A printed slot antenna fed by a microstrip line with a diamond-shaped tuning stub for bandwidth enhancement is proposed and experimentally validated. The simulated results show that the impedance matching of the proposed rotated slot antenna is greatly affected by the dimension of the slot and by the size and the position of the diamond-shaped tuning stub. The experimental results demonstrate that the impedance bandwidth is over 123% for |S₁₁|≤-10 dB ranging from 2.80 to 11.81 GHz. Moreover, the proposed antenna has a small size, and stable and omnidirectional radiation patterns are observed within the operating bandwidth.

A novel horizontally polarized (HP) antenna with omnidirectional pattern is presented in this paper. The proposed antenna applies the concept of rotating electric field method to conventional slot dipoles. Two CPW-fed slot dipoles are placed in a perpendicularly conjugate form. By properly arranging the magnitude and phase of input signals, the omnidirectional pattern can be synthesized at broadside. A prototype is developed at the 2.6 GHz band, which offers a horizontally polarized omnidirectional radiation pattern with gain of 2.5-3.4 dBi, and the measured antenna efficiency is greater than 73% through the operating band (2.4-2.8 GHz). Furthermore, a 20-dB polarization purity is achieved in this design. The overall volume of the proposed antenna is 22×22×90 mm³ (0.19λ₀×0.19λ₀×0.78λ₀). Distinct from the other proposed HP antennas provided with planar geometry, this antenna is slim in shape, and it can be readily integrated with vertical dipoles to form a polarization diversity system in current wireless router and AP applications.

The design and implementation of millimeter-wave full-band waveguide-based spatial power divider/combiner are presented in this paper. The divider/combiner is based on a compact waveguide-to-microstrip (Wg-Ms) probe-array transition structure, providing full-band frequency coverage and low insertion loss. Efficient design and analysis method for this type of power divider/combiner is developed using spectral domain method combined with the image theory. Ka-band two-way (1×2) and four-way (2×2) power combining structures are analyzed and optimized. The performances of the both optimized power dividers/combiners are evaluated by experiments in back-to-back configurations. The measured overall insertion loss for the 1×2 power divider/combiner is better than 1.4dB over the entire Ka-band, which demonstrates the low-loss performance of the divdier/combiner. The optimized 2×2 power divider/combiner shows a same performance as the 1×2 structure without any degradation in operating bandwidth and insertion loss.

A novel compact slotline power divider is proposed in this article. This presented power divider employs a novel configuration with one lumped resistor, which makes it surpass most antecedent UWB power dividers based on microstrip-to-slotline transitions in aspect of isolation between output ports and return losses at output ports. The simulated and measured results illustrate the good performances of the novel power divider on return losses at all ports, isolation, amplitude and phase balances between output ports, as well as group delay over the wide frequency band from 3.8 GHz to 10.4 GHz.

This paper presents a novel compact dual-tri bandpass microstrip filter employing meander and open stub loaded resonators. With the proposed technique, a simple transformation from dual-band to tri-band BPF is realized. A novel structure using embedded resonators is designed to generate multi-band response. The main resonators control the low-band resonant frequency, the meander resonators control the two high-band resonant frequency and the open stub resonators control the high-band resonant frequency. The meander/stub resonators are embedded into the main spiral resonators, which makes the filter compact where its size is reduced by 64% compared to traditional filters. Passbands improvements and high selectivity are realized by the short circuit stubs which generate additional transmission zeros. The proposed filter has advantages such as low insertion loss, compact size and high selectivity. The theory is validated using the commercial full-wave solver CST 2012. Finally, the proposed structure is implemented and the measurement results are found to be in good agreement with the simulation results.

We present the design of 3-D metamaterial stacked arrays for efficient conversion of electromagnetic waves energy into AC. The design consists of several vertically stacked arrays where each array is comprised of multiple Split-Ring Resonators. The achieved conversion efficiency is validated by calculating the power dissipated in a resistive load connected across the gap of each resonator. Numerical simulations show that using stacked arrays can significantly improve the efficiency of the harvesting system in comparison to a flat 2-D array. In fact, the per-unit-area efficiency of the 3-D design can reach up to 4.8 times the case of the 2-D array. Without loss of generalization, the designs presented in this work considered an operating frequency of 5.8 GHz.

A novel wideband multilayer power divider with high isolation and bandpass response is presented in this article. This presented power divider employs microstrip-slotline coupling structure to realize the basic function of dividing input power. One lumped isolation resistor is introduced to improve the isolation between output ports. In order to solder the chip resistor between output branches, bending microstrip structure is utilized. For the sake of rejecting the unwanted signals locating in adjacent channels, interdigital structure and defected ground structure are designed to obtain a bandpass response and a wide upper stopband. The experimental results have indicated that the proposed wideband power divider has good performance on return losses, isolation, amplitude and phase balances, as well as group delay over the band 4.5 GHz-10 GHz.

In this article, a novel band-notched ultra-wideband (UWB) bandpass filter based on hybrid microstrip/slotline structure is proposed. A quad-mode stubs-loaded slotline resonator is fed by two orthogonal microstrip lines and ultra-wideband bandpass characteristic is excited. A stub-loaded dual-mode microstrip resonator is externally loaded to the quad-mode slotline resonator, and a notched band with sharp roll-off characteristic is achieved. The circuit model for the dual-mode microstrip resonator loaded slotline is given and analyzed. The proposed filter is designed and fabricated. Simulated and measured return losses are -12 dB/-18 dB and -18 dB/-10 dB in lower and higher passband. The return loss in the notched band is greater than 15 dB.

A broadband CPW-fed circularly polarized square slot antenna for ultra-high-frequency (UHF) radio frequency identification (RFID) applications is proposed. It consists of a square slot embedded with a spur line along diagonal and an F-shaped feeding structure. The proposed antenna achieves an imped-ance bandwidth about 307 MHz (34.6% @886 MHz) and a 3 dB axial ratio (AR) bandwidth about 232MHz (24.3% @954 MHz). The 3 dB AR beam-width is about 96 degrees over the UHF band of 840-960 MHz. The proposed reader antenna based on CPW structure is easy to integrate. With the symmetry and bidirectional radiation pattern, there are less readers needed in some applications, such as access con-trol, than the reader with unidirectional pattern, which will definitely decrease the implemented cost. Therefore, this universal design with desired performance across the entire UHF RFID band (from 840 MHz to 960 MHz) can be applied to all the UHF RFID applications worldwide. Detailed considera-tions of the design and main parameters will be studied in this paper.

A compact UWB (Ultrawideband) MIMO (Multiple-input multiple-output) antenna with asymmetric coplanar strip (ACS)-fed structure is proposed in this paper. The antenna consists of two modified ACS feeding staircase-shaped radiation elements which are orthogonally placed, and the wideband isolation is achieved through a fence-like stub between them. The effectiveness of the fence-like stub is analyzed. Measured results show that the presented antenna can achieve a broad impedance bandwidth (|S₁₁|≤-10 dB) of 3.1-11 GHz with good performance in terms of isolation >15 dB. Radiation patterns and correlation coefficient (ECC) denote the consistent diversity performance across the entire UWB bandwidth. By introducing the ACS-fed structure, the antenna size can be considerably reduced to 43.5 mm×43.5 mm×1.6 mm compared to the recently published UWB MIMO antennas, which makes the antenna suitable for portable UWB MIMO applications.

In this letter, a new design of dual-band circularly polarized (CP) slot antenna is proposed. By embedding a vertical stub, a T-shaped strip and a slit to the ground plane, the CPW-fed slot antenna can radiate right-handed circularly polarized (RHCP) wave in two bands 3.0 GHz and 5.0 GHz. The designed antenna with a size of 33 × 27 × 1 mm³ is fed by a 50-Ohm SMA connector and fabricated on a low-cost FR-4 substrate. Experimental results show that the measured 10-dB return loss impedance bandwidths are 20.4% for the lower band and 23% for the upper band, and the measured 3-dB axial-ratio (AR) bandwidths are 14.1% and 15.8%, with respect to 3 GHz and 5 GHz, respectively.

A dual grating waveguide accelerator structure is investigated and compared with the dielectric wakefield accelerator at THz frequencies. In a dielectric wakefield accelerator, thinner liners for a given current and liners having lower dielectric constant are not preferable due to the fact that they generate much lower axial wakefields. This limits the operation of the device at THz. On the other hand, it is shown that a grating waveguide is tuned at THz with shallower slot heights with competitive wakefield gradients than a dielectric wakefield accelerator.

Two different kinds of artifical magnetic conductors (AMCs) are used to reduce the out-of-band radar cross section (RCS) of microstrip patch antenna. The principle of this method is based on the high impedance characteristic of the AMC structures. The simulated results show that out-of-band RCS of the proposed patch antenna is much lower than that of the reference antenna over the frequency range of 5-12 GHz. The in-band scattering characteristic of the microstrip patch antenna is analyzed, and two slots are cut on the patch antenna to reduce in-band RCS. Prototypes of the reference and designed antennas are manufactured and tested, and the measured and simulated results of the two antennas are in good agreement.

This paper presents a dual-band tunable bandpass filter with independently controllable dual passbands based on a novel asymmetric λ/4 resonator pair with shared via-hole ground. Because two separated passbands can be independently generated by the two λ/4 resonators with different electric lengths, the asymmetric λ/4 resonator pair can realize flexible passband allocation when it is utilized to design dual-band filters. Two varactors are placed at the two open circuit ends of the asymmetric λ/4 resonator pair to control the two dominant resonant frequencies, respectively. A prototype tunable dual-band filter with Chebyshev response is designed and fabricated. The measured results are in good agreement with the full-wave simulated ones. The results show that the first passband varies in a frequency range from 0.88 GHz to 1.12 GHz with the 3-dB fractional bandwidth of 5.1%-6.4%, while the second passband can be tuned from 1.5 GHz to 1.81 GHz with the 3-dB fractional bandwidth of 5.4%-6.4%.

This work demonstrates an all-optical slow light Time Division Multiplexing (TDM) structure based on photonic crystals (PCs). The structure shows good ability of divide time domain signal into repetition time slots signal by four tunable group velocity waveguides from 0.006*c to 0.248*c where c is the velocity of light in the vacuum at the center wavelength of 1550 nm and over a bandwidth 4.52 THz with group velocity dispersion below 10 ² ps²/km. New high efficiency Y-type directional coupling output can get larger than ~1.4 times intensity and ~93% loss improvement which are comparable to conventional output device. The proposed PCs waveguide structure is leading the way to achieve the TDM application and has good capability to extend the application of the optical communication and optical fiber sensors systems.

In Chinese Compass Navigation Satellite System (CNSS for short), dual-band antennas are more attractive, because they can provide both navigation and communication services. In this paper, we present a dual-band dual-circular-polarized planar spiral-slot CNSS antenna. This antenna works at L Band (1616±5 MHz, left-handed circular polarization, LHCP) and S Band (2492±5 MHz, right-handed circular polarization, RHCP). Numerical results show that the impedance bandwidth (S₁₁<-10 dB), 3 dB axial ratio bandwidth and antenna gain at L Band are about 242 MHz, 79 MHz and 4.92 dB, respectively, while the simulated impedance bandwidth (S₁₁<-10 dB), 3dB axial ratio bandwidth and antenna gain at S Band are about 180 MHz, 58 MHz and 5.25 dB, respectively. An experiment was carried out to verify our design. Measured results show that impedance bandwidth (S₁₁<-10 dB) and 3 dB axial ratio bandwidth L Band are about 300 MHz and 14 MHz, respectively, while the measured impedance bandwidth (S₁₁<-10 dB) and 3 dB axial ratio bandwidth at S Band are about 210 MHz, 10 MHz, respectively. The measured results basically agree with the simulated ones and meet the requirement of CNSS terminal antennas.

A compact wideband planar microstrip-fed quasi-Yagi antenna is presented. In order to achieve a high gain, the traditional rectangular director in one row is replaced by two rows of directors with an angle, and the overall size of the antenna is unchanged. By adjusting the angle between the two rows of directors, a better performance is achieved. The measurement results show that a broadband impedance about 85.5% (1.84-4.59 GHz) for S₁₁ less than -10 dB and a gain about 4.5-9.3 dBi are obtained. Simulation and measurement results are provided and discussed. The agreements between the simulation and measurement results indicate that the antenna is suitable for wireless communication applications and phased arrays.

Using the Green's dyad technique based on cuboidal meshing, we compute the electromagnetic field scattered by metal nanorods with high aspect ratio. We investigate the effect of the meshing shape on the numerical simulations. We observe that discretizing the object with cells with aspect ratios similar to the object's aspect ratio improves the computations, without degrading the convergency. We also compare our numerical simulations to finite element method and discuss further possible improvements.

Based on the Collins integral, an analytical expression of a general Lorentz-Gauss vortex beam propagating in free space is derived, which allows one to calculate the linear momentum density of a general Lorentz-Gauss vortex beam in free space. The linear momentum density distribution of a general Lorentz-Gauss vortex beam propagating in free space is graphically demonstrated. The x- and y-components of the linear momentum density are composed of two lobes with the equivalent area and the opposite sign. Therefore, the overall x- and y-components of the linear momentum in an arbitrary reference plane are equal to zero. The longitudinal component of the linear momentum density is proportional to the intensity distribution. The influences of the Gaussian waist, the width parameters of the Lorentzian part, the axial propagation distance, and the topological charge on the linear momentum density distribution of a general Lorentz-Gauss vortex beam in free space are examined in detail.

In this paper, a circular microstrip patchcentrally etched with a cross slot is studied. The slot dimensions are varied for controlling the reflection lossand thephase range of a reflectarray. It is found that the dominant TM mode of the slotted circular patch can be easily excited, and the slot length can be varied to function as a phase-changing parameter. Cross slots with equal and unequal arms are investigated. Study shows that the slope of the S curve can be made slow-changing by increasing the slot width. A maximum reflection phase range of 328.68º is achievable in the S curve. Rectangular waveguide method has been deployedfor simulating and verifying the design idea. Reasonable agreement is found between the measurement and simulation.