The C-method is an exact method for analyzing gratings and rough surfaces. This method leads to large-size dense complex non-Hermitian eigenvalue. In this paper, we introduce a parallel QR algorithm that is specifically designed for the C-method. We define the ``early shift'' for the matrix according to the observed properties. We propose a combination of the ``early shift'', Wilkinson's shift and exceptional shift together to accelerate convergence. First, we use the ``early shift'' in order to have quick deflation of some eigenvalues. The multi-window bulge chain chasing and parallel aggressive early deflation are used. This approach ensures that most computations are performed in level 3 BLAS operations. The aggressive early deflation approach can detect deflation much quicker and accelerate convergence. Mixed MPI-OpenMP techniques are used for performing the codes to hybrid shared and distributed memory platforms. We validate our approach by comparison with experimental data for scattering patterns of two-dimensional rough surfaces.

This paper presents a compact shorted stub-loaded quad-band bandpass filter. The proposed filter simultaneously operates at GSM (0.83-0.97 GHz), LTE2300 (2300-2400 MHz), WiMAX (3.3-3.7 GHz), and WLAN (5.725-5.825 GHz) bands. The filter has been designed using the technique of stub-loaded resonator (SLR). By changing the length of the center-loaded stub, the resonant frequency of the even-mode can be varied without affecting that of the odd-mode. This simplifies the design and tuning of the quad-band filter. Eight transmission zeros (TZs) around the three passband make the pass bands highly isolated. In order to validate its practicability, a quad-band bandpass filter (BPF) has been designed, fabricated and measured. Good agreement between simulated and measured results is observed.

The microwave radio links above 5 GHz suffer from attenuation due to precipitation. The need for employing higher frequencies has therefore encouraged research into rain attenuation due to precipitation. The natural variations of tropical precipitation occur in a wide range of time-scales, so does probably the behavior of radio communication links. This paper examines the variations of cumulative distribution of rainfall in Sumatra from an optical rain gauge measurement with a near continuous record of operation over eleven consecutive years (2002-2012). The worst month statistics were also examined and all results were compared with the ITU-R model. Of some natural variations of rainfall rate investigated, the diurnal variation had the most significant effect on the cumulative distribution of rainfall rate. The ITU-R model overestimated the rainfall rate for the first half of the day (00:00-11:59 LT) whereas it underestimated the rainfall rate until 0.01% of time for the second half of the day (12:00-23:59 LT) before the model starts to overestimate. The ITU model overestimated 52.85% of rainfall rate at 0.01% of time for the first half of the day and underestimates 7.59% for the second half. Considerable differences between the recorded data and the ITU-R model for the annual, seasonal, and intreaseasonal variations are only significant at small time percentage (≤ 0.01%). The relationship of worst month statistics was also slightly different from the ITU-R model. This result reinforces the previous studies on the limitation of the ITU-R model for the tropical region.

This study focuses on the length estimation of ballistic targets based on the full-polarization range profiles measured by the wideband full-polarization radar system. Firstly, the mathematical model of full-polarization range profiles is introduced, and the full-polarization range profiles characteristics of typical ballistic targets are analyzed by using the microwave anechoic chamber measurement data. Secondly, three methods are proposed for target length estimation based on single-channel detection synthesis, SPAN power synthesis and target characteristic polarization, respectively. Then, comparison experiments among the proposed methods and the method based on single-polarization range profile are carried out. The results demonstrate that the extraction accuracy and the anti-noise performance of the method based on target characteristic polarization are better than the others. Furthermore, the influence of the signal-to-noise ratio (SNR) on the length estimation is also discussed.

A small-size ultra-thin and narrow frame antenna with a switchable matching network to achieve LTE dual-wide band operation in the 700-980 and 1710-2500 MHz bands is presented for mobile phone applications. The highlight of the antenna is that it has a low profile of only 2 mm and occupies a small ground clearance of 45 × 4.5 mm², which are very attractive for ultra-thin mobile antenna applications. A folded monopole is used as a radiator fed via a switchable two-state matching circuit controlled by a PIN diode. The PIN type switchable matching network is mainly designed to tune the low band (700-980 MHz). By combining the two working states of the PIN diode, the proposed antenna can cover GSM850/GSM900/DCS1800/PCS1900/UMTS2100 and two LTE bands, LTE700/LTE2300. Details of the antenna are described in this study.

We deal with one of the computationally most critical steps of the Phase-Only synthesis of aperiodic reflectarrays, namely the fast evaluation of the radiation operator. We present an approach exploiting the use of a fast numerical algorithm using 2D Non-Uniform FFTs (NUFFTs) of NED (Non-Equispaced Data) and NER (non equispaced results) type and of parallel processing on Graphic Processing Units (GPUs). We extend the approach in K. Fourmont, J. Fourier Anal. Appl., vol. 9, n. 5, pp. 431-540, 2013 for implementing NUFFT routines to the 2D case and illustrate the parallel strategies to accelerate the approach. In particular, we show how the two levels of parallelism intrinsic in the interpolation step of the 2D NED-NUFFT can be fruitfully exploited by adopting dynamic parallelism, a feature made available in one of the latest architecture of NVIDIA cards. The presented synthesis results show that the introduction of further degrees of freedom (positions) allows improving the performance with respect to periodic reflectarrays. Also, the possibility of adopting aperiodic reflectarrays of reduced number of elements for fixed performance is demonstrated.

A coplanar waveguide-fed circularly polarized square slot antenna with the feasibility of obtaining a wider bandwidth and a relatively smaller size is proposed and demonstrated. The proposed antenna, consisting of a stepped feeding strip, a modified grounded L-shaped radiating patch, an inverted-L grounded strip and an asymmetric ground with an L-shaped slot as well as two horizontal slots, is designed, analyzed and fabricated. Good agreement between simulated and measured results is observed. Simulation and measurement results reveal that the proposed antenna can provide an impedance bandwidth of 106.3% (2.3-7.52 GHz) and a 3-dB axial ratio (AR) bandwidth of 90.2% (2.25-5.95 GHz). Additionally, within the effective circular polarization (CP) bandwidth of 88.5% (2.3-5.95 GHz), the proposed antenna has gains from 1.9 dBic to 5.2 dBic with an average gain of 3.9 dBic.

A novel fork monopole antenna is presented using metamaterial structures. The prototype monopole antenna consists of split-ring-resonators (SRR) as an electric-LC resonator and small ground. To prove the concept, the prototype antenna is designed and fabricated for wireless communication systems. The monopole structure makes UWB impedance bandwidth condition for 2-12 GHz. On the other hand, the prototype antenna shows dual notch band characteristics at 3.5-4.5 GHz and 5.3-6 GHz for WiMAX and WLAN rejection. The prototype antenna radiates omnidirectionally and has a gain altered between -4.5 and 6.2 dBi in 2.5-12 GHz, with an average gain of 4.2 dBi. The metamaterial model is suggested for the CRLH (ELC) resonator, and in addition, the parametric study for CRLH (ELC) resonator is presented for clarification of its manner on resonance controlling. Here, the final model antenna is fabricated on an FR-4, and experimental results are compared with simulations.

The near fields in the proximity of a small ferrite particle with magnetic-dipolar-mode (MDM) oscillations have space and time symmetry breakings. Such MDM-originated fields --- called magnetoelectric (ME) fields --- carry both spin and orbital angular momentums. By virtue of unique topology, ME fields are strongly different from free-space electromagnetic (EM) fields. In this paper, we show that because of chiral topology of ME fields in a near-field region, farfield orbital angular momenta (OAM) can be observed, both numerically and experimentally. In a single-element antenna, we obtain a radiation pattern with an angular squint. We reveal that in far-field microwave radiation a crucial role is played by the ME energy distribution in the near-field region.

Based on space-time duality and through the use of temporal dispersive delay lines, this paper presents a demonstration of temporal cloaking/uncloaking at microwave frequencies. Numerical simulations of pulse generation, continuous wave signal recovery and data recovery are discussed in relation to the proposed system architecture. This paper also suggests a practical means for implementation of real time dual temporal cloaking/uncloaking. Compared to traditional signal processing systems, since the recovered data emerges with a reversed form in time domain before its final decoding, an extra operation named time-reversal is needed to obtain the correct data, which could help protect the significant signals better with the proposed temporal cloaking/uncloaking system. The proposed method and achieved results indicate potential application in secure communications and data multiplexing subject to channel bandwidth requirements.

In this paper we report on a transmission-line model for calculating the shielding effectiveness of multiple-shield cables with arbitrary terminations. Since the shields are not perfect conductors and apertures in the shields permit external magnetic and electric fields to penetrate into the interior regions of the cable, we use this model to estimate the effects of the outer shield current and voltage (associated with the external excitation and boundary conditions associated with the external conductor) on the inner conductor current and voltage. It is commonly believed that increasing the number of shields of a cable will improve the shielding performance. However, this is not always the case, and a cable with multiple shields may perform similar to or worse than a cable with a single shield. We want to shed more light on these situations, which represent the main focus of this paper.

In this paper, dual-chirped arbitrary microwave waveform has been generated through photonics, incorporated with single dual parallel mach-zehnder modulator (DPMZM) inbuilt mach zehnder interferometer (MZI) structure. We have taken two cases of chirping i.e. linear and nonlinear chirps. A case of linear chirping has been explored previously. However, to the best of the authors' knowledge effect of nonlinear chirping in this paper is evaluated for the first time. Other photonics approaches are also available, such as spectra shaping and wavelength to time mapping. But due to fixed spectral response of spectral shaper, center frequency of linear chirp generated waveform is fixed. To get the large center frequency again we have to use large number of spectral shapers which will increase the system complexity. DPMZM avoids such difficulties. These MZMs are biased at the minimum transmission point to get carrier suppressed modulation. Product modulator (PM) is cascaded to the lower arm of DPMZM. Here by using DPMZM we get two advantages. First we have two complimentarily chirped microwave waveforms and second up conversion of the frequency of microwave carrier. A dual-chirped microwave waveform with centre frequency 6 GHz with bandwidth 200 MHz and 2 GHz is generated. The paper gives specific details about various performance parameters such as input signal frequency and power, output signal parameters viz output frequency, chirp rate, chirp bandwidth, time bandwidth product (TBW), etc. The overall model and its performance parameters are computed through MATLAB simulation.

In this paper, a novel quad-band combination of circularly-polarized microstrip antenna is proposed. This antenna has multi-frequency and quad-polarization with multiple coaxial probes, which cover four bands of the BeiDou navigation system (BDS), meeting different application requirements. By using a stacked structure to achieve feed and using symmetrical slotted method to place the coaxial probes, the multi-frequency antenna is connected together through the middle co-aperture. Meanwhile, the feed position and size are constantly optimized until get the most suitable one, and the necessary perturbation is obtained. We also introduce a broadband stripline 90° bridge. Ultimately, the circularly-polarized and multi-frequency operation is achieved. Furthermore, the novel design enables easy implementation, miniaturization, wide band, which can meet the application requirements and promote the development of the BDS, which can be combined with the Internet of Things technology, applied to life and production.

Electromechanical interaction between slow electromagnetic wave and anisotropic-conducting film is investigated. The physical effects associated with anisotropic-conducting film are revealed by electromagnetic theory and validated by experiment, and they have established the working principles for a class of electromechanical sensors and/or actuators, which have continuously moving part, and are sensitive to the amplitude and the direction of electromagnetic forces or fields and well able to reflect the resonance characteristics. The revealed and validated physical effects may have significance in quite different science and engineering fields and in wide frequency bands from RF to optics.

A main challenge in designing line-start permanent magnet synchronous motors is synchronization analysis and determination. The transient time-step nite element simulations are often required in the design process, which is computationally expensive. An attractive alternative is to use an analytical synchronization model, which is time ecient and thus viable to be included in an optimization procedure. In this paper, two variants of the energy-based analytical synchronization model are proposed. Their viability and performance are compared with those of the existing analytical method and validated by transient nite element simulations. It is shown that the proposed methods have a better resolution and accuracy in determining the synchronization status of line-start permanent magnet motors.

In this paper, three different frequency reconfigurable multiple-input-multiple output (MIMO) antennas are characterized in terms of their channel capacity performance in an indoor environment. Two 2×2 and one 4×4 MIMO antenna configurations are investigated. A complete MIMO system is implemented using software defined radio (SDR) platform. The antenna under test can be used at either transmitter or receiver ends. The channel capacity of the system is evaluated by computing the channel coefficient matrix. The measurements are performed at 2.45 GHz for line of sight (LOS) and non-line of sight (NLOS) scenarios. A comparison of the antennas is performed with an ideal system scenario with totally uncorrelated channels as well as an array of standard monopoles which are half-wavelength apart. The effects of antenna element efficiencies, radiation patterns and spacings on the channel capacity are discussed.

This paper investigates the design of a small antenna on a silicon substrate. The antenna on silicon substrate will be used for integration in a silicon-based GaN TR module. This Co-Planar Waveguide (CPW)-fed antenna has been successfully miniaturized up to λ/4 about 20% reductions by adding a slot to the patch antenna. Promising results are obtained from the antenna simulation and measurement. From the measurement result, the antenna bandwidth is 45% (4.8 GHz-7.5 GHz) with measured gain about 2.5 dBi over frequency range of 5 GHz-7.4 GHz.

An algorithm of solving phase ambiguity of multi-baseline direction finding system based on sparse uniform circular array is proposed in this paper. This sparse uniform circular array whose inter-element spacing is larger than half-wavelength distance suffers from cyclic phase ambiguities, which may cause estimation errors. In order to solve the above phase ambiguities, the corresponding virtual short baselines are acquired by transforming the array element phases that meet with the contraction relationship. The obtained short baselines are used to solve the phase ambiguities according to the virtual baseline and stagger baseline theory. Highly accurate estimates of direction of arrival are herein acquired. Furthermore, the direction of arrival and polarization parameter estimates are automatically matched with no additional processing. The array arrangement problem in high frequency scenario is solved. The estimation accuracy of angle of arrival is improved by means of the phase ambiguity resolution. Simulation results verify the effectiveness of this algorithm.

The parabolic equation (PE) method for estimating propagation characteristics of millimeter wave, which takes into account of attenuation caused by complex meteorological environment, is proposed. The meteorological environment is treated as a mixture composed of hydrometeors and atmospheric gases. Effective permittivity of the mixture is considered in this paper. Based on the effective permittivity, the PE model for estimating propagation attenuation of millimeter wave is developed via modifying the refractive index. Finally, the model is employed to simulate the propagation characteristics of millimeter wave in complex geographical environments of irregular terrain and rough sea surface, and in complex meteorological environments of standard atmosphere, rain and fog.

The high frequency scattering problems of electromagnetic fields scattered from electrically large scatterers are important and challenging. On the calculation of the reflected and diffracted wave fields, the high frequency methods could be classified into the current based method and the ray based method. In this paper, first, we give a review on the progress of the modern high frequency methods for solving the electromagnetic scattering problems. Next, due to the highly oscillatory property of the high frequency electromagnetic scattered fields, we propose the numerical steepest descent path method. Finally, we comprehensively address the high frequency wave physics, including the high frequency critical point contributions, the Keller's cone, the shadow and reflection boundaries and the creeping wave fields.