A broadband slant polarized cavity backed microstrip‐fed wide‐slot antenna array

This article deals with the design of a broadband cavity‐backed microstrip‐fed wide‐slot antenna array for L‐band applications. For verification purpose, a sample 1 × 4‐element antenna array has been designed, manufactured and tested. Experimental results have shown satisfactory agreement with the simulation. The proposed antenna array exhibits a measured impedance bandwidth of 1.4 GHz (90%) with frequency of 0.85 to 2.25 GHz and the gain is higher than 11 dBi. The designed antenna has small size and low weight and can be fabricated using a low‐cost fabrication process for easy integration with RF circuits and microwave components. This work is useful for some radar applications and radio frequency identification systems.     

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.     

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.     

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 novel substrate integrated waveguide cavity‐backed self‐diplexing antenna array with frequency beam scanning characteristic

This article presented a substrate integrated waveguide (SIW) cavity‐backed self‐diplexing antenna array with frequency beam scanning characteristic. The proposed array consists of 16 SIW cavity‐backed slot antennas. The SIW cavity‐backed slot antenna can be fed by two separate ports to resonate at two different frequencies and achieve high isolation better than 20 dB between two input ports. The proposed element is a typical self‐diplexing antenna. These cavity‐backed slot antennas are shunt‐fed by a compact 1 to 16 SIW power divider and series‐fed by a set of microstrip lines, respectively. As a result, this array achieves an unidirectional radiation pattern at 10.2 GHz with high gain of 15.10 dBi, and a frequency beam scanning characteristic from 7.0 to 9.0 GHz ranging from ?50° to 46°.     

Substrate integrated waveguide based cavity‐backed self‐triplexing slot antenna for X‐Ku band applications

A planar substrate integrated waveguide (SIW) based cavity‐backed self‐triplexing slot antenna is proposed for X‐Ku band applications. The antenna comprises of the SIW cavity, radiating slots, and feeding networks. The radiating slots; that are etched on the upper metallic plane of the SIW, are backed up by the three radiated quarter cavities (QCs). The radiating slots in the respective QCs are of different lengths, excited by three separated orthogonal feed lines to resonate at three different frequencies as 11.01, 12.15, and 13.1 GHz. By fine‐tuning the antenna parameters, an intrinsic input port isolation of better than 26 dB is realized which helps in achieving the self‐triplexing property. The behaviors of individual cavity modes at three resonant frequencies are explained with the help of Z‐parameter. The proposed antenna layout is easy to integrate with the planar circuit. The proposed antenna is fabricated and measured results display a close concern with the simulated results. Moreover, a unidirectional radiation pattern and gain of 5.1, 5.54, and 6.12 dBi at resonant frequencies are realized.     

A novel suspended stripline‐fed printed square slot array antenna with high‐gain

A novel suspended stripline‐fed square slot array antenna with high gain is presented. Its basic structure is a suspended stripline comprising of three layers. On the top layer, 4 × 4 square slots are etched and act as radiation elements. The middle layer consists of a suspended stripline power divider, and the bottom layer is a metal ground. After optimization by a parallel Genetic Algorithm (GA) on a cluster system, a prototype antenna is fabricated and tested. The measured results agree well with the simulated data, and show a high gain of 18.7 dBi and an impedance bandwidth of 5.7% for S11<‐10 dB are obtained. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.     

Low‐profile substrate integrated waveguide (SIW) cavity‐backed self‐triplexed slot antenna

A low‐profile self‐triplexed slot antenna is proposed for multiple system integrations. The antenna comprises of hybrid substrate integrated waveguide (SIW) cavity (a combination of a half‐mode circular and half‐mode rectangular SIW), radiating slot, and feeding network. A slot is imprinted on the upper metal‐layer of the SIW which splits the cavity into three radiating sections. It offers tri‐frequency bands when each section is excited separately. By finely tuning the antenna dimensions, it produces three frequency‐bands around 5.57, 7.17, and 7.65 GHz simultaneously utilizes a single slot with maintaining the intrinsic input‐port isolation better than 20 dB. This property helps to introduce the self‐triplexing phenomenon. Compared with the conventional multiband antennas that use an extra circuitry to ensure the port isolations, this design preserves compactness and easy to integrate with planar circuits Moreover, the proposed antenna is fabricated and the measured results mutually agreed with the simulated counterparts. The proposed design can be a feasible option for mobile transceiver applications.     

High gain substrate integrated waveguide beam scanning antenna with sub‐array elements

A method to enhance the gain of substrate integrated waveguide (SIW) beam scanning antenna is proposed in this article. 2 × 2 SIW cavity‐backed sub‐arrays are employed in array design. The antenna is constructed on two layers. The top layer places four SIW cavity‐backed sub‐arrays as radiating elements and the bottom layer is an SIW transmission line to feed the sub‐arrays. Beam scanning feature can be obtained due to the frequency dispersion. Moreover, through separating radiators to the other layer and using 2 × 2 SIW cavity‐backed sub‐arrays as radiating parts, the antenna gain is improved significantly. For a linear array, 4.1 to 6.8 dB gain enhancement is achieved compared to a conventional SIW beam scanning antenna with the same length. Then, the linear array is expanded to form a planar array for further gain improvement. A 64‐element planar beam scanning array is designed, fabricated, and tested. Experimental results show that the proposed planar array has a bandwidth from 18.5 GHz to 21. 5 GHz with beam scanning angle from ?5° to 11.5° and gain in the range of 20.5 to 21.8 dBi. The proposed high gain beam scanning antennas have potential applications in radar detection and imaging.     

Compact tri‐band MIMO antenna based on quarter‐mode slotted substrate‐integrated‐waveguide cavity

A compact tri‐band multiple‐input‐multiple‐output (MIMO) antenna based on a quarter‐mode slotted substrate‐integrated‐waveguide (SIW) cavity is proposed. By etching a wide slot, a single SIW cavity is divided into two sub‐cavities with the same size. They are fed by coaxial ports to form two MIMO elements and high antenna isolation can be achieved by this slot. To obtain multi‐band operations, two narrow slots are cut in the upper sub‐cavity and the other two slots are etched in the lower sub‐cavity. Three eighth‐mode resonances with different areas can simultaneously occur in these antenna elements. A prototype with the overall size of 0.34λ₀ × 0.34λ₀ has been fabricated. The measured center frequencies of three operating bands are 2.31, 2.91, and 3.35 GHz, respectively. The measured gain at above frequencies is 4.52, 4.29, and 4.57 dBi, respectively. Moreover, the measured isolation is higher than 16.7 dB within the frequency of interest.     

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.     

Compact bilayer substrate integrated waveguide leaky wave antenna with dumbbell‐shaped slot based on the TE20 mode

In this article, a compact dual layer leaky wave antenna array is simulated and constructed using the substrate integrated waveguide (SIW) based on the TE₂₀ mode at the X‐ and Ku‐bands. The proposed antenna is designed by creating dumbbell‐shaped slots on the upper layer of the SIW. These slots have increased the antenna bandwidth so that the proposed antenna has a bandwidth of 9.5 to 13.7 GHz and a fractional bandwidth of 36%. In addition, to excite the TE₂₀ mode, an SIW power divider is used in the feeding network of the antenna located in the bottom layer. Moreover, the gain and directivity are other advantages of the proposed antenna so that at 12.5 GHz the antenna peak gain reaches to 15.7 dB. Antenna beam scanning angle is from 5° to 81°. This antenna is simulated and analyzed by the CST Microwave Studio software. The obtained results from the antenna test lab confirm the simulation results.     

A compact substrate integrated waveguide backed self‐quadruplexing antenna for C‐band communication

This article presents a simple, compact, and lightweight substrate integrated waveguide (SIW) backed self‐quadruplexing antenna for quad‐band applications. The design procedure is straightforward. Topside of the SIW cavity is modified to form four patches of different lengths which are fed separately by four 50‐Ω microstrip feed lines and operate at 5.14, 5.78, 6.74, and 7.74. It attains 4.1, 4.96, 6.2, and 6.1 peak gain at the above frequencies, respectively. The observed front‐to‐back‐ratio is more than 17.5 dB and the isolation level is above 28 dB. This antenna topology allows to redesign each resonant frequencies as per application requirement using a single parameter and without disturbing other performances. Design guidelines for developing the proposed antenna are provided. A prototype antenna is fabricated using RT‐Duroid (5870) substrate and characterized for validation. The proposed antenna is suitable for handheld microwave devices for C‐band communication.     

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.     

Compact four‐element MIMO SIW cavity backed slot antenna with high front‐to‐back ratio

In this article, a novel design of single layer, compact, multiple input multiple output (MIMO) half‐mode substrate integrated waveguide (HMSIW) cavity backed quad element slot antenna with high front‐to‐back ratio (FTBR) is proposed. The proposed antenna consists of four rectangular SIW cavities with semi‐taper radiating slots. The antenna elements are placed in a fashion to achieve high isolation. This antenna is designed for WLAN vehicular communication system to cover the frequency range of 5.84 GHz to 5.96 GHz. It has high front to back ratio (FTBR) of more than 25 dB without using any external metallic reflector. It has more than 37 dB isolation in between orthogonal elements and more than 24 dB in between parallel elements. The envelop correlation coefficient (ECC) and diversity gain are 0.003 and 9.99 dB respectively in between all the elements. Moreover, the antenna has high gain and efficiency of more than 8 dB and 94%, respectively, in 10 dB impedance bandwidth. It can be tuned in a wide range of frequency.     

High‐gain waveguide slot antenna using simple parasitic patch's cover

In this article, a way based on using miniature patch cells has been proposed to increase gain and bandwidth of the waveguide slot antenna. In the presented approach, an array of 3 × 3 metal patches has been used as superstrate to create Fabry Perot theorem resonance cavity. The proposed high ‐ gain and simple antenna is composed of a conventional waveguide slot antenna with an extended broad wall, and an array of parasitic patches which are symmetrically placed over slot at a distance of about free ‐ space half wavelength. The slot has been created on a rectangular waveguide WR90 with 22.86 mm × 10.16 mm × 52.5 mm dimension, also extended wall dimension is 2λ₀ (67.5 mm) × 3λ₀ (107 mm). It has been shown that the proposed structure compared with the conventional waveguide slot antenna improves antenna peak gain from 6.5 to 16.5 dBi and, in the same time, antenna bandwidth from 11% to around 16.2%. More important advantage of the proposed antenna is that unlike to other Fabry Perot antenna with the same gain, there is not any dielectric material in the proposed structure. A prototype antenna was simulated, fabricated, and measured for verification.     

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.     

A compact substrate‐integrated‐waveguide monopulse slot antenna array with TE20 mode

A compact substrate‐integrated‐waveguide (SIW) monopulse slot antenna array with T_E20 mode is proposed, manufactured, and tested in this communication. The TE₂₀ mode electric field distribution is used in this antenna design. The phase difference required by the monopulse system is constructed by changing the orientation of the end of the top microstrip feed line. The microstrip line implements not only the feed function, but also the function of a monopulse comparator. The design greatly reduces the size of the monopulse comparator and the feed network, and improves the aperture efficiency of the antenna. Our measurement shows that the operating frequency of the antenna is 10.4 GHz, and the maximum gain of the sum beam is 13.7 dBi, and the difference beam null depth is ?26 dB. The antenna has the advantages of simple structure, small size, and easy integration of planar circuits. This proposed idea can open new ways for monopulse antenna design.     

Millimeter‐wave planar high gain SIW antenna using half elliptic radiation slots

This article reports a high gain millimeter‐wave substrate integrated waveguide (SIW) antenna using low cost printed circuit board technology. The half elliptic slots which can provide small shunt admittance, low cross polarization level and low mutual coupling are etched on the board surface of SIW as radiation slots for large array application. Design procedure for analyzing the characteristics of proposed radiation slot, the beam‐forming structure and the array antenna are presented. As examples, an 8 × 8 and a 32 × 32 SIW slot array antennas are designed and verified by experiments. Good agreements between simulation and measured results are achieved, which shows the 8 × 8 SIW slot array antenna has a gain of 20.8 dBi at 42.5 GHz, the maximum sidelobe level of 42.5 GHz E‐plane and H‐plane radiation patterns are 22.3 dB and 22.1 dB, respectively. The 32 × 32 SIW slot array antenna has a maximum measured gain of 30.05 dBi at 42.5 GHz. At 42.3 GHz, the measured antenna has a gain of 29.6 dBi and a maximum sidelobe level of 19.89 dB and 15.0 dB for the E‐plane and H‐plane radiation patterns. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:709–718, 2015.     

Broadband high‐gain slot grid array antenna for millimeter wave applications

A broadband high‐gain slot grid array antenna (SGAA) is proposed in this paper. Based on the electromagnetic complementarity principle, the metal elements in the traditional microstrip grid array antenna (GAA) are replaced by a wide slot element. Compared with the GAA, the proposed SGAA achieves broadband and high‐gain performance. In order to demonstrate this concept, a prototype with 9‐element SGAA is designed using wide slot radiation elements and fabricated on Rogers 5880 printed circuit board (PCB) substrates, which is fed by a 50 Ω coaxial probe. The measured and simulated results show a good agreement. The proposed SGAA achieves a measured peak gain of 14.8 dBi at 26.0 GHz, a 10‐dB impedance bandwidth from 22.2 to 28.5 GHz with a fractional bandwidth of 24.9%. These results indicate that the SGAA is with high performance and it is suitable for the fifth‐generation (5G) millimeter wave (mmW) wireless communication system.