Design of planar slotted array antenna fed by single ridge waveguide

A straightforward design procedure for slotted antenna fed by single ridge waveguide is introduced. The proposed method does not use the analytical method to derive the general relation between the backward‐ and forward‐scattering dominant mode coefficients and slot voltage. In the proposed method, general relation connecting the backward‐ and forward‐scattering dominant mode coefficients to the slot electric field distribution is derived using available electromagnetic field simulator and by fitting some proper polynomials to the derived data. Then, the well known Elliott's design procedure for arrays of longitudinal slot in the broad wall of air filled rectangular waveguide is developed for the slot array feed by single ridge waveguide. A four‐by‐five array is designed and simulated which verify the design specifications and the proposed design procedure. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010.     

Double U‐slots patch antenna for tri‐band wireless systems

A compact microstrip patch antenna with two U‐slots shape is presented. Detailed simulation and experimental investigation are conducted to understand the behavior of the two U‐slots. The proposed antenna generates three resonant frequencies at 2.7, 3.3, and 5.3 GHz. It can, therefore, be used in Worldwide Interoperability for Microwave Access compliant communication equipment. The proposed antenna has two U‐slot shaped and two bridge elements to connect both shapes together to adapt the structure to the desired interest operating frequency. A comprehensive parametric study has been applied to understand the effect of each U‐slot on the antenna's performance. Moreover, the current distribution for the three bands is investigated to give further understanding of the antenna behavior. The proposed antenna is verified experimentally and the simulated and measured results are in good agreement. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010.     

A nonuniform array of slots in the broad‐walls of rectangular waveguides partially filled with dielectric slabs

This article describes a new nonuniform slot antenna array in the broad wall of rectangular waveguides partially filled with a dielectric slab. The slot elements are nonuniformly spaced to achieve a higher side lobe level while the amplitude and phase of their excitations are identical. Each slot element is fed by one dielectric‐loaded rectangular waveguide with one end shorted for structural simplicity. Experimental results for an 8‐element linear slot array operating at X‐band show that the side lobe level is 15 dB over a frequency range from 9.5 GHz to 10.5 GHz. The simulated side lobe level can reach 20 dB for a 16‐element linear array. Experimental results show that the side lobe level of a slot array can be improved using nonuniform element spacing without degrading the broadside radiation and gain. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.     

CPW‐fed C‐shaped slot antenna for broadband circularly polarized radiation

A novel broadband circularly polarized (CP) C‐shaped slot antenna fed by a coplanar waveguide is presented. The broadband CP operation can be achieved simply using a C‐shaped slot in the ground to produce orthogonal surface currents for left‐hand circular polarization. Using the semicircle‐shaped radiator patch, wide impedance bandwidth and broad axial‐ratio (AR) bandwidth can be obtained simultaneously. The measured results show that the proposed antenna can provide a 10‐dB impedance bandwidth of 105% from 2.78 to 8.92 GHz, and a 3‐dB AR bandwidth of 70.4% from 2.9 to 6.05 GHz. Finally, an antenna prototype with a reflector for unidirectional pattern applications is also developed. The proposed antenna has broader impedance and CP bandwidths but with a more compact size compared with the previous designs. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:739–746, 2015.     

Untilted slot array antenna at the narrow wall of the waveguide using double‐ridge

In this article a novel array antenna composed of untilted slots in the narrow wall of the double‐ridge waveguide, with significantly improved cross‐polarization, is presented. In the first step, suitable radiating elements for designing a linear slot array antenna were created. An untilted slot which is created the narrow wall of the double‐ridge waveguide is suggested to be used as the radiating resonance slot. The concave and convex ridges are located under the untilted slots only. It is shown that the concave and convex double ridge waveguides can produce an orthogonal current distribution in the place of the slots. They are also placed successively to produce the required phase inversion between adjacent slots. The linear array consists of nine uniform resonant untilted slots in the double ridge waveguide and is designed at the frequency of 5 GHz using the normalized conductance of each radiating slot. Analyzing the simulation results shows that cross‐polarization of the designed array was significantly improved, it was also found that the cross‐polarization and the SLL were respectively about ?65 and ?16 dB. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010.     

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.     

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.     

Application of wiggly ridge waveguide for design of linear array antennas of centered longitudinal shunt slot

A suitable radiating element for design of linear arrays of centered longitudinal shunt slot is proposed, which allows it to largely suppress the second order beams. The proposed radiating slot consists of a centered longitudinal slot, which is cut in the broad wall of a single wiggly ridge waveguide. The wiggly ridge is placed exactly under the slot and the wiggly part is in V‐shape. It is shown that by varying the wiggle depth of the proposed slot, the amount of power coupled to the slot can be adjusted. Some Stegen's like design graphs are obtained for the proposed slot. Then, two linear arrays consist of five and six elements are designed using the obtained graphs and by neglecting the mutual coupling between slots. The arrays have Dolph‐Chebyshev distribution with 20 and 30 dB of side lobe levels. For a better comparison between the proposed slotted arrays and the conventional longitudinal shunt slot arrays, two other slotted arrays in conventional topology and with the same specifications following the well known Elliott's design procedure are designed and simulated. Comparison of the simulated results shows that the second order beams of the designed array are effectively eliminated, while the other antenna specifications are also achieved. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.     

Centered inclined slot coupling between waveguides with coplanar axes

The article presents the method of finding the complete equivalent circuit of two waveguides with coplanar axes coupled through a centered inclined slot in the common broad wall. The variational method based on dyadic Green's function is used for finding the parameters of the equivalent circuit. A cosinusoidal aperture field distribution is assumed. Considerable mathematical simplification is resulted from replacing the centered inclined slot by an equivalent magnetic dipole. Coupling slot characteristics are deduced, including resonant length, dominant mode scattering in both the waveguides. Numerical and experimental results for resonant lengths and scattering parameters are presented over a range of tilt angles, frequencies, and waveguide dimensions. These results have significant applications in linear waveguide arrays and coupler design. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

Compact‐size linearly tapered slot antenna for portable ultra‐wideband imaging systems

A compact‐size asymmetrical linearly tapered slot antenna required for portable ultra‐wideband (UWB) imaging systems is presented. The total antenna size is reduced compared with the conventional linearly tapered slot antenna by using a triangular slot on the left‐hand side of the tapered‐shaped radiator, whereas introducing a corrugated pattern of cuts on the right side. The antenna operates over a wide bandwidth extending from 3.1 to 10.6 GHz with a maximum gain of 8.5 dBi. Stable radiation patterns are observed across the operational bandwidth, with cross‐polarization levels below ?20 dB. The realized antenna structure occupies a volume of 35 × 36 × 0.8 mm³, and possesses the essential time domain fidelity needed for UWB imaging applications. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013.     

Printed slot antennas for various wideband applications using shape blending

This article presents a novel design of wide slot antenna for various wideband applications created using a shape‐blending algorithm. The proposed printed antenna consists of a wide rectangular slot and a tuning stub, which is formed by blending the shapes of from a cross and a square. Various bandwidths can be obtained based on the structure with different blended shapes. The impact of the antenna geometry on the antenna performance has been investigated and analyzed in detail. To verify the proposed designs, six prototypes of slot antennas with various tuning stub shapes are designed, fabricated, and measured. The simulated results are compared with the measured performance and show good agreement. A bandwidth range from 38.5 to 126.4% for voltage standing wave ratio (VSWR) less than 2 is exhibited by selecting different blended shapes, which can be served as an antenna design guideline. Moreover, the proposed type of antenna has a compact size and a simple structure, which make it an excellent candidate for wideband applications. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:3–12, 2016.     

Wideband slot antenna using a new feeding technique for wireless applications

This article presents a new wideband slot antenna for wireless applications at 5.8 GHz. To improve the antenna bandwidth, a new feeding mechanism based on a capacitively‐ and inductively‐coupled slot is proposed. To demonstrate this approach, an experimental antenna prototype operating at the 5.8‐GHz band was designed, fabricated, and measured. The obtained results indicate very good agreement between the numerical and experimental results. The proposed antenna achieves a 28.5% bandwidth, a 5.7‐dBi gain, and a ?15‐dB front‐to‐back ratio, which are very sufficient for broadband wireless applications. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006.     

Slot line fed dual‐band dipole antenna for 2.4/5.2 GHz WLAN applications

A printed slot line fed dual‐band coplanar dipole antenna having a dimension of 0.40λ_g × 0.20λ_g suitable for both 2.4 and 5.2 GHz (IEEE 802.11 b/g and 802.11 a) WLAN application is presented. The structure comprises of a slot line fed symmetrical L strips to achieve dual‐band operation. Design equations of the antenna are developed and validated on different substrates. The simulation and experimental results show that the proposed antenna exhibits good impedance match, gain, and stable radiation patterns in both the frequency bands. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE , 2012.     

Microstrip‐fed cusp antenna for ultra‐wide band communication systems

A novel antenna for ultra‐wideband (UWB) applications is presented in this article. The proposed antenna consists of one circular patch placed on one side of a substrate and one circular slot placed on the other side. The antenna is fed with a microstrip line connected to the circular patch. The radii of the circular patch and slot and the separation between their edges represent the three design parameters which are optimized such that the antenna satisfies the design specifications. The proposed antenna has been fabricated using printed circuit board (PCB) technology. It has been characterized both theoretically and experimentally. The measured and calculated results are presented, compared, and discussed. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.     

Annular ring slot antenna design with reconfigurable polarization

A microstrip‐fed conventional annular ring slot (ARS) antenna with linear polarization (LP) is initially studied. To generate two orthogonal degenerate modes for circular polarization (CP) radiations, two identical meandering perturbation slots (MPS) are symmetrically loaded into the ARS. By further incorporating a PIN diode switch across each MPS, the proposed antenna can switch between left‐hand CP (LHCP), right‐hand CP (RHCP), and LP. All three polarizations have shown good impedance bandwidth and broad CP bandwidth that can satisfy the wireless local area network (WLAN) 2.4‐GHz operating band (2400–2480 MHz). Furthermore, desirable gains of 1.8–2.0 dBi and 2.40–2.84 dBic are also exhibited at LP and LHCP/RHCP, respectively. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:110–120, 2016.     

A microstrip antenna design with multislots embedded into the ground plane for circular polarization

A single probe‐fed square microstrip antenna with two pairs of asymmetric narrow slots loaded into the ground plane for circular polarization (CP) is studied. To allow a simple fine tuning CP mechanism, the method of loading an additional square slot into the center of the ground plane is introduced into this proposed antenna. By tuning the overall‐size of this center square slot, the CP frequency can be easily tuned with minor effects on the CP performances. Furthermore, good axial ratio (AR) value of around 0.5 is also measured at 1575 MHz, which is suitable for GPS operation. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE , 2013.     

Multilayered substrate integrated waveguide 4 × 4 butler matrix

In this article, a multilayered substrate integrated waveguide (SIW) Butler matrix beam‐forming network is proposed, designed, and demonstrated at 24 GHz for automotive radar system applications. The proposed low‐cost SIW structure can be used to develop a highly integrated multibeam antenna platform in automotive radar systems and other applications. In this structure, an SIW H‐plane coupler is optimized with an H‐plane slit to provide the required phase shift. A class of SIW E‐plane 3‐dB couplers in doubled layer substrate are studied and designed as the fundamental building blocks to avoid crossovers usually required in the construction of a Butler matrix. A 4 × 4 matrix is investigated and designed, which shows excellent performance over 22–26 GHz frequency band. Two types of antenna are tested with the proposed matrix scheme. First, an antipodal linearly tapered slot antenna (ALTSA) is incorporated into the Butler matrix to verify the broadband performances. Second, a longitudinal slotted waveguide antenna array is examined to generate radiation patterns in the broadside direction. Measured results agree well with simulated counterparts, thus validating the proposed multilayer SIW design concepts. In the next sections, the use as feeding networks for providing the reconfigurability operation of an antenna will be illustrated. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE , 2012.     

Annular‐ring slot antenna designs with circular polarization radiation

The design of a microstrip‐fed annular‐ring slot antenna (ARSA) with circular polarization (CP) radiation is initially studied. To obtain CP radiation with broad 3‐dB axial ratio (AR) bandwidth that can cover the WiMAX 2.3 GHz (2305–2320 MHz, 2345–2360 MHz) and WLAN 2.4 GHz (2400–2480 MHz) bands, a novel technique of extending an inverted L‐shaped slot from the bottom section of the annular‐ring is proposed. To suppress the harmonic modes induced by the CP ARSA, the technique of integrating a defected ground structure into the annular‐ring slot is further introduced. From the measured results, 10‐dB impedance bandwidth and 3‐dB AR bandwidth of 44.86 and 9.68% were achieved by the proposed harmonic suppressed CP ARSA. Furthermore, average gain and radiation efficiency of ～4.7 dBic and 71%, respectively, were also exhibited across the bands of interest. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:337–345, 2015.     

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.     

Employing irises and septums to excite the centreline longitudinal slot antennas

A suitable method is introduced to excite the centreline longitudinal slot antennas. For each slot, an iris and a rectangular septum are employed at the opposite sides of the slot such that they have offset from the waveguide centreline. It is shown that to form a high performance slotted array antenna consists of the centreline longitudinal antennas, employing antenna elements where each of them is excited only by an iris or a septum is not advisable. So, employing an iris and a septum all together is proposed to excite the centreline longitudinal slot antennas. This enables one to have a better control over the characteristics of the proposed slot antennas. The performed study indicates that the proposed slot antennas can be modelled as a shunt admittance on a transmission line. In order to demonstrate the effectiveness of the proposed slot antennas, a two‐by‐three planar array is designed, constructed and tested. The efficacy of the proposed slot antennas is verified by the simulation and the measurement results.