A novel compact microstrip planar slot antenna with triple-band operations for WALN and WiMAX applications is proposed. The antenna, which occupies an overall dimension of 35×19×1.6 mm³, has a simple structure which consists of an asymmetric coplanar strip with a reverse G-shaped slot and a U-shaped open stub. The U-shaped open stub excites a resonant mode at 2.4 GHz. On the other hand the asymmetric coplanar strip could excite the resonant modes at 5.2 GHz. Meanwhile, the reverse G-shaped slot is aimed to excite resonant modes at 3.5 and 5.8 GHz. It has good omnidirectional radiation patterns in the azimuth plane and reaches 1.1 dBi at 2.4 GHz, 2.3 dBi at 3.5 GHz, 3.1 dBi at the band of 5 GHz. The designed antenna is simulated by HFSS software and a good agreement with experimental results is demonstrated.

A through wall image enhancement scheme based on Takagi Sugeno fuzzy system and principal component analysis is proposed. The scheme incorporates spectral properties of image and textural properties of eigen components of image to assign weights. The scheme overcomes the empirical setting of inference engine and output membership functions. Simulation demonstrates the effectiveness of proposed scheme in terms of accuracy.

Within the framework of the composite surface scattering model, analytical formulas for Doppler shift and bandwidth of radar echoes backscattered from time-varying sea surface are derived in the forms of three-dimensional integrals. In our derivations, the influences of the tilt modulation (TM), the hydrodynamic modulation (HM), the shadow and the curvature of large-scale undulating waves are all taken into account for achieving more reasonable results. Comparisons between our theoretical curves and the results obtained directly by exact numerical method demonstrate that our formulas can improve the simulated results. On the other hand, the simulations by our formulas can also help to estimate the effects of the TM, the HM, and the shadow of large-scale waves on Doppler behaviors individually. We find that the predicted Doppler shifts are always larger in HH-polarization than in VV-polarization due to the TM. Meanwhile, the simulations also show that the predicted Doppler shifts for both HH- and VV-polarizations would become larger when the HM is considered. In addition, at low-grazing angles (LGA), the shadow effect results in a rapid increase in the predicted Doppler shift, and on the contrary makes the bandwidth narrower.

In this paper, coupled lines are used in the design of a dual band planar multi-way Bagley polygon power divider to reduce the size is proposed. For the input port matching and transmission characters are affected by the even mode impedance only, analysis of the multi-way Bagley polygon power divider and equivalent circuit based on coupled lines, closed form design equations are presented with even mode impedance, and odd mode impedance is obtained arbitrarily. To validate the design procedure, two dual band three-way Bagley polygon power dividers are designed, simulated, and fabricated using coupled lines with areas of 3.17 cm² and 2.53 cm², and the corresponding conventional divider with areas of 17.86 cm² and 11.74 cm², respectively. When coupled lines are used, the layout is more compact with a reduction in size of more than nearly 80% compared to the conventional design.

In this work, we analyze the effects of an inter-stage capacitor located between the power stage input and the driver stage output on the overall efficiency of a RF CMOS power amplifier and on gate-drain reliability problems. To verify the analyzed effects, we designed a RF CMOS power amplifier with a center frequency of 1.85-GHz. Class-D amplifiers with a feedback resistor are used as driver stages, and a class-E amplifier is used as the power stage. A distributed active transformer is adapted for use in the output power combiner for high efficiency. The inter-stage capacitor between driver and the power stage is removed to enhance the switching operation of the power stage. By eliminating the inter-stage capacitor, the supply voltage of the driver stage can be decreased compared to that in a general amplifier. Accordingly, the power-added efficiency is improved and the gate-drain reliability problems are moderated compared to a general amplifier. The analyzed effect of the inter-stage capacitor is verified successfully using the measured results of the designed amplifiers.

This paper presents a propagation model and inductive link budget based on link equations for chains of inductive loops as the basis for determining the link budget of an inductive communication and wireless power transfer systems. The link between the transmitter and receiver is modeled in similar format as in radio frequency systems. The transmitter antenna gain, path loss model and receiver antenna gain are also modeled for the inductive case. This allows the magnetic path loss to be estimated accurately. Also the induced receiver current due to a transmitter voltage can be computed apriori enabling efficient design of inductive links and transceivers.

A stacked rectangular microstrip antenna with a shorting plate combined with a rectangular ring microstrip antenna is proposed for triple band operation (GPS, VICS and ETC) in ITS. The two microstrip antennas are excited by an L-probe feed. In the ETC band, axial ratio deteriorates due to asymmetrical distributions of the electric current in the ring microstrip antenna. In this paper, an approach to improve the axial ratio for ETC is also proposed. The proposed antenna has the proper radiation patterns and impedance matching for the GPS, VICS and ETC.

In this paper, a novel substrate integrated waveguide (SIW) to substrate integrated coaxial line (SICL) transition using the 3 dB SIW power divider (PD) and SIW 180° phase shifter (PS) is proposed. The SIW-to-SICL transition realizes the easy integration of SIW, SICL, and active device in the same microwave communication system based on the substrate-integrated technology (SIT). To validate the design concept, the prototype has been fabricated and measured. Measurements are in good agreement with simulations, and shows that the SIW-to-SICL transition features ultra-low insertion loss lower than 0.25 dB and with a fractional bandwidth over 10%.

In this paper, reflection and transmission coefficients at dielectric fractal-fractal interface are discussed. The ratio of permittivity of the two dielectric fractal media is kept constant, while the dimension is varied in order to get the desired results. Conventional results are recovered for the integer dimensions. The proposed expressions are useful to study the behavior of electromagnetic waves for non-integer dimensions, multiple fractal interfaces and waveguides. Moreover, it is also helpful to understand the variation in the magnitudes of reflection and transmission coefficients with the difference in dimensionality at interface of the two fractal media.

Dynamical stability of a system of bilaterally coupled periodic Gunn oscillators (BCPGO) has been studied employing Melnikov's global perturbation technique. In the BCPGO system, a fractional part of the output signal of one oscillator is injected into the other through a coupling network. The injected signal is considered as a perturbation on the free running dynamics of the receiving oscillator and the amount of perturbation is quantified by a parameter named coupling factor (CF). The limiting values of CFs leading to chaotic dynamics of the BCPGO system are predicted analytically by calculating the Melnikov functions (MFs) in the respective cases. Also the effect of the frequency detuning (FD) between the Gunn Oscillators (GOs) on the computed values of MFs has been examined. A thorough numerical simulation of the BCPGO dynamics has been done by solving the system equations. The obtained results are in qualitative agreement with the analytically predicted observations regarding the roles of the system parameters like CF and FD.

We carefully investigate the structure of single- and multi frequency imaging functions, that are usually employed in inverse scattering problems. Based on patterns of the singular vectors of the Multi-Static Response (MSR) matrix, we establish a relationship between imaging functions and the Bessel function. This relationship indicates certain properties of imaging functions and the reason behind enhancement in the imaging performance by multiple frequencies. Several numerical simulations with a large amount of noisy data are performed in order to support our investigation.

A near-field focused antenna used as a feed for linear array is presented in this paper. This antenna is an H-plane sectoral horn with a biconvex dielectric lens placed in its aperture. This antenna focuses the beam in one plane (H-plane) to illuminate a linear array with a small width and provide a large aperture on the other plan to illuminate the length of the array. The simulated field distribution on the array is found to be in good agreement with the measurement of a prototype at 9.41 GHz.

Dual-mode square patch resonator is well known in the design of a single band quasi-elliptic bandpass filter response. Here, the dual-mode square patch resonator is employed to achieve a dualband bandpass filter. A 6 pole dual-band bandpass filter response with 3 poles at each passband will be presented. The dual-band filter also exhibits a transmission zero between the two passbands. A detailed discussion on the design procedure together with the simulation and experimental results will be presented.

A new design of a compact circularly polarized shorted annular stacked patch antenna has been introduced for Global Navigation Satellite System (GNSS) in this paper. The wideband characteristic is achieved by employing L-probe coupled feeding structure. The antenna is fed by four-output-ports strip line feeding network composed of three normal Wilkinson power dividers. As a result, the designed antenna has an effective bandwidth of 94.3% from 0.7 GHz to 1.95 GHz for VSWR< 2, and 57.1% 3-dB axial ratio bandwidth from 1.0 GHz to 1.8 GHz, respectively. The designed antenna has a compact size of 100 mm×100 mm×13 mm. The final antenna provides very good circularly polarized radiation for GNSS including GPS, GLONASS, Galileo and Compass.

A novel half Hemispherical Dielectric Resonator Antenna (HDRA) with an array of slots has been designed. The dielectric material used is Rogers TMM₁₀, which is a ceramic thermoset polymer composite material having a dielectric constant of ε_r = 9.2. Periodic holes lower down the Q factor of the antenna and hence enhance the impedance bandwidth. The measured value of the 10 dB bandwidth is close to 1 GHz (~17.74%). The mode investigated is a TM₁₀₁ like mode. Further, the effect of increasing the probe length on the resonance and the radiation pattern is also studied. As the probe length is increased, a shift in the resonant frequency is observed and the Dielectric Resonator Antenna (DRA) behaves as a monopole antenna loaded with the DRA. The experimental results confirm that a wide bandwidth of 1.3 GHz (~29%) with a high gain of 7.2 dBi can be obtained. The radiation pattern of such an antenna is directive in nature.

This paper presents results from an indoor LOS channel measurement campaign at the 60 GHz band. The results include the Ricean K-factor and time dispersion/frequency selectivity, which dominate the data-rate and error-performance limitations of the channel. Finally, three clusters are identified and the well known Saleh-Valenzuela model is used to statistically describe the interarrival times and the power decay of clusters and multipath components in the clusters.

This paper presents a multiconductor reduction method for modeling electromagnetic crosstalk of complex cable bundles in the vicinity of a 60 degree corner. Based on the image theory and wide separation assumption, the per-unit-length parameters of the cable bundle can be obtained analytically. A modified six-step procedure is established to define the electrical and geometrical characteristics of the reduced cable bundle model compared with the original equivalent cable bundle method (ECBM). Numerical simulations are performed to demonstrate the viability and effectiveness of the method. This work can find wide applications in real environments.

A novel single-cavity dual mode substrate integrated waveguide (SIW) filter with mixed source-load coupling (MSLC) is presented. By using an interdigital slot-line (ISL) to introduce mixed coupling between source and load, the proposed filter with only one cavity could have three transmission zeros which can be controlled flexibly. Under the circumstances, the filter exhibits better frequency selectivity in comparison with conventional dual mode SIW filters. An experimental filter with a center frequency of 10 GHz and a 3 dB fractional bandwidth of 6.0% is designed, fabricated, and measured to validate the proposed structure. Measured results are provided to show good performance and in agreement with the simulated ones.

The systematic design of size-confined, polarization-independent metamaterial absorbers that operate in the microwave regime is presented in this paper. The novel unit cell is additionally implemented to create efficient multi-band and broadband structures by exploiting the scalability property of metamaterials. Numerical simulations along with experimental results from fabricated prototypes verify the highly absorptive performance of the devices, so developed. Moreover, a detailed qualitative and quantitative analysis is provided in order to attain a more intuitive and sound physical interpretation of the underlying absorption mechanism. The assets of the proposed concept, applied to the design of different patterns, appear to be potentially instructive for various EMI/EMC configurations.

In this work, the multiple filtering phenomenon in a photonic crystal made of single-negative (SNG) materials is investigated. We consider a finite photonic crystal (AB)^N immersed in air, in which A, B are epsilon-negative (ENG) and mu-negative (MNG) materials, respectively, and N is the stack number. It is found that such a photonic crystal can function as a multichannel transmission filter with a channel number equal to N-1. The required condition is that the thickness of MNG layer must be larger than that of ENG layer when magnetic plasma frequency is greater than electric plasma frequency. The channel frequencies can be red-shifted as the thickness of MNG layer decreases. The channel positions can be tuned by the incidence angle for both TE and TM polarizations. That is, the peak frequency is blue-shifted when the angle of incidence increases. Additionally, the influence of the static permeability of ENG medium and permittivity of MNG medium is also illustrated. The proposed structure can thus be used to design as a tunable multichannel filter which is of technical use in signal processing.