A comparison of various double loops frequency selective surfaces in terms of angular stability

This paper presents the comparison of Frequency Selective Surfaces (FSS) structure performance based on three different double loops: square, circular and hexagonal structures. The simulation process of the double loops FFS structures are carried out by using the Computer Simulation Technology (CST) Microwave Studio software. The dielectric substrate used in the simulation is the FR-4 lossy substrate

High capacity and miniaturized flexible chipless RFID tag using modified complementary split ring resonator

This paper aims to produce a high data capacity and miniaturized flexible chipless RFID tag based on the frequency signature using the Modified Complementary Split Ring Resonator (MCSRR). The proposed 19 bits chipless RFID tag using the frequency shifting technique consists of five slotted overlaying MCSRR with Different Width (MCSRR with DW) structures and the dimension of 48 mm x 48 mm. The structure is designed by using a flexible (Polyethylene Terephthalate ) PET substrate with permittivity of 0.2. The operating frequency is between 0.9 GHz and 2.7 GHz. The advancement of slotted overlaying MCSRR with DW structures has successfully miniaturized the chipless RFID tag structure to about 107 mm2/ bit, 0.02/2 mid =bit and 0.09 GHz/bit by maximizing the number of resonators in a limited space and minimizing the frequency separation between the resonators. The omnidirectional tag antenna is incorporated with the proposed MCSRR structure using the retransmission measurement method. The log-periodic antenna with a gain of 5-7 dBi is used for this measurement to improve the range distance between tag and reader system. Based on the retransmission measurement involving the antenna tag, the 19 bits chipless RFID tag which consists of five MCSRR with DW structures can be detected with a maximum range distance of 30 cm and a power transmitted level of 30 dBm

Microwave technique for moisture content and pH determination during pre-harvest of mango cv. Chok Anan

The maturity of mango is usually assessed by the determination of its moisture content (m.c.), soluble solid content (SSC) and pH. However, these techniques are either time consuming, tedious or destructive. In this research, we extend the application of the open-ended coaxial probe technique to determine m.c. and pH of Chok Anan mango from its dielectric properties from week 5 to week 17 after anthesis. The effects of frequency and m.c. on the values of the dielectric constant and loss factor were also investigated. The critical frequency separating the different polarizations was found to be inversely proportional to m.c. Also, in this research we proposed a new classification of fruit ripeness related to the number of weeks after anthesis. The actual dielectric properties, m.c., SSC and pH of Chok Anan mango were measured using standard methods. Relationships were established between the dielectric constant, loss factor, critical frequency, pH and m.c. The accuracy for the determination of m.c. and pH using the coaxial probe was within 1.7% and 3.0%, respectively

Subminiature panel (SMA-P) coaxial sensor for the determination of moisture content of mango cv. Chok Anan

The research describes the development of a simple, cheap and efficient open-ended coaxial sensor for the determination of moisture content of Chok Anan mango during fruit ripening from week 5 to week 17. The sensor was a modification of a standard subminiature panel (SMA-P). The finite element method was used to calculate the numerical values of the reflection coefficient. The reflection coefficient of the sensor was measured using a Microwave Network Analyzer in the frequency range from 1 to 4 GHz. The actual moisture content was obtained using standard oven drying method. A calibration equation was obtained to predict moisture content from the measured reflection coefficient at 1 GHz with accuracy within 1.5%. The results indicate that the amount of m.c. in Chok Anan mango can be determined with excellent accuracy using a SMA-P coaxial sensor as an OEC sensor

Development of a microcontroller-based microwave instrumentation system for determination of moisture content in oil palm fruits and ginger

In agriculture, moisture content (MC) is among the important factors that are closely correlated to the properties of agriculture products. There is a diverse range of techniques such as Near-Infrared (NIR) spectroscopy, magnetic resonance, X-ray and computed tomography that have been used for the quality assessment in agriculture products. However, the microwave aquametry technique which applies MC measurement and correlates it to the quality of the agriculture products, has been widely used due to the fast, precise, cost and energy saving as well as compliance with safety regulations. Several sensors such as, microstrip and coplanar which are based on the attenuation measurement, have been suggested previously for the MC determination but these techniques required laborious preparation. The Keysight OEC probe has been used to determine the permittivity of agriculture products, however, it requires a network analyzer which is bulky and expensive. As a solution to this limitation, the low cost microcontroller-based microwave instrumentation system for determination of MC percentage in oil palm fruits and gingers is developed in order to determine the quality of samples by relying on MC measurement. This thesis describes in detail the development of a microcontrollerbased microwave instrumentation system for the determination of MC percentage in oil palm fruits and ginger to determine the quality of samples by relying on MC measurement. This instrumentation system or also known as reflectometer operates at 2GHz includes a stripline directional coupler, two diode detectors, a PIC microcontroller, liquid crystal display (LCD), and sensors such as open ended coaxial-stub contact panel and monopole sensors. The stripline directional coupler’s design, analysis and also performance testing are accomplished by using Microwave Office Software. The Flow Code version 5.5 was used to program the PIC16F690 microcontroller for data acquisition as well as to calculate the MC based on measured reflected voltage, processing and LCD display. The permittivity measurement is carried by using the Keysight 85070B dielectric probe kit that utilize with the computer controlled HP 8720B vector network analyzer software. The COMSOL Multiphysics® software is used to visualization of the electric field distribution of both the open ended coaxial-stub contact panel and monopole sensors based on the permittivity value measured. The calibration equations relating the measured reflected voltage by using the reflectometer to the actual MC, and permittivity (dielectric constant (ԑ′) and loss factor (ԑ")) has been established. The predicted percentage of MC in samples is calculated based on the measured reflected voltages can by interchanging the y and x axes. On the other hand, for the predicted permittivity measurement, the calibration equation between the reflected voltage and MC is substituted into the relationship between permittivity and MC. The accuracies of the calibration equations were determined by comparing the predicted MC with the actual MC using microwave oven drying method on another batch of the samples while for the permittivity measurement, the accuracy is determined by comparing the predicted and actual permittivity values that obtained from the another batch of permittivity measurement by using Keysight OEC probe. All of the calibration equations shows a good agreement for input reflected voltage which utilizing the reflected voltage values to determine the MC, ԑ′ and ԑ" by utilizing the mean relative error formula. For oil palm fruits, the accuracies for MC, ԑ′ and ԑ" were within 3.8%, 4.1%, and 4.5%, respectively. While for ginger, the accuracies for MC, ԑ′ and ԑ" were within 2.9%, 2.7%, and 3.6%, respectively

Bandwidth Enhancement by Interconnecting Double Hexagonal Loops FSS

International audienceThe paper proposed a mosaic frequency selective surface (MFSS) which comprises of the integration between Koch fractal and a basic double hexagonal loop FSS. Through this integration, the bandwidth (BW) within the first bandstop and bandpass frequency responses achieved a wideband frequency response (fractional bandwidth (FBW) > 50%), while the BW of the second bandstop frequency response improved (FBW similar to 20%). The simulation process is conducted by using the CST software, and the FR4 substrate is used as the dielectric substrate for all of the proposed unit cells. With narrow trace width of the MFSS, the structural element can be further applied for optical transparency application with wideband filtering characteristics

Effect of Array and Substrate Configurations on Transparent Mosaic Frequency Selective Surface

International audienceThis study investigated the effect of the array and substrate configurations on the performance of the optically transparent Mosaic Frequency Selective Surface (MFSS). The MFSS structural element integrates the double hexagonal loops and Koch fractal structural elements. The transparent polycarbonate substrate (permittivity of 2.9, loss tangent of 0.02, substrate thickness of 1.5 mm) is used, where the silver conductor layer (thickness of 0.006 mm and conductivity of 4.3 x 106S/m) of the MFSS periodic array is patterned on the substrate surface. In this work, three types of configurations are assessed for the optically transparent MFSSs - single-sided MFSS (MFSS), double-sided MFSS (MFSS2), and multilayered MFSS (MFSS3). The simulation of the MFSSs is conducted using the Computer Simulation Technology (CST) Microwave Studio software. Based on the obtained result, it was concluded that the increase of the array and substrate configurations allowed the enhancement of bandwidth, especially for the first and the second bandstop frequency responses, and contrariwise for the bandpass frequency response. Meanwhile, the obtained cross-polarisation (Tyx) value showed that the simulated Tyx degraded consequently as the array and substrate configurations of the MFSSs increased. © 2023 IEEE

Mosaic Frequency Selective Surface with Wideband Response for the Optically Transparent and Absorber Applications

International audienceThis study investigated the performance of a Mosaic Frequency Selective Surface (MFSS) structure for two different applications: optical transparency and absorber. The MFSS for optical transparency application is comprised of a polycarbonate substrate with permittivity, epsilon(r) of 2.9, and the MFSS for absorber application utilized a Polyethylene Terephthalate (PET) substrate with epsilon(r) of 2.7. The MFSS unit cell is composed of a conductive metallic element design that integrates the Koch fractal and the double hexagonal loop for the optical transparency application. Meanwhile, the resistive MFSS unit cell with sheet resistivity of 100 Omega/sq is utilized for the absorber application. A Computer Simulation Technology (CST) Microwave Studio software is employed to carry out the calculation and frequency response analysis for both applications. Based on the results, it was concluded that the transparent MFSS yielded a wideband stopband and passband responses (fractional bandwidth (FBW) > 50%) with a low cross-polarization (-37 dB), and a wideband absorptivity response was achieved with thin MFSS absorber. In addition, the simulated and measured responses of the transparent MFSS achieved well-fitted correlations. The findings indicated that the proposed MFSS unit cell able to provide wideband response for both applications

Mosaic frequency selective surface with wideband response for the optically transparent and absorber applications

This study investigated the performance of a Mosaic Frequency Selective Surface (MFSS) structure for two different applications: optical transparency and absorber. The MFSS for optical transparency application is comprised of a polycarbonate substrate with permittivity, varepsilon_{r} of 2.9, and the MFSS for absorber application utilized a Polyethylene Terephthalate (PET) substrate with varepsilon_{r} of 2.7. The MFSS unit cell is composed of a conductive metallic element design that integrates the Koch fractal and the double hexagonal loop for the optical transparency application. Meanwhile, the resistive MFSS unit cell with sheet resistivity of 100 Omega/text{sq} is utilized for the absorber application. A Computer Simulation Technology (CST) Microwave Studio software is employed to carry out the calculation and frequency response analysis for both applications. Based on the results, it was concluded that the transparent MFSS yielded a wideband stopband and passband responses (fractional bandwidth (text{FBW}) > 50%) with a low cross-polarization (-37 dB), and a wideband absorptivity response was achieved with thin MFSS absorber. In addition, the simulated and measured responses of the transparent MFSS achieved well-fitted correlations. The findings indicated that the proposed MFSS unit cell able to provide wideband response for both applications

Optically Transparent Tri-Wideband Mosaic Frequency Selective Surface with Low Cross-Polarisation

International audienceAcquiring an optically transparent feature on the wideband frequency selective surface (FSS), particularly for smart city applications (building window and transportation services) and vehicle windows, is a challenging task. Hence, this study assessed the performance of optically transparent mosaic frequency selective surfaces (MFSS) with a conductive metallic element unit cell that integrated Koch fractal and double hexagonal loop fabricated on a polycarbonate substrate. The opaque and transparent features of the MFSS were studied. While the study on opaque MFSS revealed the advantage of having wideband responses, the study on transparent MFSS was performed to determine the optical transparency application with wideband feature. To comprehend the MFSS design, the evolutionary influence of the unit cell on the performance of MFSS was investigated and discussed thoroughly in this paper. Both the opaque and transparent MFSS yielded wideband bandstop and bandpass responses with low cross-polarisation (-37 dB), whereas the angular stability was limited to only 25 degrees. The transparent MFSS displayed high-level transparency exceeding 70%. Both the simulated and measured performance comparison exhibited good correlation for both opaque and transparent MFSS. The proposed transparent MFSS with wideband frequency response and low cross-polarisation features signified a promising filtering potential in multiple applications