Volume 74, Issue 1-2 -

In a novel mm-wave localization system, dielectric resonators (DR) have been proposed as passive chipless RFID tags to mark fixed reference nodes. To counter clutter and improve the limited read range due to the low RCS level of a DR at millimeter-wave frequencies we propose a combination of several DRs with a dielectric spherical lens which allows improvement of up to 30 dB. The paper presents the design principle and shows simulation results and experimental verification of a scaled tag operating in the 10–12 GHz range and covering a range of incidence angle of the reader signal of ± 50°. A frequency sweeping RF reader can identify the tag (information) by the peak of the RCS level at its DR resonant frequency. For a multiple-tag scenario we can realize up to 12 different tags which can be discriminated unambiguously by their resonant frequencies in a 1: 1.2 frequency bandwidth.

In this paper, we propose a new structure based on photonic crystals to realise a demultiplexing operation for dense wavelength division multiplexing transmission systems. In this demultiplexer, the resonant cavities were responsible for selecting the wavelength. By imposing defect rods to these cavities, the modes could resonate at the desired frequencies. As we wanted to see the nonlinear effects, the material that was chosen for defect rods were doped glass. The refractive index of this glass in 1550 nm is 1.41. Increasing the input power causes variation in the refractive index of defect rods and as a result resonant condition of whole cavity alerts so a tenable demultiplexer can be investigated. Based on the results, the average pass bands of channels are near to 1.5 nm and the channel spacing is approximately 3.95 nm. The proposed demultiplexer acts in a near-complete transmission efficiency and the mean value of the crosstalk was −19 dB.

In this paper, near zero parameter based metamaterial superstrate is presented for mutual coupling reduction in multiple-input-multiple-output (MIMO) antenna. The proposed design offers a peak isolation of 38 dB with edge-separation of 0.042λ 0 at resonating frequency. To verify the simulations results, a prototype of the proposed antenna is fabricated and experimentally measured. The two elements MIMO is designed with measured impedance bandwidth of 5.6 to 5.95 GHz with a peak measured gain of 7.4 dBi and efficiency above 95 %.The measurement established an isolation enhancement of 30 dB with minimum correlation coefficient of 0.05 within operating band. The proposed method offers a good design technique for high gain and closely packed MIMO antenna system for WLAN applications.

In the paper, a tri-band angularly stable frequency selective surface (FSS) with controllable resonances for electromagnetic shielding is proposed. Different from traditional single-layer structure, the FSS proposed is based on cascaded structure that creates three adjustable blocking bands around frequency 5.93 GHz, 7.33 GHz and 9.17 GHz, respectively. The designed FSS has a low profile with thickness of λ 0 /100, where the λ 0 represents wavelength of the first band-stop resonance frequency. Besides, the proposed FSS exhibits stable frequency response up to 70° with respect to different polarizations. Therefore, this FSS is flexible and can be used in electromagnetic shielding field where needs conformal screen. To investigate and understand the operating mechanism better, a equivalent circuit model (ECM) is deduced and given in the Section 2, the calculated results match the full-wave EM simulation results perfectly. Finally, a prototype of this FSS is fabricated and measured, the measurement results are in accordance with the simulation results.

Outdoor radar cross section (RCS) measurement suffers background clutter. Such clutter needs to be minimized, especially when measuring low RCS level objects. To do this, a pair of corrugated horn antennas with a rectangular aperture has been designed, fabricated, and measured to improve the performance of outdoor RCS measurement. This antenna consists of a coaxial-waveguide adaptor, a square-rectangular waveguide transition, a corrugated rectangular horn, and chokes. A comparison of the performances of several corrugation profiles is provided. The tangential profile surpasses others because it provides the necessary low sidelobe level and narrow elevation beamwidth. The proposed antenna achieves −30 dB sidelobe level, fan-shaped beam pattern, and dual-polarization with −26 dB cross-polarization level over the band from 8.5 GHz to 12.5 GHz. The effectiveness of the antenna has been verified experimentally on a roof with two corner reflectors that were deployed intentionally to enlarge the effects of background clutter.

In this article, a new structure comprising of a novel compact slot loaded polarization dependent Electromagnetic Band Gap structure (SLPDEBG), which enhances the performance of circularly polarized rotated square patch antenna by placing SLPDEBG unit cells around it, has been designed. The proposed antenna, having dimensions 0.640 λo x 0.640 λ x 0.0128 λo (λo stands for the free space wavelength at 2.39 GHz), shows that the measured impedance bandwidth and AR bandwidth is 120 MHz and 50 MHz, respectively, with a peak gain of 3.52 dB. Some prominent features of the proposed structure are: front to back ratio of 64, 3 db, beamwidth of 92° at xz-plane and 74° at yz-plane. This prototype antenna finds its application in wireless communication of ISM band. Good performance of the proposed antenna is verified by the close agreement between the simulated and measured results.

This paper presents a compact quad-band bandpass filter. The filter is realized by multi-embedded stub-load resonators. By utilizing multi-embedded structure, the whole filter exhibits a compact size. And due to the multi-section stub-loaded lines, four passbands can be realized and the center frequency of the four passbands can be controlled individually to accommodate different communication protocols. Moreover, by using 0° degree feed structure, there are two transmission zeros locates at left and right side of a passband, which greatly enhance the selectivity. To validate the proposed idea, a quad-band bandpass filter, which operates at 2/2.7/3.45/4.55 GHz is implemented. The insertion loss is smaller than 2 dB and return loss is better than 10 dB. Good agreement between the predicted and measured results demonstrates the proposed idea.

In this paper, a microstrip dual-band bandpass filter (DBBPF) based on an octagonal loop resonator (OLR), tapered resonators and open bended stubs (OBSs) is designed and analysed. The proposed structure produces two passbands with the centre frequencies of 3.65 and 5.67 GHz. The marked advantages of the proposed filter are as follows: Two centre frequencies can be individually tuned. The bandwidth of the upper passband can also be controlled. Furthermore, the DBBPF benefits from an ultra-wide upper stopband from 5.9 up to 21 GHz with an attenuation level of higher than 20 dB and a small size of 0.21 λ g  × 0.26 λ g , where λ g is the guided wavelength at 3.65 GHz. The designed filter is horizontally and vertically symmetrical leading to a reciprocal S matrix. Other remarkable specifications of the proposed filter are the insertion loss < 0.62 dB, the return loss > 20.2 dB and sharp response. To provide an analytical description, the LC equivalent circuits of initial and main resonators are presented. Acceptable similarity between simulated and measured results verifies the design process.

Partial discharge (PD) is the main cause of the insulation decay and hence periodical testing of the insulation condition of a distribution transformer is necessary. This paper presents a model of PD acoustic wave propagation, detection, and localization in an oil-filled distribution transformer using finite element method supported by COMSOL Multiphysics software. Using an acoustic module and AC/DC module of COMSOL Multiphysics software, oil filled distribution transformer, and the acoustic piezoelectric sensor are simulated to analyze and detect the PD inside the transformer. PD is numerically simulated in the transformer windings, core, and oil ducts that produce acoustic wave signal. The distribution of the acoustic pressure wave inside the model transformer is analyzed first. Next, the acoustic piezoelectric sensors are modelled at four different locations of the model transformer to detect the pressure acoustic wave signal induced due to PD in the transformer. Finally, using an artificial neural network (ANN), the localization, and identification of PD in various parts of the transformer have been analyzed. The results obtained for location and detection are quite encouraging.

A 3–12 GHz ultra-wideband (UWB) low noise amplifier (LNA) is proposed in this paper. The first stage common-gate (CG), common-source (CS) noise canceling approach is used to achieve low noise-figure (NF). CG configuration at the input stage provides wideband input-matching. The noise of CG transistor is cancelled by systematically added two parallel CS transistors, whose outputs are cascoded in second stage. In order to achieve flat power gain (S 21 ) response, a series peaking inductor is used in the second stage. The proposed LNA is designed in 90 nm CMOS process with chip-layout area of 0.467 mm 2 and in comparison to the existing LNAs, it consumes a low power of 5.7 mW from a 1 V supply. The achieved input-reflection coefficient (S 11 ) is <−7.5 dB, output-reflection coefficient (S 22 ) is <−7.6 dB with NF < 5.8 dB for 3–12 GHz UWB and third-order intercept point (IIP3) of −19 dBm. It achieves high and flat S 21 of 20.84 ± 0.28 dB over 4.2–10 GHz, with NF ranging from 2.6–3.6 dB.