Fractal array antenna design methodology is an artistic type of design methodology. Hence fractal array antennas are also called as artistic array antennas. This article proposed a concentric elliptical ring sub array generator geometric design methodology for a methodical expansion of multi-beam fractal array antennas. Using this new geometric design methodology any polygon shape can be constructed. This geometric design methodology provides a systematic approach for multiple beams of fractal array antennas, with unit amplitude constriction, using multi-beam sub arrays and without any increase in hardware complication. In this paper, a four element rhombus fractal array antenna examined using a proposed design methodology up to four concurrent iterations and for different eccentric values. Due to the recursive nature of the proposed methodology, the rhombus fractal array antenna shows multi-beam performance with abatement of beam width and better side lobe level. In the third and fourth iterations of rhombus fractal array for expansion factor two, beam width reached to single digit values of 7.2˚, 3.6˚ with side lobe level angles of 15.5˚ and 8.1˚ respectively. The behavior of the proposed array shows better performance than four element fractal array antenna generated by concentric circular sub array generator. Proposed fractal array antennas are analyzed and simulated by MATLAB programming.

The problem of axially-symmetric TM-wave diffraction from a perfectly conducting bi-cone is analyzed. Bi-cone is formed by finite and semi-infinite conical shoulders and illuminated by ring magnetic source. The problem is formulated in a spherical coordinate system as a mixed boundary problem for Helmholtz equation. The unknown H_φ-diffracted field is sought as expansion in series of eigenfunctions for each region, formed by the bi-cone. The solution of the problem then is reduced to the infinite set of linear algebraic equations (ISLAE) of the first kind by means of mode matching technique and orthogonality properties of the eigen functions. The main parts of the asymptotic expressions of ISLAE matrix elements, determined for large indexes, identify the convolution type operator. The corresponding inversed operator is represented in an explicit form. Two of these operators are applied to reduce the problem to the ISLAE of the second kind and to determine the new analytical regularization method for the solution of wave diffraction problems for bi-conical scatterers. The unknown expansion coefficients can be determined from the ISLAE with the given accuracy by the reduction method. The particular cases such as low frequency approximation and transition from bi-cone to conical monopole and disc-cone scatterer are analyzed. The numerically obtained results are applied to the analysis of scattering properties of hollow conical monopoles and disc-conical scatterers.

A single stage 900 MHz power amplifier (PA) with linearization bias circuit is designed with HHNEC 0.5 μm BIS500G power SiGe BiCMOS process. It is implemented by single-ended common emitter structure as a class AB power amplifier. The adopted active bias circuit is originally explained by using two virtue current sources, so that the mechanism of the improvement of linearity can be described more clearly. Then the mechanism is applied to guide the design of a power amplifier with an active bias circuit, which shows better linearity than resistor biased power amplifier by simulation. Through further design and measurement, the fabricated single stage power amplifier exhibits output power 1 dB compression point (OP1 dB) of 18.9 dBm, with power added efficiency (PAE) of 26.75% and power gain of 20.9 dB under 3.3 V voltage supply.

A frequency selective surface (FSS) with polarization rotation which provides a quasi-elliptic bandpass response is presented in this paper. Based on substrate integrated waveguide cavity (SIWC), 90 degrees polarization rotation is obtained when electromagnetic wave passes through the frequency selective surface at specially appointed polarization in a range of 16.28-16.70 GHz. Moreover, TM₁₂₀/TM₂₁₀ dual-mode configuration appears in the cavity within the passband. The design has been proved with high stability to electromagnetic wave of different incident angles. And the measured results in anechoic chamber provide good agreement with those from commercial software simulations.

A microstrip power splitter with band-pass responses is presented in this paper. The design is based on square open loop resonator topology. This filtered power splitter does not require quarter wavelength transformers and will result in a smaller size than a conventional Wilkinson power divider with integrated band-pass filter. It is a two-way equal power splitter with fifth order band-pass filter characteristics. The power splitter is designed to have Chebyshev band-pass response function. A theoretical analytical circuit model will be presented. From the theoretical model, a microstrip filtered power splitter will be designed and simulated. The proposed filtered power splitter is small in size and reduces circuit complexity. The power splitter is simulated and measured, and the results are presented.

The miniaturization of the patch antenna has become an important issue in reducing the volume of entire communication system. This paper presents an improved method of size reduction of a microstrip antenna using the genetic algorithm. The shape of a typical rectangular patch is modified in order to reduce it resonance frequency keeping the physical volume of the antenna constant. Indeed, the initial patch is divided into 10 × 10 small uniform rectangles (Pixel), and the genetic algorithm searches, the optimal configuration for the desired goal. The resonance frequency of a micro-strip patch is shifted from 4.9 GHz to 2.16 GHz and a rate of miniaturization is up to 82%. To validate the procedure, an antenna prototype has been fabricated and tested with an FR4 substrate. The measurements results were in good agreement with simulation ones.

In this paper, low side lobe radiation pattern (i.e., pencil-beam pattern) synthesis problem is formulated for symmetric linear antenna arrays. Different array parameters (feed current amplitudes, feed current phase, and array elements positions) are considered as the optimizing variables. The newly proposed evolutionary algorithm, Symbiotic Organisms Search (SOS), is employed to solve such a pattern optimization problem. The design objective is to obtain radiation patterns with very low interference in the entire side lobes region. In this context, SOS is used to minimize the maximum side lobe level (SLL) and impose nulls at specific angles for isotropic linear antenna arrays by optimizing different array parameters (position, amplitude, and phase). The obtained results show the effectiveness of SOS algorithm compared to other well-known optimization methods, like Particle Swarm Optimization (PSO), Biogeography-based optimization (BBO), Genetic Algorithm (GA), Firefly Algorithm (FA), and Taguchi method. Unlike other optimization methods, SOS is free of tuning parameters; one just has to set the value of the population size and the number of iterations. Moreover, SOS is robust and is characterized by relatively fast convergence and ease of implementation.

A new compact 30:1 bandwidth ratio balun and its application to balanced antennas are presented in this paper. To realize the balun-type function, two different types of wideband transition structures are adopted for unbalanced and balanced outputs of the balun. Further, a Vivaldi antenna integrated with the proposed balun is designed and fabricated to validate the feasibility of the new approach. Results indicated that the proposed balun can operate from 0.2 GHz to 6 GHz (a bandwidth ratio of 30:1). And it exhibits a good balanced performance within 0.5 dB magnitude imbalance and less than 6 degree phase imbalance between the two balanced outputs. In addition, the antenna can operate from 0.9 GHz to 6 GHz with good unidirectional radiation patterns.

A circularly polarized (CP) substrate integrated waveguide (SIW) cavity-backed slot antenna is proposed. A slot split ring (SSR) etched on the top metal surface of an SIW resonator is employed to generate the right-handed circularly polarized (RHCP) wave. The proposed antenna is excited directly by a coaxial probe with a proper distance from the symmetric axis of the SSR resonator. A prototype of the proposed CP antenna at the center frequency of 10 GHz is manufactured. As a result, the proposed antenna exhibits the advantages of both conventional planar antennas and metallic cavity backed antennas, including simple structure, compact size of 15.8×15.8 mm², light weight, easy fabrication, high gain and wide axial ratio bandwidth. It is proved by experiment that an impedance bandwidth of 10.2% for the reflection coefficient less than -10 dB, an axial ratio (AR) bandwidth of 1.72% for AR less than 3 dB, and a RHCP gain 5.5 dBi have been obtained.

This paper proposes a copper nanoparticle inkprinted frequency selective surface (FSS) for cellular signals suppression. The FSS pattern is deposited on a polyimide film by using an inkjet printing technique. The printed FSS elements undergo the post-processing called sintering,where the optimum exposure duration and temperature are determined in order to form a conductive path across the metal pattern. Later, the conductivity of the printed FSS structure deposited on polyimide film is observed. The signal suppression ability of the printed FSS is conducted using the Computer Simulation Technology (CST) Microwave Studio software.

In this work we report an ultra-thin all-dielectric antenna that was designed, built, tested, and compared with simulated data. The objective of this research was to develop an antenna that is easily manufactured by common 3-D printers available today. 3-D printing is quickly revolutionizing manufacturing and the need to incorporate electrical elements like antennas is rising. Multi-material 3-D printing that can build parts with conductors and dielectrics is the future, but at present it is very immature and largely inaccessible. The antenna presented here represents our first steps in developing all-dielectric antennas that can be manufactured today with commonly available 3-D printers and materials. A monolithic antenna would have additional mechanical benefits when subjected to bending or thermal cycling. With this goal in mind, an ultra-thin all-dielectric antenna was developed. The antenna operates by taking advantage of total internal reflection and exciting a leaky whispering gallery mode. The antenna reported here operates at 2.4 GHz and was able to be as thin as 1.5 mm.

A broadband microstrip line-to-waveguide (MSL-to-WG) transition is developed for E-band applications. In order to achieve a sufficient and broadband coupling between the microstrip line (MSL) and waveguide (WG), a radial electric probe at the end of the MSL and extended ground (GND) planes on the dielectric substrate are proposed. Results are compared against a simple transition (S-Tr) with a straight electric probe. For the case of operational bandwidth (BW) for an input return loss (S₁₁) below -20 dB, the proposed transitions using the radial probe and extended GND planes show the BW enhancement of 33.8% and 61.9%, respectively, compared to the S-Tr. The proposed and simple transitions were fabricated on a low-loss liquid crystal polymer (LCP) dielectric substrate. The measured bandwidth (BW) for S₁₁ below -10 dB of the proposed transition is over 28 GHz, which is satisfied at all test frequencies from 67 to 95 GHz. Its measured insertion loss can be analyzed as -1.33 and -1.41 dB per transition at 70 and 80 GHz, respectively, considering the loss contribution of the cable adapter and waveguide transition.

A compact Phi-shaped monopole antenna for super wideband applications is proposed. It consists of a Phi-shaped radiator derived from a conventional elliptical monopole and quarter elliptical CPW ground plane. An impedance bandwidth from 3.5 to 37.2 GHz is achieved with a ratio bandwidth of 10:1. It provides an average peak realized gain of 3.5 dB with a group delay of less than 0.5 ns. The proposed antenna structure provides large bandwidth with the advantage of miniaturized dimensions compared to other SWB antenna structures.

In this paper, a tunable multiband LTE antenna is designed for metal-rimmed smartphone applications. The antenna only uses a broken metal ring, which comprises an IFA (Inverted-F antenna) section and a parasitic section, and generates three resonant modes through this layout for the feeding point and shorting point. In addition, loading a matching circuit at the feeding point and a RF switch at shorting point of the IFA is used to switch low frequency to lower frequency. The bandwidth can completely cover 824-960 and 1710-2690 MHz. So the proposed antenna can work at GSM850, 900; DCS1800; PCS1900; WCDMA band 1, 2, 4, 5, 8; TD-SCDMA band 34, 39; CDMA BC0,BC1 and LTE band 1, 3, 7, 38, 39, 40, 41. Also, the total size of the cellphone is 150 mm×75 mm×3.5 mm, which is very suitable for 4G slim smart mobile phone applications.

This paper describes a convenient technique of precise radial velocity estimation for inverse synthetic aperture radar (ISAR). In order to keep both the range profile and phase history of the echoes coherent, direct sampling with high sampling rate using high performance analog-to-digital converter and matched-filter correlation processing in pulse compression are used for the ISAR system. Due to the coherence property of the echoes, the translational motion compensation parameters for ISAR imaging are just the radial motion parameters of the target. Thus, the coarse velocity estimation is obtained by range alignment and fine velocity estimation is achieved by phase adjustment. The fine velocity estimation is ambiguous and the coarse velocity estimation is used for ambiguity resolution. The advantage of this technique is the high precision with range error values at sub wavelength levels, and it achieves velocity information and translational motion compensation at the same time. Both simulated and experimental validations are presented to verify the effectiveness of the proposed method.

A thin phase-correcting element that consists of four identical metallic and three identical dielectric layers is presented for the design of microwave and millimeter-wave transmitarrays. The metallic layers consist of the octagon conducting strip, which are tuned to obtain the desired phase compensation on an incident wave, while maintaining a high amplitude of transmission coefficient. A transmitarray is designed at K band using the element. Fed by a standard horn and three planar slot-fed patch antennas with different beamwidths alternately, the wave-focusing performance of the transmitarray was demonstrated by simulations and experiments.

This paper presents a third-order digital tunable bandpass filter based on digitally tunable capacitor loaded microstrip open ring resonator. Magnetic dominated mixed coupling is utilized to make the coupling coefficient meet the requirement of stable bandwidth response. Electric source-load coupling is designed to generate a transmission zero for improving the frequency selectivity. This filter is designed, fabricated and measured. The measurement shows that the filter can be digitally tuned by 5-bits pure digital command. The fractional bandwidth is 9±1%, and the tuning range is from 410 MHz to 820 MHz.

A novel dual-band substrate integrated waveguide (SIW) filter with multiple transmission zeros and good out-of-band rejection performance is presented in this paper. For this purpose, an orthogonal input/output (I/O) feeding structure directly connected to the substrate integrated waveguide (SIW) cavity is designed to split the resonant frequencies of the degenerate pair of mode. The filter can be modeled with a multi-path circuit formed by three modes (TE₁₀₁, TE₂₀₁ and TE₁₀₂ modes) and weak cross coupling between I/O ports, thereby producing three transmission zeros which make the dual-band high selectivity. The offset of the input/output ports shifts the second transmission zero to a lower frequency from the upper passband. Several filter prototypes are designed and fabricated for demonstration, and the measured results validate the new structure for high selectivity applications.

The aim of this work is to characterize the electrical conductivity of composite conductors deposited on an alumina substrate. Several half-wavelength coplanar resonators are realized using several pure conductors, silver (Ag), copper (Cu), gold (Au) and tin (Sn), to compare their quality factors (Q₀), related to losses, with those from analytical methods. In the literature, losses in coplanar components have been estimated by different analytical methods. We have put in evidence the relationship between electrical conductivity of the conductor and the resonator quality factor. An overall good agreement among quality factor values obtained by the analytical formulas, by numerical simulations and by microwave measurements is observed. The surface roughness is taken into account to better estimate real conductor losses. Therefore, these analytical formulas are used to extract the electrical conductivity values of the composite conductors (Ag-aC, AgSnIn and AgSn), from measured quality factors.

A novel uniplanar slot dipole antenna fed by a coplanar waveguide (CPW) is proposed for dual-band operation. The frequency ratio between the first spurious and fundamental modes of the slot dipole antenna can be conveniently adjusted with the use of four slot stubs introduced on its two arms. Furthermore, the radiation patterns at the first spurious mode are modified by adding four parasitic slots along its two arms to resemble those of the fundamental mode. Under the assistance of the slot stubs together with the parasitic slots, another resonant mode can be generated and merged with the first spurious mode, and therefore improve the bandwidth significantly. An antenna prototype was fabricated and measured to validate the design concept. The measured results show that dual-band operation with 10-dB impedance bandwidths of 2.99-3.83 GHz (24.6%) and 5.21-6.89 GHz (27.8%) has been obtained. The antenna has stable broadside and bidirectional radiation patterns with low cross-polarization components over the two operating bands.