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    Single-Frequency Sensor for Thick Rind Fruit Quality Assessment
    (2025-01-01)
    Leekul, Prapan
    ;
    Dao, Hoang Nam
    ;
    Sirisuk, Phaophak
    ;
    Phongcharoenpanich, Chuwong
    ;
    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
    ;
    Mgawe, Bonny
    ;
    Kazema, Twahir
    ;
    Dao, Hoang Nam
    ;
    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
    ;
    Mgawe, Bonny
    ;
    Kazema, Twahir
    ;
    Dao, Hoang Nam
    ;
    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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    Identification of pure and impure palmyrah palm juice by using microwave sensor system
    (2015-10-01)
    Kanahna, Rachen
    ;
    Keowsawat, Panisa
    ;
    Promwong, Sathaporn
    ;
    Phongcharoenpanich, Chuwong
    The objective of this research was to construct a microwave sensor system for identifying the pure and impure palmyrah palm juice. The microwave sensor system consisted of the signal generator, the detector circuit and the processing unit. The system measured the transmission signal between a pair of antennas at the frequency of 2.45 GHz. The transmission signal sending through the pure palmyrah palm juice and the impure juice that was added the granulated and coconut sugar was measured. The results showed the difference of transmission signal magnitude with the different kinds of juice and total soluble solid (TSS). The results that were measured by the proposed microwave sensor system get along well with the results from the network analyzer. Then, this proposed system can be used to distinguish the pure and impure juice.
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    Microwave sensor response in relation to durian maturity
    (2009-12-01)
    Suttapa, S.
    ;
    Varith, J.
    ;
    Krairiksh, M.
    ;
    Noochuay, C.
    ;
    Phimpimol, J.
    This research studied the microwave response in relation to maturity development of durian fruit (Durio zibethinus Murry cv. Monthong) using a microwave sensor at frequency of 2.45 GHz. The microwave sensor applied two patch antennas to couple the microwave signal from durian. The experiment was conducted on 30 intact durian fruits at 91-123 days after full-bloom. One intact fruit on the tree was attached with the microwave sensor onto durian peel. The microwave sensor response was recorded everyday. Meanwhile, three durian fruits with the same size and age were picked from the tree for every third day to determine their maturity indices e.g., reducing sugar, starch, moisture content, dry matter and dielectric properties of durian pulp. Result showed that the microwave sensor response linearly decreased during the first period day 91-103, then linearly increased during day 104-118. As the wave from microwave sensor penetrated through the peel, it may interact to one of the maturity indices in the pulp, possibly moisture content during maturity of 50- 70% maturity and starch content during maturity of 70-90%. Dielectric constant of durian pulp at 2.45 GHz was found as a confound factor affecting microwave sensor response relating to durian maturity. The transition of microwave response was approximately at day 103, implying that durian maturity was about 70%, corresponding to an onset of reducing sugar. The microwave responses may be beneficial for durian farmers to predict the suitable harvesting period because of its nondestructive characteristic for durian maturity prediction.