Transient electromagnetic topology (TEMT) method is presented briefly first and then three typical configurations, namely, a transmission line network, a wire penetrating a cavity aperture and then connecting to a device, and two systems connected by a shielded cable radiated by an electromagnetic pulse, are analyzed by using the TEMT method. The currents induced at the loads obtained by the TEMT method are compared with those from the experiment. The good agreement of the numerical results with the experimental ones validates the TEMT method.
A numerical solution for the dipole antenna with a bi-isotropic object in the vicinity is developed. This solution is based on the combined surface integral equation which could deal with homogeneous situation. A fields splitting scheme is deployed to circumvent the difficulties caused by the complexity of constitutive relationships of bi-isotropic materials. With the aids of MoM, a FORTRAN program can be developed. At the end of this paper, some numerical results are presented.
A CPW-fed UWB antenna with WiMAX and WLAN band-notched characteristics is presented in this paper. The proposed antenna is fed by a CPW structure and provides the band-notched characteristics by etching an arc slot on the monopole plate and integrating the antenna with electromagnetically coupled microstrip resonator into a single module. In order to prevent interference problem due to existing nearby communication systems within the UWB operating frequency, the two band-notches are designed to reject possible interference with the existing 3.25-3.75 GHz band for IEEES02.16 WiMAX and 5.15-5.825 GHz band for IEEES02.11a WLAN and HIPERLAN/2 WLAN The two notched bands can easily be controlled by a few geometry parameters of the arc slot and the microstrip resonator. Surface current distributions and conceptual equivalent-circuit models are used to analyze the effect of the slot and the resonator. The proposed antenna is simulated and fabricated. Moreover, the performances of the antenna are demonstrated along with simulated and measured results.
Several studies have investigated the possibility of using the Radar Target Signature (RTS) of a tumour to classify the tumour as either benign or malignant, since the RTS has been shown to be influenced by the size, shape and surface texture of tumours. The Evolved-Topology Spiking Neural Neural (SNN) presented here extends the use of evolutionary algorithms to determine an optimal number of neurons and interneuron connections, forming a robust and accurate Ultra Wideband Radar (UWB) breast cancer classifier. The classifier is examined using dielectrically realistic numerical breast models, and the performance of the classifier is compared to an existing Fixed-Topology SNN cancer classifier.
This article presents a compact dual band-notched UWB antenna with a pair of L-shaped and modified L-shaped slots on either side of the ground plane for the 3.5/5.5 GHz dual band-notched characteristics. The radiating patch of the proposed antenna has a ladderlike structure symmetrically and fed by a 50-Ω microstrip transmission line. By etching two sets of L-shaped slots on the ground plane, dual band-notched properties in the WiMAX/WLAN bands are achieved, respectively. The proposed antenna has the promising performance including matched impedance, consistent radiation pattern and stable gain.
This paper reports design and development of an innovative compact Stepped Truncated-Circular Waveguide Branching Ortho-Mode Transducer (STCWB-OMT) operating at 4.5-4.8 GHz for horizontal and vertical polarizations. STCWB-OMT is derived by introducing branch waveguide via coupling slot on a stepped truncated-circular waveguide. This configuration possesses inbuilt rectangular-to-circular transition; therefore it does not require any additional square-to-circular transition to combine it with horn antenna. The challenge in the design incorporated is to obtain a mechanically compact design with low mass while compliant with the specified electrical performances; since this device is developed for space-borne application. Achieved return losses at both direct and coupled ports are >17 dB, insertion losses <0.08 dB for both polarizations, isolation is <-60 dB and cross-polarization discrimination >40 dB with the OMT length = 1.98λ atcenter frequency and weight = 250 gm The agreement between measured and computed results provides a validation of the proposed OMT configuration.
We study the rectangular tips of the dipole photoconductive antenna, which has been widely used for terahertz radiation and detection, with different blend radii effect on the emission performance of terahertz (THz) radiation. For the amplitude of THz radiation pulse is proportional to the local electric field in the gap, the increased maximum bias electric field by blending tips is able to achieve higher THz radiation power. Both considering the influence to the maximum bias electric field and the emission efficiency, the blend radius of the rectangular tips is suggest to be larger than 5 μm and the radiation power is largely enhanced. Comparing to the previous work, our method has better THz radiation performance.
In this paper, a novel design of dual-band microstrip antenna with complementary split ring resonators (CSRRs) is presented. A simple and successful dual-band antenna can be realized by etching three CSRRs in the ground plane of a conventional patch antenna. The proposed antenna shows good performances at both resonant frequencies. The CSRRs embedded in the ground plane make a major contribution to the first operating band, but has minor effect on the second operating band. It is beneficial for designing a dual-band antenna as well as a miniaturized antenna flexibly. The simulation results are analyzed and compared with measured results in a good agreement.
In this paper, a novel design of open slot antenna for bandwidth enhancement is proposed and investigated. The bandwidth enhancement of the proposed antenna is achieved by simply attaching a rectangular stub to the circular radiating patch. Experimental results indicate that the bandwidth of the antenna can achieve an operating bandwidth of about 139% over a wideband frequency range from 2.57 to 14.23 GHz. This antenna has a small size of dimensions 20×35 mm2 and is suitable for wideband applications in various wireless communication systems.
A coplanar waveguide (CPW)-fed planar monopole antenna with triple-band operation for worldwide interoperability for microwave access (WiMAX) and wireless local area network (WLAN) applications is presented. The antenna comprises dual rectangular ring with open-end. The triple operating bands with 10-dB return-loss bandwidths of about 30.8% ranging from 2.2 to 2.97 GHz, 23.4% ranging from 3.17 to 3.99 GHz, and 25.4% ranging from 4.91 to 6.31 GHz, covering the required bandwidths of 2.4/5.2/5.8 GHz WLAN and 3.5/5.5\,GHz WiMAX standards, are obtained.
The knowledge of electromagnetic properties of biological tissues is required to assess the radio frequency energy deposition in children exposed to electromagnetic fields. The issue whether children should be considered a dosimetric sensitive group in comparison to adults, to which the confirmation of age-dependence of human tissue electromagnetic properties potentially may contribute remains debatable at scientific forums. This paper derives the formula for calculation of electromagnetic properties (permittivity and conductivity) of children tissues, as a function of height, weight, and age, respectively. By using the proposed formula, we have calculated and presented electromagnetic properties of the muscle, brain (gray matter) and skin for 1-year-old to 10-year-old children for 900 MHz, 1800 MHz and 2.4 GHz, at which frequencies most of radio frequency devices used by children operate. The trend over the age of child electromagnetic properties has been presented, and electromagnetic properties at different frequencies for the same child age have also been compared. For certain tissues, comparison between the children at various age and adult electromagnetic parameters has been given. A database with electromagnetic properties for children, of all ages, tissues and frequencies may be built up with the proposed approach. It will further advance research on the assessment of children exposure to electromagnetic fields. Formula can also be used for the determination of electromagnetic parameters for children with specific height and weight.
A novel coplanar waveguide (CPW) fed wide tapered slot antenna (WTSA) is presented in this paper. A wideband CPW-to-wide slotline (WSL) transition is employed to feed the antenna. The corrugated edge structure and broken line tapered profile are also applied in this design to achieve wideband performance, as well as maintain compact size. A prototype of the antenna is fabricated. The measured results indicate that the antenna is a good candidate for UWB detection and imaging applications.
A compact dual-band high impedance surface (HIS) electromagnetic band-gap (EBG) structure is designed as a reflector for a dual-band coplanar waveguide (CPW)-fed planar monopole antenna. The reflector comprises an array of metal square patches which are etched square ring slots. Details of the HIS structure and dual reflection phase frequency bands characteristics are presented and discussed. The simulated and measured results show that the combination of the HIS reflector and the antenna provides directional properties for both frequency bands. At the same time, compared to the antenna integrated with a metal reflector, the profile of the proposed antenna is reduced by more than 60%; the radiation efficiency is increased by 23% (simulated result); and the front-back ratio is increased by 17 dB and 11 dB at the two operating frequency bands, respectively.
Miniature bandpass filter constructions based on a novel dual-mode suspended stripline resonator are proposed. Because of a special structure of the resonator, the frequencies of two first oscillation modes may be brought closer together. That allows realizing narrowband filters with the wide upper stopband. The filters have low insertion loss in the passband at small dimensions. Several transmission zeros substantially improve the filter performance. The derived coupling coefficients account for some features in the frequency response of the filter. The second-order and fourth-order filters with transmission zeros have been fabricated and measured.
A novel and compact dual-mode defected ground structure (DGS) resonator is presented. Distinct characteristics of the proposed resonator are investigated. Using this type of resonator, a bandpass filter with the center frequency of 2.38 GHz and the fractional bandwidth of 6.7% is simulated and fabricated. The results show that this filter not only has an inherent transmission zero near the passband, but also has a very wide upper stopband with rejection better than 20 dB up to about 12 GHz.
The performance degradation in traditional adaptive beamformers can be attributed to the imprecise knowledge of the array steering vector and inaccurate estimation of the covariance matrix. The inaccurate estimation of the covariance matrix is due to the limited data samples and presence of desired signal components in the training data. The mismatch between the actual and presumed steering vectors can be mainly due to the error in the look direction estimate. In this paper, we propose a novel algorithm to estimate the look direction and to reconstruct the covariance matrix so that near optimal performance without the effect of saturation can be achieved as the input SNR increases. Numerical results also show that all existing beamforming algorithms suffer from saturation effect as the input SNR increases.
Measurements of the radiation patterns from a planar array of bow-tie slot antennas coupled through an extended hemispherical lens are reported. The design operates over 10% bandwidth centred at 30 GHz with a return loss of 10 dB. A moderate directivity from the integrated lenses of 13 dB with half-power beamwidth (HPBW) of 10º is achieved. The reduced size of this design is suitable for the integration with millimetre wave circuits.
A novel microstrip-fed ultra wideband (UWB) elliptical antenna with dual band-notched characteristics is proposed. Dual band-notched characteristics are achieved by employing a pair of U-shaped slots on the ground plane and a T-shaped parasitic strip on the backside of the substrate. The operation bandwidth of the designed antenna is from 2.9 to 12 GHz for voltage standing wave ratio (VSWR) less than 2, except two frequency stop-bands of 3.2-3.9 GHz for WiMAX system and 4.9-6.1 GHz for WLAN system. Moreover, the proposed antenna provides good radiation patterns across the working bands and a relatively flat gain over the entire frequency band excluding the rejected bands.
A novel compact branch-line coupler operating in two arbitrary frequencies is proposed, analyzed and designed. Stepped-impedance stubs are used in the branch-line coupler to achieve dual-band applications. Parameters of the structure are chosen and provided for design guidelines. Broader operating frequency ratios and compactness are achievable. For the purpose of validation, a microstrip coupler operating at 2.4/5.2 GHz is fabricated and measured.
In this letter, the design and measurement of a new ring power divider exhibiting wideband high isolation is presented. Coplanar techniques are used to achieve a compact and truly uniplanar design. The design is demonstrated by a prototype, operating at K-band, that has been monolithically fabricated using a GaAs MMIC process with airbridge technology. The measured insertion loss is 0.6 dB at the center design frequency of 25 GHz. The output port isolation is better than 20 dB across a wide bandwidth from 10 MHz to 50 GHz. The output amplitude and phase balance is within ±0.5 dB and ±2°, respectively, in the bandwidth from 10 MHz to 43 GHz.
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