A substrate integrated cavity‐fed dual‐polarized filtering patch antenna with high isolation

This article presents a dual‐polarized filtering patch antenna, which uses two orthogonal modes (TE₂₁₀/TE₁₂₀) of the substrate integrated cavity (SIC) to couple with two orthogonal modes (TM₁₀/TM₀₁) of the patch by the cross slot, respectively. The second‐order filtering response on dual polarizations can be achieved by using just one SIC resonator and one slotted square patch, which display simple structure of the proposed antenna. The slotted square patch provides a new way to obtain same external quality factor of the radiator on dual polarization, which makes the performances on two polarizations agree well with each other when changing the bandwidth. High isolation can be achieved by controlling the space of the vias of the SIC. Radiation nulls can be produced by connecting the coupled lines with the feeding lines in parallel. A prototype with the entire height of 0.019 λ₀ (λ₀ is the free‐space wavelength at center frequency) achieves a 10‐dB bandwidth of 1.6%, the gain of 4.9 dBi at the center frequency, the port isolation of 43 dB, and the out‐of‐band rejection level of 25 dB.     

A novel millimeter‐wave dual‐band circularly polarized dielectric resonator antenna

In this article, a novel dual‐band circularly polarized (CP) dielectric resonator antenna (DRA) for millimeter‐wave (MMW) band is presented. The rectangular dielectric resonator with layered truncated corners is excited by a microstrip‐coupled cross‐slot. CP radiations in the lower band are realized by utilizing two quasi‐TE₁₁₁ modes operating at 21.7 GHz and 23.8 GHz, while CP radiations in the upper band are obtained by exciting a quasi‐TE₁₁₃ mode at 28.2 GHz. The dual‐band DRA is fabricated and measured. Due to the higher order mode, the average gain of the DRA in the upper band is about 3 dB higher than that in the lower band. The measured impedance bandwidths (|S₁₁| < ?10 dB) are 17.0% (20.5‐24.3 GHz) and 15.2% (26.1‐30.4 GHz), while the measured axial ratio (AR) bandwidths (AR < 3 dB) are 12.8% (21.2‐24.1 GHz) and 5% (27.4‐28.8 GHz). In addition, the peak gain values are 5 and 8 dBic.     

Empirical design formulae for series‐fed substrate integrated waveguides power divider

In this article, empirical design formulae for a unit cell of series‐fed substrate integrated waveguide power divider for a wide range of power division ratio from 1:1 to 1:40 are presented. These formulae are determined through extensive simulations carried out in Ansys HFSS. The physical dimensions of the power divider for any given power division ratio can be directly determined through the design formulae presented in the article. A simple design procedure is discussed and verified with the help of experimental and simulation results. For experimental verification, a power divider is designed to operate in X band, and its prototype is developed on RT Duroid 5880, the measured results for this power divider are in close agreement with simulated as well as predicted results. Also, for validating the design procedure over a wide range of frequencies, many power dividers are designed with different power division ratios, different operating frequencies and different cut‐off frequencies of TE₁₀ mode. The cut‐off frequency (f_c) of TE₁₀ mode is varied from 15 to 25 GHz, and the operating frequency is adjusted in between 1.2f_c and 1.8f_c. That is, 18–40 GHz, which is suitable for many microwave and millimeter wave applications. The obtained results are very close to the desired power division ratios.     

Wideband dual‐polarized hybrid fed patch antenna

A broadband dual‐polarized patch antenna with hybrid feed structure is proposed in this article. Two different feeding mechanisms are designed to excite two orthogonal modes on a single radiating patch. One of the modes is excited by a magnetic‐coupled feeding structure, while the other is excited by an electric‐coupled feeding structure. The magnetic‐coupled feeding structure consists of a metallic loop with a gap and an open‐ended transmission line. The electric‐coupled feeding structure is composed of a series capacitor and an impedance transformer, which realizes 180° phase shifting. Measured results show that the proposed antenna has 52.3% (1.63~2.78 GHz) and 47.3% (1.68~2.72 GHz) impedance bandwidth with return loss (RL) > 10 dB for port 1 and port 2, respectively. Owing to the hybrid feed structure, the isolation between two ports is better than 26.5 dB. The proposed antenna is suitable for modern wireless communication systems.     

Planar integrated substrate integrated waveguide circularly polarized filtering antenna

A new design of substrate integrated waveguide (SIW) circularly‐polarized (CP) filtering antenna is presented, which is based on dual‐mode (TE₁₀₂ and TE₂₀₁) cavities. The satisfying filtering performance of the antenna is realized by a coupled‐resonator circuit of two dual‐mode SIW cavities. And the radiating element of the antenna is a cavity‐backed CP slot antenna which is formed by a nonuniform ring slot integrated with the back cavity. To demonstrate the idea, a prototype antenna operating at X band is designed, fabricated, and measured. Measured results show that the 10‐dB impedance bandwidth is 4.2% (from 11.6 to 12.1 GHz), the 3‐dB axial‐ratio (AR) bandwidth is 4%, and the gain is 5.6 dBi at the center frequency of 11.8 GHz.     

A dual‐polarized cross‐dipole antenna with wide beam and high isolation for base station

In this paper, a dual‐polarized cross‐dipole antenna with wide beam and high isolation is designed and analyzed for base station. The proposed antenna consists of two planar cross dipoles with four square patches, two L‐shaped microstrip lines, two ground plates, four parasitic patches, and a reflector. The square patches are placed between the center of cross dipoles to couple with L‐shaped microstrip lines. By introducing the parasitic patches, the wide beam can be realized. The measured results show that the proposed antenna achieves an impedance bandwidth (|S₁₁| < ?10 dB) of about 18.7% (1.9‐2.35 GHz) and an isolation better than 30 dB. A measured gain of 5.7 dBi and a half‐power beamwidth over 120° at the center frequency are obtained. Furthermore, the size of the proposed antenna is only 0.5λ₀ × 0.5λ₀ × 0.22λ₀ (λ₀ is wavelength at the center frequency).     

Compact dual‐polarized dipole antenna with high isolation using hybrid balun circuit

In this article, a crossed dipole antenna with compact size (43 × 43 mm²) and high isolation (42 dB) is proposed using a hybrid balun circuit. The hybrid balun consists of a tapered balun and a Marchand balun. The tapered balun transforms the microstrip line into the parallel feeding lines for one pair of dipoles, and the Marchand balun transforms the stripline transmission line into a couple of out‐of‐phase feeding lines for the crossed pair of dipoles. Due to the low coupling between two different baluns, a high isolation of the antenna can be achieved when the crossed dipole antenna is cascaded with the hybrid balun. Moreover, these two baluns can improve impedance matching and therefore further miniaturize the size of the crossed dipole antenna. The impedance matching of two baluns can be controlled and adjusted independently. As a result, the proposed dual‐polarized antenna has the bandwidth of 1.7 to 2.8 GHz for S11 < ?15 dB with compact size and high isolation. The proposed antenna with the hybrid balun circuit are fabricated, and the simulated and measured results meet well.     

Low‐profile omnidirectional circularly polarized antenna based on substrate integrated waveguide technology

A substrate integrated waveguide (SIW) circularly polarized (CP) antenna with omnidirectional radiation in the azimuthal plane is proposed. The antenna consists of five identical end‐fire CP antenna elements in a pentagonal array configuration, which is loaded on a circular substrate. Each element contains an H‐plane horn antenna in SIW structure and a printed dipole antenna. Five parasitic curve elements are introduced to improve the omnidirectional property of the antenna. Combined with complementary dipoles theory and SIW technology, prototype antenna is designed, fabricated and measured. With a low profile of 0.024λ₀, the antenna has a 10‐dB return‐loss impedance bandwidth of 4.08% (2.4～2.5 GHz) and a 3‐dB axial‐ratio (AR) bandwidth of 5.76% (2.36～2.50 GHz). The antenna works well in the 2.45 GHz ISM band, with good cross‐polarization and excellent omnidirectional property.     

Millimeter‐wave wideband circularly polarized monopulse antenna using the sequential rotation feeding technique

This article presents the design and implementation of a single‐layer wideband millimeter‐wave circularly polarized (CP) monopulse cavity‐backed antenna based on substrate integrated waveguide (SIW) technology. The antenna consists of a 2× 8 array of CP cavity‐backed antenna elements, a 90° 3‐dB coupler, power dividers, and phase shifters. In order to enhance the operating bandwidths, the sequential rotation feeding technology is adopted in the design of the monopulse antenna. To validate the proposed concept, a prototype operating at 42 GHz was fabricated and measured. The measured 3‐dB axial ratio (AR) bandwidth for the sum beam can cover a frequency range from 37 to 46 GHz. The measured gain for the sum beam at the center frequency of 42 GHz is 17.5 dBiC, while the null‐depth of the difference beam is measured to be ?36.8 dB. The proposed monopulse antenna has advantages of low‐cost, easy‐fabrication, and easy integration with planar circuits.     

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.     

Recent advances in theory and applications of substrate‐integrated waveguides: A review

The use of substrate integrated waveguides (SIW) for microwave and millimeter wave integrated components has increased dramatically over the last decade. They mimic the performance of conventional metallic waveguides and they are fabricated using printed circuit boards using the top and bottom metallization with two rows of vias forming the side walls. This creates a low profile, compact, and light weight alternative to conventional metallic waveguides, and they allow a direct interconnection with printed circuit boards and active components. This article reviews the fundamental theory, documents the research that has been performed over the past decade, and summarizes progress up to the recent state‐of‐the‐art including novel SIW structures for passive circuits and antennas as well as new applications for reconfigurable and printed circuits using SIW technology. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:129–145, 2016.     

A dual band leaky wave antenna based on modified substrate integrated waveguide

In this article, a new leaky wave antenna (LWA) based on modified substrate integrated waveguide (SIW) is introduced. At first, the modified SIW structure is presented and it is shown that it supports propagation of quasi‐TEM with nearly uniform electric field distribution. Then, a new cell based on diagonal‐shaped slots embedded on top surface of the structure is introduced and its dispersion characteristics and its different radiation regions are determined. A LWA made of 15 unit cells is designed and a prototype of the antenna is fabricated. The proposed LWA is simulated using a software package and its radiation characteristics are also measured. It is shown that a good agreement is obtained between simulated and measured results and two frequency bands are obtained. In the frequency range of 7 GHz to 8.25 GHz, it radiates in forward region with maximum gain of 11.3 dB and scan angles from 54° to end‐fire. In addition, it radiates in backward region from ?70° to broadside from 14 GHz up to 20 GHz with maximum gain of 16.47 dB. High gain, compactness, and wide scan angles are the advantages of the proposed LWA.     

High isolation dual‐frequency patch antenna integrated with cascade defected microstrip structure

This article presents a high‐isolation dual‐frequency rectangular patch antenna utilizing microstrip feed line integrated with a cascade defected microstrip structure (CDMS). Two types of CDMS are added, T‐shaped CDMS and Dumbbell‐T‐shaped CDMS. Simulation results show using these structures improve isolation up to 70 dB and reduce harmonic signals from transmitter. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

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.     

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.     

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.     

Dual‐band beam scanning filtering antenna using dual‐eighth mode substrate integrated waveguide‐based metamaterial structure

In this article, a dual‐band beam scanning antenna with filtering capability is proposed by using novel dual‐eighth mode substrate integrated waveguide‐based dual‐band metamaterial (DB‐MTM) structure. The novel DB‐MTM structure consists of two interconnected modified eighth mode substrate integrated waveguide (EMSIW) structures, which is designed by etching four interdigital fingers on the upper ground, and has two balanced composite right/left‐handed (CRLH) passbands. Taking advantage of the continuous phase constant changing from negative to positive values within the two CRLH passbands of the DB‐MTM structure, a beam scanning antenna, which is composed of 11 dB‐MTM unit cells, is designed to achieve continuous beam scanning from backward to forward directions within dual operating frequency bands. For verification, the proposed dual‐band antenna is fabricated and measured. According to the measurements, the fabricated antenna can scan its main beam from ?72° to +57° and ?70° to +38° over the two operating frequency bands of 3.40‐4.95 GHz and 5.85‐6.80 GHz, respectively; and exhibits very sharp transitions at the band edges over the two operating frequency bands. Besides, the measured peak gains in the two operating bands are 14.0 dB at 4.5 GHz and 14.5 dB at 6.4 GHz. Moreover, the measurements show good agreement with the simulations, proving the validity of the design method, and further expanding the applications of EMSIW.     

3D‐printed high‐gain circularly polarized antenna for broadband millimeter‐wave communications over the power line

It is well known that high transmission loss occurs when millimeter waves traveling through the atmosphere. As an alternative, power line is proposed as a transmission media to combat the high loss. In this article, a three‐dimensional (3D) printed high‐gain circularly polarized antenna was proposed for millimeter‐wave broadband power line communications. It has a simple structure, where tapered slots are designed between the upper and lower layers of the waveguide to generate the circularly polarized operation. A wide impedance bandwidth of 31.58% (24‐33 GHz) and an axial ratio bandwidth of 28.07% (24.5‐32.5 GHz) are achieved by the proposed design. A maximum gain of 11.2 dBi is measured from the 3D printed structure. The proposed antenna has a simple structure which is easy to adjust to any working frequency. The antenna can be excited by properly integrated to the waveguide that connected to the power line end. The use of 3D printing technology enables a low‐cost solution millimeter‐wave broadband communications over the power line.     

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.     

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.