New multiband integrated slot antennas for mobile handsets are presented for GSM, DCS, PCS and WCDMA, GPS and WIFI 2.4 GHz. Prototypes, both simulated and measured, are realised in the metal back cover away from the hand. Perturbations due to tissue proximity are simulated using a CTIA compliant hand phantom.

A novel compact coplanar waveguide (CPW)-fed printed antenna with triple bands for WLAN and WiMAX applications is presented. By using a parasitic circular patch, a pair of symmetrical inverted-L strips and a 50-Ω transformer, the antenna can effectively provide a good input impedance matching. The tuning effects of the ground size, the parasitic circular patch and the symmetrical inverted-L strips to the resonance and matching condition are then examined, and the prototype of the proposed antenna is further fabricated and measured. The experimental and numerical results exhibit that the antenna has impedance bandwidth for S₁₁≤-10 dB of 2.32-2.80 GHz, 3.06-4.13 GHz and 5.03-6.04 GHz, which can cover both the WLAN 2.4/5.2/5.8 GHz bands and the WiMAX 2.5/3.5/5.5 GHz bands. Also, a stable monopole-like radiation pattern and an average antenna gain of 3.06 dBi across the operating bands have been obtained.

This letter demonstrates a technique for a folded slot antenna fabricated on low resistive silicon wafer, using pre-etched cavity and Benzocyclobutene (BCB) support membrane. The most distinctive feature of this method is that a cavity is pre-etched before the antenna fabrication process using low-cost potassium hydroxide (KOH) wet etching. BCB membrane is employed to support the antenna above the cavity for its low permittivity as well as excellent thermal and mechanical stability. The fabrication process discussed in detail and the fabricated antenna was characterized. Experimental results show that the antenna resonates at 15.4 GHz with a very wide impedance bandwidth, up to 14.6%.

In this article, artificial aerosol metaparticles are investigated. These particles are based on interacting single split rectangular resonators (SRRs) imprinted on a one-sided thin dielectric substrate. These particles produce sharper transmission bandstops with adjustable bandwidths compared to conventional artificial aerosol obscurants like fibers, spheres, discs. The particle design is performed in the microwave region with the intention to be scalable to the infrared. Particles with couplings between two, three, and four SRRs are introduced. Numerical simulations and experimental measurements of the transmission parameter of the particles are introduced and compared with fibrous aerosols. These particles may be used as good electromagnetic obscurants in the atmosphere.

A spacecraft will experience the well-known ``blackout'' problem in the re-entry into the Earth's atmosphere, which results in communication failures between the spacecraft and ground control center. It is important to study the blackout mitigation method. The effects of external magnetic field on electromagnetic wave propagation in plasma are studied by theoretical and experimental methods in this paper. The numerical results show that the attenuation of electromagnetic wave in plasma is reduced by the presence of a magnetized field. The propagation properties of electromagnetic wave in unmagnetized and magnetized plasma have been studied experimentally with plasma torch, and the experimental results are in good agreement with the theory. Both the theoretical and experimental results indicate that magnetic window is an alternative and promising way to improve the radio blackout issue.

Broadband beamforming has been an important issue on antenna array processing due to many practical demands on communication, radar, or sonar applications. Although several effects deteriorating array performance have been addressed for narrowband beamforming, few of them are considered for the broadband scenario. Besides, the definition of output signal-to-interference plus noise ratio (SINR) and the way to simulate broadband signal sources are usually vague, which further obstructs the development of broadband beamforming. In this paper, the performance of discrete Fourier transform (DFT) beamformers operating in block processing and sliding window modes are investigated when the correlation matrices are known or estimated by finite data samples. The output SINR of DFT beamformers is well-defined, and the generation of broadband signals is clearly introduced. Simulation results with respect to the signal bandwidth, the number of frequency bins, and the number of data samples are presented for illustration and comparison.

There is an impetuous need for easy-to-build electrical machines with high specific thrust for various applications. The paper deals with a new modular variable reluctance tubular machine. It is a transverse flux machine without permanent magnets. Its construction is detailed and the novelty of the proposed structure is emphasized. A sample machine is analyzed by analytical and numerical means. The results of the analyses are validated by testing a laboratory model of the motor.

In this paper, a dual-fed circularly polarized antenna design with high isolation is presented for radio frequency identification(RFID) reader. The proposed antenna is excited by two fed ports connected with a circular split-ring microstrip line underneath the ground plane. A radial aperture in the ground plane provides coupling between the split-ring microstrip and radiating patch. For multiple RFID band requirements, the dimension of the aperture can be modified to obtain high isolation on different RFID Band. Finally, an antenna prototype for China RFID Band(920-925 MHz) is fabricated. The measured results agree well wit13h simulation, and show 10-dB matching bandwidth of 18%(820-1000 MHz), 3-dB axial ratio(AR) bandwidth of 11%(854-960 MHz), and 25-dB isolation bandwidth of 11 MHz(917-928 MHz).

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.