This paper proposed a new approach, which is based on minimum mean-square error (MMSE) criterion, for wideband signal spatial direction-of-arrival (DOA) estimation when there is array error, and the impact of random array error to the new algorithm is analyzed in this paper. Pass the wideband signal mixed with array error through a bank of narrowband filters to obtain narrowband signals, then recover the sparse representation of the narrowband signals by re-iterative method in the MMSE frameworks, and estimate the number and DOA of sources from the sparse representation. The new method do not require the number of sources for direction finding, furthermore, it can estimate the DOA of coherent signals and the robustness of new algorithm to array error is better than coherent subspace algorithms. The simulated results confirmed the effectiveness and robustness of the new method.

In this paper, an ultra-wideband (UWB) printed dipole antenna with semicircular dipoles is presented. A balanced microstrip line is used for feeding the dipole antenna. By introducing the loading disc, an ultra wide frequency band from 3.2 GHz to 15.6 GHz with VSWR < 2 is obtained. Through analyzing the surface current of the antenna, the equivalent array radiation models of standing wave current and traveling wave current are obtained. These models can well explain the antenna's radiation characteristic, which matches measured results well.

This paper investigates the performance of DCS1800/CD-MA-EVDO dual-mode dual-link (DM-DL) UE, and presents an effective solution which is based on our designed high isolation antenna for the UE local electromagnetic interference (EMI). To this end, a DCS1800/CDMA-EVDO DM-DL UE model is firstly brought out, together with its system model, interference analysis and performance evaluation. Simulated results show that the DCS1800 (CDMA-EVDO) local interference will cause a sharp deterioration of the CDMA-EVDO (DCS1800) receiving sensitivity. To solve this problem, then, a compact and high isolation double-band handset antenna is given with its structure designed and performance validated by measurement. On the basis of this antenna and existing UE bandpass filter, we introduce a solution called ``passive isolation" to eliminate the local interference. Finally, the performance of DCS1800/CDMA-EVDO DM-DL UE is researched again by our solution, simulated results indicate that the isolation effect is quite good and the DM-DL UE can work normally.

We present a polarisation rotator based on a dielectrically embedded metal Mesh Half Wave Plate (MHWP) working in the W-band frequency range (75-110 GHz). The device was realised using metallic grids with sub-wavelength anisotropic geometries able to mimic the behaviour of natural birefringent materials. The device was designed using a combination of transmission line codes and finite-element analysis able to achieve phase accuracy down to a fraction of degree. Very accurate intensity and phase measurements were carried out using coherent radiation from a Vector Network Analyser (VNA). The presented device performs better and it is much thinner than previous devices having reduced the number of grids by a factor two and minimised their inductive losses. The new mesh HWP has excellent performances in terms of differential phase-shift flatness and cross-polarisation, respectively 180.4±2.9° and -28 dB across a 25% bandwidth.

A multi-stub-loaded resonator is presented in this paper. The resonators can be conveniently applied to design high-order dual-band bandpass filters (BPFs). Base on the analysis of the resonator, the first two even-mode resonant frequencies are controlled independently by the lengths of the loaded stubs. Two high-order dual-band BPFs using the first two even-mode resonant frequencies of the multi-stub-loaded resonators are proposed. The bandwidth of each passband can be adjusted independently by the coupling strength of the adjacent resonators. This paper deals with the analysis and design of the proposed high-order dual-band BPFs as well as the experimental validations of the predicted dual-band performance.

This paper presents a study of the effects of line width on the resonance frequency and bandwidth of a microstrip square-ring antenna at its primary resonance frequency. Although such ring antennas operating in TM11 mode are smaller than regular patch antennas, they are not explored much as they are considered to have poor bandwidth and efficiency at this mode. We have used a transmission line model to study their input characteristics and found that a non-uniform width ring antenna has significantly better (nearly double) bandwidth and radiation efficiency than a uniform width square ring antenna. Extensive simulations were done and a prototype non-uniform width square ring antenna is fabricated and tested to verify these results.

This paper presents an integrated millimeter-wave (mmW) low noise amplifier (LNA) which is implemented by using 0.15-μm baseline GaAs pHEMT technology. The design utilized modified co-planar waveguide (CPW) to perform a slow wave transmission line (TLine) with electromagnetic band gap (EBG) ground structures for the input/output matching networks. The low noise V-band LNA chip size was hence reduced by adopting the new EBG transmission lines. The developed amplifier exhibited a noise figure of 6.21 dB, and a peak gain of 17.3 dB at 66 GHz. Additionally, the amplifier has linear characteristics and its measured third-order intercept (IIP3) point is greater than -0.5 dBm a dc power consumption of 75 mW.

The increasing need for automatic identification and object tracking in supply chains has led to the development of radio frequency identification (RFID) systems. High frequency (HF) and ultra-high frequency (UHF) bands are frequently used because of their advantages over other bands. Although many HF and UHF band tags exist, some are unsuitable to handle the hostile environment of a supply chain. Therefore, this paper contributes to the research on a dual band RFID tag antenna operating on both the HF (13.56 MHz) and the UHF (919 MHz to 923 MHz) band, the UHF band used in Malaysia, by embracing the advantages of both HF and UHF bands to overcome the previously mentioned problems. The compact design is constructed by locating the UHF band antenna inside the HF band antenna and by reducing the number of turns of the HF band antenna compared to previous designs. The -10 dB bandwidth for the proposed design covers 12.9 MHz to 14.2 MHz for the HF band and 914.0 MHz to 929.0 MHz for the UHF band. The proposed antenna also overcomes the degradation problem by obtaining a high efficiency around 94% and a gain of 3.709 dB.

A simple method and structure to design a dual-band filter by using λ/4 stepped impedance resonators (SIRs) is presented in this paper. This filter has enhanced performance, including a good rolloff in the stopband and good insertion-loss response. The structure is compact and easy to fabricate. The circuit is investigated with the even-odd mode theory to prove the existence of transmission zeros. The dual-band response is analyzed by using SIR theory and the parallel-coupled line theory. Based on the proposed filter topology, two dual-band filters center operating frequency at 2.4 GHz and 5.2 GHz respectively with different configurations have been designed and one of them was tested, which validates the diversity of the filter configuration. Experimental results show that the measured and simulated performances are in good agreement. The overall area of the fabricated filter is 12mm * 12 mm.

This paper presents a novel design of a 4x4 two-layer wideband Butler matrix using a CB-CPW wideband multilayer directional coupler as well as a novel CB-CPW wideband elliptic directional coupler. With this configuration, the proposed matrix was designed to avoid crossovers as in conventional Butler matrices, thus reducing its size, losses and the design complexity while leading to a broad bandwidth of 3 GHz. To evaluate the performance of the proposed matrix, experimental prototypes of the directional elliptic coupler, the CB-CPW multilayer directional coupler and Butler matrix were fabricated and measured. Furthermore, a 4-element antenna array was connected to the matrix to form a beamforming antenna system at 5.8 GHz. As a result, four orthogonal beams were realized in the band 4.5-7.5 GHz.

A simple geometrical Asian-hand model with human tissue properties posed at two common talk-mode positions is proposed for comparative study. The newly designed hand is formed by measuring adult female hand at open-hand position before being posed into the presented styles. Four human hand tissues are included; skin, bone, muscle, and tendon, and also three homogeneous set of hands using specific anthropomorphic mannequin (SAM) hand phantom dielectric properties. A candy-bar type mobile phone with Planar Inverted-F Antenna (PIFA) is used to radiate dual-band frequency of GSM900/1800 in the vicinity of the SAM head phantom. The mobile phone casing is made out of plastic and only two components were considered: the FR-4 ground plane and PIFA. The specific absorption rate (SAR) averaged over a mass of 10 gram and 1gram is calculated after obtaining the power loss density and electric field value from simulation in CST Studio Suite 2011. The SAR and return loss results of six hand structures, including the SAM hand phantom are compared. The antenna performance with the inclusion of hand does not decrease as much as 1800 MHz in 900 MHz range, but absorbs energy more in the hands for 1800MHz compared to 900 MHz SAR values.

Cavity reflex antenna (CRA) employing a circular patch type FSS (Frequency Selective Surface) superstrate is investigated. Analysis in terms of gain, bandwidth (impedance and gain) and radiation pattern has been presented. The aim of this work was to study low profile CRA having very thin superstrate sizes. In this CRA a circular patch antenna is used as a feeding source. The circular patch type FSS possesses some unique properties favorable for thin superstrate sizes. In practice when the excitation source of the CRA is a probe-fed microstrip antenna with finite ground plane, substrate and superstrate, cross-polarization increases. In the presented design, the cross polar level has been reduced by choosing the optimum air gap and superstrate geometrical and electrical properties. A CRA with circular patch type FSS offers better performance both in terms of gain and impedance bandwidth for, thin superstrates (0.008) while giving a gain of 13 dBi and considerably reduced crosspolar level. The proposed antenna exhibit nearly equal E-plane and H-plane radiation pattern. Measurement results are provided to support the simulated results (by Ansoft HFSS). The circular patch type FSS is easy to fabricate and can be embedded into the host profile.

In this paper, we present a new synthesis method for a generalized symmetric multiple band bandpass filter. By using frequency transformations on the low pass prototype, the poles and zeros of the single/dual band filtering function are obtained. These poles and zeros are combined and re-arranged to get the multiband filtering function. The coupling matrix is obtained from this multiband filtering function. A variety of filters are synthesized in order to validate the proposed theory. A triple band and quadruple band filters have been designed, fabricated and measured. The measured results have good agreement with the simulated results.

The dynamics of a system of two bilaterally coupled chaotically oscillating X-band Gunn oscillators (GOs) has been studied by numerical simulation and by hardware experiment. The effect of variation of the coupling strengths between two oscillators in two paths has been explored. The chaotic oscillations in two GOs have become synchronized in most of the cases when coupling factors (CFs) are around 20% or more. However, the transformation of chaotic states of the GOs to quasi-periodic ones has been observed for some values of CFs. A detailed numerical analysis on the instantaneous error parameters of the GO state variables is presented to identify different steady state dynamical conditions of the system. Experimental observations of the GO output frequency power spectra and the averaged product of the two GO outputs in the coupled mode confirm the occurrence of synchronization as well as quenching of chaotic oscillations for different values of CFs.

Features of the spatial power spectrum (SPS) of multiple scattered ordinary and extraordinary waves in randomly inhomogeneous magnetized plasma are investigated using the smooth perturbation method taking into account diffraction effects. Second order statistical moments are derived for arbitrary correlation function of electron density fluctuations at oblique illumination of magnetized plasma by mono-directed incident radiation. Numerical calculations have been carried out for anisotropic Gaussian correlation function taking into account anisotropy factor and angle of inclination of prolate irregularities with respect to the external magnetic field. It was shown that SPS has a double-peaked shape. External magnetic field narrows SPS for ordinary wave and the gap arises in the direction of prolate irregularities. For extraordinary wave the gap increases with a distance passing by the wave in anisotropic magnetized plasma, the width broadens and maximum slightly displaced.

This paper presents a low voltage wideband down-conversion mixer using current-mode approach for multi-standard receivers. The proposed mixer uses a current mirror amplifier with an embedded passive switching core to achieve mixing function, which can combine the advantages of active and passive mixers simultaneously. The mixer is implemented using a 0.18 μm CMOS technology and covers frequency band from 0.5 GHz to 4.0 GHz. A comparison with conventional CMOS down-conversion mixer shows that this current-mode mixer has advantages of large conversion gain, low noise figure and high linearity. Over the entire bandwidth, the mixer features a conversion gain of 8.0~8.7 dB, a double-sideband (DSB) noise figure of 6.7~9.1 dB and an input third-order intercept point (IIP3) of 1.5~5.2 dBm, while consuming 8 mA from a 1.2 V supply voltage. The mixer occupies the active area of 0.43×0.46 mm² including testing pads.

We have applied the phase unwrapping technique to resolve the phase ambiguity problem arising from complex expressions of scattering parameters, for reflection-only measurement configurations, since, at some instances, only one side of the sample under test is accessible for electromagnetic measurements. We considered two different measurement configurations for testing the applicability of the phase unwrapping technique as: 1) two identical samples with different lengths flushed by a short-circuit termination and 2) one sample shorted by a varying short-circuit termination. For each measurement configuration, the underlying expressions for the reflection scattering parameters are derived. For both cases, we evaluated the suitability of the phase unwrapping technique by considering a highly-dispersive medium (distilled water) as our test sample. We note that continuity of the real part of the complex wavelength is a key issue in the unwrapping technique for (one-port) reflection-only measurements.

The multimode beam wave interaction behavior in a tapered, cylindrical cavity RF interaction structure of a 42 GHz gyrotron operating in the TE₀₃ mode has been investigated through nonlinear analysis and PIC simulation. A technique for producing the annular gyrating electron beam in PIC simulation code CST Particle Studio has been described. An energy transfer phenomenon from electron beam to RF has been demonstrated. The performance of cavity has been monitored to ensure the device operation in the desired mode and frequency. In the PIC simulation, the effect of beam velocity spread on the power output has been discussed. Using multimode behaviour, the effect of presence of nearby modes on the cavity performance has been observed. The simulation results have been compared with the results obtained from self-consistent single-mode analysis and time-dependent multimode analysis. It has been found that output power is well above the desired 200 kW level for the designed 42 GHz gyrotron operating in TE₀₃ mode.

Electromagnetic (EM) scattering properties from the ship wakes on the two-dimensional (2-D) perfect electric conductor (PEC) sea surfaces are studied by utilizing the small-slope approximation (SSA) theory. Considering the limitations of using the ideal plane EM wave incident upon a rough sea surface of the limited size, the expressions of the scattered field and scattering amplitude are derived by utilizing the modified tapered incident field. Based on a simplified segmented ocean spectrum model, the bistatic and monostatic normalized radar cross sections (NRCS) from the PEC sea surfaces with and without ship wakes are calculated, respectively. Meanwhile, the variation of scattering coefficient as scattering angles is given and compared under different polarization states. The results show that the scattering from the PEC sea surfaces with ship wakes is evidently different from that without them in bistatic and monostatic scattering. This provides a basis to extract ship wake characteristics. Also it shows that the SSA is a very effective analysis method to deal with the EM scattering from the rough sea surface. Finally, the effect of different tapered factors on backscattering coefficient is discussed, and it is concluded that an artificial reflection from the boundaries and a scattering upwarping from low-grazing incidence can be avoided just when the tapered factor is relatively smaller. This gives the theoretical basis for the analysis of EM scattering characteristics of ship wakes on the PEC sea surface.

This paper gives an overview of various electric machines for application to renewable energy harvesting, and reveals the corresponding challenges and research opportunities. After introducing various renewable energies and electric machines, the concept of renewable energy machines is coined. Then, the existing machines, including the DC, induction and synchronous types, for renewable energy harvesting are challenged. Consequently, research opportunities of advanced machines, including the stator-permanent magnet (PM), direct-drive PM and magnetless types, are elaborated. Finally, both near-term and long-term renewable energy machines are identified especially the emerging stator-PM, vernier PM and stator doubly fed doubly salient types.