A planar hexa-band internal antenna designed for mobile phone applications is presented. The antenna occupying a small area of 45×12 mm2 is placed on the top no-ground portion of the system circuit board with a ground-plane size of 45×100 mm2. The design begins with constructing a meandered monopole. With a parasitic and an impedance-adjustment structure subsequently added, the resulting antenna can be viewed as a printed planar inverted-F antenna with a parasitic resonant element. Two wide impedance bands can be generated by the designed antenna to support GSM 850, GSM 900, DCS, PCS, UMTS, and 2.4-GHz WLAN operations. The measurement was found to agree reasonably well with the simulation. Design procedures and rules along with the design concepts behind are all presented in detail.
We have derived a one-variable metric function for fast and accurate complex permittivity extraction of low-to-high-loss materials using reflection-only microwave non-resonant measurements at one frequency. The metric function can be modified to facilitate fast computation of the complex permittivity of materials for various applications (e.g., relative complex permittivity measurement of low-loss materials). It is useful as a measurement tool for broadband measurements of complex permittivity of samples with substantiate lengths. In addition, the method is applicable for measurement of complex permittivity of dispersive materials or complex permittivity of non-dispersive samples in limited frequency-band applications, since it is based on point-by-point (or frequency-byfrequency) extraction. It is validated by a numerical analysis and measurements of a liquid sample.
We derive integral representations suitable for studying the focusing of electromagnetic waves through a symmetrically hyperbolic focusing lens into uniaxial crystal in the presence of cylindrical and coma aberrations using Maslov's method. The uniaxial crystal used is the negative crystal LiNbO3. Numerical computations are made to obtain the results for focused fields inside negative uniaxial crystal with several different orientations of the optical axis in the plane of incidence. The effects of aberrations inside uniaxial crystal and isotropic medium are also noted. The results are compared with those obtained by Kirchhoff-Huygens integral and Maslov's method which are in good agreement.
In this work, based on the principle of the electromagnetic reflection and transmission, we first present a theoretical analysis of a super-resolving lens with anti-reflection and phase control coatings (ARPC). This ARPC is capable of reducing the reflectivity of superlens surface and making phase difference approaching zero. The principle of ARPC is discussed in detail and the engineer condition for super-resolution imaging is obtained and the best range of the permittivity of ARPC coatings is obtained. The results demonstrate that the subwavelength resolution of our lens with ARPC has been enhanced. Such remarkable imaging capability using ARPC promises new potential for nanoscale imaging and lithography.
Antenna arrays with shaped power patterns have many applications in communications and radars. Many antenna array synthesis techniques for shaped patterns have been developed in the past years, and most of them deal only with uniformly spaced arrays. In this paper, a new method is proposed for the synthesis of nonuniform linear antenna arrays with shaped power patterns. The proposed synthesis method consists of three steps. First, we find a satisfactory power pattern for the required radiation characteristics by solving a constrained least-squares problem which is obtained with the help of non-redundant representation of squared magnitude of a linear array factor. Then, we factorize the polynomial associated with the power pattern by using polynomial rooting, and consequently obtain the corresponding field patterns. Finally, the forward-backward matrix pencil method is used to obtain a nonuniform linear array with optimized excitation magnitudes, phases and locations for a specific choice of field patterns. The synthesized array has a smaller number of elements than the one with uniformly spaced elements for the same pattern performance. Several synthesis experiments are conducted to validate the effectiveness and advantages of the proposed synthesis method.
Ultra wideband (UWB) Microwave imaging is one of the most promising emerging imaging technologies for breast cancer detection, and is based on the dielectric contrast between normal and cancerous tissues at microwave frequencies. UWB radar imaging involves illuminating the breast with a microwave pulse and reflected signals are used to determine the presence and location of significant dielectric scatterers, which may be representative of cancerous tissue within the breast. Beamformers are used to spatially focus the reflected signals and to compensate for path dependent attenuation and phase effects. While these beamforming algorithms have often been evaluated in isolation, variations in experimental conditions and metrics prompts the assessment of the beamformers on common anatomically and dielectrically representative breast models in order to effectively compare the performance of each. This paper seeks to investigate the following beamforming algorithms: Monostatic and Multistatic Delay-And-Sum (DAS), Delay-Multiply-And-Sum (DMAS) and Improved Delay-And-Sum (IDAS). The performance of each beamformer is evaluated across a range of appropriate metrics.
This paper presents a reconstruction approach which exploits the field detected by a holographic radar in order to localize and geometrically qualify a set of scattering objects. In particular, thanks to the adoption of the Kirchhoff Approximation, the problem is formulated as a linear inverse one wherein the unknown function is the characteristic function accounting for the support (location and geometry) of the target(s). The reconstruction performances of the approach have been investigated through an accurate numerical analysis, and an experimental validation has also been performed with the aim of testing the effectiveness and the practical relevance of the proposed method.
Resonant modes of multi-layer structures which contain the regions of negative epsilon material (such as a metal in the visible range) are analyzed. Existence of two separate classes of resonant modes is demonstrated. One is related to the excitation of the surface mode at the interface of the regions with opposite signs of the dielectric constant and involve energy transport by evanescent modes throughout the whole structure. The second class involves propagating modes (which form the resonant standing wave) in some regions and the evanescent waves in other layers with ε＜0. It is shown that the resonant transmission is related to the existence of quasi-stationary leaky modes having a finite life-time and characterized by large wave amplitude in the trapping region. It is shown that both types of resonances can coexist in multi-layer structures. It is also shown that the interaction of the symmetric and anti-symmetric surface eigen-modes widens the resonant transmission region.
In this article, a time-domain calibration procedure is proposed for pulsed Terahertz Integrated Circuits (TIC) used in on-chip applications, where the conventional calibration methods are not applicable. The proposed post-detection method removes the unwanted linear distortions, such as interfering echoes and frequency dispersion, by using only one single-port measurement. The method employs a wave-transfer model for analysis of the TIC, and the model parameters are obtained by a proposed blind estimation algorithm. A complete implementation of the method is demonstrated for a fabricated TIC, when used in an on-chip sensing application. The features of interest in the measured signal, such as absorption lines, can be masked or weakened by the distortion of the THz signal happening in a TIC. The proposed signal recovery approach improves the detection of those otherwise hidden features, and can significantly enhance the performance of existing TICs. To show the effectiveness of the proposed de-embedding method, numerical results are presented for simulated and measured signals. The method presented in this article is enabling for accurate TIC applications, and can be utilized to optimally design novel TIC structures for specific purposes.
The angle-dependent properties of wave reflection in the lossy single-negative (SNG) materials are theoretically investigated. A model structure of SNG bilayer consisting of a lossy epsilon-negative (ENG) material and a lossy mu-negative (MNG) is considered in this work. The wave properties are investigated based on the calculated reflectance for the s wave (transversal electric wave) and the p wave (transversal magnetic wave) in addition to the degree of polarization. It is found that the angle-dependent reflectance of p wave is larger than that of s wave, which is contrary to the usual material with both positive epsilon and positive mu. The effects of losses coming from the ENG and MNG materials are specifically explored and the roles played by their thicknesses are also numerically elucidated.
This paper proposes a multilevel Green's function interpolation method (MLGFIM) to solve electromagnetic scattering from objects comprising both conductor and bi-isotropic objects using volume/surface integral equation (VSIE). Based on equivalence principle, the volume integral equation (VIE) in terms of volume electric and magnetic flux densities and surface integral equation (SIE) in terms of surface electric current density are first formulated for inhomogeneous bi-isotropic and conducting objects, respectively, and then are discretized using the method of moments (MoM). The MLGFIM is adopted to speed up the iterative solution of the resultant equation and reduces the memory requirement. Numerical examples are presented to show good accuracy and versatility of the proposed algorithm in dealing with a wide array of scattering problems.
Born approximation is widely used in (inverse) scattering problems to alleviate the computational di±culty, but its validity and applicability are not well defined. In this paper, a universal criterion to identify the validity of Born approximation is put forward based on applying the operator theory on the scattering integral equation. In comparison with the traditional criteria, the new one excels in its ability to give a wider and more rigorous valid frequency range, especially while non-uniform scatterers are under consideration. Numerical examples verify the validity and advantage of the new criterion.
Breast imaging using Confocal Microwave Imaging (CMI) has becoming a difficult problem, primarily due to the recently-established dielectric heterogeneity of normal breast tissue. CMI for breast cancer detection was originally developed based on several assumptions regarding the dielectric properties of normal and cancerous breast tissue. Historical studies which examined the dielectric properties of breast tissue concluded that the breast was primarily dielectrically homogeneous, and that and that the propagation, attenuation and phase characteristics of normal breast tissue allowed for the constructive addition of the Ultra Wideband (UWB) returns from dielectric scatterers within the breast. However, recent studies by Lazebnik et al. have highlighted a very significant dielectric contrast between normal adipose and broglandular tissue within the breast. Lazebnik also established that there was an almost negligible dielectric contrast between broglandular and cancerous breast tissue at microwave frequencies. This dielectric heterogeneity presents a considerably more challenging imaging scenario, where constructive addition of the UWB returns, and therefore tumor detection, is much more difficult. Therefore, more sophisticated signal acquisition and beamforming algorithms need to be developed. In this paper, a novel imaging algorithm is described, which uses a rotating antenna system to increase the number of unique propagation paths to and from the tumor to create an improved image of the breast. This approach is shown to provide improved images of more dielectrically heterogeneous breasts than the traditional fixed-antenna delay and sum beamformer from which it is derived.
This paper presents a GPU-based multiresolution shooting and bouncing ray (MSBR) method with the kd-tree acceleration structure for the fast radar cross section (RCS) prediction of electrically large and complex targets. The multiresolution grid algorithm can greatly reduce the total number of ray tubes, as it adaptively adjusts the density of ray tubes for regions with different complexities of their structures, while the kd-tree acceleration structure can highly decrease the number of ray-patch intersection tests. The multiresolution grid technique and kd-tree traversal algorithm are fully implemented on the GPU to further accelerate the SBR by exploiting the massively parallel computing ability. Numerical experiments demonstrate that the proposed GPU-based MSBR can significantly improve the computational efficiency. It is about 40 times faster than the CPU MSBR, and at least 4.8 times faster than the GPU-based SBR without the multiresolution grid algorithm.
An ultra wide band (UWB) band-pass filter (BPF) utilizing one modified composite-right/lefthanded (CRLH) unit cell is proposed. By introducing the capacitive cross coupling to the traditional CRLH structure, the phase shift in the right-handed pass-band can be controlled, meanwhile, the cross coupling has negligible effect on the left-handed pass-band. The appropriate cross coupling can create three controllable transmission zeros. Thus, an UWB BPF with high selectivity is developed using only one unit cell, which leads to low insertion loss (less than 1.35 dB) and compact size (0.47λ0×0.28λ0). The fabricated filter exhibits a rejection level higher than 20 dB at the stop-band from 11.95--16 GHz and flat group delay across the pass-band.
This paper presents a D-band power amplifier for high-speed communication system. The capacitive effect of interconnection via on transistor performance at high frequency is analyzed and a new via structure is employed to reduce the capacitive effect. The on-chip matching technique for high frequency amplifier is analyzed and the thin-film microstrip line matching network is used, which is combined with biasing network to reduce RF signal loss and silicon cost. The amplifier is fabricated in 0.13-μm SiGe BiCMOS process. The experimental results show a 7 dB gain at 130 GHz with 3-dB bandwidth of 30-GHz. The input return loss is better than 10 dB over 23 GHz. In addition, this amplifier achieves saturated output power (Psat) of 4.5 dBm and input 1-dB gain compression point (P1dB) of -4.5 dBm. The chip size of implemented power amplifier is only 0.22mm2.
A thin Artificial Magnetic Conductor (AMC) structure for Radar Cross-Section (RCS) reduction applications is presented. The manufactured prototype, which combines two unit-cell metallization sizes, presenting two resonant frequencies, shows broad AMC operation bandwidth, polarization angle independency, and its angular margin when operating under oblique ncidence is also tested. It is shown that significant RCS reduction can be achieved with the proposed AMCs combination even if a 180º phaseshift between reflected waves is not met. Two designs are considered: the already mentioned design combining AMCs with overlapped frequency bands and the second one combining Perfect Electric Conductor (PEC) and AMC surfaces. A comparison between these two designs regarding RCS reduction, supported by measurements in an anechoic chamber, is presented.
Based on the active coupled line concept, a novel approach for efficient noise performance modeling of millimeter-wave field-effect transistors is proposed. This distributed model considers the effect of wave propagation along the device electrodes, which can significantly affect the noise performance especially in the millimeter-wave range. By solving the multi-conductor transmission line equations, using the Finite-Difference Time-Domain technique, this procedure can accurately determine the noise correlation matrix of the transistor and then its noise performance.
A new defected ground structure (DGS) is firstly proposed in this paper, which has better slow-wave effect than that of cross or dumbbell one. Using the model of transmission line, its equivalent parameters are extracted. With good omni-directional properties, the proposed DGS is then used in the design of a proximity coupled antenna for its miniaturization. The size of the developed antenna is about 68% smaller than that of the conventional one. Further, two artificial cells are added on the feed line to reduce the protrudent stub length from 26.9mm to 18.94 mm. With the utility of the DGS and artificial cells, the size of proximity coupled antenna is reduced significantly. By introducing a PIN diode at the end of feed line, the antenna is switchable in both x- and y-direction linear polarizations. Such miniaturization in antenna size has little negative effect on its cross polarization, with both simulated and experimental results presented for comparison.
In this paper, we presented the design of a high performance diplexer for applications of global positioning system (GPS) at 1.575 GHz and wireless local area network (WLAN) at 2.4 GHz, simultaneously. Two bandpass filters (BPFs) using the modified stepped-impedance resonators (SIRs) operated at 1.575 GHz and 2.4 GHz are main blocks for the proposed diplexer. By discussing and analyzing the admittance of the even and odd modes, the transmission zero of the modified SIR can be found, and the location of the transmission zero can be precisely predicted, thus having a wide and deep stopband for the BPFs, in turn the high performance diplexer. Furthermore, due to the appearance of the transmission zeros near the passband edges, the passband selectivity of the BPFs as well as the diplexer can be improved. By using the impedance matching between two BPFs, a high isolation of 50 dB between two channels is obtained. The proposed diplexer was designed, fabricated and measured. The simulated and measured results had a good agreement with the proposed design concept.
This paper presents an extension over a novel, three dimensional high frequency method for the calculation of the scattered electromagnetic (EM) field from a Perfect Electric Conductor (PEC) plate, which is based on the Physical Optics (PO) approximation and the Stationary Phase Method (SPM). This extension defines a new analytical method which is proved to be very efficient in computer execution time and enhances the accuracy of its predecessor around the area of the main scattering lobe. This new analytical method accomplishes high accuracy through the use of higher order approximation terms, which imply the use of Fresnel functions (SPM-F method). By using higher order Fresnel approximation terms, no impact on the time efficiency of the SPM method appears to occur, since the extended SPM-F method just removes the troublesome vanishing denominators when the stationary point coincides with the edges of the scatterer. The SPM-F results are compared to other straightforward numerical and exact solution methods for the same problem in the far field, Fresnel zone and the near field area of the scatterer.
This paper proposes a new electronic-continuously variable transmission (E-CVT) system for power-split hybrid electric vehicles (HEVs). The key is to integrate two permanent magnet motor/generators (M/Gs) together with a coaxial magnetic gear (CMG). By designing the modulating ring of the CMG to be rotatable, this integrated machine can achieve both power splitting and mixing, and therefore, can seamlessly match the vehicle road load to the engine optimal operating region. With the one-side-in and one-side-out structure and the non-contact transmission of the CMG, all the drawbacks aroused by the mechanical gears and chain existing in the traditional E-CVT system can be overcome. Moreover, the proposed E-CVT system possesses the merits of small size and light weight, which are vitally important for extending the full-electric drive range of HEVs. The working principle and the design details are elaborated. By using the finite element method (FEM), the electromagnetic characteristics are analyzed.
A non-resonant microwave method has been proposed for accurate complex permittivity determination of low-loss materials. The method uses two measurement data of the magnitude of transmission properties of the sample. While the first datum must correspond to a frequency point resulting in a maximum magnitude of transmission properties, the other can be any datum at a frequency different than the first datum and not far distant from the first datum. Two closed-from expressions are derived for a good initial guess using the above data. The limitations of each expression are discussed. The method has been validated by transmission measurements at X-band (8.2-12.4 GHz) of a low-loss sample located into a waveguide sample holder.
A compact microstrip bandpass filter (BPF) with multispurious suppression is presented. The filter consists of two coupled half-wavelength stepped impedance resonators (SIRs) and tapped input/output (I/O) lines. With tuning the impedance ratio (K) and length ratio (α) of SIRs, a very wide stopband can be easily achieved. The filter is designed at 2.4 GHz (f0) with a wide stopband to 20 GHz (8.16f0) and an average rejection level better than 25 dB. This study provides a simple and effective method to achieve a filter with very wide stopband and compact circuit size simultaneously. Good agreement between the full-wave electromagnetic (EM) simulation and measurement is compared.
Explicit Green's tensors for the diffusive electric field in a configuration with two homogeneous half spaces are of interest for primary-secondary formulations of frequency domain and time domain modeling schemes. We derive the explicit expressions for the Green tensor of the electric field generated by an electric dipole in space frequency and space time. Both source and receiver can have arbitrary positions in the vertical transverse isotropic (VTI) half space below a non conductive half space. Apart from their use in modeling schemes, the expressions can be used to understand the effect of the interface between the VTI and the non conducting half space. We show that the TE-mode refracts against the interface, and its effect in the VTI half space decays exponentially as a function of depth and is inversely proportional to horizontal distance cubed for horizontal source receiver distances larger than three times the source depth. In exploration geophysics, this part of the field is known as the "airwave". The contribution from the "airwave" has a late time behavior that differs from the other contributions to the electric field. This makes time domain systems relevant for exploration geophysical applications.