Search

Automatic modulation classification (AMC) is an essential technique in intelligent receivers of non-cooperative communication systems such as cognitive radio networks and military applications. This article proposes a robust automatic modulation classification model based on a new architecture of a convolutional neural network (CNN). The basic building convolutional blocks of the proposed model include asymmetric kernels organized in parallel combinations to extract more meaningful and powerful features from the raw I/Q sequences of the received signals. These blocks are connected via skip connection to avoid vanishing gradient problems. The experimental results reveal that the proposed model performs well in classifying nine different modulation schemes simulated with different real wireless channel impairments, including AWGN, Rician multipath fading, and clock offset. The performance of the proposed system systems shows that it outperforms its best rivals from the literature in recognizing the modulation type. The proposed CNN architecture remarkably improves classification accuracy at low SNRs, which is appropriate in realistic scenarios. It achieves 86.1% accuracy at −2 dB SNR. Furthermore, it reaches an accuracy of 96.5% at 0 dB SNR and 99.8% at 10 dB SNR. The proposed architecture has strong feature extraction abilities that can effectively recognize 16QAM and 64QAM signals, the challenging modulation schemes of the same modulation family, with an overall average accuracy of 81.02%. [ABSTRACT FROM AUTHOR]

In this paper, for the first time, a wideband low -loss high-power equally splitting power divider based on the new half-height pin form is introduced with bandwidth from 10 to 13.5 GHz centered at 11.75 GHz. Also, for the first time, a wideband transition from coaxial line to half-height pin gap waveguide with no need of any matching sections with excellent results at the band of (10:20 GHz) was achieved. The proposed transition shows excellent return loss which is lower than 30 dB (measured) at the transition bandwidth center frequency which is (15 GHz) with 0.2 dB (measured) insertion loss and return loss lower than 20 dB (measured) with 0.55 dB insertion loss at the rest of the bandwidth. The proposed transition and power divider designs were validated using circuit and 3D full-wave simulations and confirmed using experimental measurements with all agreements. The power divider has simple manufacturing due to the new pin form; hence, it is suitable for low-cost mass production of high-power mm-wave power dividers. [ABSTRACT FROM AUTHOR]

Proposed in this paper is a new configuration for a quad-band antenna based on using a metamaterial-inspired defected ground structure. The presented structure is introduced as a new modified metamaterial Complementary Split Ring Resonator (CSRR) with a compact electrical size. The new modified CSRR has been employed in Composite Right/Left-Handed (CRLH) transmission line configuration for ultra-size reduction. Validation for the particle small size is introduced and the detailed analysis for the NRI characteristics has been discussed by extracting the cell constitutive parameters. Hence, a multi-band antenna is designed based on using only one cell of the proposed NRI-TL. Subsequently, a small multi-band antenna is presented for different multi-band functionalities and different radiation properties. The antenna displays quad-resonances at 1.78 GHz, with the typical omnidirectional radiation pattern, 3.28 GHz, 4 GHz, and 4.3 GHz, with the directive broadside radiation properties. The proposed antenna footprint is 10 × 10 cm2, which exhibits a size reduction of up to 80% in comparison with a rectangular patch antenna operating at the lowest frequency band. [ABSTRACT FROM AUTHOR]

In this paper, a novel metasurface-based Fabry–Perot Cavity antenna is presented. The antenna is wideband, directive and has a high front-to-back ratio. The idea of the antenna is based on loading a microstrip narrow band patch antenna resonating at 4.6 GHz by a metasurface superstrate. The metasurface superstrate consists of an aperiodic array of holes in contrast to the periodic nature of unit cell previously explored in the literature. The metasurface is designed as a near-zero-refractive-index material (NZRIM). By controlling the phase reflection properties of the structure, improved radiation pattern, improved front-to-back lobe ratio (7–25 dB), improved directivity (by 3 dB) and antenna bandwidth (five times) are obtained compared to a conventional microstrip antenna. The enhancement in bandwidth and directivity simultaneously using just a single layer of metasurface superstrate demonstrated for the first time, to best to authors' knowledge, are obtained. [ABSTRACT FROM AUTHOR]

An ultrathin, compact, and highly efficient antenna based on the $\Pi $ -section composite right/left-handed (CRLH) methodology is presented. It operates at 2.45 GHz of the Industrial, Scientific and Medical (ISM) band with a physical size of 25 mm $\times25$ mm, a realized gain of 2.34 dBi, and a total efficiency of 87% in free space. Nevertheless, to maintain resonance at 2.45 GHz with body-loading scenarios, a high separation was required, leading to an overall large size. To circumvent that, an all-textile $2 \times 2$ artificial magnetic conductor (AMC) array was placed in-between the antenna and the human body. In free space, the low-profile integrated design exhibited a gain of 7.63 dBi (enhancement of 5.29 dBi) and total efficiency of 96.4%. The integrated design achieved a gain and total efficiency enhancements by 14.88 dBi and 72.4%, respectively, as well as, lower specific absorption rate (SAR) levels, in comparison with the CRLH antenna alone, for human loading cases. Results are achieved through circuit model and full-wave electromagnetic simulations. In addition, the CRLH antenna and AMC array structure were fabricated and measurements were undertaken, which agreed well with the simulated ones. Therefore, the integrated design is highly suggested to be recognized in wireless body area network (WBAN) and medical applications. [ABSTRACT FROM AUTHOR]

In this paper, a compact novel simple design of ultra‐wide bandpass filter with high out of band attenuation is presented. The filter configuration is based on combining an ultra‐wide band composite right/left‐handed (CRLH) band pass filter (BPF) with simple uni‐planar configuration of complementary split ring resonator (UP‐CSRR). By integrating two UP‐CSRR cells, the ultra‐wideband CRLH filter roll‐off and wide stopband attenuation are enhanced. The filter has 3 dB cutoff frequencies at 3.1 GHz and 10.6 GHz with insertion loss equals 0.7 dB in average and minimum and maximum values of 0.48 dB and 1.05 dB, respectively over the filter passband. Within the passband. The transition band attenuation from 3 dB to 20 dB is achieved within the frequency band 1.9 GHz to 3.1 GHz (48%) at lower cutoff and the frequency band 10.6 GHz to 11.4 GHz (7%) at upper stopband. Moreover, the filter has a wide stopband attenuation >20 dB in frequencies 11 GHz to 13.6 GHz (21%) and ends with 3 dB cutoff frequency at 14.8 GHz. Furthermore, the designed filter size is very compact (23 × 12 mm2) whose length is only about 0.17 λg at 6.85 GHz. The filter performance is examined using circuit modeling, full‐wave simulations, and experimental measurements with good matching between all of them. [ABSTRACT FROM AUTHOR]

This article introduces analysis of the new configuration; inductor loaded left‐handed composite right‐/left‐handed transmission line ((L‐CRLH TL). Compared to conventional CRLH and dual CRLH, this configuration has the advantage of very slow phase (almost constant) and nonlinear propagation coefficient which enables it to be very effective in designing compact size and ultra‐wideband (UWB) microwave components. The theoretical and circuit model of the L‐CRLH TL is discussed. As an application, a compact UWB (3.1‐10.6 GHz) L‐CRLH power divider is designed using only one L‐CRLH cell with size of 2.7 × 8.6 mm2 whereas the whole power divider photoprint is 12.14 × 18.83 mm2. The size is 58.5% smaller compared to the conventional narrow band T‐junction power divider designed at the mid frequency. The results reveal good insertion losses (3.2 ± 0.2 dB for both S21 and S31), and good return losses (better than 10 dB within the passband). [ABSTRACT FROM AUTHOR]

A dual-band, low profile, high gain, and low specific absorption rate (SAR) triangular slotted monopole antenna backed with a $4\times 4$ artificial magnetic conductor (AMC) array is presented for wireless body area network (WBAN) applications. The antenna is printed on a Rogers ULTRALAM 3850 substrate, whereas the AMC array is printed on a RO3003 substrate. The design operates at 3.5 GHz, for WiMAX wireless applications, and at 5.8 GHz for the ISM Band. The proposed antenna preserved the dual-band resonance and exhibited acceptable gain and SAR at a separation of 15 mm from the human body model. To reduce such separation and achieve enhancements to gain and SAR, an AMC array was utilized. In free space, gain enhancements by 6.8 and 3.7 dBi were achieved at both frequencies, respectively. Furthermore, over a gap of 1 mm from the human body, gain enhancements by 23.3 and 13.9 dBi were achieved at both frequencies, respectively. In addition, SAR reductions by almost 99% were attained. The antenna was fabricated and measured where a very good agreement was observed between simulated and measured results, with and without the incorporated AMC array. With such results, the proposed design can be highly recommended for wearable medical applications, specifically for diabetic patients. [ABSTRACT FROM AUTHOR]

A rectangular microstrip patch (RMSP) antenna is designed to be used in a two-element Multi-Input Multi-Output (MIMO) antennas at which they operate at 5.8 GHz. The two antennas are positioned opposite to each other with a separation of 10 mm (0.2 λ 0) from their radiating edges. A novel uni-conductor electromagnetic bandgap (UC-EBG) periodic cells are introduced in this paper as effective barriers for surface waves compared to the conventional UC-EBG. Each unit cell has a compact size area 7.3 × 5.8 mm2 where it is 20% more compact than the conventional cell. Two of the proposed modified EBG periodic cells are placed in-between the two antennas causing an excellent reduction in the coupled power of 46 dB. This strong isolation definitely enhances the performance of antennas in MIMO communication systems, where 0.0001 and 0.03 values for correlation coefficient have obtained from S-parameters and far-field information, respectively, due to this strong isolation. [ABSTRACT FROM AUTHOR]

A small size and wide-band band pass filter with high performance for WiMAX applications is introduced. The filter is designed by utilizing one composite right left handed transmission line (CRLHTL) metamaterial cell and two gap lumped capacitors. The filter has a center frequency of 5.3 GHz and a 3dB bandwidth from 4.2 GHz to 6.4 GHz. A lower than 0.5 dB insertion loss within pass-band is achieved. A single transmission zero at 6.52 GHz is achieved to increase the selectivity of the proposed filter. The rejection band is extended to be up to 10 GHz. A comparison between circuit simulation, EM simulation and measured results is introduced with good consistency between them. The filter has a small size (26.8 × 16.5 mm2) which is smaller than recently reported wide band filters. [ABSTRACT FROM AUTHOR]

Abstract In this paper, an efficient technique proposed for surface wave filtering in radar array antennas. The filtering reduced the correlation between high directive TX/RX array antennas. The filtering has been done using a small defected ground filter that achieves more than 20 dB isolation between the two antennas with a very close separation between the two antennas (less than 0.06 λ 0). The presented results confirm the advantage of the applied technique in reducing the correlation coefficient between the two antennas to less than 0.005. The results demonstrate that 99.68% of coupled power can be reduced. The integrated isolated radar array antennas have been studied theoretically, simulated using electromagnetic simulation, and measured experimentally. [ABSTRACT FROM AUTHOR]

Abstract This paper presents the experimental verification of the tunable characteristics of a ferrite composite right/left handed coupled line coupler. The coupler is designed using two coupled CRLH-CRLH transmission lines. The coupler is designed to demonstrate equal through and backward coupling. The novel coupler has been designed and realized in coplanar waveguide configuration on a ferrite substrate. The tunable characteristics are achieved by changing the applied DC magnetic bias to the ferrite substrate. The measurement results reveal that the coupler's fractional bandwidth can be tuned from 29% to 69% by varying the applied DC magnetic bias from 1000 Oe to 1750 Oe. Within the tunable bandwidth, the maximum backward coupling is −5 dB. The coupler has high forward coupling isolation, close to −30 dB at its centre operating frequency. In addition to its tuning capability, the coupler has the advantages of its compact size; it has the length of 11.5 mm and not-so-tight line separations of 2.5 mm. Furthermore the coupler only requires low DC magnetic bias. [ABSTRACT FROM AUTHOR]

This paper presents analysis and experimental measurements of CPW and microstrip compact monopole antennas loaded with resonator circuits inspired from simplified half-mode composite right / left-handed unit cell. The antennas were designed to have a typical omnidirectional radiation pattern. The CPW fed dual-band antenna resonates at 2.4 and 5.8 GHz, respectively. The antenna size is 20 × 30 mm2 and the radiator patch is only 25% at 2.4 GHz and 60% 5.8 GHz in comparison with a conventional patch antenna. The microstrip triple-band antenna covers the frequency bands from 2 to 2.4 GHz, 5.4 to 6 GHz and 6.8 to 8 GHz. The antenna size is 28 × 25 mm2 which is less than 25% at lower frequency band compared to the size of the conventional patch antenna. Detailed theoretical and full-wave analysis is presented and experimental results demonstrate a good agreement between the measured and the simulated. The suggested antennas can be employed for compact size and multi-band functionalities in wireless applications. The loading technique can be adapted for more frequency bands. [ABSTRACT FROM AUTHOR]

A heterogeneous network (HetNet), combining different technologies, is considered a promising solution adopted by several upcoming generations of mobile networks to keep up with the rapid development of mobile users' requirements while improving network performance. In this scenario, a vertical handover (VHO) algorithm is responsible for ensuring the continuity of the ongoing user connection while moving within the coverage of the HetNet. Although various VHO algorithms were proposed, achieving efficient performance from both network and user perspectives remains challenging. This paper proposes an adaptive optimized vertical handover algorithm based on a multi-attribute decision-making (MADM) algorithm integrated with particle swarm optimization and gravitational search algorithm (PSOGSA) as a framework to implement the handover process. The algorithm includes three main ideas. Firstly, a network selection framework is proposed considering the most important criteria, including signal strength and other networks' attributes, along with users' characteristics regarding their mobility and service preferences. Secondly, two new parameters are introduced as control handover parameters named load factor (LF) and score priority (SP) to reduce unnecessary handovers and the overall HetNet power consumption while achieving balanced load distribution. Lastly, the desired aims are formulated as an objective function, then the PSOGSA algorithm is used to reach the optimal values of both LF and SP, which will be considered when executing the handover algorithm. The presented algorithm is simulated in a heterogeneous wireless network where the fifth-generation (5G) wireless technology coexists with other radio access networks to improve the evaluation field of the proposed algorithm. Also, the proposed algorithm's performance is evaluated in the case of using various MADM algorithms. The simulation results show that the proposed adaptive optimized approach attains efficient performance by decreasing unnecessary handovers by more than 40% and achieving much better load distribution by around 20% to 40%, outperforming traditional handover approaches. [ABSTRACT FROM AUTHOR]

An electrically small antenna ensures easy integration with devices without compromising the form factor. The performance in terms of bandwidth, gain and so on for these antennas is extremely critical and is governed by fundamental limitations in size, i.e. Chu's limit. This study initially presents an analysis of these limits and corresponding performance parameters. Next, a compact dual-band antenna has been designed using an electric field driven LC (ELC) resonator and a coplanar ground plane which operates at GSM 1800 and Wi-MAX. This proposed antenna has a compact size of 0.31λ0 × 0.08λ0 × 0.01λ0 in the first band which is resonant at 1.89 GHz. Finally, a conducting layer is placed below the ELC resonator and both are connected through a via. This provides stronger capacitive coupling between the radiator and the feeding arm and thus, results in miniaturisation of 76.9% in the area. The new antenna is electrically small and covers various cellular bands such as GSM 900, Bluetooth, Wi-Fi and Wi-MAX. Prototypes of both designs have been fabricated and experimentally tested in order to validate the simulation results. [ABSTRACT FROM AUTHOR]

This study introduces a compact asymmetric coplanar strip (ACS)-fed composite right--left-handed (CRLH) multipleinput--multiple-output (MIMO) antenna for multiband operation. The ACS fed MIMO antenna is composed of two elements; each is operating at 5, 5.8 and 6.3 GHz; for different wireless applications. The overall MIMO antenna size is compact (46 x 26 mm²). A unit cell of the CRLH connected to 50 Ω ACS fed is considered the main block of the antenna. The edge-to-edge separation between antenna elements equals 0.4λ0 at 5 GHz. The insertion loss, correlation coefficient, diversity gain and channel capacity are used to evaluate the performance of the ACS-fed MIMO antenna. The isolation higher than 25 dB and envelope correlation lower than 0.05 have been achieved without using any extra decoupling structures. The experimental results are reasonably well agreed with simulated ones. [ABSTRACT FROM AUTHOR]

In this paper, the time domain analysis of an Ultra Wide Band antenna flexible circular monopole antenna is presented. The antenna is fabricated on liquid crystalline polymer flexible substrate with a compact geometry that makes it suitable for wearable applications under different bending conditions. The antenna is fed by coplanar waveguide transmission line and has a compact total size of 40 × 22 mm 2 . Moreover, the antenna has good radiation efficiency (97%) over the bandwidth. The presented antenna has a good performance over the operating spectrum for straight and bending configurations. The design principals along with simulation and experimental results are presented in this contribution. [ABSTRACT FROM AUTHOR]

This paper discusses the properties of hybrid terminated metamaterial CRLH resonant antennas. The antenna proves that the hybrid termination can increase the electrical length of based antennas and hence it can increase the number of possible frequency bands at compact size. This is emphasized through developing a dual band hybrid termination CRLH cell antenna resonating at 2.4 GHz and 5.2 GHz. The antenna design and performance is compared to open/short circuit termination CRLH resonant antennas. All the discussed antennas in this paper have same compact size (21 × 31 mm2). An experimental measurements are carried out for the hybrid terminated CRLH resonant antenna as further validation. The proposed antenna can find possible applications in WiFi/WiMAX services. [ABSTRACT FROM AUTHOR]

In this paper, two different triple band dipole antennas loaded by new modified composite right left handed cell are presented. The modified cell can introduce large electrical length in small size. Thus, the two antennas are designed with smaller operating frequency or reduced physical length compared to a single frequency reference dipole. The designed antennas can serve different wireless services for GPS (1.27 GHz and 1.55 GHz), UMTS (1.85 GHz), and WiFi (2.4 GHz) in triple band functionalities. The lower operating frequency antenna size is (70 × 70 mm 2 ) whereas the reduced physical length antenna size is (60 × 70 mm 2 ). At mid band frequencies the reduced frequency antenna length is (0.29 λ 0 , 0.37 λ 0 , and 0.52 λ 0 ), whereas that of the reduced physical length is (0.28 λ 0 , 0.41 λ 0 , and 0.56 λ 0 ), at triple band mid frequency, respectively. Compared to a typical dipole antenna, the designed loaded dipoles can achieve a length reduction that can reach up to 50%. Moreover, the antenna has good gain at the triple bands (−1.2 dB, 1.9 dB and 3.5 dB for reduced operating frequency antenna and −3.1 dB, 1.2 dB and 3.4 dB for the reduced length antenna. The two antennas have good radiation efficiency that can reach up to 84% on a low cost antenna substrate. The mathematical analysis, full wave simulation and experimental measurements of the reported antennas are introduced. [ABSTRACT FROM AUTHOR]

This article presents a new small size dual band metamaterial antenna. The antenna is realized using a single cell of a suggested modified version of composite right left handed transmission line terminated by a hybrid capacitive loading with short circuit termination. The hybrid termination leads to decrease the size of the antenna whereas the modified composite right left handed cell configuration leads to introduce dual band antenna functionality at 2.5 and 2.92 GHz. The antenna size is only 31 × 26 mm2. Compared to, single band, non-selective, conventional patch antenna, the size of the proposed antenna is only 9 and 11.5% at the two former frequencies, respectively. Despite the small size, the antenna gain is more than 3.5 dBi at the two operating frequencies. Moreover, the antenna has a high roll off beyond the operating frequency band which leads to high selective characteristics. The antenna can suppress 100% of the nearby signal power beyond its bands by 300 MHz at lower band and 200 MHz at upper band. The antenna design is discussed; the full wave simulation and experimental measurements are introduced for validating the results. [ABSTRACT FROM AUTHOR]

ABSTRACT A compact size and high selective bandpass filter is presented in this paper. The filter is designed to serve at 3.5 GHz with two transmission zeros at 3.35 GHz and 3.85 GHz. The filter is designed as two gap capacitor coupled to two coupled composite right-left handed transmission lines. The coupled lines were designed to demonstrate a zeroth order phase at 3.5 GHz. Also, the transmission zeros were achieved as a consequence of the electrical/magnetic couplings between the two coupled transmission lines. The employed cell, filter design equations are emphasized. The filter S-parameters were extracted based on the circuit model, full wave simulation, and experimental measurements. A good agreement between modeled, simulated, and measured results is achieved. The measured center frequency of the bandpass filter is 3.55 GHz and 100 MHz bandwidth which is suitable for WiMAX applications. Also, the filter has low measured insertion loss which does not exceed 1 dB within passband. Finally, the filter has advantages of compactness (size is 20 × 18 mm2) which is only 50% compared to conventional non-selective one-stage coupled line filter. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:1248-1251, 2017 [ABSTRACT FROM AUTHOR]

ABSTRACT This study presents the design of an electrically small metamaterial antenna with dual-band characteristics for WLAN and WiMAX applications with coplanar ground. The proposed antenna consists of stepped-impedance closed ring resonator (SICRR) and a small rectangular patch which is designed by etching a split ring resonator (SRR) from a rectangular patch which is turn fed through main feed. Such metamaterial composite exhibits dual-band behavior with first band operating at 2.45 GHz with an impedance bandwidth (| S11| < −10 dB) of 8.16% while second band is resonant at 3.37 GHz having an impedance bandwidth of 23.74% respectively. The proposed antenna is designed specifically to operate at WLAN (2.5 GHz) and WiMAX (3.5 GHz) and shows compact nature with a radiating element size of 0.16λo × 0.097λo × 0.013λo. Equivalent circuit of proposed antenna has also been modeled which is in good agreement with the antenna behavior. The proposed structure shows end fire radiation pattern in H-plane and omni-directional radiation pattern in E-plane at all operating frequencies with low cross polarization levels. The prototype has been fabricated and experimentally tested to validate the simulation results which are in good agreement with the measured results. The antenna is suitable for use in Bluetooth, WLAN and WiMAX. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:573-578, 2017 [ABSTRACT FROM AUTHOR]

In this paper, we introduce a compact dual-band two-element array antenna in a substrate integrated waveguide (SIW) configuration for C-band applications. A new geometry based on an asymmetric composite right–left-handed transmission line cells was suggested for the single antenna element. The proposed geometry has the advantage of having arbitrary dual-frequency design. The array elements are fed with a wideband SIW impedance transformer. The results indicate that the proposed antenna element size is only 15 × 12.8 mm2, which approximately represents up to 70% size reduction at similar frequencies. The radiation properties of the array antenna have broadside radiation pattern at the two bands. The detailed analytical design explanation, full wave simulations, and experimental measurements are introduced. [ABSTRACT FROM AUTHOR]

This study presents a hybrid electromagnetic isolation mechanism in a transceiver array antenna operating at 5.8 GHz. Maximum isolation between transmitting and receiving array antennas, at a very close spacing (3 mm = 0.0580), and minimum mutual coupling between each array elements is achieved without antenna radiation pattern degradation. The achieved separation is equivalent to 44% size reduction compared with conventional half wavelength spacing criterion. Each of the transmitting and receiving array antennas is a four-element linear microstrip patch array antenna. The employed hybrid isolation technique is composed of defected ground structure, to minimise coupling between array elements, and uniplanar electromagnetic bandgap, to minimise the coupling between the transmitting and receiving antennas. The resulting transceiver array antenna system fulfils -35 dB mutual coupling between array elements, and 60 dB isolation between opponent transmitting and receiving array antennas. The proposed design procedures are discussed and analysed using electromagnetic full wave simulations. Results were verified through experimental measurements for reflection coefficient, mutual coupling and radiation characteristics in which a good agreement with simulated results is granted. [ABSTRACT FROM AUTHOR]

ABSTRACT This article presents a new compact asymmetric coplanar strip -fed UWB MIMO antenna. The UWB MIMO antenna consists of two identical elements which have quarter elliptical ring radiating element with asymmetric coplanar strip-fed. By designing the antenna using asymmetric coplanar strip-fed, the antenna size can be reduced (its size is only 6 × 2.6 cm2). The distance between the two antenna elements equals 0.37 λ0-The single antenna element is operated at frequencies from 3.1 GHz to 10.6 GHz with reflection coefficient lower than −10 dB. In addition, the designed antenna elements have less than 15 dB coupling isolation between the two input ports. The diversity performance between two antenna elements such as envelope correlation coefficient and diversity gain are investigated and they are within their allowed limits. This analysis confirms that the designed antenna is suitable for portable UWB MIMO applications. The proposed antenna is designed; simulated and measured. There is a good agreement between the simulated and measured results. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:31-36, 2017 [ABSTRACT FROM AUTHOR]

A design of CRLH MIMO metamaterial with reversal CRLH configuration antenna is presented. The two antenna elements are designed to operate at 5.8 GHz for wireless applications. The two antenna elements are designed using reversed one left handed unit cell for high mutual coupling isolation in close separation. The two elements of MIMO antenna are put together with very small separation between them where the distance between the edges of two antenna elements is only 0.034 λ 0 . The MIMO antenna has compact size (its size is only 2.93 × 2.6 cm 2 ). The designed antenna elements have better than 35 dB coupling isolation between the two inputs without using extra structures. The performance of MIMO antennas is evaluated by studying the correlation coefficient, diversity gain and total active reflection coefficient. A good agreement is achieved between simulation and measured results. [ABSTRACT FROM AUTHOR]

This paper discusses a study made for good asymmetric three-stage electromagnetic coilgun launching medium-weight projectile. Different lengths, number of turns, and switching times are chosen for each individual coil to get better results. Two detailed investigated models have been presented, including the effect of the switching time. Medium-caliber projectile of \text weight = 0.5 kg is employed in this paper. The results confirm that the second model asymmetric coilgun has 16.96% higher output speed, 63.92% lower length, and 57.5% lower launching time than the first model asymmetric coilgun. The obtained results have been recorded using the transient time electromagnetic simulations. [ABSTRACT FROM PUBLISHER]

The theoretical study and experimental results of a compact tunable left-handed (LH) zeroth order metamaterial ferrite resonator is presented. The resonator has been designed and realised using a LH coplanar waveguide transmission line on a ferrite substrate. The theoretical analysis of the operation principles of the resonator has been provided. The detailed measurement setup and experimental results are discussed. The resonator is only 0.19 λg (65% reduced in size comparing with conventional one) at 4 GHz. The resonator has fractional bandwidth of 0.1% and average insertion loss, approximately 4.5 dB. Moreover, the zeroth order metamaterial ferrite resonator has tuning capability and requires lower DC magnetic bias. [ABSTRACT FROM AUTHOR]

This study presents the design of switching techniques for dual-notched ultra-wideband antenna. The dual bandnotched frequencies are achieved by using switched defected microstrip structure band stop filter inserted in the microstrip feed line and a switched meandered slot etched in the radiation patch. The switching reconfiguration is accomplished by combining the two ideal switches to introduce a notch filter response to prevent the interference to the primary users operating in the middle and upper WiMAX wireless local area network bands. The proposed structure has four modes by controlling the two switches on and off. The proposed antenna has good matched impedance from 2.5 to 12 GHz with two notched bands from 3.3 to 3.8 GHz (middle WiMAX applications) and from 5.1 to 5.9 GHz (upper WiMAX applications). The antenna is fabricated and tested. Good agreement is achieved between the simulated and measured results. [ABSTRACT FROM AUTHOR]

In this study, the authors present a novel compact non-reciprocal ferrite forward composite right-/left-handed (CRLH) coupled-line coupler (CLC). The proposed forward coupler is realised in coplanar waveguide configuration using series air gap capacitors and shunt planar segment inductors. A theoretical coupled mode analysis of a general non-ferrite CRLH forward CLC has been proposed. The mode analysis is then extended to ferrite CRLH forward CLC. The ferrite coupler's performance has been further analysed numerically and verified experimentally. Both numerical and experimental results have shown that the coupler demonstrates non-reciprocal operation for both forward coupling and through propagations. The coupler can achieve ~10 dB forward coupling and through levels with nonreciprocity isolation up to 30 dB. Moreover, the coupler has high backward coupling isolation better than 20 dB and very compact size with coupling length = 0.08 λ0 or (0.2 λg) at 8 GHz which is significantly smaller compared with any forward coupler reported to date in the similar operating frequency bands. Although, a conventional ferrite forward CLC can be non-reciprocal, it has long length, resulting in very high losses. This is not the case for the proposed CRLH coupler. Hence, the novelty and advantage of the coupler are its combined properties in compactness and nonreciprocity. Furthermore, the coupler requires very low external DC magnetic bias because of its much lower demagnetisation compared with the microstrip configuration. [ABSTRACT FROM AUTHOR]

Introduced in this letter is a thin, flexible, compact, and fully fabric I‐shaped quarter‐wavelength antenna, where a 3 × 3 array reflector, is in the antenna rear end. In free space, the I‐shaped antenna radiates at 2.45 GHz of the Industrial, Scientific, and Medical band with simulated realized gain of 1.65 dB and 90% worth of simulated radiation efficiency. The array reflector is utilized to diminish the specific absorption rate (SAR) in human evaluation scenarios. At the operating frequency, in free space, the antenna realized gain is improved by 75% after incorporating the artificial magnetic conductor (AMC) array. Moreover, over 1 g of tissue, a SAR reduction of 99.5% is attained at 2.45 GHz. Simulation and measured S11 and radiation pattern comparisons are highlighted in this letter. Based on the accomplished outcomes, the integrated antenna, comprised of the fully fabric I‐shaped quarter‐wavelength antenna and the AMC array, might be considered for wearable applications. [ABSTRACT FROM AUTHOR]

In this paper, a submillimetric/THz metasurface polarization/oblique independent absorber is designed and characterized. The absorber is designed using a periodic arrangement of a modified split ring resonator unit cell. The symmetric absorber is insensitive to the variation of incident angles and polarization angles. The results confirm that perfect absorption is achieved (close to 100%) for either TM or TE polarization at 300 GHz. Moreover, the absorber is efficient for normal and oblique incident angle (above 90% for 45° angle of incidence). In all the presented cases, the full width half maximum bandwidth is 20 GHz. The absorber unit cell size is only 0.0052 λ0 × 0.0052 λ0 and it has a low-profile thickness = 0.0002 λ0, at the operating frequency. Also, an absorber-based biosensor is presented. The sensing has proved the coating analyte thickness can be detected by shifting the absorption frequency. The maximum sensitivity is 24.9% RIU−1 with a low-profile maximum of 50 µm thickness. Analytical formulas for the frequency shift have been extracted. The presented results are discussed based on 3D full-wave EM simulations. [ABSTRACT FROM AUTHOR]

This paper presents an ultra compact dual-band coplanar waveguide metamaterial filter based on generalized metamaterial transmission line. The detailed theoretical design steps of the filter are explained. The dual-band filter design performance has been validated using equivalent circuit modeling, electromagnetic full wave simulations, and practical measurement. The results illustrate the filter has dual passbands centered at 0.82 and 1.48 GHz with approximately 1 dB insertion loss and minimum 12 dB return loss. Good agreements between the circuit modeling, electromagnetic full wave simulations, and practical measurements are achieved. Moreover, the filter size is only (18 × 28 mm2) which is only less than (0.2λg × 0.31λg) at the center frequency of the first passband and (0.36λg × 0.56λg) at the center frequency of the second passband. [ABSTRACT FROM PUBLISHER]

This study presents, for the first time, a novel π - T generalised negative refractive index (NRI) transmission line (TL) configuration. It is innovated for increasing the possible passbands in designing microwave components. It is proved that the proposed transmission line can introduce up to seven passbands for completely unbalanced transmission line condition. The detailed mathematical analysis of that configuration based on the periodic network analysis and equivalent circuit model is introduced. As an application for the novel π - T generalised NRI TL configuration, a new compact triple band coplanar waveguide (CPW) metamaterial filter is introduced. The proposed triple bands CPW filter design steps are introduced and its performance is validated using equivalent circuit model simulation, electromagnetic full wave simulation and experimental measurements. Good agreements between the circuit modelling, electromagnetic full wave simulation and practical measurement results are achieved. All the results confirm that the proposed filter has triple passbands from 900 to 960 MHz, 1.4 to 1.48 GHz and 2.4 to 2.45 GHz. Moreover the filter size is compact whose length is only 12.1% λg at first passbands, 18.2 λg% at second passbands and 31.7 λg% at third passbands. [ABSTRACT FROM AUTHOR]

In this paper, a wideband high-power ridge gap waveguide (RGW) T junction power divider within the frequency band from 10 to 13.5 GHz is introduced. In this configuration, the air has the ridge gap to have maximum power handling capability. An excitation transition, from coaxial cable to the ridge gap waveguide, is introduced. The ridge gap waveguide power divider was fabricated using aluminum sheets to gain the advantage of low cost. The power divider has a wider bandwidth (30%) than the recent most successful RGW power divider along with the high handling power capability (more than 20 K Watts). The power divider design was validated using circuit and 3D full wave electromagnetic simulations and confirmed using experimental measurements with all agreements between results. It has been proved that the power divider attenuation has good matching (15 dB return loss) and equal 3 dB power division with less than 0.05 dB insertion loss. The power divider can be used as a feeder for many high-power application components. [ABSTRACT FROM AUTHOR]

In this paper, a validation study for the metamaterial accurate modelling using the electromagnetic numerical transmission line matrix (TLM) computation method is presented. In our work, the three-dimensional symmetrical condensed node (SCN) TLM algorithm has been modified to fully simulate non-linear and dispersive metamaterial structures. The modification code principles have been explained theoretically. The propagation computation using our modifying TLM code has been tested for a metamaterial ground slab loaded by split ring resonator structure. The tested structure acts as a metamaterial radar absorber. Moreover, experimental measurements were carried out and compared to the computed ones. The results confirmed the good agreement between measured and TLM computed results. Furthermore, the propagation computation was confirmed by measuring the backscattering for different incident angles which demonstrate very good agreement for our modified TLM code. The measurement results confirm the versatility and power of the modified SCN TLM algorithm to handle metamaterial structures. [ABSTRACT FROM AUTHOR]

In this paper, a novel compact and tunable impedance transmission line transformer is presented for the first time. The transformer is designed using a left handed coplanar waveguide transmission line on a ferrite substrate. Based on the dispersive properties of the ferrite medium, the theoretical study of the transformer has been carried out using its equivalent circuit analysis and the composite right / left handed transmission line theory. The theoretical study was verified through full wave electromagnetic numerical simulations. The results show that the transformer matches a 25 Ω load to a 50 Ω line with tunability from 2.55 GHz to 3.2 GHz. The return loss at center frequency is better than 20 dB with insertion loss better than -1 dB. The transformer has a very compact size with dimensions of 4.25 × 21 mm, showing approximately 64% reduction in size in comparison with a conventional right-handed transformer within the same operating frequency band. Moreover, the proposed coplanar waveguide transformer configuration has smaller demagnetization factor and hence it requires smaller DC magnetic bias values compared to microstrip configuration. [ABSTRACT FROM AUTHOR]

A novel coplanar waveguide ferrite-coupled line (CPW FCL) is presented and numerically verified for the first time. The proposed CPW FCL exhibits a low insertion loss for both even and odd mode excitations, equal power division for single power excitation with both isolation, and return loss better than 10 dB over the whole operating bandwidth, and 20 dB in the best cases. The coupler has a much wider operation bandwidth compared to any other configurations reported to date. In addition, the .CPW FCL demonstrates better phase flatness within the operating bandwidth compared to microstrip FCL. [ABSTRACT FROM AUTHOR]

This paper presents, for the first time, a tunable left handed coplanar waveguide zeroth-order resonator on a ferrite substrate. Analysis and design procedures of the proposed resonator are introduced. The proposed resonator is designed to be tuned over the frequency band from 3 to 4.85 GHz with lower than 3-dB insertion loss and better than 10-dB return loss. The dimensions of the proposed resonator are 8.3 x 20 mm. The advantages of the proposed resonator are its tuning capability in addition to its compact size. [ABSTRACT FROM AUTHOR]

A novel ferrite nonreciprocal left-handed (LH) transmission line is presented. The proposed structure is composed of a coplanar waveguide over a ferrite substrate, horizontally magnetized and periodically loaded with only shunt inductors. The line has a nonreciprocal LH propagation with transmission level better than -5 dB with isolation level up to 20 dB over a moderate bandwidth. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2810–2814, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22848 [ABSTRACT FROM AUTHOR]

A polarization independent conformal wideband metamaterial absorber has been proposed in this study. The proposed absorber unit cell consists of a circle and a slotted sector, loaded with four lumped resistors between them to improve the absorption bandwidth. Measured and simulated results exhibit more than 90% absorption in the frequency band from 3.90 GHz to 10.5 GHz under the normal incidence angle, and the fractional bandwidth is 91.6%. The proposed absorber is polarization independent due to the symmetrical nature. The absorber unit cell is compact in configuration with a unit cell size of 0.16 λo × 0.16 λo, where λo is the wavelength at 3.9 GHz and the substrate thickness is 0.098 λo. Once the proposed absorber is wrapped on the cylindrical surface, it shows good absorptivity in the absorption frequency band. The effects of many designed parameters have been studied to understand the performance of the wideband absorber. To recognize the absorption phenomenon of the absorber, normalized impedance, electric field distribution, and surface current density have been demonstrated. Finally, the proposed conformal absorber fabricated and measured the absorption for flat and curved surfaces, which exhibits good agreement between the simulated and the experimental results. [ABSTRACT FROM AUTHOR]

This paper introduces a novel design of compact tunable monopole antenna array, employing composite right/left handed (CRLH) feeding network. The feeding network configuration is coplanar waveguide (CPW). A graphene sheet is placed beneath the CRLH cell to achieve the tunability behavior in the antenna design. The antenna array configuration achieves the tunability function with an accepted gain. The surface conductivity of the graphene sheet is tuned by changing the applied DC bias voltage. The DC voltage changes the chemical potential of the graphene sheet. The antenna array is tuned from 2.5–2.46, 2.43, and 2.42 GHz when the chemical potential of graphene is changed from 0.0, 0.15, and 0.2 eV, respectively. The array antenna has a reasonable gain of 5.34 dB without placing the graphene sheet. By placing the graphene and changing the chemical potential, the array gain values become 4.42, 3.82, and 3.74 dB at the specified chemical potential. The radiation properties of the array are studied at the desired resonant frequency. The proposed design can be fabricated by using the transparent transfer process. All the presented designs are verified using the electromagnetic solver CST Studio. [ABSTRACT FROM AUTHOR]

This article introduces a new design and analysis of a compact reconfigurable bandpass/lowpass filter based on compact negative refractive index metamaterial transmission line. The filter equivalent circuit has been designed as a cascade of three cells of bisected‐Π/Π configuration. The reconfigurable function was achieved using inserted switches in ON and OFF modes within the cells. The filter works as bandpass when all switches are in ON condition and for lowpass switch‐1 is in OFF and switch‐2 in ON condition. The low pass filter has 3‐dB cutoff frequency of 3.25 GHz with a selectivity of 170 dB/GHz. The bandpass filter is cantered at 3.65 GHz and has a well‐matched pass band with insertion loss of 0.2 dB and wide stop band with two transmission zeros (TZs). The frequency positions of TZs are independently varying with series and shunt loading elements. The filter performance has been validated through circuit model, electromagnetic simulation, and experimental measurements. The electrical size of bandpass filter excluding feed line is 0.22 λg × 0.20 λg (12 × 11 mm2) at center frequency of 3.65 GHz and for lowpass filter is 0.19 λg × 0.18 λg at cutoff frequency of 3.25 GHz. The filter can be applied in suitable for different wireless applications. [ABSTRACT FROM AUTHOR]

The objective of our study was to assess the efficacy and safety of dexmedetomidine given in a small dose for a 1-h infusion as an adjuvant to local analgesia in ophthalmic operations. The study was double-blind prospective, randomized, and placebo controlled. We studied the effects of a small dose of dexmedetomidine (0.5 µ·kg−1·h−1 for 10 min followed by 0.2 µ·kg−1·h−1 for 50 min. Patients were divided randomly into two groups with 20 patients in each: group A was the study group and group B was the placebo group. Heart rate, systolic blood pressure, and diastolic blood pressure were significantly lower in the dexmedetomidine group than the placebo group. Bispectral index values were significantly lower in the dexmedetomidine group than the placebo group. Also, intraocular pressure significantly decreased in the dexmedetomidine group compared to the placebo group. The study revealed that dexmedetomidine in the studied dose has a sedative effect, provides safe control of heart rate and blood pressure, and also decreases intraocular pressure during ophthalmic surgery under local anesthesia. [ABSTRACT FROM AUTHOR]

Fifth‐generation millimeter‐wave devices with multiple antennas require minimal mutual interference for better overall performance. This article presents a simple but novel technique to improve the isolation between closely packed slot antenna arrays. A printed ridge gap waveguide (PRGW) structure is used to realize a low loss millimeter‐wave array's feeding mechanism. By optimally introducing a defective upper plate within the PRGW structure, the measured port isolation of the antenna elements is improved by 17 dB at 61.3 GHz. The antenna array is impedance matched to the feeding PRGW structure over a wide frequency range of 54–67 GHz. Moreover, the radiation patterns are consistent showing broadside radiation before and after introducing the defect in the PRGW structure. The fabricated prototype of the PRGW fed slot antenna array validated the predicted isolation and return‐loss bandwidths of the proposed radiating system. [ABSTRACT FROM AUTHOR]