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Single-Frequency Sensor for Thick Rind Fruit Quality Assessment
(2025-01-01)
Leekul, Prapan
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Dao, Hoang Nam
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Sirisuk, Phaophak
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Phongcharoenpanich, Chuwong
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Krairiksh, Monai
A sensor capable of estimating the dielectric properties of the outer and inner materials of a concentric dielectric sphere is essential for assessing the quality of thick rind fruits. This article presents a sensor design that operates at a single frequency and is straightforward. The underlying principle of the sensor involves transmitting a microwave signal to a concentric dielectric sphere with two power levels. The low-power signal yields backscattered waves from the outer sphere, while the high-power signal provides information about backscattered waves from both the outer and inner spheres. The sensor, which operates at a frequency of 10 GHz using cost-effective components, effectively detects defects in spherical-shaped fruits, e.g., mangosteens. The accuracy in classifying translucent mangosteens from normal mangosteens is 92.5%, enabling effective classification of defected fruits.
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Simple and Effective Design Concept for Constructing In-Situ Soil Dielectric Property Sensor with Dual Low-Cost COTS Microwave Modules
(2022-01-01)
Leekul, Prapan
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Mgawe, Bonny
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Kazema, Twahir
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Dao, Hoang Nam
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Sirisuk, Phaophak
This paper presents a compact sensor system for estimating the dielectric properties of materials based on commercial, off-the-shelf (COTS) modules. The dielectric constant and conductivity of a material under test can be determined from the measurement of the microwave reflected from the material. By using dual microwave sensor modules with a slightly different radio frequency, an identical intermediate frequency at the mixers of the modules was obtained. The intermediate frequency was chosen such that the associated microwave and data processing components could be easily obtainable, leading to a practical realization of the sensor system. Synchronization of the two microwave sensor modules was achieved using electronically controlled relays that simultaneously switch on the power supplies of both modules. Two microcontrollers were used to capture the corresponding signals. The sensor was designed at a 10 GHz band for measuring reflected waves from various kinds of materials, especially soils with different moisture and fertilizer contents. The evaluation results indicate a good agreement between the measured results from the proposed sensor and the ones from a network analyzer, verifying that the proposed sensor is fully functional for monitoring variation in the dielectric properties of materials, including soil. The average sensitivity for the dielectric constant of moist soil is 0.26/% moisture content and the error rate for dielectric constant measurement is 4.83%.
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Dielectric Constant Determination using Dual Doppler Modules
(2021-01-01)
Leekul, Prapan
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Mgawe, Bonny
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Kazema, Twahir
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Dao, Hoang Nam
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Sirisuk, Phaophak
This paper presents a dielectric constant determination system based on dual Doppler modules. The key principle is to assign two slightly different radio frequencies to each module. It is demonstrated that dielectric constant of a material under test can be determined from the measured reflection coefficient. The concept was validated at 10 GHz band by measuring reflected waves from various materials including soil with different moisture content. Results illustrated good agreement between measured results from the proposed sensor as compared with the literatures. The results confirm that the proposed technique is applicable for monitoring soil characteristics.
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Measurement of Radiated Field from Transmitting Antennas Located in Various Environments
(2019-04-01)
Krairiksh, Monai
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Kittiyanpunya, Chainarong
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Limpiti, Thunyawat
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Tantisopharak, Tanawut
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Leekul, Prapan
In microcellular communications, the transmitting antennas can be installed at low heights above the ground. However, even for low elevation towers, installation cost is still high. One of the possible ways for the deployment of base station antennas is to install them near the ground in order to do away with the tower. The main purpose of this paper is to suggest installation of the radiating antennas near the ground and tilting their orientation toward the sky - a totally nonintuitive solution. It will be shown that such deployments have the potential of reducing slow fading and can further enhance the signal strength close to the radiating antenna. This paper provides measured data for the received fields to validate the theoretical conjecture of such a deployment in various environments. The measured results are presented for 245, 800, 1000, and 2400 MHz. It is illustrated that such an unorthodox deployment can result in a low cost for the installation of base station antenna as the towers are not necessary. This can be useful in restoring communications in emergency situations where minimum infrastructure exists.
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Measured natural frequencies of mangosteens
(2018-11-15)
Leekul, Prapan
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Krairiksh, Monai
Our previous work demonstrated that nondestructive fruit classification using Cauchy method is applicable for mangosteen. This work illustrated the experimental results that the frequency difference of normal and translucent mangosteens is about 12 MHz.{This frequency difference is sufficient for classifying translucent mangosteens from the normal ones. This technique is very useful for quality control of fruit exporting.
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A sensor for continuous fruit classification using Rician k-factor
(2018-07-02)
Leekul, Prapan
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Krairiksh, Monai
The quality control in fruit industry is more and more demanded. For thick-peel fruit like durian, the UHF and microwave frequency bands are suitable. For a large number of fruits to be classified, a continuous process is desirable. The system using Rician k-factor has been analyzed and found to be feasible. This paper presents design and experimental results that describe the feature of a sensor system for fruit classification in a continuous process. The results show that the Rician k-factors from a single frequency-monostatic and wideband-bistatic measurements can be used as indicators for classifying maturity stage of durian fruits.
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Beam-Scanning Reflectometer for Detecting Granulated Fruits
(2017-03-01)
Kittiyanpunya, Chainarong
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Leekul, Prapan
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Phongcharoenpanich, Chuwong
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Krairiksh, Monai
The problem of granulation in fruits costs vendors a big chunk of their revenue, hence a non-destructive sensor that can identify granulated fruits without destroying good fruits is highly desirable. This paper presents such a sensor system based on beam-scanning reflectometer operating at 2.45 GHz. Beams of scattered waves from several directions around the fruit are reflected by a conical reflector and scanned by a phased array of pattern reconfigurable Yagi-Uda antennas equipped with 1-b phase shifters for lowest loss in feed network. The collected data are used to calculate the Rician k-factor. The system was tested with plasticine spheres and real tangerines. It was found that the system with an eight-beam array was better than one with a four-beam array. This system may prove useful for quality control of tangerines and other agricultural products.
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Rician k-Factors-Based Sensor for Fruit Classification by Maturity Stage
(2016-09-01)
Leekul, Prapan
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Chivapreecha, Sorawat
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Phongcharoenpanich, Chuwong
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Krairiksh, Monai
This paper has proposed a non-destructive, non-invasive sensor system for classifying durian fruits according to the maturity stages. The design of the sensor system has adopted the principle of wireless communications in which the Rician k-factors were utilized to determine the fruit maturity. The sensor is operable at the 915 MHz frequency. The simulation and experimental results revealed that the export grade durian had the higher reflected wave-based k-factors but lower scattered wave-based k-factors, when compared with the immature durian. The findings also showed that the k-factor thresholds for the reflected and scattered waves of 3 ×10<sup>4</sup> and 128 could achieve an accuracy rate of as high as 92.7% with regard to the durian maturity.
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Microwave sensor for tangerine classification based on coupled-patch antennas
(2016-08-02)
Leekul, Prapan
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Chivapreecha, Sorawat
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Krairiksh, Monai
This paper deals with a microwave sensor for classifying tangerines by flavour using coupled-patch antennas. The operating frequency of the antennas is 2.45 GHz. The sensor determines the flavour of each tangerine by measuring the magnitudes of coupled signals of the antennas with the tangerine fruit at the centre. The sorting is carried out using an artificial neural network implemented on a field programmable gate array. The classification performance of the sensor is 95% accurate, so it has potential for use in sorting tangerines by flavour. In addition, the system uncertainty is analysed to determine optimal operating conditions.
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Remote sensing of the physical qualities of fruits
(2014-03-25)
Leekul, Prapan
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Limpiti, Thanyawat
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Tantisopharak, Thanawut
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Yoiyod, Paiboon
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Chivapreecha, Sorawat
Fruits are important exporting products for the countries in the tropical zone. Since the market requires the quality control, this paper discussed some techniques for classification of fruits which durian is an example.

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