Volume 73, Issue 5-6 -

This paper reports a novel polarization-reconfigurable antenna array based on the theory of mode combination (MC), which can electronically alter its polarization states between left-hand circular polarization (LCP) mode, right-hand circular polarization (RCP) mode, and two combined linear polarization (LP) modes. The array element is adopted as the L-probes fed circularly-polarized antenna reported by Luk et al . [1]. To verify the concept, a prototype of 2×2 antenna array is manufactured and tested. By properly exciting the feeding probes, four polarization modes can be switchable. Measurement results show that the proposed antenna has an overlapped −10 dB impedance bandwidth around 34 % for both CP modes and LP(2) mode, and an overlapped 3 dB axial-ratio bandwidth around 22.0 % of the CP modes. The average realized gains are around 12.4 dB for CP modes and LP(1) mode, which remain stable in the axial-ratio bandwidth.

The RCS of flat cylindrical Dielectric Resonators (DR) is investigated and found to be too low for an application of the resonators as tags in a novel indoor localization system at mm-wave frequencies. As a method to increase the RCS of a DR tag, we propose the combination with a constant-index spherical lens. The collimation and scattering properties of this lens type are found suitable for a combination with DRs. The optimum relative permittivity of the lens is found in the range of ϵ r =1.6 to 2.8 and the optimum distance between lens surface and DR is found slightly larger than the radius of the DR. RCS enhancement is found to vary with the modes of the DR but increases approximately with the fourth power of the lens radius. However, RCS signatures become corrupted by scattering due to mismatch effects of large lenses such that the lens diameter has to be limited to 4 to 5 wavelengths with the RCS enhancement limited to about 30 to 35 dB. Simulation and experimental verification are performed at a down-scaled frequency range from 4 GHz to 7 GHz using lenses of 60 mm and 120 mm diameter made of paraffin wax.

In this paper, substrate-integrated waveguide (SIW) and half mode substrate integrated waveguide (HM-SIW) periodic leaky wave antennas (LWAs) are presented for the antenna applications. The continuous beam scanning (CBS) is realized by optimizing the unit cell by matching its impedance to the characteristic impedance of the waveguide. This leaky wave antenna is capable of total 60 ° scanning from −38 ° to + 22 ° as the frequency changes from 10.17 GHz to 16.3 GHz with a maximum gain of 11 dBi. Moreover, for further miniaturization, HM-SIW technology is employed in the presented LWA. This LWA is also capable of CBS from −50 ° to + 26 ° in the frequency band of 10 GHz to 16.5 GHz with a maximum gain of 12 dBi. The final prototypes of the both these antenna are fabricated and measured results are in agreement with the simulated ones.

In this study, an algorithm to the detection and imaging of hidden arms for passive millimeter-wave (PMMW) imaging systems is proposed. This technique is; in fact, an improved version of our previously developed auto-classification algorithm by extending it by exploiting the Otsu ’ s multi-level thresholding method. The detailed derivation and the brief steps of the proposed algorithm are given. The proposed algorithm is tested and validated by real PMMW images obtained by a real radiometric imaging system. Resultant measured images are obtained with the employment of signal and image processing procedures of the suggested technique. It is demonstrated by the constructed PMMW images that proposed technique successfully detects a concealed metal threat and also predicts its size by drawing the shape outline based on Otsu ’ s multi-level thresholding routine that was specially tailored to our auto-classification technique.

The Nanomaterial is a pioneer in the field of modern research for its unique properties. Human exposure analysis is inevitable due to the rapid growth in technology. The concern for human welfare indicates a need for reduction of human exposure towards the radiation caused by the devices. The dielectric properties of the nanomaterials can be ideal for exploration in the field of biomedical engineering. Specific absorption rate (SAR) is a vital parameter for exposure analysis. This paper investigates the impact of Nanomaterials on the human exposure analysis. For this purpose, a dipole radiating structure operating at GSM frequency of 900 MHz and 1800 MHz are designed with conventional Copper material and compared with Carbon nanomaterials such as Graphene, Single-walled carbon nanotube (SWCNT) and Multi-walled carbon nanotube (MWCNT) for performance evaluation. Further, the specific absorption rate estimates absorption of radiation in IEEE Sam phantom human head with equivalent tissue properties. The comparison of calculated SAR with the radiating structures that are designed with the equivalent properties of that of Nanomaterials. The evaluation of Nanomaterial Antennas at the center frequency is estimated, and performance is evaluated. The designed Nanomaterials interact with IEEE SAM Phantom and SAR is calculated. The analysis of SAR impact with nanomaterials is investigated in this work.

A balanced dual-band bandpass filter (BPF) is proposed by embedding two nested coupled complementary split-ring resonators (C-CSRRs) into a H-type balanced stepped-impedance slotline resonator in this paper. C-CSRR is composed of a complementary split-ring resonator (CSRR) with a pair of coupling slotlines in the open end, which can generate a bandpass response. In order to improve the passband selectivity further, source-load-coupled structure is employed. Moreover, it can be found that the proposed BPF has a wideband common-mode (CM) suppression, which is independent from the differential-mode (DM) passbands. Therefore, the design procedure can be significantly simplified. In order to validate its practicalbility, one balanced dual-band BPF is fabricated. The predicted results on S parameters are compared with the measured ones and a good agreement is found.

This letter presents an approach to design two-pole source-load coupling and four-pole cross-coupling substrate integrated waveguide (SIW) bandpass filters based on multilayer process. Utilizing the field distribution, the vertical magnetic and electric coupling of fundamental mode is designed by suppressing the first spurious mode. Then, source-load and cross-coupling schemes are realized with controllable features in two-pole and four-pole filters, respectively. The harmonic passband produced by TE 102 mode can be suppressed by proper coupling technique enabling the connection with TE 102 mode in two- and four-pole filter designs, respectively. Three transmission zeros, which are derived from source-load coupling, are introduced around the passband of two-pole filter to improve its selectivity. In the four-pole filter design, a six-order cross-coupling scheme including source and load produces four transmission zeros around the passband, leading to a sharp selectivity. In addition, another transmission zero is generated at the adjacent location of the passband to improve the out-of-band rejection. Compared with conventional horizontally coupled filters made of single layer, the proposed filters show a compact size. To demonstrate the proposed design method, a two-pole and a four-pole double-layered SIW bandpass filters are fabricated and measured. Measured results show that the proposed filters exhibit high selectivity and good out-of-band rejection, as well as a good agreement between simulated and measured results.

In this article, a new microstrip lowpass filter with ultra-wide stopband using T-shaped resonators and folded structures is described. The structure of this filter is very simple, so that only a T-shaped resonator is used as main resonator without any particular changes in these resonators. The designed T-shaped main resonator has a −3 dB cut-off frequency of 1.4 GHz. On the other hand, T-shaped resonators with low base length are utilized as suppressing cells. To provide an ultra-wide stopband, two pair of T-shaped resonator and two high frequency suppressing cells are employed. The structure of this filter is folded to have compact size. The measured results shows −3 dB cut-off frequency of 1.4 GHz. The transition band is equal to 0.25 GHz from 1.4 to 1.65 GHz, with corresponding attenuation levels of −3 to −20 dB. The ultra-wide stopband with −22 dB suppression level is from 1.68 to 40 GHz. Also, the total size of the proposed lowpass filter is 16.8×11.3 mm 2 .