A new type of cascaded series feed beamforming networks (BFNs) is introduced. The network architecture is based on a dual-series Nolen matrix topology. It is able to produce tapered output amplitude distributions from NxN configurations. The general concept, analysis and systematic design of the BFNs are given. The networks are designed and intended to be used mainly for low Sidelobe Level (SLL) linear Multibeam Antennas (MBAs). Several design examples are presented, along with fabrication and measurements of an S-band prototype.

In this paper we present seasonal results of the effective earth radius factor distribution in South Africa using recently (2007-2009) acquired radiosonde data from the South African Weather Service (SAWS) for seven locations in South Africa. Two data modeling methods are used to formulate the solution for the distribution of the effective earth radius factor. The seasonal effective earth radius factor statistics obtained from the radiosonde measurements are then interpolated, gridded and presented in contour maps to cover the rest of the country for the four seasons defined by ITU-R recommendation P.453-12. The Integral of Square Error is used to check the performance of the data modeling techniques while the Root Mean Square Error is used to compare the performance of the different interpolation methods used.

In this paper, a novel algorithm named multi-scan mixture particle filter is proposed for joint detection and tracking for a varying number of targets. The posterior distribution of multiple target state in a single-target state space is a multi-mode distribution with each mode corresponding to either a target or clutter. A general global posterior distribution is adopted in this work, which consists of existing components and new components. The new components are generated at each time step to capture the new modes due to newly appeared targets or clutter. In order to distinguish targets from clutter, multiple scan information is incorporated. The history of each component's associate weights is stored in a multi-scan sliding window, which is used to judge whether the component is from a target or clutter. Moreover, a novel sampling method which combines the likelihood sampling and prior sampling is proposed to draw particles from the desired parts of the state space at each time step. From the simulation results, it could be seen that the proposed algorithm can effectively detect the appearance/disappearance of the targets as well as track the existing target.

In this paper, design and analysis of omnidirectional single feed circularly polarized, wide axial ratio beamwidth resonant sidefed bifilar helix antennas that do not require a ground plane is presented. The simulation and measurement results show that side-fed helix antennas of various radii gives near perfect circular polarization (CP) almost over the whole sphere except at and around nulls, at a certain turn angle by properly proportioning the area of loop (A) with the product of pitch (p) and radianlength (l) of helix. Helix antennas with smaller radii give axial ratio (AR) close to one at higher values of turn angle with lower value of resonant input impedances but CP is less sensitive to inaccuracy in turn angle. However helix antennas with larger radii results in AR close to one at lower values of turn angle and provides better values of input resistance but its AR is more sensitive to variations in turn angle. The simulated results show that the polarization solid angle beamwidth (for AR ≤ -3 dB) varies from 3.96π to 4π steradian. The gain and 3dB beamwidth of the antennas are 2dBi and 90° respectively. The polarization bandwidth varies from 34% to 65%. The simulated results are verified by experimental measurements.

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.