Vol. 18

A dual-feed dual-polarized dielectric resonator antenna (DRA) with high isolation is proposed in this paper. The high isolation is achieved by using two hybrid feeding mechanism: one port having an H-shaped aperture coupled feed and the other with two out-of-phase probe feeds. The antenna is designed to operate at around 5.2 GHz for WLAN (Wireless Local Area Network) applications and experimental results show that it has more than 35 dB isolation over the entire impedance bandwidth. Good symmetric broadside radiation patterns with low cross polarizations are observed in the two principal planes, and in addition, the front-to-back (F/B) ratios for Port 1 and Port 2 are 10 and 18 dB, respectively.

In this letter, a novel high selectivity microstrip filter with source-loaded coupling is proposed using the dual-mode resonator. The resonator can generate one odd mode and one even mode in the desired band. The folded stepped-impedance open stub at the central plane can control the even mode resonant frequencies, whereas the odd mode ones are fixed. A transmission zero is created near the lower cut-off frequency due to the main path signal counteraction. Two additional transmission zeros attributed to source-loaded coupling are generated near the upper cut-off frequency and in the upper-stopband. A dual-mode filter prototype is simulated, fabricated and measured. The EM simulated and measured results are presented and excellent agreement is obtained.

A novel low-pass filter (LPF) is designed and fabricated based on stepped-impedance resonator (SIR). Semi-circles are used to reduce the size of the filter. The open-circuited stubs are used in the filter, and its simplified equivalent circuit is also proposed. The measured 3 dB cutoff frequency is 5.2 GHz with no more than 0.3 dB ripple level in the pass-band. From 5.5 to 14 GHz, the investigated LPF has a rejection level batter than 20 dB. Measured results show good agreement with simulated ones.

The straightforward comparison between electromagnetic environment measurements and immunity levels for industrial, scientific, and medical equipment has been used in the technical literature as an ordinary method to provide electromagnetic compatibility management within critical areas, such as hospital and industrial environments. This paper addresses a theoretical discussion concerning emission and immunity test features to focus the aforementioned problem. Finally, a more reliable comparison method is proposed, the environmental compatibility level definition, using analytical analysis and measurement results.

This paper presents the high frequency electromagnetic field expressions for perfect electromagnetic conductor (PEMC) Gregorian system. In this Gregorian system both the reflectors are PEMC and are embedded in homogenous chiral medium. Depending upon the values of chirality parameter (kβ) two cases are analyzed. In the first case, chiral medium supports positive phase velocity (PPV) for both the left circularly polarized (LCP) and right circularly polarized (RCP) modes. In the second case, chiral medium supporting PPV for one mode and negative phase velocity (NPV) for the other mode is taken into account. Since geometrical optics (GO) fails at the focal point, so Maslov's method is used to find the field expressions at the focal point. Field plots for different values of admittance (M) of the PEMC and the chirality parameter (kβ) are given in the paper.

A highly integrated up-converter MMIC is presented for low cost and high performance Ka-band transmitter module application. The multiple functions of the up-converter, such as local oscillator (LO) amplifier, single sideband subharmonic mixer, LO bandstop filter, and three-stage RF amplifier, are integrated into a single chip. A proper circuit topology for the complete integrated circuit is selected to achieve the miniature chip size. The combination of lumped and microstrip lines are used to realize the compact sub-circuits. The layout of the circuit is optimized using electromagnetic (EM) simulations. The chip is fabricated in WIN 0.15 μm PHEMT technology on 4-mil GaAs substrate with a layout area of only 2.8 mm×0.8 mm (2.24 mm²). Measured conversion gain is 12±1 dB over 28-37 GHz for the LO pumping power of 0 dBm. The sideband and 2×LO suppressions are above 20 dBc. The 1 dB gain compression output power (P-1dB) is 12 dBm. LO to RF isolation is about 35 dB.

A novel subharmonically pumped resistive mixer (SHPRM) with a chip dimension of 0.8×0.81 mm² is fabricated through a standard 0.18-μm CMOS process. An impedance-transforming active quasi-circulator is monolithically integrated with an nMOS field-effect transistor (FET) to perform up-converter mixing while simultaneously enhancing all port isolation through a broadband operation. The design analysis of impedance-transforming active quasi-circulator is also presented for matching between circulator and resistive transistor. As shown in the measured results, the mixer exhibits a 9-14.5 dB conversion loss. All port-to-port isolations better than 16.5\,dB over a radio frequency (RF) of 10-20 GHz can be achieved.

New dual-band bandpass filters with compact coupling and sizes reduction are proposed by using split ring stepped-impedance resonators and two paths coupling. In the new design, split ring SIR and defected ground structure are applied not only to reduce filter size but also to improve the filter performances. The presented filters have advantages of compact and novel structures, miniaturization and dual-band with nicer performances such as high selectivity, low passband insertion losses and so on, and these performances are demonstrated by measurement. The new design may be quite useful in wireless communication systems.

In this paper, the surface states (or so called Tamm states) of a nonlinear self-focusing slab sandwiched between a uniform medium and a one-dimensional photonic crystal has been investigated based on the first integral of nonlinear Helmholtz wave equation. The consider slabs can be a left-handed metamaterial or a conventional material. It is shown that the structure can support the Tamm states with two different transverse electric structure. In one kind, the surface waves has a hump at the surface of photonic crystal, and the other one has two humps. We reveal that in the case of self-focusing left-handed metamaterial slab, there is possibility for change of total flow's direction of surface waves by adjusting of the intensity of exciting electromagnetic field.

In this paper, a study on the dual-frequency box-shaped antenna is presented. With a 5-branch feeding strip and two plates of shorting strips, the antenna shows broadband and compact property. Then a U-shaped slot is etched for dual-band operation. Simulated and measured results all show that this antenna exhibits dual-wideband characteristic, covering several present wireless communication systems, such as GSM800/900 (824--960 MHz), WLAN11b (2.4--2.5 GHz), WiMax802.16 (2.5--2.7 GHz), and Bluetooth band (2.4--2.8 GHz). The simulated impedance bandwidth (2:1 VSWR) is 21.5% and 37.2% in the lower and higher band, ranging from 790MHz-980MHz and 2.3 GHz--3.35 GHz. Then details of the antenna are described and the prototype is fabricated and tested. A measured bandwidth of 19.8% and 38.9% in the two bands, ranging from 820 MHz--1000 MHz and 2.28 GHz--3.38 GHz, is observed, shown good agreement with simulated results. Moreover, the antenna has a coaxial feed with a compact size of 0.27λ×0.22λ×0.036λ (λ is the wavelength referenced to the lowest edge of the operating band 820 MHz).

Recent research demonstrates that sparse beam pattern constraint can suppress the sidelobe level of the linear constraint minimum variance beamformer. Here we improve the standard beam pattern by replacing it with a combination of a total difference minimization constraint on the mainlobe and a standard C₁ norm minimization constraint on the sidelobe. As the new constraint matches the practical beam pattern better, the sidelobe level is further suppressed, while the robustness against the mismatch between the steering angle and the direction of arrival (DOA) of the desired signal, is maintained.

A probe-fed air-substrate patch antenna with an inclined radiating patch for generating a downtilt main beam for WLAN operation in an on-wall access point is presented. The proposed antenna has a simple structure and consists of two major parts: an L-shaped ground plane and an inclined radiating patch, which is easy to implement. Constructed prototypes suitable for operating in the 2.4 GHz WLAN band are demonstrated. Results indicate that, simply by varying the inclination angle of the radiating patch, a downtilt main beam with a wide range of downtilt angles can be achieved. In addition, by selecting the proper inclination angle of the radiating patch, the proposed antenna shows a narrower 3-dB beamwidth in the elevation plane, resulting in an enhanced antenna gain, which is very suitable for on-wall 2.4 GHz WLAN access point applications. Details of the proposed antenna design are described, and experimental and simulation results are presented.

The nucleation and growth of primary Al₂Cu phase in the Al-34.3wt%Cu hypereutectic alloy without and with a 12 T magnetic fields have been investigated by differential thermal analysis (DTA). The DTA curves indicated that the nucleation temperature of primary phase was significantly reduced in a magnetic field. The X-ray diffraction (XRD) patterns confirmed that the c-axes of primary Al₂Cu crystals oriented along the direction parallel to a magnetic field. The microstructures showed that primary crystals aligned along a magnetic field and that their number distinctly increased with increasing a magnetic field as well. The suppression of nucleation in a magnetic could be caused by the increase of the interfacial energy between the liquid and nucleus and the reduction of atom diffusion rates while the orientation of primary crystals were mainly attributed to both of the magnetic toque and the thermoelectric magnetohydrodynamic (TEMHD) flows.

A new broadband circularly polarized (CP) square slot antenna is evaluated numerically and verified experimentally. The proposed antenna uses a lightening-shaped feedline protruded from the signal line of the feeding coplanar waveguide (CPW). Two symmetrical F-shaped slits embedded in opposite corners of ground plane are designed to obtain an excellent CP bandwidth. By adjusting the dimensions of the lightening-shaped feedline, the CP bandwidth can be further enhanced. Measured results show that the 3-dB axial-ratio bandwidth of the proposed antenna can reach 51.7% (2150 MHz-3650 MHz), and the impedance bandwidth is as large as 60.2% (2150 MHz--4000 MHz) with VSWR ≤ 2. Measured results are in good agreement with the simulation. The proposed antenna can be easily fabricated because of the simple coplanar geometry.

Utilizing the special physical characteristic of a high impedance surface, a radio frequency identification tag antenna working at 920 MHz for metallic ground is proposed. The antenna not only overcomes the problem of impedance mismatching when placing on a metallic object, but also exhibits a low-profile antenna structure.

Scattering of electromagnetic plane waves from an infinitely long nihility cylinder, coated with a chiral layer of uniform thickness, is presented. Cylindrical vector wave functions have been used to express the fields in different regions. The solution is determined by solving the wave equation for different regions and applying the appropriate boundary conditions at the discontinuities. Both TM and TE polarizations as incident plane wave have been considered in the analysis. Obtained Numerical results for the chiral-coated nihility cylinder are compared with a chiral-coated PEC cylinder.

Simultaneous switching noise (SSN) is a significant problem in high-speed circuits. To minimize its effect and improve the electrical characteristics of circuits such as signal integrity (SI) and power integrity (PI), a novel power plane with planar electromagnetic bandgap (EBG) structure is proposed for SSN suppression in printed circuit boards (PCB) in this paper. In which a kind of improved long bridge is used and the equivalent parallel inductance can be increased significantly. Compared to the typical spiral bridge EBG structure with the same parameters, the long bridge EBG structure will change bandgap into dual-band, with lower center frequency and wider bandwith. The effectiveness and accuracy of this structure are verified by both simulations and measurements.

The memristor theory of Chua [1] provides a connection with the charge and magnetic flux in an electric circuit. We define a similar relation for the electric and magnetic flux densities in electromagnetism. Such an attempt puts forward interesting results. For example, the magnetic charges do not exist in nature however the electric charges behave as the magnetic monopoles in special media. We support our theory with results of the recent experiments on materials named as spin ice.

In this paper, a wide-slot triple band antenna fed by a coplanar waveguide (CPW) for WLAN/WiMAX applications is proposed. The antenna mainly comprises a ground with a wide square slot in the center, a rectangular feeding strip and two pairs of planar inverted L strips (PIL) connecting with the slotted ground. By introducing the two pairs of PIL's, three resonant frequencies, 2.4/5.5 GHz for WLAN, and 3.5 GHz for WiMAX, are excited. Prototypes of the antenna are fabricated and tested. The simulated and measured results show that the proposed antenna has three good impedance bandwidths (S11 better than -10 dB) of 300 MHz (about 12.6% centered at 2.39 GHz), 280 MHz (about 8% centered at 3.49 GHz) and 790 MHz (about 14.5% centered at 5.43 GHz), which make it easily cover the required bandwidths for WLAN band (2.4--2.48 GHz, 5.15--5.35 GHz, and 5.725--5.825 GHz) and WiMAX (3.4--3.6 GHz) applications. Moreover, the obtained radiation patterns demonstrate that the proposed antenna has figure-eight patterns in E-plane, and is omni-directional in H-plane. The gains of the antenna at operation bands are stable.

Novel compact microstrip quadruple-mode stub-loaded resonator and broadband bandpass filter (BPF) are proposed in this letter. As a starting part of designing a quadruple-mode broadband BPF, the initial novel triple-mode open impedance-stepped stub loaded resonator characteristic is investigated to choose its proper dimensions. Based on these pre-determined dimensions of the triple-mode resonator, two identical short-circuited stubs are loaded against the impedance-stepped open stubs in the resonator to generate a tuned resonant mode and a transmission zero in lower stopband which leads to a high rejection skirt. A compact broadband BPF with the quadruple-mode resonator is simulated, fabricated and measured. The measured results agree well with the EM simulations.