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.

Microwave induced thermo-acoustic tomography (MITAT) has great potential in early breast cancer detection because it utilizes the advantages of both microwave imaging and ultrasound imaging. In this paper, we develop a fast and efficient simulation approach based on a hybrid method which combines finite integration time domain (FITD) method and pseudo-spectral time domain (PSTD) method is developed. By using this approach, energy deposition of biology tissue illuminated by electromagnetic fields can be accurately simulated. Meanwhile, acoustic properties of the tissue can be efficiently simulated as well. Compared to traditional methods, such as finite difference time domain (FDTD), et al, the developed method can well process real 3-D electromagnetic-acoustic complex models. Based on this approach, a MITAT model is created and some simulated results are analyzed. Furthermore, some real breast tissues are adopted to perform the thermo-acoustic imaging experiment. Comparisons between experimental and simulated results are made. The feasibility and effectiveness of the proposed approach are demonstrated by both numerical simulations and experimental results.

The influence of beam convergence on the photonic band-gaps, or stop-bands (SBs), of onedimensional photonic crystals (1D PCs) is investigated. The investigation is based on an analysis of the gap map obtained from reflection spectra, calculated by the transfer matrix method for various angles of light incidence, φ, The calculated data is compared with reflection spectra taken using Fourier Transform Infrared microspectroscopy. It was found that the introduction of the parameter, Δφ to account for the focused light beam, for angles up to 20°, has little effect on the first, or lowest SB and the SBs adjacent to it. However, an increase in the order of the SB causes an increase in the influence of this parameter.

This study presents a novel wideband absorber for radar cross section (RCS) reduction. Unlike previous absorber designs that use multilayer lossy materials, this study proposes a design based on a planar antenna array that adopts a bowtie dipole structure as the unit cell. The complete design procedure was investigated by using examples for single- and dual-polarized incident wave designs. The measurement results show that the bandwidth of both designs exceeded 81% of 10 dB RCS reduction when the thickness is less than 12% of the free space wavelength at the lowest operating frequency. The high RCS reduction of the proposed absorbers was demonstrated using commercial ground-penetrating radar. Results show that the proposed absorber is invisible to radar.

A nonlinear electrical transmission line with an intersite circuit element acting as a nonlinear resistance is introduced and investigated. In the continuum limit, the dynamics of localized signals is described by a non-linear evolution equation belonging to the family of nonlinear diffusive Burgers' equations. This equation admits compact pulse solutions and shares some symmetry properties with the Rosenau-Hyman K(2,2) equation. An exact discrete compactly-supported signal voltage is found for the network and the dissipative effects on the pulse motion analytically studied. Numerical simulations confirm the validity of analytical results and the robustness of these compact pulse signals which may have important applications in signal processing systems.

An investigation of dual-band balanced-to-unbalanced (blaun) bandpass filters (BPFs) is presented in this letter. Two types of balun BPFs named Type-A and Type-B filters based on coupled ring resonators are discussed and fabricated. Both the simulated and measured results show that these balun-BPFs have not only good amplitude performances but also excellent phase difference performances. The center frequencies of these balun BPFs are set at 2.4 GHz/5.6 GHz for Type-A and 1.57/4.65 GHz for Type-B balun filters. The differences are 180° ± 5° in phase and within 0.6 dB in magnitude of type A and 0.73 dB of type B, respectively. Thus, these balun BPFs can be used in many wireless communication systems.