. The length of the stepped slot is equal to a quarter wavelength to create a resonance in the desired frequency. Three L‐shaped slots with various sizes are etched in the ground plane to reject three frequency bands in C‐band (3.7‐4.2 GHz), WLAN (5.15‐5.825 GHz), and X‐band (7.25‐7.75 GHz), respectively. The notched‐band frequency can be controlled by changing the length of the L‐shaped slot. The proposed antenna has a very small size (20.25 × 8 × 1.27 mm³) compared with previous works. The measured and simulated results show a good agreement in terms of radiation pattern and impedance matching.     

Metamaterial inspired CPW‐fed compact antenna for ultrawide band applications

A small size, planar and co‐planar waveguide fed metamaterial inspired antenna is proposed for ultra‐wideband (UWB) application. The main radiating element consists of three split‐ring resonators (SRR) and placed along one axis. Moreover, coplanar waveguide (CPW)‐fed line along with modified ground plane is used to improve the impedance matching. The physical size of proposed antenna is 25(W) × 22 (L) × 1.6 (H) mm³. The CPW‐fed metamaterial inspired antenna provides bandwidth of 10.4 GHz from 3.1 to 13.5 GHz based on the 3:1 (voltage standing wave ratio [VSWR] <2). Over the range of UWB frequency, peak realized gain varies from 2.5 to 4 dBi. The proposed antenna provides omnidrectional radiation patterns. Further, fidelity factor of the proposed antenna is also calculated and measured. The calculated fidelity factor is suitable for UWB applications. Finally, prototype of the antenna is developed and tested using network analyzer. The simulated and measured results are in good agreement.     

Computer aided equivalent circuit model of SIW cavity backed triple band slot antenna

In this article, a study of planar triple band unidirectional Substrate Integrated Waveguide (SIW) cavity backed slot antenna using equivalent circuit model is presented. The proposed antenna uses a modified dumbbell shaped slot of much larger length placed in a planar SIW cavity to excite three closely spaced SIW cavity hybrid modes which help the slot to radiate into free space. The design is analyzed with the help of equivalent circuit model to predict the resonant frequencies of the design and also to explain the excitation mechanism of the proposed slot antenna. The proposed circuit model is validated by comparing its performance with the simulation model for a wide range of parametric variation. The relationship between modification in design dimension with the variation of coupling between feed line and cavity modes is studied which gives a design guideline for the proposed antenna. The fabricated prototype of the antenna resonates at 7.39, 9.43, and 14.79 GHz with a gain of 3.2, 4.9, 4.7 dBi and front‐to‐back ratio (FTBR) of 10 dB, respectively, at three resonant frequencies which makes it suitable for C (4–8 GHz), X (8–12 GHz), and Ku (12–18 GHz) band applications.     

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.     

Compact CPW‐Fed slot antenna with harmonic suppression

A compact coplanar waveguide (CPW)‐fed uniplanar antenna with harmonic suppression characteristics is presented. The above characteristics are achieved by properly modifying the ground plane and adjusting the signal strip of an open‐ended CPW‐fed transmission line. The simulated and experimental characteristics of the antenna are presented, compared, and discussed. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

Design of wideband antenna with band notch characteristics based on single notching element

In this article, a coplanar waveguide (CPW) fed planner monopole antenna with a compact size of 0.32λ × 0.30λ × 0.0056λ mm³ is presented. The radiator is fed with 50 Ω CPW feed line that provides impedance matching from 1.7 to 30 GHz for VSWR ≤2. In addition, three narrow bands are filtered out in the ultra‐wideband (UWB) range. The narrow notched bands are filtered for WiMAX (3.52‐4.2 GHz), WLAN (5.04‐5.40 GHz), and X band (8.22‐9.10 GHz) application. The rejecting bands are achieved by loading a single tri‐square ring resonator (SRR) on the backside of the feed line. The dimensions of SRR control the notch resonance frequencies. A single‐, dual‐, and tri‐notch frequencies have been achieved by using single‐, dual‐, and tri‐SRR, respectively. The measured results of antenna structures in the absence and presence of the SRR are compared with the simulations. The measured results validate the proposed design.     

Design and analysis of a quad‐band substrate‐integrated‐waveguide cavity backed slot antenna for 5G applications

A planar and compact substrate integrated waveguide (SIW) cavity backed antenna and a 2 × 2 multi‐input multi‐output (MIMO) antenna are presented in this study. The proposed antenna is fed by a grounded coplanar waveguide (GCPW) to SIW type transition and planned to be used for millimeter‐wave (mm‐wave) fifth generation (5G) wireless communications that operates at 28, 38, 45, and 60 GHz frequency bands. Moreover, the measured impedance bandwidth (|S₁₁| ≤ ? 10 dB ) of the antenna covers 27.55 to 29.36, 37.41 to 38.5, 44.14 to 46.19, and 57.57 to 62.32 GHz bands and confirms the quad‐band characteristic. Omni‐directional radiation characteristics are observed in the far‐field radiation pattern measurements of the antenna over the entire operating frequency. The reported antenna is compact in size (9.7 × 13.3 × 0.6 mm³) and the gain values at each resonance frequency are measured as 3.26, 3.28, 3.34, and 4.51 dBi, respectively. Furthermore, the MIMO antenna performance is evaluated in terms of isolation, envelope correlation coefficient and diversity gain.     

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.     

Design of ultrawide band planar inverted‐F antenna with slotted broad feed

This article presents a low ‐ profile planar inverted‐F antenna (PIFA) for broadband applications. The proposed antenna geometry is simple and does not use any parasitic elements, which makes its fabrication easier. The antenna's radiator is composed of a top loading plate, broad feed plate, and a shorting plate; occupies a total volume of (L × W × H ) 20 × 12 × 6 mm³. The proposed antenna design achieved the wideband characteristics by using the method of bringing resonances to proximity; furthermore, the low ‐ profile feature is achieved by removing some portion of the ground plane according to the volume ratio of PIFA. To validate the simulated results, an antenna prototype has been fabricated. The simulated and measured radiation patterns, gain, group delay, and simulated peak ‐ specific absorption rate (SAR) are presented. The measurement result demonstrates that the proposed antenna design achieved the maximum bandwidth of 142% (3.1–18.5 GHz) for |S ₁₁| ≤ ?10 dB.     

Design of multi‐band antenna for LTE wearable device with shared slots and radiators for smart watch

In this study, multi‐band antenna for LTE wearable device with shared slots and radiators for smart watch was present. This study incorporated 4G communication frequency bands, a GPS positioning system, and BT/Wi‐Fi in a 43.6 × 43.6 × 5.8 mm³ metal case to achieve satisfactory radiation fields and performance efficiency within a small space. This article presents an overview of the theory. There are four ports in the system. Frist, Port 1 is a low‐frequency antenna offering LTE 700 and GSM 850/900. The maximal gain and efficiency are respectively 3.9 dBi and 82%. Second, Port 2 is a high‐frequency monopole with a winding long path on the side of the frame to achieve a reflection loss bandwidth that fully encompasses GSM 1800/1900/UMTS and LTE 2300/2500. The maximal gain and efficiency of this port are respectively 5.3 dBi and 92%. There are also have GPS (Port 3) and Wi‐Fi (Port 4) antenna implement IFA and loop excitation mechanisms, respectively. This antenna system can fulfill the market demand. As confirmed through both simulation and measurement, the antenna can cover LTE bands. Increasing the path capacity of a MIMO system to increase the transmission speed is a crucial focus in mobile communication research and development.     

A wideband circularly polarized slot antenna with antipodal strips for WLAN and C‐band applications

A single‐fed circularly polarized square shaped wide slot antenna with modified ground plane and microstrip feed has been presented. The field in the slot is perturbed by introducing an antipodal strips section attached with a microstrip line to produce circular polarization in a wide band of frequencies. The antipodal strip section consists of a group of four strips of unequal length and separation. The presence of asymmetric perturbations in the slot is mainly responsible for exciting two orthogonal modes in the slot having equal magnitude and 90° phase difference which results in circular polarization. A wide bandwidth of 3.3 GHz (4.4 GHz‐7.7 GHz) has been achieved for an axial ratio value AR < 3 dB with the minimum axial ratio value being 0.3 dB. The impedance bandwidth for |S₁₁| < ?10 dB ranges from 4.3 GHz to 8 GHz, and therefore covers most of the C‐band communication systems. The antenna exhibits stable radiation patterns throughout the circular polarization bandwidth with a gain around 6 dBi in entire operational bandwidth. A prototype of antenna was fabricated and measured. The antenna has a planar size 0.40λ₀ × 0.40λ₀ and thickness of 0.02λ₀ where λ₀ is the wavelength in free space at the lowest frequency. With its compact size and low profile, the antenna is a favorable choice for WLAN (5.15‐5.85 GHz) and a wide variety of C‐band wireless applications.     

Design of dual‐mode dual‐band rectangular waveguide filtering antenna

A dual‐mode dual‐band rectangular waveguide filtering antenna with fourth‐order Chebyshev response is presented. First, design equations and processes of filtering networks are presented. Then, filtering antenna is constructed through cross‐shaped slot for radiation instead of the output port of filtering networks. A pair of degenerated modes are exploited in waveguide resonator design to miniaturize the whole size and form two passbands. In addition, the bandwidth can be adjusted flexibly in proper range. A prototype at C‐band is fabricated and measured, showing two operation channels of 5 to 5.05 GHz and 5.1 to 5.15 GHz with high rejection between two bands. Good agreement is achieved between the simulations and measurements, showing excellent performance in terms of filtering, out‐of‐band rejection, and gain in bands.     

Design of dual‐band microstrip patch antenna with right‐angle triangular aperture slot for energy transfer application

This work focusing on the dual‐band antenna design with rectifying circuit for energy transfer system technology for enhancement gain performance. The air gap technique is applied on this microstrip antenna design work to enhance the antenna gain. The work begins with designing and analyzing the antenna via the CST Microwave Studio software. After validation on acceptable performance in simulation side is obtained, the return loss, S₁₁ of the antenna is measured using vector network analyzer equipment. The rectifier circuit is used to convert the captured signal to DC voltage. This projected dual‐band antenna has successfully accomplished the target on return loss of ?44.707 dB and ?32.163 dB at dual resonant frequencies for 1.8 GHz and 2.4 GHz, respectively. This proposed antenna design benefits in low cost fabrication and has achieved high gain of 6.31 dBi and 7.82 dBi for dual‐band functioning frequencies.     

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.     

Penta‐band notched ultra‐wideband monopole antenna loaded with electromagnetic bandgap‐structures and modified U‐shaped slots

In this article, a planar monopole penta‐notched ultra‐wideband (UWB) antenna is designed and investigated. Three notches (2.81 GHz radar surveillance, 3.38 GHz WiMAX, and 3.87 GHz C‐band satellite downlink) have been realized by integrating three modified U‐shaped slots on the radiating surface. Furthermore, to create two additional notches (2.33 GHz ISM band and 5.75 GHz WLAN), two meander line electromagnetic bandgap (EBG); one located near to the feed line and another on the radiating surface, have been introduced in the design. These unit cells play a fundamental role in generating notches at higher as well as lower frequencies. The proposed antenna possesses an overall size of 34.9 × 31.3 × 1.6 mm³ and has been designed over FR4 substrate. A 50 Ω microstrip line is used to feed the antenna. The antenna without any extra arrangement exhibits an impedance bandwidth of 7.6 GHz. A parametric analysis is studied in detail to observe the band rejection characteristics. The ANSYS HFSS simulation software is used for simulating the proposed design structures. For validation purpose, a prototype is fabricated and characterized. A very good agreement is achieved between simulated and measured results.     

Design of a microstrip fed printed monopole antenna for bluetooth and UWB applications with WLAN notch band characteristics

In this article, a microstrip fed printed dual band antenna for Bluetooth (2.4–2.484 GHz) and ultra‐wide band (UWB; 3.1–10.6 GHz) applications with wireless local area network (WLAN; 5.15–5.825 GHZ) band‐notch characteristics is proposed. The desired dual band characteristic is obtained by using a spanner shape monopole with rectangular strip radiating patch, whereas the band‐notch characteristics is created by a mushroom‐like structure. The Bluetooth and notch bands can easily be controlled by the geometric parameters of the rectangular strip and mushroom structure, respectively. The proposed antenna has been designed, fabricated, and tested. It is found that the proposed antenna yields both the Bluetooth and UWB performance in the frequency regions of 2.438 to 2.495 GHz and 3.10 to 10.66 GHz, respectively for |S₁₁| ≤ ?10 dB with an excellent rejection band of 5.14 to 5.823 GHz to prevent WLAN signals. The experimental results provide good agreement with simulated ones. Surface current distributions are used to analyze the effects of the rectangular strip and mushroom. The designed antenna exhibits nearly omnidirectional radiation patterns, stable gain along with almost constant group delay over the desired bands. Hence, the proposed antenna is expected to be suitable for both Bluetooth and UWB applications removing the WLAN band. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:66–74, 2015.     

A dual‐band dual‐polarized cubical DRA coupled with new modified cross‐shaped slot for ISM (2.4 GHz) and Wi‐MAX (3.3‐3.6 GHz) band applications

In this article, a new modified cross‐shaped coupled cubical dielectric resonator antenna (DRA) has been investigated for dual‐band dual‐polarized applications. The linearly polarized (LP) fields in DRA has been generated by using a single slot in the ground plane and kept at either 45° (S_L1) or ?45° (S_L2) from the microstrip feed line. Combining these two slots (S_L1 and S_L2) in the modified ground plane, the proposed structure able to generate circularly polarized (CP) field in DRA. But the generated CP field is not enough to cover ISM 2400 band. To achieve CP in ISM 2400 band, an extra slot (S_L3) to the existing slots and an extra strip (S_T) in the circular ring feed line have been included. This modified final antenna arrangement has been able to produce LP (due to loading effect, ie, slot and DRA) and CP fields (orthogonal modes have been generated, ie, TE ^x₁₁₁ and TE ^y₁₁₁), simultaneously. The measured CP and LP, ?10 dB impedance bandwidths are 11.85% (2.38‐2.68 GHz) and 9.11% (3.25‐3.56 GHz) in combination with the 3‐dB axial ratio bandwidth of 4.11% (2.38‐2.48 GHz). The generated CP and LP fields are used for different wireless communication bands such as ISM 2400 and Wi‐MAX (3.3‐3.7 GHz) bands.     

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.