A novel twin-diamond-shaped antenna is presented for wideband circularly polarized (CP) radiation. By introducing a twin-diamond-shaped patch and a gap-coupled feed structure, a left-handed circularly polarized (LHCP) antenna in bore-sight direction is obtained. The gap-coupled feed structure consists of a horizontal microstrip arm of approximately 0.285λ₀ at the centre frequency and two small diamonds, which greatly contributes to wideband characteristics. The experimental bandwidths of 10-dB return loss and 3-dB axial ratio (AR) for the antenna prototype are about 20% and 9.2%, respectively. The measured gain is more than 6.8 dBi over the entire bandwidth.

In this work, results are given for controlling waves arbitrarily inside a new type of spatially variant lattice. To demonstrate the concept, an unguided beam was made to flow around a 90° bend without diffracting or scattering. Control of the field was achieved by spatially varying the orientation of the unit cells throughout a self-collimating photonic crystal, but in a manner that almost completely eliminated deformations to the size and shape of the unit cells. The device was all-dielectric, monolithic, and made from an ordinary dielectric with low relative permittivity (ε_r = 2.45). It was manufactured by fused deposition modeling, a form of 3D printing, and its performance confirmed experimentally at around 15 GHz.

In this work a 12 element patch planar antenna array is designed, fabricated and tested along with its radio frequency (RF) feed network at 2.45 GHz. The array is designed to be embedded in the wing structure of a fixed wing hobby-type UAV. The planar array allows for beam steering with two degrees of freedom (θ_b,Φ_b). The maximum mutual coupling between antenna elements was -25 dB. The RF combiner was phase compensated to minimize the phase imbalance between its branches. The maximum measured antenna gain was 21.4 dB. The 3D Radiation pattern at several steering angles was measured at an outdoor antenna range facility. Measured and simulated values were in good agreement.

The waveguide has a perfectly conducting surface. Its cross section domain is bounded by a singly-connected contour of a rather arbitrary but enough smooth form. Possible waveguide losses are modeled by a homogeneous conductive medium in the waveguide. The boundary-value problem for the system of Maxwell's equations with time derivative is solved in the time domain. The real-valued solutions are obtained in Hilbert space L₂ in a form of transverse-longitudinal decompositions. Every field component is a product of the vector element of the modal basis dependent on transverse coordinates, and the modal amplitudes dependent on time and the axial coordinate. Three examples are included. The dynamic properties of the modal waves and concomitant energetic waves are studied and their dependence on time illustrated graphically.

This work presents results for the path loss due to foliage at 2.4 GHz using RF equipment and XBee-PRO ZB S2B transceiver modules in Agricultural fields (Corn, Paddy and Groundnut) and Gardens (Coconut garden with green grass, open lawn with dry green grass and wet green grass) targeting short-range, near ground RF propagation measurements for planning and deployment of Wireless Sensor Communications for precise agriculture and plantation management applications. Path Loss (PL), Path Loss Exponent (PLE) and corresponding Root Mean Square Error (RMSE) values were deduced from the measured RSS from various positions in these environments. Empirical foliage loss prediction models such as COST 235, Early ITU Vegetation and Weissberger models were compared with the experimental results.

The problem of detecting point-like sources whose frequency spectrum is unknown is addressed. Limitations of single-frequency approaches are identified by analytical as well as numerical arguments. To overcome these limits, different multifrequency approaches which combine frequency data incoherently are compared. In particular, a novel multifrequency MUSIC-like algorithm based on interferometric idea is proposed. Results show that the algorithm outperforms other methods under comparison.

In this work a new quality indicator for two-tier calibration procedures that use only reflection standards is presented and applied to coaxial-to-waveguide transitions. The quality indicator is based on the algebraic conditioning of the system of equations solved for obtaining transition characteristics. The study has been carried out in a wide bandwidth as a difference with previous works. The obtained results indicate that a threshold value for this indicator around 10% can be established. For values below this limit the error grows to unacceptable values. Additionally, it has been shown that an exponential relationship between quality indicator and the error can be predicted.

A compact multiband handset antenna including MIMO antenna operation for LTE 13 band (746~787 MHz) applications is proposed. The proposed antennas are separately located on the top and bottom portions of a mobile handset in order to use the antenna area more effectively. The proposed antenna achieves isolations of higher than 14 dB, enveloped correlation coefficients (ECC) of less than 0.25, and total efficiencies of greater than 40%. The operating frequency bands of Antenna 1 and Antenna 2 include the LTE 13 (746~787 MHz)/DCS/PCS/UMTS (1710~2170 MHz) bands and the LTE 13 (746~787 MHz)/GSM850/900 (824~960 MHz) bands, respectively.

In this work, we present a new design of a tunable nanofocusing lens using a circular grating of linear-variant depths and nonlinear-variant widths. Constructive interference of cylindrical surface plasmon launched by the sub-wavelength metallic structure forms a sub-diffraction-limited focus, the focal length can be adjusted by varying the geometry of each groove in the circular grating. According to the numerical calculation, the range of focusing points shift is much more than other plasmonic lens, and the relative phase of emitting light scattered by surface plasmon coupling circular grating can be modulated by the nonlinear-variant width and linear-variant depth. The simulation result indicates that the different relative phase of emitting light lead to variant focal length. We firstly show a unique phenomenon for the linear-variant depths and nonlinear-variant widths of the circular grating that the positive change and negative change of the depths and widths of grooves can result in different of variation trend between relative phases and focal lengths. These results paved the road for utilizing the plasmonic lens in high-density optical storage, nanolithography, super-resolution optical microscopic imaging, optical trapping, and sensing.

Ground-based microwave radiometer is the main device to remotely sense atmosphere passively which can detect the water vapor density, temperature, integral water vapor, etc. Because of the influence of liquid water in cloud on the brightness temperature measured by microwave radiometer, the cloud needs to be modeled to retrieve the parameters of atmosphere. However, the difference between cloud model and actual cloud may bring on error in retrieval. Based on the relation between absorption coefficient of liquid water and frequency, a dual-frequency method of eliminating liquid water radiation which is not based on modeling cloud is put forward to retrieve the parameters of cloudy atmosphere. Historical radiosonde data are employed in the calculation of retrieval coefficients to profile the water vapor. The simulation and experiment results show that the dual-frequency method can eliminate the affection of liquid water effectively. So the error in modeling cloud can be avoided to improve the retrieval precision. The integral water vapor in cloudy atmosphere is also retrieved by the dual-frequency method, and the precision is almost the same with the method of modeling cloud.

An improved nonlinear least-square method is presented in this paper. This method changes the traditional least-square method's shortness of being sensitive to its initial conditions. Pattern synthesis for concentric circular arrays using nonlinear least-square method is introduced. The excitation amplitudes and phases of the array elements are optimized. This method can make the design of the feeding network much easier because the excitation amplitudes of the elements placed on the same ring are equal. The number of parameters to be optimized is reduced which leads to a faster simulation speed and makes the simulation results much more accurate. Also, the cost of designing the feeding network is reduced. The simulation results show the good agreement between the synthesized and desired radiation pattern. Also, the peak side lobe level (PSLL) of the synthesized radiation pattern is quite low.

In this article, an S-band two-way inverted asymmetrical Doherty power amplifier (IADPA) using LDMOS FET is proposed. Due to the compact inverted load network with low inserted loss and the asymmetrical structure, the amplifier exhibits a high efficiency when operating at an output power back-off beyond 6 dB. For experimental verification, an IADPA has been implemented and a modulated Long Term Evolution (LTE) signal with 20-MHz channel bandwidth is applied as excitation. According to the measured results, the proposed amplifier can achieve a drain efficiency of 47.6% at the output power back-off of 7.7 dB from saturated power point and an adjacent channel power ratio (ACPR) less than -53 dBc with digital pre-distortion (DPD) when operating at 2.65 GHz.

In this paper, a novel moment-matching reduced order model technique termed the multi-dimensional well-conditioned asymptotic waveform evaluation (MDWCAWE) method is presented. The MDWCAWE method can be used to efficiently determine the radar cross section (RCS) of arbitrarily shaped objects, in both the frequency and angular domains simultaneously. Numerical results are given in order to demonstrate the accuracy and robustness of the MDWCAWE method. All scattering problems investigated in this work are formulated using the two-dimensional volume-surface electric field integral equation (EFIE). We consider problems involving scattering from both dielectric dispersive and conducting objects.

The dispersion equation governing the guided propagation of TE and TM fast wave modes of a circular cylindrical waveguide loaded by metal vanes positioned symmetrically around the wave-guide axis is derived from the exact solution of a homogeneous boundary value problem for Maxwell's equations. The dispersion equation takes the form of the solvability condition for an infinite system of linear homogeneous algebraic equations.The approximate dispersion equation corresponding to a truncation of the infinite-order coefficient matrix of the infinite system of equations to the coefficient matrix of a finite system of equations of sufficiently high order is solved numerically to obtain the cut-off wave numbers of the various propagating modes. Each cut-off wave number gives rise to a unique dispersion curve in the shape of a hyperbola in the ω-β plane.

A novel dual-broadband circularly polarized folded slot antenna with single-feed is presented. The proposed antenna consists of two folded annular slots. By adjusting the asymmetric widths of the two slots, circularly polarized radiation can be achieved in two different bands. By optimizing the parameters of the proposed antenna, two wide impedance bandwidths of 35.0% (1.91-2.72 GHz) and 46.5% (4.36-7.00 GHz) can be obtained, and two axial ratio bandwidths are 2.36-2.56 GHz and 5.68-6.04 GHz, respectively. The antenna with simple structure is fabricated and measured. Good agreement between the simulated and measured results is also achieved.

A novel cascade microstrip filter with mixed electric and magnetic coupling is proposed and examined. For the first time, we designed a novel multilayer configuration resonator with a compact size. Compared with conventional open-loop filter, the size decreased 75%. First, using novel multilayer configuration resonator instead of monolayer configuration resonator, the size decrease about 45%. Meanwhile, two microstrip patches can be served as inner coupling capacitor, which create and strengthen electric field. Owing to this inner coupling, the size of filter can be further reduced. What's more, with a section of high characteristic impedance transmission line connected to the ground though a via-hole, it can be served as coupling inductor and create main magnetic filed, base on this structure mixed EM coupling is realized, and can generate additional transmission zero. That's means adopt low-order filter can achieve same characteristic as high-order filter. Based on the above solutions, the filter size can be sharply decreased to 12.5 mm×7.7 mm (i.e.,0.05λ_g×0.033λ_g). Furthermore, advantages of using this type filter are not only low insert loss, but also increased attenuation out-of-band with controllable transmission zeros.

This paper presents the theory, design, and experimental investigation of an ultra thin (6% λ₀) and triple band metamaterial radar absorber. The theoretical design of the reported absorber is investigated. The absorber performance was validated using the electromagnetic simulations and confirmed by experimental measurements for different incidence angles. The results confirm that the proposed metamaterial absorber can demonstrate triple bands with better than -15 dB reflection coefficient for all incident angles.

Recent advances in satellite communication technologies in the tropical regions have led to significant increase in the demand for services and applications that require high channel quality for fixed and mobile satellite terminals. Due to lack of reliable investigations regarding accurate performance evaluation, experiments, and analysis on the satellite communication link in tropical regions under atmospheric impairments for both scenarios, accurate signal quality performance analysis is necessary. This paper presents the link characteristics observations and performance analysis with propagation measurements done in tropical region to provide an accurate database regarding rain attenuation in the tropics for fixed and mobile scenarios. The paper also presents a newly developed extension attached to the measurements setup for improved packet error rate (PER) performance evaluation related to the degradations occur in channel quality for different types of impairments (rain, mobility, and physical obstacles) for 4 modulation schemes, namely QPSK, 8-PSK, 16-QAM and 32-QAM. The results show that the rain impairments at Ku band cause up to 12.5 dB and 23 dB at 77.5° and 40.1° elevation angles respectively in two tropical regions inside Malaysia for fixed scenario with a significant increase in PER at higher M-ary modulation schemes. For mobile scenario, the PER appeared at higher M-ary scheme due to the lower signal power degradation in which, in turn, exceeded 1 dB when the vehicle speed exceed 100 km/hr at clear sky. The obstacles at the satellite communication link are shown to have significant effect on the power and PER received by satellite terminal especially at higher M-ary modulation schemes.

To save the computation time and improve the accuracy of reconstruction results by support vector machine (SVM), a multi-output least square SVM (LS-SVM) algorithm is proposed to reconstruct the position of a 2-D perfect electric conductor cylinder below a rough surface. Firstly, the scattered electromagnetic field at a number of observation positions is calculated by the method of moment to generate the training and testing data. Then the multi-output LS-SVM is trained to reconstruct the coordinate of the object center. Numerical results show that this approach is accurate and efficient even with some additive Gaussian noise.

A novel switchable beam textile antenna (SBTA) for wireless body area network (WBAN) applications is proposed. The SBTA is centrally-fed by a coaxial probe and the power distributed over four circular radiating elements. Four RF switches are integrated through which the SBTA is able to generate beam steering in four directions: 0°, 90°, 180°, and 270°, with a maximum directivity of 6.8 dBi at 0°. Its small size (88 mm x 88 mm) and flexibility enables the structure to be easily integrated into safety jackets, rain coats, etc., for tracking, and search and rescue communication purposes. The structure successfully integrates reconfigurability into a wearable textile antenna.