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This paper presents a novel microwave sensor using optical activation for measuring in real-time the water contamination in crude oil or its derivatives. The sensor is constructed from an end-coupled microstrip resonator that is interconnected to two pairs of identical fractal structures based on Moore curves. Electromagnetic (EM) interaction between the fractal curves is mitigated using a T-shaped microstrip-stub to enhance the performance of the sensor. The gap in one pair of fractal curves is loaded with light dependent resistors (LDR) and the other pair with microwave chip capacitors. The chip capacitors were used to increase the EM coupling between the fractal gaps to realize a high Q-factor resonator that determines the sensitivity of the sensor. Empirical results presented here show that the insertion-loss of the sensor is affected by the change in LDR impedance when illuminated by light. This property is used to determine the amount of water contaminated oil. The sensitivity of the sensor was optimized using commercial 3D EM solver. The measurements were made by placing a 30 mm diameter petri dish holding the sample on top of the sensor. The petri dish was filled up to a height of 10 mm with the sample of water contaminated crude oil, and the measurements were done in the range between 0.76 GHz to 1.2 GHz. The Q-factor of the oil sample with no water contamination was 70 and the Q-factor declined to 20 for 100% contamination. The error in the measurements was less than 0.024%. The sensor has dimensions of 0.1270×0.1270×0.0040 and represents a new modality. Compared to existing techniques, the proposed sensor is simple to use, readily portable and is more sensitive.

This paper presents an enhancement in radio frequency (RF) harvesting for conventional patch antenna using a metasurface layer (MSL). The key point behind such enhancement is inspired by Friis’ equation which states; increasing the antenna gain leads to an increase in the received power. To achieve this goal, a MSL consists of 5×5-unit cells of a modified Jerusalem cross are proposed. The proposed MSL provides gain enhancement of about 10 dBi while the gain of the patch antenna is about 1 dBi. The proposed MSL is fabricated, compacted to the antenna and experimentally characterized. The empirical results indict an excellent agreement with the numerical results in terms of |S11| and radiation patterns. In addition, a set of RF harvesting measurements are made for patch antenna with and without the MSL. The comparison between measurements shows a significant enhancement in the output voltage when the MSL is involved.

The permittivity of a material is an important parameter to characterize the degree of polarization of a material and identify components and impurities. This paper presents a non-invasive measurement technique to characterize materials in terms of their permittivity based on a modified metamaterial unit-cell sensor. The sensor consists of a complementary split-ring resonator (C-SRR), but its fringe electric field is contained with a conductive shield to intensify the normal component of the electric field. It is shown that by tightly electromagnetically coupling opposite sides of the unit-cell sensor to the input/output microstrip feedlines, two distinct resonant modes are excited. Perturbation of the fundamental mode is exploited here for determining the permittivity of materials. The sensitivity of the modified metamaterial unit-cell sensor is enhanced four-fold by using it to construct a tri-composite split-ring resonator (TC-SRR). The measured results confirm that the proposed technique provides an accurate and inexpensive solution to determine the permittivity of materials.

This paper presents a novel metasurface antenna whose radiation characteristics can be remotely controlled by optical means using PIN photodiodes. The proposed reconfigurable antenna is implemented using a single radiating element to minimize the size and complexity. The antenna is shown to exhibit a large impedance bandwidth and is capable of radiating energy in a specified direction. The proposed antenna consists of a standard rectangular patch on which is embedded an H-tree shaped fractal slot of order 3. The fractal slot is used to effectively reduce the physical size of the patch by 75 % and to enhance its impedance bandwidth. A metasurface layer is strategically placed above the patch radiator with a narrow air gap between the two. The metasurface layer is a lattice pattern of square framed rhombus ring shaped unit-cells that are interconnected by PIN photodiodes. The metasurface layer essentially acts like a superstrate when exposed to RF/microwave radiation. Placed below the patch antenna is a conductive layer that acts like a reflector to enhance the front-toback ratio by blocking radiation from the backside of the patch radiator. The patch’s main beam can be precisely controlled by photonically illuminating the metasurface layer. The antenna’s performance was modelled and analyzed with a commercial 3D electromagnetic solver. The antenna was fabricated on a standard dielectric substrate FR4 and has dimensions of 0.778λo × 0.778λo × 0.25λo mm3 , where λo is the wavelength of free space centered at 1.35 GHz. Measured results confirm the antenna’s performance. The antenna exhibits a wide fractional band of 55.5 % from 0.978 to 1.73 GHz for reflection-coefficient (S11) better than − 10 dB. It has a maximum gain of 9 dBi at 1.35 GHz with a maximum front-to-back ratio (F/B) of 21 dBi. The main beam can be steered in the elevation plane from − 24◦ to +24◦. The advantage of the proposed antenna is it does not require any mechanical movements or complicated electronic systems. Dr. Mohammad Alibakhshikenari acknowledges support from the CONEX-Plus programme funded by Universidad Carlos III de Madrid and the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 801538. The authors also sincerely appreciate funding from Researchers Supporting Project number (RSP2023R58), King Saud University, Riyadh, Saudi Arabia. Additionally, this work was supported by Ministerio de Ciencia, Innovación y Universidades, Gobierno de España (Agencia Estatal de Investigación, Fondo Europeo de Desarrollo Regional -FEDER-, European Union) under the research grant PID2021-127409OB-C31 CONDOR. Besides above, the Article Processing Charge (APC) was afforded by Universidad Carlos III de Madrid (Read & Publish Agreement CRUE-CSIC 2023).

This paper presents a microwave sensor design for moisture detection contents in petroleum productions based on metamaterials. The proposed sensor occupies a compacted size of 40×40×1.6 mm3 by using low-cost FR4 substrate. The proposed sensor consists of a transmission line and two split-ring resonators (SRRs) mounted on two sides. The transmission line is coupled to the outer ring of the SRRs to provide two resonant frequencies at 1.03 GHz and 3.04 GHz. It is observed that most of the electric fields fringing is come out of the air gap on the SRRs. Two pans are mounted on the sensor to contain the sample under test (SUT). The simulation studies are carried out by using the Computer Simulation Technology (CST) Microwave studio. After introducing the pans, frequency shifts, △f1=150 MHz and △f2=424 MHz, are detected in the resonant frequency which is associated with the perturbation phenomenon when the water concentration is varied from 0% to 100%. The proposed sensor exhibits a reliable detection percentage of various different amounts of the moisture content in crude oil introductions. Generally, a good detection methodology is discovered by applying the proposed sensor for detecting the crude oil quality productions.

This paper presents a compact, tri-bands, rectangular patch antenna based on H-Tree fractal slots structure for modern wireless communication systems has been introduced. The antenna structure consists of a 70.70×56mm2 rectangular patch printed on 173×173×1.6mm3 FR4 substrate. H-Tree slots fractal geometry with the defective ground plane on the other side to enhance gain and bandwidth. The suggested antenna is fed by a 50 Ω microstrip line. The antenna shows three resonance frequencies: 0.784, 1.158, and 1.772 GHz. The suggested antenna offers a total size reduction of about 75 %. The designed antenna possesses fractional bandwidths of 3.976 %, 7 %, and 2.7866 % for the first, second, and third resonances, respectively. Finally, the proposed antenna is a candidate for Global System for Mobile communications (GSM).

In this study, an investigation is conducted to realise the possibility of organic materials use in radio frequency (RF) electronics for RF-energy harvesting. Iraqi palm tree remnants mixed with nickel oxide nanoparticles hosted in polyethylene, INP substrates, is proposed for this study. Moreover, a metamaterial (MTM) antenna is printed on the created INP substrate of 0.8 mm thickness using silver nanoparticles conductive ink. The fabricated antenna performances are instigated numerically than validated experimentally in terms of S 11 spectra and radiation patterns. It is found that the proposed antenna shows an ultra-wide band matching bandwidth to cover the frequencies from 2.4 to 10 GHz with bore-sight gain variation from 2.2 to 3.43 dBi at maximum. The antenna size is compacted to a 32 mm × 24 mm using a fractal-shaped MTM when mounted on the INP substrate with a relative permittivity e r = 3.106-j0.0314 and a relative permeability μ r = 1.548-j0.0907. Finally, the maximum obtained voltage from the proposed antenna is found about 2 V at 2.45 GHz and 2.5 V at 5.8 GHz, where, the corresponding measured equivalent isotropic radiated power is about 2.35 W at 2.45 GHz and 6.12 W at 5.8 GHz.

This paper presents a method to control gain enhancement of a microstrip antenna based on a reconfigurable metasurface layer. The proposed layer is maintained the antenna and consists of $5 \times 5 -$unit cells. The proposed unit cell is designed to has four PIN diodes for structure reconfiguration into states ON and OFF. Therefore, the layer may have many distribution patters of ON-OFF unit cells. Each certain distribution pattern can enhance antenna gain to a certain value. Four patterns of the layer are suggested to enhance the antenna gain of about 1 dBi to 2, 5, 8, and 11 dBi. An equivalent circuit is introduced to describe the performance of the proposed unit cell. Besides, full CST MWS simulations for the system are conducted. To experimentally verify the presented method, a prototype of the system is fabricated and partially tested. The measurements show a good agreement with simulations.

In this paper, a novel structure of a reconfigurable Electromagnetic Band Gap (EBG) layer is presented for direct antenna Amplitude Shift Keying (ASK) digital modulation. Therefore, the modulation process, in this paper, is realized without the need to include conventional parts like filters, mixers or power amplifiers. Beside many advantages, the proposed modulation process offers cost, complexity, and weight reductions to suit many modern applications including 5G systems. The reconfigurable EBG layer has two statuses: ON and OFF. Each status produces a certain level of gain enhancement. Via controlling the reconfigurable EBG statuses, the amplitude of the transmitted wave can be controlled. The results show such a system design can modulate the electromagnetic signals directly by varying the gain from 2 dBi for logic_0 (OFF) to 11 dBi for logic_1 (ON). For this, a mathematical model based on ray tracing analysis is conducted to explain the principle of operation of the proposed EBG layer. The antenna and EBG structures fabrication as a system is realized and tested experimentally. The measurements show good agreements with the proposed mathematical model and CST MWS simulations.

In this paper, a compact configuration of zeroth-order resonator antenna is described. The unit cell zeroth-order resonator properties are introduced by composite right/left-handed transmission line approach is fed by coplanar waveguide. The proposed resonator is analyzed by changing the coupling space and stub length of the unit cell. The size of implemented resonator is (0.185 λ0 × 0.185 λ0 × 0.027 λ0) at the centre frequency. In this work, a zeroth-order resonator antenna design with enhanced bandwidth has been presented, and the size reduction by using the metamaterial inclusion. The proposed zeroth-order resonant antenna (ZORA) achieves a 64% reduction compared to a traditional λ/2 microstrip patch antenna. The bandwidth for the 10 dB return loss is 5.66 GHz (2.76 GHz to 8.42 GHz), the peak value of gain is 0.8 dBi and radiation efficiency of the designed antenna is 87% at 5.5 GHz. The return loss is about -59.48 dB at the center frequency. The competition among the simulated performances and other antennas shows that the proposed resonator achieves wide bandwidth. The performance of zeroth-order resonator antenna is evaluated by full-wave electromagnetic (EM) simulator HFSS11.

In this paper a new approach for first order Chebyshev parallel coupled Bandpass filter resonant at 1 GHz is presented to obtain better results (wideband rejection, high selectivity and low bandpass insertion loss) compared to conventional design. The proposed filter (a tri-formation consisting of CSRR, SRR and stubs of stepped impedance are loaded microstrip resonator) can be configured, by laying split ring resonator (SRR) and complementary split ring resonator (CSRR) with 50 Ω microstrip lines, in addition to effect of loading two stubs of stepped impedance around center of midline microstrip with impedance line 55.36 Ω of parallel coupled. The proposed filter produces high selectivity from passband to stopband transition equals to 307.5 dB/GHz and an excellent wide stopband performance extend from 1.22 GHz to 5 GHz (harmonics repression till for 5 ƒ0); all are bellow -20 dB excepting one transmission zero of -19 dB, that can be eliminate the harmonic superior frequencies without using any external Bandstop filter. Also, enhancement low bandpass insertion loss level, where it reaches 0.25 dB at fundamental centered frequency (ƒ0 = 0.96 GHz) with 21% bandwidth. The proposed filter is designed and simulated with computer aided of Ansoft HFSS software package which ordinarily used in microwave application.

in this paper, a gain enhancement of the UWB Tapered slot Vivaldi antenna (TSVA) for radar imaging application is presented. The proposed antenna has 41×48×1 mm3 dimensions. The proposed antenna operates from 2.7 GHz to more than 12 GHz. The antenna is printed on a 1 mm FR4 dielectric substrate thickness with an exponentially tapered slot shape. The suggested Vivaldi antenna is modified by inserting a polygon form dielectric lens and some periodic unequal lengths director elements consist of three metallic strips on the dielectric lens, which produces an improvement in gain significantly along with center frequency band about 2 dB. The radiation pattern of the proposed antenna has a stable variation with respect to frequency.

In this paper a novel tri band, small size microstrip antenna based on fractal slots geometry for wireless and mobile applications has been introduced. The proposed antenna was created by etching out a rectangular radiating patch with two equal slits, yielding three conductors. This process is repeated again for the created patches. The designed antenna was fed with from 50Ω microstrip fed line. The antenna gives three resonance frequencies, (GSM 0.925 GHz, GSM 1.8 GHz and WLAN 2.4 GHz) and has suitable bandwidth for these applications. The antenna shows high reduction in size about 85% at GSM resonance frequency. The antenna is designed for 3.15×31.75mm FR4 substrate material and simulated using HFSS v.13 EM simulator from Ansoft. The simulation results show that the designed antenna possesses impedance bandwidths 11.2%, 7.75% and 3.3% for the first, second and third resonance respectively.

In this paper, a novel compact, low profile, low cost, microstrip fed line with single and double band-notch characteristics ultra wideband (UWB) patch antenna is presented. The proposed antenna satisfying UWB operation from 3 GHz - 11 GHz with two notches and have maximum gain 4.9 dB. The first band-notch is designed to reduce the electromagnetic interference in WiMAX frequency band (3.8 GHz), while the second band notch of WLAN IEEE 802.1a (5.35 GHz). By inserting seven different size arms of a single parasitic split ring resonator (SPSRR) band notch in the range of 3.3501-4.5857 GHz is obtained. Furthermore, the second band notch around from 5.1 - 5.6 GHz for WLAN is obtained by etching circular complementary split ring resonator (CSRR) near the microstrip feed line. A very high agreement between simulation and experimental results is achieved. The proposed antenna can be considered as a good candidate for UWB communication applications with very low electromagnetic interference.