Volume 76, Issue 9-10

Conductive flexible polypyrrole-silver (PPy-Ag) composite films were prepared on Biaxial Oriented Polyethylene Terephthalate (BOPET) substrate with surfaces treated by (3-aminopropyl) trimethoxysilane (APTMS). The surface treatment was carried out to improve the adhesion, morphology, and electrical properties of the deposited film to enhance the Electromagnetic Interference Shielding Effectiveness (EMI-SE). APTMS grafting on the BOPET substrate was confirmed by X-ray Photoelectron Spectroscopy (XPS) and Atomic Force Microscopy (AFM) analyses. All structural, morphological, and electrical features of PPy-Ag raised from different AgNO 3 molar ratio were investigated. The shielding effectiveness properties, experimentally determined for the synthesized PPy-Ag films were compared to those simulated analytically and numerically based on the transmission line matrix method (TLM). Both analytical and numerical models showed a good agreement with experimental measurements. The obtained results confirmed that the PPy-Ag films of 0.5 M/1 M molar ratio exhibits high EMI shielding performance of about 21 dB along with an electrical conductivity of 47 S/cm. Therefore, the treated surface flexible PPy-Ag films can be considered as potential candidate for high frequency electromagnetic interference shielding applications.

In this paper, hybrid integration of planar microstrip line and Photonic Band Gap (PBG) structure is proposed for the dielectric characterization of liquids. To implement the PBG structure of the microstrip line, a microfluidic channel with periodic form is introduced into the substrate and filled with different liquids. Based on this configuration, the operation principle of the sensor is based on a frequency shift due to the variation in the center of the bandgap, which in turn changes with the variation of the permittivity of LUT filled in the microfluidic channel. The proposed sensor exploits the behavior of the bandgap as a reflector to construct a resonant structure sensitive to the variation in LUT permittivity. The dimensions of the planar structure are optimized to achieve high precision and discrimination capability. The different empirical expressions describing the complex permittivity with the measured parameters were carried out. To validate the proposed concept, the sensor prototype is designed, fabricated, and tested. The frequency shift related to a change of 3.2 in LUT permittivity corresponds to 180 MHz around 6 GHz. The resonant-mode sensor spans a permittivity range from 1 to 80 with a precision better than 7.2%. The proposed sensor is simple in design and low cost, which may be applied in different applications at the industrial.

In this study, a bio-radar system has been constituted using a frequency modulated continuous wave (FMCW) radar with low cost and limited bandwidth, taking into account of the lack of range the continuous wave (CW) radar. The displacement and vibration frequencies have been determined at a distance of 3.5–5 m for single and multiple targets via the help of the target test mechanism. Then, the detection of vital signs has been achieved with healthy human subject measurements. For a single human subject, respiration rate (RR) errors at 3.5 m and 5 m distances are 4% and 4.42%, respectively, and 13.25% and 15.16% for heartbeat rate (HR). In multiple targets measurements, although targets do not create an obstacle to each other, a slight deterioration has been observed in the signals and the error rates increase. The results show that bio-radar have a promising future to replace contact devices in medical applications.

In this paper, a compact circular shape ultra-wide microstrip antenna is proposed for the detection of breast tumor. The proposed antenna is a two-port MIMO antenna of 1 × 2 elements. The dimensions of the proposed antenna are 34 mm × 18mm × 1.6 mm. It is designed over a lower-cost FR-4 epoxy substrate with a partial ground plane. The antenna is operated between the frequency range of 3.1–9.6 GHz. Isolation between the antenna element is less than −22 dB from 3.1 GHz to 7 GHz and −25 dB between 7 GHz and 10.6 GHz. The obtained ECC of the designed MIMO antenna is less than 0.01 and also DG is almost 10 dB in the entire UWB range. Further, the 3D breast phantom model is also simulated for analysis of the effect of SAR. Due to the variation in the electrical properties of cancerous cells and healthy cells it is possible to identify the cancerous tumor using SAR analysis. The obtained maximum Average SAR value without a tumor is 41.97 W/kg and with a cancerous tumor is 72 W/kg. Also, the variation in reflection coefficient helps to detect the tumor of the same composition but having different locations and having different sizes inside breast phantom. The principal component analysis is done to change the multi-variation in reflection coefficients data value to a single point value for better analysis.

A unique metamaterial-based UWB band notched textile antenna for Body Area Network (BAN) is created in this paper, with an operational frequency range of 3–11 GHz, spanning the Ultra Wide Band (UWB) band (3.1–10.6 GHz). Using the textile material Jeans, which has a permittivity of 1.67, the antenna’s size is lowered. To enhance the impedance bandwidth, the ground plane is made of partially conductive material and is rectangular. The hexagonal slot is used to increase the electric field dispersion along the borders of the hexagonal slot, which improves bandwidth. The gain of the UWB of the antenna maximum is obtained at 7.52 dB and minimum is obtained at 5.25 dB. The VSWR of the UWB of the antenna maximum is obtained at 1.92 and minimum is obtained at 1.45. The fabrication uses a Denim substrate with a thickness of 1 mm and a microstrip feed. The designed antenna is investigated for its return loss and gain characteristics.

In this study, a new compact dual-band antenna with overall size of 11 × 14.46 × 1.6 mm 3 has been designed, fabricated and tested. The proposed antenna consists of two inverted Ω-shaped strips loaded with two different comb structures. The fist comb of six elements connected to the first Ω-shaped radiating branch is used to decrease the second band lower cut-off frequency and cover the intended WLAN and WiMAX applications. In order to cover the 2.45 GHz WLAN band and further reduce the antenna dimensions, a second comb structure of 14 elements is attached to the upper radiating branch. The fabricated antenna covers the frequency bands from 2.42 to 2.6 GHz and from 4.25 to 6.77 GHz with a reflection coefficient of |S 11| ≤ −10 dB. The antenna shows an omnidirectional radiation pattern in the H-plane and a monopole-like radiation pattern in the E-plane. The measured results agree well with the simulated ones which indicate that the proposed antenna is suitable to be used in the WLAN/WiMAX applications.

In recent days, miniaturized antennas have gained significance in portable ultra-wideband (UWB) applications owing to its broad coverage spectrum. Fractal antennas have become popular in this context owing to the three properties: self-similarity, space-filling, and lacunarity, thereby producing miniaturization with a broad spectrum. Conventional Fractal antennas achieve a good impedance bandwidth, relatively high gain, at the cost of trade-off between compact size, radiation characteristics and broad spectrum. In this paper, an asymmetric coplanar waveguide–fed hexagonal monopole antenna with Boomerang-shaped Fractals is proposed for UWB characteristics with relatively high antenna gain and wide bandwidth. The miniaturization of the antenna is realized by the Fractal structure. The size of the antenna is to be 0.287  λ r  × 0.287  λ r  × 0.009  λ r , where λ r is the resonating wavelength at 3.45 GHz. The proposed antenna is printed on a 0.8-mm-thick FR-4 substrate with relative dielectric constant of 4.4 and a loss tangent of 0.02. From frequency-domain analysis, the experimental results reveal that the fractional bandwidth is 101.7% and the peak antenna gain detected is 5.1 dBi. The radiation performance of the antenna was nearly omnidirectional. From the time-domain analysis, group delay and three different Fidelity Factors i.e. Fidelity Factor (FF), System Fidelity Factor (SFF), and Fidelity Factor of System (FFS), the proposed antenna is found to have negligible distortion. As the bandwidth meets up to fractional bandwidth above 20% and absolute bandwidth greater than 500 MHz, the proposed antenna is suitable for 3.45–10.6 GHz UWB applications.

In this work, a unique tri-band notch and multiband UWB antenna sensor has been designed for microwave sensing system to find out the cancerous tissues. The crescent shaped slot loaded antenna has been designed to avoid interferences between the antennas in UWB ranges. Using notches, the antenna sensitivity increases for detection. The proposed method has been verified through simulation and validated using measurements. S11 plot of the proposed antenna shows three notches at 3 GHz, 4.75 GHz and 7.25 GHz. It also shows four bands and omnidirectional radiation pattern over the UWB frequency range. Ground plane has been chosen to be hexagonal to achieve fourth band. I-shaped and U-shaped parasitics improve the antenna performance in third band. Crescent shaped and C-shaped slots improve the performance of first and second band of the antenna respectively. Additionally, phantom without tumors and with single and multiple tumors are fabricated. S-parameter analysis is a better approach to detect the cancerous tissues in the breast. Concept of principal component analysis of statistical machine learning has also been used to distinguish S-parameter of normal breast phantom from malignant breast phantom.

The most important characterizing parameters which determine the antenna performance are axial ratio bandwidth, impedance bandwidth and gain of wireless systems. The improvement of these parameters are presented in the proposed antenna. Basically, the proposed design consists of an inverted L -shaped microstrip feed line and modified ground plane. The size of the antenna is 0.4 × 0.28 × 0.0128  λ 0 (where λ 0 be the free space wavelength at f r of 2.4 GHz). The designed antenna has been fabricated and the measured results of fabricated antenna are compared with the simulated results. It is found that the results are very good in agreement. Novelty of the research work is the improvement of axial ratio (less than 3 dB) bandwidth. As a result, the antenna is circularly polarized for a good amount of bandwidth which is desired in the modern communication system. Circularly polarized antenna is able to transmit and receive both vertically and horizontally polarized electromagnetic waves.

In this paper, a novel ultra-compact metamaterial unit-cell is introduced. The proposed unit-cell consists of one modified rings which has been designed based on the fractal technique and meander technique. These techniques are used to reduce the physical size of the conventional complementary split ring resonators (CSRRs). In the proposed metamaterial unit-cell which is called the fractal/meander CSRR (FMCSRR), the slot lines in the conventional CSRRs are replaced by the fractal and meander slots, simultaneously. The FMCSRR unit-cell is a planar metamaterial element which exhibits negative permittivity and is considered as electric dipole when excited by an axial electric field. Thus, the FMCSRR unit-cell is modeled as a shunt resonator tank. Therefore, by using the proposed FMCSRR configuration, all of the interior space of the ring has been used and the slot lines have been increased. Consequently, the higher inductance has been achieved and the resonance frequency of the proposed FMCSRR unit-cell becomes lower compared with the conventional CSRR. That’s mean the electrical size of the introduced unit-cell FMCSRR unit-cell is smaller than the conventional CSRR with the same physical sizes. A microstrip notch band filter, a microstrip band-pass filter, a half mode substrate integrated waveguide (HMSIW) band-pass filter and three HMSIW filtering power dividers (FPDs) with different power division ratios of 1:1, 1:4, and 1:8 have been designed to illustrate the ability of the proposed FMCSRR unit-cell in the size reduction. All of the designed devices operated at 2.4 GHz which are suitable for WLAN applications. For verification the performance of the utilized techniques in miniaturization of the dimension, the designed equal/unequal HMSIW FPDs have been fabricated and tested. A reasonable agreement between simulated and measured results has been achieved. The results confirmation that a miniaturization about 79% has been obtained. The total size of the proposed HMSIW FPDs are about 0.09 λ g × 0.09 λ g . The proposed HMSIW FPDs have many advantages in terms of compact size, low insertion loss, high selectivity, easy integration with the other planar circuits, and controllable bandwidth.

By introducing an open stub loaded resonator (OSLR) and a uniform impedance resonator (UIR) into balanced stepped-impedance microstrip-slotline transition structures, a balanced dual-band bandpass filter (BPF) with high selectivity and low insertion loss performance is presented in this paper. The balanced microstrip-slotline transition structures can achieve a wideband common-mode (CM) suppression. Meanwhile, the differential-mode (DM) passbands are independent from the CM responses, which greatly simplifies the design procedure. In addition, four varactors are loaded into OSLR and UIR to achieve the electrical reconfiguration. The proposed balanced dual-band BPF can realize quasi-independently tunable center frequencies and bandwidths. In order to verify the feasibility of the proposed design method, a prototype circuit of the proposed reconfigurable balanced dual-band BPF is simulated, fabricated and measured. A good agreement between the simulation and measurement results is observed.

This paper presents the design and characterization of an efficient high-output-power 55 GHz fundamental oscillator. The performance parameters of the oscillator are analysed as a function of the contributors of the tank capacitance, and the design choices in the varactor for phase noise and for tuning range are exemplified. The circuit was implemented in 22 nm FD-SOI CMOS technology and occupies 0.046 mm 2 area including the matching network. On-wafer measurement results have demonstrated 6.5 dBm peak output power, 22% peak DC-to-RF efficiency and −98.3 dBc/Hz phase noise at 1 MHz offset frequency, while the core draws 8.3 mW power. To the best knowledge of the authors, the efficiency is the best, while the output power is the second best among CMOS oscillators in the same frequency range, and the phase noise is the best result for V-band fundamental CMOS oscillators reported to date.