A new compact microstrip UWB bandpass filter with triple band-notched characteristics is presented in this paper. The initial circuit topology and its corresponding electrical parameters of the basic microstrip UWB BPF are desired by a variation of genetic algorithm (GA) technique. Then, triple-notched bands inside the UWB passband are implemented by coupling a novel triple-mode stepped impedance resonator (TMSIR) to the main transmission line of the basic microstrip UWB BPF. The triple-notched bands can be easily generated and set at any desired frequencies by varying the designed parameters of TMSIR. To illustrate the possibilities of the new approach, a microstrip UWB BPF with triple-notched bands respectively centered at frequencies of 5.2 GHz, 6.8 GHz, and 8.0 GHz is designed and fabricated. Measured results agree well with the predicted counterparts.
A broadband Fabry-Perot cavity antenna (FPCA) operates at Ka band with high gain and dual-polarization is reported. The proposed antenna employed a double-sided complementary-circular partially reflective surface (PRS) to enhance the directivity bandwidth. A square patch coupled by two orthogonal slots and fed by two microstrip lines was applied as the primary feed to achieve dual-polarization operation. To further improve the impedance bandwidth and directivity, a series of metal vias were suggested to surround the primary patch. This FPCA design was verified by the measurements. The experimental results show that the common impedance bandwidth of the two ports for the reflection coefficient (S11) below -10 dB is 2.5 GHz from 34 GHz to 36.5 GHz (7.1%), which covers the common 3 dB gain bandwidth of the two ports. At the center frequency of 35 GHz, the measured peak gains at the two orthogonal ports are 16.1 dBi and 15.1 dBi, respectively. The isolation between the two ports is higher than 30 dB within the bandwidth.
To enable the quest for high data rates in telecommunications, wide-band radio designs as well as antennas are required. This paper demonstrates a unique bandwidth enhancement technique for L-probe fed patch antenna. This is a novel technique to enhance patch antenna bandwidth with desired radiation properties. One circular shape main patch and two elliptical shape parasitic patches on PCB give wide-band response by exciting multiple resonances. The designed antenna array gives almost 45%, -10 dB impedance matched relative bandwidth. This is a very simple and inexpensive patch antenna solution for the wide-band wireless application. A two-element array of this antenna has been formed, and wide-band radiation properties of the array are reported.
In this paper, the design of a printed circuit antenna based on lotus flower patch of a miniaturized profile is proposed. The antenna consists of three layers including a patch and a ground plane of a thin copper layer separated by a Roger RT/duroid®5880 substrate for high gain-bandwidth product applications including the portable biomedical devices. The patch structure is patterned with triangular defects to provide a fractal structure. Nevertheless, the ground plane is defected with Electromagnetic Band Gap (EBG) structures. The antenna is found to show a first resonant mode around 3 GHz, while the other frequency modes are obtained around 4.2 GHz and 6 GHz which are below -10 dB. Moreover, the antenna operates over the frequency range from 7.8 GHz up to 15 GHz with a bore-sight gain varing from 4 dBi up to 6 dBi when operates in free-space environments. The antenna size is reduced to a 32 mm×28 mm×0.5 mm using shorting plates on the substrate edges. The antenna performance characteristics are examined using CST and HFSS commercial software packages, which are based on the Finite Integration Technique (FIT) and the Finite Element Method (FEM), respectively. Finally, the antenna performance is tested experimentally for both S11 spectrum and radiation patterns to show an excellent matching with the obtained numerical results.
In this paper, a CPW-fed reconfigurable clover-shaped antenna with switchable circular polarization is proposed. This antenna consists of a clover-shaped patch, four p-i-n diodes, and two pairs of quarter-circular-rings. By electrically controlling the four p-i-n diodes to form two orthogonal bow-tie shaped current paths, the proposed antenna can be operated in two modes: the left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP) modes. Two pairs of quarter rings are used to improve the bandwidth and AR performance of the antenna. The measured 10-dB reflection coefficient and 3-dB axial-ratio (AR) bandwidth of the prototype antenna is approximately 12.3% and 19%, respectively, which is enough for some wireless applications such as WLAN IEEE 802.11 b/g (4%). Gain and radiation pattern are also presented.
The paper presents a hybrid evolutionary algorithm suitable for the optimization of large-domain electromagnetic problems. The hybrid technique, called Genetical Swarm Optimization (GSO), combines Genetic Algorithms (GA) and Particle Swarm Optimization (PSO). GSO algorithm is modelled on the concepts of Darwin's theory based on natural selection and evolution, and on cultural and social rules derived from the swarm intelligence. The problem is formulated and solved by means of the proposed algorithm. The examples are simulated to demonstrate the effectiveness and design flexibility of GSO in the framework of synthesis of multi-beam linear antennas arrays.
This paper addresses the miniaturization of Quadrifilar Helix Antennas (QHAs) for space applications (VHF Telemetry, Tracking and Command). Several shape miniaturization techniques were presented, and the impact of height reduction is quantified in terms of radiation pattern, gain and phase center. Simulated and experimental results demonstrate that Compact Quadrifilar Helix Antennas (CQHAs) with a height reduced up to 70% reported to the reference QHA can be designed. By using an appropriate optimization method, the impact of the miniaturization on CQHA performances in terms of radiation pattern and polarization purity can be minimized. Moreover, the impact on the gain is quantified, and design rules are reported. Finally a closed-form expression for estimating the gain of CQHAs from the height reduction factor is found.
This paper presents a novel and robust design for a new kind of photonic crystal fiber with dodecagonal and circular array of air holes, aiming at a highly nonlinear coefficient, ultra-flattened dispersion and ultra-low confinement loss. In this structure, circular lattices are added in two inner layers to obtain both ultra-low dispersion and ultra-flattened dispersion in a wide wavelength range. The proposed structure has a modest number of design parameters for easier fabrication. The finite difference method with perfectly matched boundary layer is used to analyze guiding properties. Analysis results prove that the proposed highly nonlinear dodecagonal photonic crystal fiber obtains a nonlinear coefficient greater than 43 (W.Km)-1 and low dispersion slope 0.003 ps/(nm.km) at 1.55 μm wavelength. Ultra-flattened dispersion of 0.8 ps/(km.nm) is also obtained ranging from wavelength 1.3 μm to 1.7 μm with confinement loss lower than 0.5×10-6 dB/m in the same wavelength range.
Two major performance degrading factors in free space optical communication systems are rainfall and atmospheric turbulence. We study the outage probability and bit-error rate for free-space communication links with spatial diversity and Gaussian-Schell electromagnetism beams over the raining turbulence fading channels by double inverse Gaussian distribution proposed in this paper. Assuming intensity-modulation/direct detection with on-off keying and perfect channel state information, we derive expressions of average bit-error rate and outage probability of multiple-input multiple output free space optical communication systems over double inverse Gaussian model. The effects of scintillation index of raining turbulence, spatially coherence of source, pointing errors and spectral index of non-Kolmogorov turbulence on the outage probability and bit-error rate of multiple-input multiple-output free space optical communication systems are examined.
In this paper, a printed planar monopole antenna (PPMA) is presented for PCS, UWB and X-band. The antenna is designed in two stages. In the design of the preliminary PPMA used to obtain the proposed PPMA, the structure is divided into sections, and they are optimized in the sense of bottom to up strategy. The bandwidth is enhanced by employing tapered transitions and inset feed. The resulting antenna operates between 2.37 GHz and 12 GHz with VSWR<2 and an average peak realized gain (Gpr) of 4.95 dB. Therefore, the preliminary antenna can be considered to be suitable for Bluetooth, WLAN, WiMAX, UWB and X-band. The proposed PPMA is designed by implementing slots on the preliminary PPMA to include PCS, and to suppress Bluetooth and commonly used WLAN and WiMAX bands, the ones allocated out of UWB. The proposed antenna operates in the 1.67 GHz-1.91 GHz and 3 GHz-15 GHz bands with VSWR<2. The Gpr in PCS is 1.32 dB at 1.8 GHz, and the average Gpr is 5 dB for the 3 GHz-15 GHz band. The group delay performances are also examined, and the maximum group delay deviations of preliminary and proposed PPMAs are observed as 1 ns and 1.25 ns, respectively.
In this paper, a nonlinear phase enhancement of multi-resonance composite right/left-handed unit cell for multi-band antennas is presented. Different antennas with nonlinear enhanced phase which can operate up to five different frequency bands are introduced. Meanwhile, the proposed antennas have compact size so that they can demonstrate size reduction up to 60% compared to conventional patch antennas operating at the same frequencies. The achieved phase enhancement has been validated by comparing two different configurations of composite right/left-handed cells. The analysis, electromagnetic full wave simulations and experimental results are discussed. A reasonable agreement is achieved between the measured and simulated results.
A novel idea of conformal corrugated edges (CCE) is put forward in this paper for tapered slot antennas to obtain improved low-frequency characteristics. The CCE is realized using conformal slots whose two longitudinal boundary lines are modelled using curvilinear function of the curves that form the tapered slots. So the conformal slots can sufficiently corrugate edges of the tapered slot antennas with one set of structural parameters by comparing with the typical rectangular slot, which makes the corrugated edges design for tapered slot antennas much simpler. Moreover, when used to corrugating edges with the same width of a tapered slot antenna, the conformal slot is longer than the typical rectangular slot, as a result of which the CCE can better improve low-frequency characteristics of the tapered slot antennas. For verification, the CCE using exponential slot is proposed for typical Vivaldi antenna in this paper. Comparisons among antenna structures, port characteristics and radiation characteristics of Vivaldi antennas with the proposed CCE and the typical rectangular slot corrugated edge are carried out, and the Vivaldi antenna with its proposed CCE is fabricated and measured. The remarkable improvement for low-frequency characteristics demonstrates the correctness of the idea.
A novel dual-band balanced power amplifier (DBPA) using a pair of branch-line couplers with four arbitrary terminated resistances is designed in this paper. The DBPA operating at 2.02 GHz and 2.6 GHz consists of two identical single-stage class-AB PAs connected in parallel and two branch-line couplers for power division and combination. Due to the usage of branch-line couplers with four arbitrary terminated resistances, the load/source-pull impedance obtained by ADS (Advanced Design System) can be matched to an arbitrary real impedance which decreases the complexity of dual-band matching network of the DBPA. To demonstrate the proposed design, a prototype based on CREE's GaN HEMT CGH40010F is fabricated and measured. The simulated results exhibit 67.9% and 73.6% power-added efficiency (PAE) values with output power of 44.1 and 43.4 dBm at 2.02 GHz and 2.6 GHz, respectively.
Energy selective surface (ESS) proposed in recent years is one of the most effective means for defending high intensity electromagnetic wave attacking. This paper presents an improved ESS structure and its systematic design method. An ESS prototype is designed and fabricated based on a given requirement. Its insertion loss is measured in an anechoic chamber, and its shielding effectiveness is tested under HPM and UWB irradiation. Measured results show that the ESS sample meets the given requirement.
A dual-band multiple-input-multiple-output (MIMO) antenna system for LTE 700/2300/2500, UMTS2100, GSM 1800/1900 mobile phone applications is presented. The whole system consists of four identical 3-D IFAs (inverted F antenna) loaded with lumped inductors and folded on FR4 cuboids. Without any special designed decoupling structures, the measured isolation among antenna elements is higher than 13 dB. Return loss characteristics, correlation coefficient, gain and radiation performance are also presented.
In this communication, a systematic approach for design of planar monopole ultra-wideband (UWB; 3.1~10.6 GHz) antenna for wireless USB dongle has been proposed. The simple planar monopole antenna consists of a rectangular metallic radiating patch whose modal analysis is carried out first by means of the Theory of Characteristic Modes (TCM), in order to identify the different radiating modes and get the physical insights of these radiating modes of the antenna. Further, based on the physical evidences obtained from the radiating modes of the similar planar monopole antenna, a bevel transition feed with rectangular slot has been used to enhance the bandwidth and obtain the desired radiation characteristics of the proposed antenna. The modal analysis is carried out using characteristic modes (CM) analysis tool in CADFEKO 7.0 simulation software. The proposed antenna exhibits a very compact dimensions of 12 mm × 16 mm × 5 mm and yields a good insights in simulated and measured impedance bandwidth of 3.1~12 GHz with VSWR < 2. Furthermore, the proposed antenna exhibits symmetrical radiation patterns, stable-high gain and efficiency and ultra-wide bandwidth making it suitable candidate for practical UWB-USB applications.
An ultra-wide band 45° phase shifter based on a new planar artificial transmission line which can be used for UWB communication systems is presented. The planar artificial transmission line is composed of host line, grounded interdigital capacitors and meandered-line inductors. The phase shifter was measured to have a bandwidth about 114.7% (2.9 GHz to 10.7 GHz) for a maximum phase deviation of 2.9°, a maximum insertion loss of 1.2 dB, a minimum return loss of 13 dB and a compact size of 16.35 mm × 5.2 mm.
A tunable planar bandpass filter based on a technique that utilizes a half mode substrate integrated waveguide (HMSIW) and novel inter-resonator coupling is presented. The tunable HMSIW based bandpass filter is implemented using two half triangle shaped cavities coupled together through inter-resonator coupling forming half mode bowtie-shaped structure. The bowtie-shaped filter exhibits similar performance as found in rectangle- and circle-shaped SIW based bandpass filters. This concept reduces the circuit foot print, and miniaturization high quality factor is maintained by the structure. The tunable filter utilizes packaged RF MEMS switches; switching between different configurations of switches achieves four distinctive frequency states between 4.8-5.3 GHz. The filter maintains a constant absolute 1 dB bandwidth of 100±10 MHz for all frequency states.
In this work, a low-profile metamaterial backed planar antenna structure designed to work in the UHF/VHF range is presented. The antenna has right-hand circular polarization. It is ideal for satellite-based communications and radar systems. An artificial magnetic conductor was designed using a metamaterial composed of a split ring resonators to reduce the size of the planar antenna and ground plane system. The proposed artificial magnetic conductor has more confined surface waves at the reflecting plane than previous designs and is suitable for circular polarization. Through numerical simulations, performance characteristics including return-loss, and realized gain of the antenna systems are calculated and analyzed in the VHF range. The proposed antenna system is narrowband and is linearly scalable in the range of 100 MHz-1 GHz.
The waveguide re-entrant or inverted re-entrant turnstile circulator relies for its operation on either a quarter wave long cylindrical or prism resonator mounted on either a circular or an equilateral platform with its open face separated from the top waveguide wall by a suitable gap. The adjustment of the prism geometry, the main endeavour of this paper, is characterized by two degrees of freedom. One degree of freedom is the orientation of the prism inside the junction with respect to a typical waveguide feed. The others are the aspect ratio of the gyromagnetic resonator and the choice of platform or piston. The agreement between some calculations based on a Finite Element (FE) engine and experiment is excellent. The work undertaken here indicates that the preferred geometry is that for which the platform has the crosshairs section of the resonator.