In this paper, a metasurface-based aperture-coupled circularly polarized (CP) antenna with wideband and high radiation gain is proposed and analyzed. The proposed antenna is comprised of coplanar waveguide coupling with 4 × 4 corner truncated square patches, which show compact size and low profile. The mechanism of the CP antenna is analyzed theoretically based on the mode analysis and equivalent circuit analysis. The parameters of feeding structure and truncated corner are studied and optimized to achieve wide impedance bandwidth (BW) and axial ratio (AR) BW. Finally, an overall size of 38.8 mm × 38.8 mm × 3.5 mm (0.71λ0 × 0.71λ0 × 0.064λ0 at 5.5 GHz) CP antenna is proposed and fabricated. The simulated results demonstrate that over 41.7% impedance BW (S11 < −10 dB) of 4.55–6.95 GHz and 3 dB AR BW of 5.05–6.15 GHz (fractional BW is about 19.6%) are achieved. In addition, the antenna yielded a broadside CP radiation with a high gain average about 7.5 dBic. Experimental results are in good agreement with the simulated ones.

A novel wideband circularly polarized printed antenna is proposed in this paper. It consists of asymmetrical ground and monofilar spiral stubs connecting to it. By employing an inverted L-shaped microstrip feedline to excite the slit etched in the ground and spiral stubs, a wideband culalry polarized performance of the proposed antenna is realized. After optimization, the measured results of the final structure demonstrate that a 10 dB bandwidth of 76.2% from 2.6 to 5.8 GHz and a 3 dB axial-ratio bandwidth for circular polarization of 72.9% from 2.7 to 5.8 GHz could be achieved which could completely cover the Wimax (3.3–3.8 GHz) band.

In this paper, a developed theory of a novel approach of the wave concept iterative process (WCIP) method is presented. This method is well used to demonstrate many attractive properties of metamaterials and to analyze metamaterial-based negative refractive index lenses by easy and speedy computation of the electromagnetic field distribution. These metamaterial-based circuits are established by using periodic L–C and C–L networks. The results of simulation using the proposed method are justified theoretically.

In this paper, multiple-input–multiple output (MIMO) antenna with dual-band frequency reconfiguration is presented. The proposed antenna consists of two symmetrical pentagon radiating elements. These radiating elements support bands of 1.5 GHz (GPS) and 2.4 GHz (Wi-Fi) frequency. The two PIN diodes are appropriately located on slot line in order to control the current flowing through the radiator. All simulated results are compared and confirmed with measured results. The antenna has VSWR ⩽1.8 and isolation of −28 dB. The advantage of this antenna is that bandwidth is increased by switching of PIN diode in the range from 80 MHz up to maximum 300 MHz. These characteristics demonstrate that proposed antenna is an attractive solution for a multimode application such as GPS, Wi-Fi routers, vehicular communication, etc. where wideband is required.

In this paper, a single-feed dual-frequency dual-linearly-polarized dielectric resonator antenna is proposed which finds application in two- way internet satellite system and modern radar system. In order to achieve dual linear polarization at distinct frequencies, two rectangular dielectric resonators of same dimensions are excited in ${\rm TE}^{x}_{\delta 11}$ and ${\rm TE}^{y}_{1\delta 1}$ modes by a narrow longitudinal and transverse slot, respectively, etched on the top wall of the substrate integrated waveguide. The −10 dB impedance bandwidth of the proposed antenna is 6.76% for both the frequency bands. The antenna radiates along the broadside direction and the gain of the antenna varies from 5.37 to 6.24 dBi and 5.62–7.96 dBi across 8.14–8.71 GHz and 10.29–11.01 GHz, respectively.

A compact coplanar waveguide (CPW)-fed circular polarization (CP)-antenna for new generation applications with dual bands filtering performance along with CP feature based on unit-cell semi-fractal is proposed in this paper. The CP-antenna privileges from semi-fractal radiator causes to have a miniaturized size. The stopped bands are designed to suppress the interference with present WLAN and ITU-R satellite systems. These properties are obtained by embedding semi-fractal unit-cell patterns stubs at the radiator and applying two rectangular-shaped slits inside CPW ground plane and a pair of grounded L-shaped strips. By introducing the first step of semi-fractal strips, and the mirrored defected ground surface structures, dual-band rejection functionality at WLAN (5–6 GHz) and ITU-R (7.725–8.5 GHz) are practically obtained. Besides that, semi-fractal strips results to two orthogonal modes stimulation on the radiator and CP attribute are obtained at WiMAX (3.1–3.7 GHz). CP-antenna presents omni-directional radiation H-plane patterns over the applicational frequency band. The CP-antennas size is 25 mm × 25 mm and fabricated on commercially available FR4-epoxy substrate with 1 mm thickness. Measured results illustrate that the proposed ultimate CP-antenna with miniaturized structure, efficient impedance tuning characteristics, and adequate radiation performances is the best choice for new generation of wireless communications.

In this paper, a four-way dual-band Gysel power divider (GPD)/combiner based on a back-to-back microstrip structure method is proposed and investigated. A two-layer substrate is adopted to implement this PD. In order to divide the input signal into four equivalent signals, the input and four output ports of the proposed PD are placed on the top and the four external isolation resistors are placed on the bottom layer of the substrate. Furthermore, the dual-band response is achieved by adding a short-circuit stub and an open-circuit stub to the structure. Then, the theoretical closed-form design formulas are derived based on the considered conditions and circuit transmission line theory. Finally, for verification purpose, a prototype PD is designed, fabricated, and measured which works at dual frequencies of 1 and 2 GHz simultaneously. The good agreement between simulation and measurement results, which show good impedance matching, isolation, as well as power transmission, verifies the correctness of the design theory.

This paper presents a procedure to model an ultra wide-bandwidth (UWB) microstrip monopole antenna. The proposed antenna is composed of three different lengths of semi-circular shapes connected with circular disk and half circular modified ground plane. The proposed antenna has a size of 50 × 50 mm2 on a low-cost FR4 substrate. The antenna demonstrates impedance bandwidth of −10 dB extended from 1.5 to 11 GHz with discontinuous bandwidth at different interior operating bands. Two pairs of split ring resonator as metamaterial structure cells are inserted closely located from feeding transmission line of the antenna to achieve good impedance matching over the entire band of operation and improve the antenna performance. The fundamental parameters of the antenna including reflection coefficient, gain, radiation pattern and group delay are obtained and they meet the acceptable UWB antenna standard. High-frequency structure simulator ver. 14 is used as full-wave electromagnetic solver then the prototypes are fabricated and measured. Results show that the antenna is very suitable for the applications in UWB as well as wireless communication systems.

This contribution deals with array elements for K/Ka-band satellite communication terminals. It proposes an end-fire design realized in substrate integrated waveguide technology and featuring dual-band functionality, and dual circular polarization. The latter is achieved by means of a dual-band orthomode transducer. An extended hemispherical dielectric lens ensures good matching and radiation properties. The feed structure is composed of a multilayer printed circuit board and tapered superstrates. The design procedure of the components is explained in detail and three different variants of the antenna are compared. The measured scattering and far-field parameters validate the concept.

This paper presents an active Q-enhanced LC dual-band band-pass filtering approach using parallel synthesis techniques at X- and Ku-bands in 0.13 µm SiGe BiCMOS technology. By employing two independently tunable parallel LC-tanks with either in-phase and out-of-phase addition, independently tunable dual-band filtering is achieved. For higher out-of-band (OOB) attenuation, subtraction of the two 2nd-order bandpass filter is implemented. The two bands are independently tunable in terms of Q and center frequency. The dual-band filter at 9.7 GHz and 13.9 GHz achieves a normalized dynamic range of 165–154.5 dB.Hz with an OOB attenuation of >50 dB below 3 GHz. In between the two bands, the attenuation is 22 dB when the two passbands have 200 MHz bandwidth each. The total group delay is 0.8 ns and 1.9 ns for Q of 20 and 50, respectively. The filter achieves better OOB rejection with wider band channels at X- and Ku-bands compared with state of the art integrated filters. The filter consumes 115–130 mW of DC power. The core die area is 0.53 × 0.7 mm2.

This paper presents a new technique for the enhancement of axial ratio (AR) bandwidth of a circularly polarized dielectric resonator antenna with a single feeding. To enhance the AR bandwidth, adjacent 3-dB AR passbands are merged by inserting the notches and conductive coating in the dielectric resonator. The dimensions of the notches and conductive coating are selected in such manner that impedance bandwidth remains approximately unchanged. The antenna provides the measured AR and impedance bandwidths of 55.22% and 66.45%, respectively.

By using a metasurface (MS) structure, a linearly polarized wave is converted to circularly polarized waves. Both right- and left-handed circular polarizations (RHCPs and LHCP) are obtained by a simple configuration in the proposed structure which consists of 16 unit cells arranged in a 4 × 4 layout. Each unit cell contains five horizontal and parallel strips embedded in a rectangular frame in which a single diagonal strip is placed from one corner to the opposed one. It is shown that the orientation of the diagonal line determines the handedness of the converted signal to be either LHCP or RHCP. In order to show the working conditions of the MS structure, scattering parameters are found for both co-polarized and cross-polarized responses. Axial ratio, an indicator for polarization conversion, is then obtained by dividing cross-polar response to co-polar response to demonstrate the transformation. The structure works for horizontally and vertically polarized linear waves in a wide band frequency range which is approximately 510 MHz. Since the suggested MS model is composed of a simple geometry for polarization conversion, it can be easily adjusted in any desired frequency bands for a variety of applications from the defence industry to medical, education, or communication areas.

In this paper, two new feed network designs for single layer and double layer slotted waveguide array antennas are presented. A microstrip to substrate integrated waveguide transition is applied to the single layer antenna. The aperture coupling mechanism is used in order to find the optimum feed network for double-layer structure and to obtain stable radiation characteristics over the frequency band. The prototypes of the proposed antennas have been fabricated and tested. The measured results were compared very well with the simulation results obtained from CST microwave studio and showed low side lobe level at the center frequency of 11.5 GHz for the low-profile 4-channel slotted waveguide arrays.