A multi-band ferrite-based metamaterial has been investigated by experiments and simulations. The negative permeability is realized around the ferromagnetic resonance (FMR) frequency which can be influenced by the saturation magnetization 4πM_s of the ferrites. Due to having multiple negative permeability frequency regions around the multiple FMR frequencies, the metamaterials consisting of metallic wires and ferrite rods with various 4πM_s possess several passbands in the transmission spectra. The microwave transmission properties of the ferrite-based metamaterials can be not only tuned by the applied magnetic field, but also adjusted by the 4πM_s of the ferrite rods. A good agreement between experimental and simulated results is demonstrated, which confirms that such a ferrite-based metamaterial possesses a tunable multi-band behavior. This approach opens a new way for designing multi-band metamaterials.

In this study, a novel dual band-notched ultra-wideband (UWB) antenna has been proposed and discussed. The proposed antenna is fed by a micro-strip line and in the square-etched radiation patch a T-shape parasitic stub is attached. On the other hand, a pair of parasitic parallel micro-strip lines are also added on the ground plane, one of which is shorted to the radiation patch by a short-pin through dielectric substrate. The two parasitic units are to achieve band-notched characteristics at 3.3-3.7 GHz and 5.15-5.85 GHz, respectively. In order to realize impedance matching over the ultra-wideband, two arc-shape cuts are made symmetrically at the junction of feed-line and radiation patch. The simulated and measured results, including return loss, radiation pattern, group-delay and peak gains are in good agreement with theory analysis which validates our design concept.

This work focuses on the development of multiscale meshless technique in area of scattered fields from paramagnetic scatterers. The radial point interpolation method (RPIM), as the most common meshless technique, is employed for above purpose. Due to high frequency analysis, some special considerations must be applied, particularly in subdomains near the incident face. So, to ensure the accuracy, a multiscale meshless technique in wavelet frames sounds necessary. Simulating the scatterers using above method, specifically an elliptic paramagnetic scatterer, shows some efficient aspects such as less computational time and more precision compared with some other numerical methods.

The paper deals with the design and optimization of a novel magnetic switchable device based on Halbach array. The magnetic field in air gap is adjustable by rotating the center axis of adhesion mechanism so that the magnetic adhesion force is variable, and it is convenient for device to adsorb on and detach from the ferromagnetic workpiece or surface. The magnetic field model is established by Fourier series method, and the optimal dimensions of configuration are obtained by finite element parameter approximation method for best performing design. The magnetic force of novel optimal device is measured, and a good agreement between simulation and measurement is found. The results are compared to the traditional mechanism, and it is shown that the utilization ratio of magnets of novel optimal mechanism is 2.2 times larger than the H-type one with the same usage of magnets, while its consumption of soft iron is only 12.7% of the H-type one.

An asymmetric coplanar waveguide (ACPW)-fed zeroth-order resonant (ZOR) antenna with extended bandwidth is investigated. By embedding a strip connected between the metallic patch and an ACPW ground plane, another resonant frequency at 2.53 GHz is achieved. The bandwidth enhancement of designed antenna can be obtained when the zeroth-order resonant frequency and the resonant frequency at 2.53 GHz are merging together. The size of the antenna is only 15×22×0.8 mm³ with simple planar structure. A prototype of the proposed antenna has been constructed and experimentally studied. The measured results show that operating bandwidths with 10 dB return loss are about 510 MHz (2.49-3.0 GHz), the simulated peak gain of 1.59 dBi at 2.68 GHz, which is suitable for WiMAX (2.5 GHz-2.69 GHz) application.

In this paper, a novel compact ultra-wideband (UWB) microstrip bandpass filter (BPF) with a notched band using the proposed multi-stub loaded ring resonator (MSLRR) is presented. The MSLRR is constructed by loading four open stubs in a ring resonator, i.e., one pair of high-impedance stub at the top side and another two low-impedance stubs at the bottom side locations. Five modes, including two odd modes and three even modes, could be designed within UWB band. Moreover, two transmission zeros (TZs) are generated by the ring structure, leading to a quasi-elliptic function response that enhances the selectivity significantly. Two slotline split-ring resonators (SRR) are used to create a narrow notched band at 8.3 GHz. The simulated and measured results are in good agreement and show good in-band filtering performance and sharp selectivity.

This work presents a methodology for the development of microwave systems and circuits. Starting from the system decomposition, the proposed method is aimed at estimates the requirements of each component of the system taking into account the effects on the whole system and the interactions with the others microwave components. The obtained requirements are then used to design or optimize each device with standard design methodologies or CAD tools. The problem is recast as an optimization one by defining a suitable cost function able to take into account the interactions between all the components of the system. The cost function is then minimized with an evolutionary optimization technique, namely the particle swarm optimizer. The obtained preliminary results, concerning the design of a broad-band bidirectional amplifier, demonstrate the potentialities of the proposed approach.

In a recent study, we proposed improved quasi-static expressions for the electromagnetic field components excited by a vertical electric dipole lying on the surface of a flat and homogeneous lossy half-space. The present paper introduces an analytical approach to derive analogous formulas for the case of the horizontal electric dipole. The procedure is based on the expansion of the integral representations for the fields into power series of the ratio between the wavenumbers in free-space and in the conducting medium. Later, the terms in the expansions up to the second order can be reduced to known tabulated integrals. Numerical results are presented to illustrate the improvement in accuracy that follows from using the second-order approximations for the fields in place of the zeroth-order ones. In the quasi-static frequency range and beyond, use of the new formulation makes it possible to reduce the maximum relative error in the calculation of the fields from about 23% down to less than 7%.

In Part I of this work, travelling-wave modelling of uniform multi-conductor transmission line networks was analytically established with direct applicability to narrowband transmission, covering any network formed of lossy (in the general case), diagonalisable uniform multi-conductor transmission lines of either distinct or degenerate eigenvalues. As the whole work applies especially in the field of Power-Line Communications, in Part II, a validating experimental paradigm is first provided using a common cable type for indoor power electric networks. Then, direct applicability to narrowband transmission is addressed, along with potential expandability towards wideband signalling. A comparative evaluation with other existing methods of time-domain modelling is also included and relevant directions for future research are suggested.

In Part I of this work, analysis of uniform multi-conductor transmission line networks is performed on travelling-wave basis, via "quasi-TEM" approach. Narrowband interpretation of the modal theory in the time domain and quantification of the multiple reflections effect are both included. Theoretical demonstration and analytical formulation are provided, along with guidelines towards computational implementation. Any network formed of lossy, diagonalisable uniform multi-conductor transmission lines of either distinct or degenerate eigenvalues is covered. This work applies especially in the field of Power-Line Communications, as High-Frequency transmission over the power electric network is dominated by multipath propagation.

A compact quad-band microstrip band-pass filter (BPF) based on novel step-impedance ring resonator (SIRR) is investigated in this paper. The proposed BPF is composed of one ring resonator and input/output coupled structure. The novel resonator is studied and employed to generate four desired independent passbands. A compact quad-band BPF centered at 1.57, 2.45, 3.5 and 5.2 GHz is designed and fabricated. The predicted results are compared with measured data, and good agreement is reported.

Electromagnetic fields associated with the electric current flowing along a horizontal conductor located over perfectly conducting ground are estimated using electromagnetic fields pertinent to acceleration of electric charges. It is shown that the electric and magnetic fields that exist below a long overhead horizontal conductor are nothing but the radiation fields generated by the acceleration of charge at the point of injection of current into the horizontal conductor.

In order to realize bandpass filter with Chebyshev and elliptic function responses using a single resonator only, a dual-mode square resonant structure is proposed. Four small square loops are added into a large loop. One of small loops is defined a perturbation element, other small ones are references. By changing the thickness of the perturbation element with respect to that of a reference element, the resonator can produce a capacitive or inductive coupling between two degenerate modes. The capacitive coupling can acquire an elliptic function characteristic since it can create the transmission zeros on both the lower and upper sides of the passband, while the inductive coupling cancels them which exhibits a Chebyshev characteristic. Therefore, both Chebyshev and elliptic function responses can be obtained in a filter. The proposed bandpass filter is with a wider stopband and more compact in size. Experiment results have been verified this design.

This work presents a novel broadband monopole antenna for digital video broadcasting-terrestrial (DVB-T) application. The proposed antenna consists of a grating zigzag patch and a concave rectangular ground plane. The zigzag patch is used to enable the antenna height reduction for fixed ranges of operating frequency. The proposed antenna can operate from 420 MHz to 1050 MHz frequency range corresponding to 85% of impedance bandwidth for |S₁₁| better than -10 dB. This covers the working frequency band (470-862 MHz ) of DVB-T system. The radiation pattern of the proposed antenna is omnidirectional across the desired operating frequency band. Details of the proposed antenna design and experimental results of the constructed prototypes are presented and discussed. Furthermore than the bandwidth enhancement, we have also arranged the structure for network antennas application.

A closely-packed (4 mm) diversity slot antennas operating in the UWB frequency is proposed. High isolation (S₂₁ < -20 dB) of two closely-packed slot antennas can be easily achieved in a broad band by taking advantage of the directional radiation characteristics of slot antenna. Quarter-wavelength slot resonator is adopted to improve the isolation in the low-band of the UWB. The simulated current distribution and the radiation patterns of the single antenna element with and without slots are also presented to explain the mechanism of decoupling in the diversity system. Furthermore, the diversity performance of correlation coefficient, mean effective gains (MEGs), diversity gain (DG) are also studied.

A compact, parasitic array antenna printed on both sides of the substrate to generate dual Notches is introduced. The antenna is composed of one driver and two directors. Both directors are discretely segmented and are twisted with each other to minimize the radiation interference from one director to the other at each resonance. The antenna is optimized for realized gains in the director direction at the two resonant frequencies. The optimized antenna has been fabricated and measured to verify the simulated results. At both resonances, the measured realized gains in the director direction are greater than 8.5 dBi, and the front-to-back ratios are more than 10 dB.

In this paper, a K-band ground-based hyperspectral microwave radiometer for atmospheric sounding is proposed, which improves the profile error and vertical resolution of moisture profiling under the high water vapor condition. The hyperspectral microwave radiometer (80 K-band spectral channels) can observe the rapidly changing weather with high sensitivity and accuracy of brightness temperature by using a stable high-speed receiver and an improved tipping calibration method. By combining several advantages of traditional microwave receiver, the MMIC receiver has good ultra-wideband performance, high linearity, and short measuring time. Moreover, through correcting the calibration parameters of traditional tipping calibration, the proposed calibration method can increase calibration accuracy based on the radiative transfer equation in the atmosphere. Measurement results demonstrate that the radiometer achieves a sensitivity of 0.1 K for 2 s of integration time and an accuracy of better than 0.77 K. For the water vapor profile, the variational retrievals method is used to extract the redundant information under the microwave hyperspectral condition. Preliminary comparisons of measured water vapor profiles with traditional results show good improvement of the profile error and vertical resolution.

In this paper, a multilevel time domain fast dipole method (TD-FDM) is proposed for solving time-domain magnetic field integral equations. It is the extension of TD-FDM to the multilevel. This proposed scheme starts by multilevel grouping. At each level, the far-field interaction can be expanded through the Taylor series and reconstructed via aggregation-translation-disaggregation procedure, which reduces the memory requirement and the computational cost of the marching-on in-time (MOT) method. Numerical results about the electromagnetic scattering from perfect electric conductor (PEC) objects are given to demonstrate the validity and efficiency of the proposed scheme.

In this paper, a novel tunable antenna using graphene-based artificial magnetic conductor (AMC) is proposed and investigated. The resonance frequency of the AMC ground plane can be electrically tuned by applying a gate voltage. A bowtie-shaped antenna is mounted above the 15×15 AMC units. It is observed that the operating frequency of the antenna system shifts in a large range when varying the external electric field. The bandwidth of the antenna system can reach as high as 47% with a gain higher than 9 dB.

A novel miniaturized composite right/left-handed (CRLH) transmission line based on the structure of spiral inter-digital is proposed and analyzed in this article. Compared with the conventional inter-digital CRLH, the proposed CRLH realizes a 25% resonace frequency shift, and the miniaturization is realized. Then, a compact bandpass filter centered at 1.00 GHz with minimum insertion loss 0.42 dB was designed, fabricated and measured. The measured results show that the band width is 61.6% and that the sharpness at the two edges of passband is 212.5 dB/GHz and 607.1 dB/GHz. This designed filter has very high selectivity. Besides, the whole size of the designed filter is 0.114λ×0.054λ. The filter realizes the miniaturization effectively, and this designed bandpass filter has good performances and smaller size than the same works in references.