A novel dual-band substrate integrated waveguide (SIW) filter with multiple transmission zeros and good out-of-band rejection performance is presented in this paper. For this purpose, an orthogonal input/output (I/O) feeding structure directly connected to the substrate integrated waveguide (SIW) cavity is designed to split the resonant frequencies of the degenerate pair of mode. The filter can be modeled with a multi-path circuit formed by three modes (TE₁₀₁, TE₂₀₁ and TE₁₀₂ modes) and weak cross coupling between I/O ports, thereby producing three transmission zeros which make the dual-band high selectivity. The offset of the input/output ports shifts the second transmission zero to a lower frequency from the upper passband. Several filter prototypes are designed and fabricated for demonstration, and the measured results validate the new structure for high selectivity applications.

The aim of this work is to characterize the electrical conductivity of composite conductors deposited on an alumina substrate. Several half-wavelength coplanar resonators are realized using several pure conductors, silver (Ag), copper (Cu), gold (Au) and tin (Sn), to compare their quality factors (Q₀), related to losses, with those from analytical methods. In the literature, losses in coplanar components have been estimated by different analytical methods. We have put in evidence the relationship between electrical conductivity of the conductor and the resonator quality factor. An overall good agreement among quality factor values obtained by the analytical formulas, by numerical simulations and by microwave measurements is observed. The surface roughness is taken into account to better estimate real conductor losses. Therefore, these analytical formulas are used to extract the electrical conductivity values of the composite conductors (Ag-aC, AgSnIn and AgSn), from measured quality factors.

A novel uniplanar slot dipole antenna fed by a coplanar waveguide (CPW) is proposed for dual-band operation. The frequency ratio between the first spurious and fundamental modes of the slot dipole antenna can be conveniently adjusted with the use of four slot stubs introduced on its two arms. Furthermore, the radiation patterns at the first spurious mode are modified by adding four parasitic slots along its two arms to resemble those of the fundamental mode. Under the assistance of the slot stubs together with the parasitic slots, another resonant mode can be generated and merged with the first spurious mode, and therefore improve the bandwidth significantly. An antenna prototype was fabricated and measured to validate the design concept. The measured results show that dual-band operation with 10-dB impedance bandwidths of 2.99-3.83 GHz (24.6%) and 5.21-6.89 GHz (27.8%) has been obtained. The antenna has stable broadside and bidirectional radiation patterns with low cross-polarization components over the two operating bands.

In this paper, an analytical method of capacitance and characteristic impedance is proposed, which is for asymmetrical coplanar waveguide with defected ground structure (ACPW-DGS). The capacitance equivalent model of ACPW-DGS is established. Using conformal mapping method and first category of incomplete elliptic integrals F(φ, k), the closed-form expressions of capacitance and characteristic impedance are obtained for the first time. Computed results match the simulated ones well.

Novel types of dual circular polarizer are developed to convert TE₁₀ mode into two different polarizated TE₁₁ modes in a circular waveguide. These designs have MHz bandwidth and high power transmission capability. They can be used for broadcasting and receiving circular polarized signals.

An innovative decoupling microstrip antenna array is designed. In the design approach, a decoupling and folding microstrip circuit is proposed instead of lumped element circuit, so that the circuit structure is simplified, and the antenna array is fabricated easily in print. Inverted L shape is used as its radiator in order that the size of the antenna array is miniaturized. Stepped impedance transformer is added for the sake of weakening ports reflection. The simulation and measurement results show that the proposed antenna array works at 2.45 GHz, and its reflection coefficient and isolation are both below -20 dB in the working band (2.4 GHz-2.48 GHz). The proposed antenna array has patterns close to omnidirectional.

Sea ice plays an important role in global climate. Many researches focus on the measurement of the sea ice thickness. In this paper, we present a method for the ice-detecting combining frequencymodulated continuous-wave (FMCW) technology and synthetic aperture radar (SAR) technology. It can provide a good resolution both in the range dimension and the azimuth one. Then a simulation is conducted to verify the accuracy and the feasibility of this algorithm. The physical properties of the sea ice, such as reflection and scatter properties of the ice surface and the transmission characteristic when the electromagnetic wave travels through the ice, are considered in the simulation. The results of the simulation demonstrate that this algorithm has a good performance in ice penetrating.

A novel and compact highpass filter (HPF) is proposed in this article. This filter is based on a hybrid-coupled dual-metal-plane microstrip/DGS (defected ground structure) on a single-layer substrate. The resonator etched in the grounding plane shows a wide-band dual-mode resonant response within the desired high-pass frequency band, and is composed of a modified U-shaped slot resonator embedded with an L-shaped slot. The wideband highpass filtering performance is achieved by the dual-mode resonator at the bottom of single-layer substrate coupled broadside to the top microstrip stubs. Simulated results from the electromagnetic (EM) analysis software and measured results from a vector network analyzer (VNA) show a good agreement, and an excellent performance with nearly 40 dB attenuation at the lower stopband has also been obtained across an ultra-wide highpass range. A designed and fabricated prototype filter, having a 3-dB cutoff frequency (f_c) of 5.9 GHz, shows an ultra-wide highpass range, i.e., from 5.9 to 15.52 GHz, and exhibits the highest pass-band frequency up to 2.6f_c. The printed circuit board (PCB) area of the implemented filter is approximately 0.086λ_g×0.13λ_g, λ_g being the guided wavelength at f_c.

Pattern reconfigurable antennas (beam steerable antennas) are essential for various applications in electronic engineering such as telecommunication and radar. They mitigate interference by channelling the antenna's radiation to the direction of interest. This ability is vital for millimetre wave frequency applications such as small cell backhaul links where high path loss, attenuation from obstacles, and misalignment due to wind sway and accidents are prevalent. Several techniques have been used to implement beam steering over the years, most of which achieves steering at the expense of antenna performance. In this article, we surveyed the various techniques used in achieving beam steering and analyse each based on some figures of merit with the aim of identifying areas of improvements for each beam steering technique.

In this work, we present a new systematic technique for the design of a flat lens using modified commercial off-the-shelf (COTS) materials, as opposed to metamaterials (MTMs) that are often required in lens designs based on the Transformation Optics (TO) approach. While lens designs based on Ray Optics (RO) do not suffer from the drawback of having to use metamaterials, they still require dielectric materials that may not be commercially available off-the-shelf. This paper describes a systematic procedure for realizing the desired materials by modifying the COTS types, and illustrates its application with some practical examples.

An alternative to the traditional method of sampling radar cross section data from measurements or electromagnetic code is presented and evaluated. The Cubed Sphere sampling scheme solves the problem of oversampling at high and low elevation angles and at equal equatorial resolution the scheme can reduce the number of samples required by approximately 25%. The analysis is made of an aircraft model with a monostatic radar cross section at C-band and a bistatic radar cross section at VHF-band, using Physical Optics and the Multilevel Fast Multipole Method, respectively. It was found that for the monostatic radar cross section, the Cubed Sphere sampling scheme required approximately 12% fewer samples compared to that required for traditional sampling while maintaining the same interpolation accuracy over the entire domain. For the bistatic data, it was possible to reduce the number of samples by approximately 35% for high sampling resolutions. Using spline interpolation the number of samples required could be reduced even further.

A compact dual-band dual-polarized antenna is proposed in this paper. The two pair dipoles with strong end coupling are used for the lower frequency band, and cross-placed patch dipoles are used for the upper frequency band. Breaches are introduced at the ends of the dipoles of the upper band, which can benefit the compactness and bandwidth of the antenna. The ends of the dipoles for upper frequency band are cut off a corner, which also benefit the compactness and matching of the antenna. An antenna prototype was fabricated and measured. The measured results show that the antenna can cover from 790 MHz to 960 MHz (19.4%) for lower band and from 1710 MHz to 2170 MHz (23.7%) for upper band with VSWR<1.5. It is expected to be a good candidate design for base station antennas.

The improved ultra-wide band characteristic basis function method (IUCBFM) is an efficient approach to analyze the wide-band scattering problems because the improved ultra-wide characteristic basis functions (IUCBFs) can be reused for any frequency sample in the range of interest. However, the number of the IUCBFs constructed at the highest frequency point is excessive, and the computational complexity will be increased when applying the same number of IUCBFs at the lower frequency points. To mitigate this problem, an adaptive IUCBFs construction method is presented which can decrease the computational complexity at the lower frequency points. In the proposed method, the given frequency band is adaptively divided into multiple sub-bands in consideration of the number of the IUCBFs. The adaptive IUCBFs are obtained at the highest frequency point in each sub-band, which leads to smaller number of IUCBFs and significant reduction of solver time at lower frequency band. The numerical results have demonstrated the accuracy and efficiency of the proposed method.

In this paper, a methodology to design non-50 Ω antennas for energy harvesting is presented. Two prototypes are simulated and realized on an epoxy substrate: one operating at 433 MHz and 900 MHz, the other at 900 MHz and 2.4 GHz. These antennas are designed to match the input impedances of an integrated radio-frequency harvester for an output voltage of 1 V, value chosen considering the voltage needed to power the new generation of micro-controllers and electronic circuits for the Internet of Things. The measurement results indicate a reflection coefficient below -10 dB at the frequencies of interest, validating the methodology.

An analytic model of the field-to-line coupling in time domain for electrically small lines using a transverse electromagnetic (TEM) cell is proposed in this paper. This model uses mutual capacitance and mutual inductance to represent electric and magnetic field couplings which can be obtained based on voltage and current dividers. The measurement and calculation results validate the accuracy of the model. The termination effect on electromagnetic interference (EMI) responses and the separation of electric and magnetic field couplings are investigated by the model. The results indicate relevant suppressions for radiated immunity. This model is convenient for fast radiated immunity estimations.

A low profile, compact antenna operating around 162 MHz with omnidirectional vertically polarized radiation is proposed. The antenna is a short monopole capacitively coupled to short-end quarter-wavelength printed line optimized at 162 MHz for Automatic Identification System (AIS) application. The antenna dimensions are less than λ/185 in height and λ/20 in lateral dimension, and the small size of antenna provides a narrow band of 0.34% and gain of -11.6 dBi. The simulated and measured results are in good agreement.

This paper presents a novel design of dual-band filters with individually controllable passband responses and orders. Besides the center frequency and bandwidth, the response and order of each passband can be different and controlled individually. The dual-band filter is formed by synthesizing each filter element (resonator, inverter) one by one, exploiting the corresponding individual single-band filters design tables/formulas for different prototype responses and orders. Trisection stepped-impedance resonators (TSSIR) are adopted with novel considerations as dual-band resonators, whose additional design parameters could help to realize the required in-band responses (resonances, slope parameters) and improve simultaneously the out-of-band performances (transmission zeros of TSSIR). Furthermore, they can be used to design a dual-band filter with far separation between two passbands. Meanwhile, stepped-impedance inverters are chosen as dual-band inverters with novel additional conditions to obtain symmetric passbands, which can also provide different inverter immittance parameters J/K at two center frequencies when the response or order of each passband is different. To illustrate the two passbands being controlled individually, two dual-band filters with different orders and responses are demonstrated.

This paper presents a novel multi-way multi-stage power divider design method based on the theory of small reflections. Firstly, the application of the theory of small reflections is extended from transmission line to microwave network. Secondly, an explicit closed-form analytical formula of the input reflection coefficient, which consists of the scattering parameters of power divider elements and the lengths of interconnection lines between each elements, is derived. Thirdly, the proposed formula is applied to determine the lengths of interconnection lines. A prototype of a 16-way 4-stage power divider working at 4 GHz is designed and fabricated. Both the simulation and measurement results demonstrate the validity of the proposed method.

Vertical transition structure between grounded coplanar waveguide (GCPW) and stripline by Low Temperature Co-fired Ceramic (LTCC) technology is presented in this paper. In this structure, the top ground of the stripline is used as the GCPW lower ground, while the signal via goes through the middle ground plane. With increasing vertical signal via height, it can be more widely used in the higher height of multilayer System in Package (SiP) module packaging. The circular openings in the ground plane and additional shield vias around the transmission lines can provide great advantage in the radiation loss and decrease parasitic effects. The measurement results show that the return loss is less than -10 dB from 6 GHz to 35 GHz. Meanwhile, the insertion loss is better than -2 dB up to 28.4 GHz.

A fast and simple design methodology for transformation optics (TO) is described for devices having completely arbitrary geometries. An intuitive approach to the design of arbitrary devices is presented which enables possibilities not available through analytical coordinate transformations. Laplace's equation is solved using the finite-difference method to generate the arbitrary spatial transforms. Simple techniques are presented for enforcing boundary conditions and for isolating the solution of Laplace's equation to just the device itself. It is then described how to calculate the permittivity and permeability functions via TO from the numerical spatial transforms. Last, a modification is made to the standard anisotropic finite-difference frequency-domain (AFDFD) method for much faster and more efficient simulations. Several examples are given at the end to benchmark and to demonstrate the versatility of the approach. This work provides the basis for a complete set of tools to design and simulate transformation electromagnetic devices of any shape and size.