The paper introduces a new class of adaptive CFAR methods to cope with the problem of outliers due to the presence of clutter edges and interfering targets. A fundamental distinction between the proposed approach and existing adaptive CFAR approaches is that in order to maintain robust performance the former uses information on positions at which estimated outlier-free cells appear in the full reference window and the statistics of the sample in the cell under test. The performance of one of the possible implementations of new adaptive CFAR methods is studied and compared with that of an existing adaptive CFAR approach. The results show significant advantages of the proposed class of adaptive CFAR methods in both the false alarm regulation property and detection performance.

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 (G_pr) 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 G_pr in PCS is 1.32 dB at 1.8 GHz, and the average G_pr 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.

A novel planar ultra-wideband (UWB) antenna with triple-notched bands is investigated and presented in this paper. The initial UWB antenna consists of a circular-shaped radiating element, a 50 Ω microstrip feed line, and a partially truncated ground plane. Then, by embedding a square ring short stub loaded resonator (SRSSLR) beside the microstrip feedline of the basic UWB antenna, band-rejected filtering properties in the satellite communication/wireless local area network/radio frequency identification for microwave access bands are generated. The notched frequencies can be adjusted according to specification by changing the SRSSLR. The results indicate that the proposed compact antenna not only retains an ultra wide bandwidth, but also owns triple band-rejections capability. The UWB antenna demonstrates omnidirectional radiation patterns across nearly the whole operating bandwidth that is suitable for UWB communications.

This paper deals with a fast and simple computational method of 3D near-field (NF) radiation from 2D planar frequency- and time-dependent data. The established calculation method can be used to predict the electromagnetic (EM) emission from various types of electronic devices. The proposed method is originally applicable to the computation of the EM NF along the arbitrary shaped curvilinear 3D surface of multi-shape objects. The EM computation consists in the application of the planar NF-to-NF transform using plane wave spectrum. The relevance of the established method is verified with three different validation tests of analytical and practical demonstrations. The first validation is based on the analytical NF radiation from set of elementary dipoles excited by a harmonic signal. The second validation test is based on the experimented data from a hybrid active printed circuit boards (PCBs) in the frequency domain. The last validation test is performed with the measured NF data from a microstrip planar circuit in the time-domain. For all the different test cases, the plots of EM NF on arbitrary curvilinear surfaces are presented. Applications with 3D visualization or holographic surface with arbitrary geometry of EM radiation from planar data in both frequency- and time-domains confirm the effectiveness of the proposed method to predict the EM NF emission from complex PCBs. The developed 2D-to-3D computational method is particularly useful for radiated EM compatibility engineering.

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 new microstrip ultra-wideband (UWB) bandpass filter (BPF) with triple-notched bands is presented in this paper. The circuit topology and its corresponding electrical parameters of the basic microstrip UWB BPF are designed by modified genetic algorithm (MGA). Then, triple-notched bands inside the UWB passband are implemented by coupling a novel triple-mode stepped impedance resonator (SIR) 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 triple-mode SIR. For verification, a new microstrip UWB BPF with triple-notched bands respectively centered at frequencies of 4.4 GHz, 5.9 GHz and 8.0 GHz is designed and fabricated. Both simulated and experimental results are provided with good agreement.

A simple 2×3 reconfigurable beam-forming network (R-BFN) for four-beam reconfiguration application is designed and implemented. The proposed R-BFN with two input ports and three output ports consists of a 2:1 power divider, a 90° hybrid, a 180° hybrid and a 2-bit phase shifter. The 2-bit phase shifter has two states: one is a 180° phase shifter (State 1); the other is a 0°/360° phase shifter (State 2). By introducing the 2-bit phase shifter, the constant phase differences of three output ports can be reconfigured. Specifically, as different input ports are excited, the R-BFN provides three output signals with equal power levels and the progressive phases of -120° and 120° when the 2-bit phase shifter at state 1, while -60° and 60° when the 2-bit phase shifter at state 2, respectively. When the proposed R-BFN is connected to an antenna array, a four-beam reconfiguration is obtained. Simulated and measured results show that good impedance matching, high port isolation, equal power division, and constant phase difference have been achieved simultaneously within the operation band of 2.4-2.6 GHz. The capability of the proposed R-BFN to reconfigure beams is also verified experimentally by using a 2.5 GHz dipole array.

The results of experimental measurements of the complex dielectric permittivity (CDP) of powders of quartz granules with different sizes saturated with water and salt solution of weak concentration are given in the frequency band from 20 kHz to 1 GHz. It is shown that at values of saturation level from 0.6 to 0.9 the relaxation phenomena caused by interfacial polarization on the water-air bound can be observed. The result shows considerable reduction of attenuation in gradually saturated rocks, which allows for deeper sensing during georadar mapping. It is determined that in the dielectric relaxation band and at frequencies below it the hysteresis of the real part of the CDP and equivalent specific conductivity can be observed. Its character significantly depends on the sizes of granules. It is shown that the behavior of CDP and attenuation of an electromagnetic wave at frequencies from 0.1 to 10 MHz complicatedly depends on the sizes of granules, saturation level, salinity of the saturating solution and saturation history.

The electromagnetic (EM) fields inside a rotating circular hollow dielectric cylinder were numerically calculated in two dimensions, and the numerical results were presented in this paper. The simulation was carried out by using the method of characteristics (MOC) for the solutions of the time-domain Maxwell equations with the application of the passing center swing back grids (PCSBG) technique in the modified O-type grid system. To illustrate the effects of the rotating hollow dielectric cylinder on the EM fields inside the cylinder, the cylinder may be set to rotate at impractically, extremely high angular frequencies. The use of PCSBG is to overcome the difficulty of the deformed grid cells resulting from the rotating object while the modified O-type grid system satisfies the requirement of minimum number of grid within the shortest wavelength of interest in the larger radius regions where the regular O-type grid fails. A Gaussian EM pulse is utilized as excitation source and set to illuminate the hollow cylinder which is made of either non-magnetic or impedance matching materials. For clear examinations the numerical results of EM fields at and around the cylinder center are exhibited. Several electric field distributions are also shown.

Millimeter wave (MMW) imaging has found rapid adoption in security applications such as concealed object detection under clothing. However, the imaging quality is often degraded due to resolution limit and low signal level. This study addresses shape feature analysis following concealed object detection. The object region is extracted by multi-level segmentation. Shape features are composed of several descriptors which are object area, perimeter, major and minor axes of the basic rectangle, rectangularity, compactness, and eccentricity. In the experiments, three objects (gun, hand ax, and plastic bottle containing liquid skin aid) concealed under clothing are captured by the passive MMW imaging system. The extracted shape features are compared with the true features from the object model showing good accuracy.

A new circularly-polarized metasurfaced dipole antenna (MSDA) with wide axial-ratio(AR) beamwidth and radar cross section (RCS) reduction properties is proposed and studied in this paper. This antenna is a quite simple half-wavelength linear dipole right above a metasurface which consists of 9 double-head arrow-shaped unit cells arranged in a 3×3 layout. By cautiously choosing the geometrical parameters of the metasurface and tuning the distance between the dipole and the metasurface, the whole structure turns out to be a circularly-polarized antenna with RCS reduction feature. Simulation results show that the MSDA in circular polarization achieves an operating bandwidth of 410 MHz and a wide AR beamwidth of 123˚ and 90˚ in φ = 0˚ and φ = 90˚ planes respectively, together with a maximum RCS reduction of 10.4 dB in the whole operating band.

Nosecone radomes of hypersonic flight vehicles show degradation of electromagnetic (EM) performance characteristics due to variations in the dielectric parameters (dielectric constant and electric loss tangent) of the radome wall resulting from heating due to extreme aerodynamic drag. It is indicated that the EM performance predictions based on conventional monolithic half-wave wall based on average dielectric parameters corresponding to temperature ranges in hypersonic conditions may not be accurate. This necessitates the radome wall under hypersonic conditions to be modeled as an inhomogeneous dielectric structure for accurate EM performance predictions. In the present work, the hypersonic radome is considered as an inhomogeneous dielectric radome such that the cross-section of the radome wall in each EM window region is considered as an inhomogeneous planar layer (IPL) model with stacked layers of varying dielectric parameters. The material considered is RBSN Ceralloy 147-010F (an alloy of silicon nitride), which has excellent thermal shock resistance, dielectric and mechanical properties required for hypersonic radome applications. The EM modeling of a section of the radome wall in hypersonic conditions (i.e. IPL structure) is based on Equivalent Transmission Line Method. A comparative study of basic EM performance parameters of the radome wall (power transmission, power reflection, and insertion phase delay) for both the IPL model and conventional monolithic half-wave model are carried out over a range of incidence angles corresponding to the antenna scan ranges in each EM window region of the radome. Further the study is extended to compute the EM performance parameters of an actual tangent ogive nosecone radome (made of RBSN Ceralloy 147-010F) enclosing an X-band slotted waveguide planar array antenna, in a hypersonic environment. The antenna-radome interaction studies are based on 3-D Ray tracing in conjunction with Aperture Integration Method. It is observed that the EM performance analysis based on conventional monolithic radome wall design cannot accurately predict the radome performance parameters in actual operating conditions during hypersonic flight operations. The current work establishes the efficacy of Inhomogeneous Dielectric Radome model for better EM performance predictions of streamlined airborne radomes in hypersonic environments.

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.

The parabolic equation(PE) method is widely used in radiowave propagation predictions. It has the advantages of high efficiency and stability, but it will lead to greater predicting errors in some situations, because the effects of transverse terrain gradients are not modeled. This problem can be solved by extending the 2D PE to the three-dimensional (3D) PE. However, the computing efficiency will degrade because of large scale matrix operations. In this paper, a new method is presented, in which the 3D PE is decomposed into two 2D PEs. It increases the computational efficiency and accuracy effectively. To verify the capability of the proposed method in radiowave propagation prediction, an experiment platform was set up. The computational results using this new method are compared with the experimental and Method of Moment(MoM) numerical computational results. Good agreements are achieved in the comparison.