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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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Approximated Backscattered Wave Models of a Lossy Concentric Dielectric Sphere for Fruit Characterization
(2022-05-02)
Dao, Hoang Nam
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Phongcharoenpanich, Chuwong
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Krairiksh, Monai
Approximated models of electromagnetic waves scattered from a sphere with two different dielectric layers were developed and reported in this paper. We proposed that the dielectric properties of a concentric dielectric sphere object, for example, some types of fruit, could be estimated by this model, from some wave components of the backscattered wave. The models were suitable for lossy objects because only a single bounce of the wave was assumed. In terms of first bounce as well as total backscattered wave results, the reported values agreed well with the values calculated by a commercial software. The measurement results verified the calculated wave components. The dielectric properties determination of real fruits was performed and exhibited the potential in fruit characterization. The main advantage of these models is that they can provide the magnitude and phase information of each backscattered wave component, which makes quality monitoring of fruits to be possible.
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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 properties of fertilized soil in a Catena: A case of mwanza, tanzania
(2021-09-13)
Mgawe, Bonny
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Kazema, Twahir
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Dao, Hoang Nam
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Krairiksh, Monai
This work reports the investigation results on how dielectric properties of soil change with fertilizer concentration for catena in Mwanza of Tanzania at 945 MHz frequency band using reflection measurement. Composite soil samples were collected from three catenas: upper, middle, and lower catena sites in Misungwi district located in Mwanza, Tanzania. Two chemical fertilizers UREA and CAN were used since they are widely used in these areas. With the low-cost equipment, reliable results are obtained that show relationship of soil fertility and dielectric properties. The results provide essential information for preparing on-farm measurement to get soil fertility contour that supports land management.
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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
;
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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Narrow-Beam Antenna for Short-Distance Non-Destructive Sensor in Fruit-Ripeness Monitoring
(2020-01-01)
Dao, Hoang Nam
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Phongcharoenpanich, Chuwong
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Krairiksh, Monai
Radiation pattern subtraction is a useful technique for narrowing a receiving antenna's radiation pattern in a short-distance, non-destructive sensor. The sensor's antenna was developed to be compact and light-weight as well as to operate in real-time. This work applied the principle of radiation pattern subtraction to narrow the beamwidth of an antenna. Our experimental data demonstrated that a simple narrow-beam three-element antenna with a 35° half-power beamwidth and a small size of $5.9\times 6.5\,\,\textrm {cm}^{2}$ could be realized. In the experiment, the radiation pattern of an array antenna (consisting of two halfwave dipoles with a reflector) was subtracted from the radiation pattern of an element antenna (consisting of a halfwave dipole with a reflector) for the three-element antenna to achieve a narrow beamwidth and compact size. The antenna had a simple feeding network that operated at 10.525 GHz and 35° half-power beamwidth. The angular resolution of the receiving antenna was tested with mango fruits: it was able to resolve an 80 mm separation between the fruit of interest and the nearby fruit, which was sufficient, in terms of practicality, for mitigating the interfering effect of nearby fruits to the fruit of interest. This type of antenna is useful as a short-distance, non-destructive sensor such as a pre-harvest sensor.
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Resolution Improvement in Preharvest Sensor
(2019-10-01)
Dao, Hoang Nam
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Krairiksh, Monai
This work illustrates the benefit of subtracted beam antenna we presented earlier for a sensor system in fruit pre-harvesting. The angular resolution pattern of a receiving antenna that shows how far the unwanted object (fruit) can be eliminated from the desired target (fruit under test) is proposed. The link budget for the beam subtracted antenna is also calculated to indicate the transmitting power for ensuring the receiving power for a normal sensitivity of the sensor. This calculation shows that the beam subtracted antenna can be employed in pre-harvesting of fruits.
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A Sum-Difference Pattern Reconfigurable Antenna for Narrow Down Beamwidth of the Subtracted Pattern
(2019-09-01)
Dao, Hoang Nam
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Krairiksh, Monai
In this paper, a pattern reconfigurable antenna which can be switched between sum and difference (SUM and DIF) beams in E-plane is proposed. Based on the beam switching, a narrow radiation pattern antenna is achieved by subtracting the DIF pattern from the SUM one. With a compact size and simple design, this proposed antenna provides 6.5° narrower beamwidth than that of the SUM beam. It is useful for eliminating unwanted object in short range radar (SRR) applications.
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A Design of switched-beam yagi-uda antenna for wireless sensor networks
(2016-12-01)
Dao, Hoang Nam
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Krairiksh, Monai
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Le, Dinh Thanh
In this paper, we present a design of the Yagi-Uda antenna, which can be switched to achieve radiation patterns toward different angles with a step of 45 degree. The antenna covers the ISM band for SRDs with a center frequency of 2.45 GHz. There are eight Yagi-Uda antennas combined in a circle form. Each Yagi-Uda antenna consists of a bended reflector, a bended driven and a bended director. The bended reflector is shared for different Yagi-Uda antenna by PIN diodes. Simulated results show that eight switching beams covered all directions in E plane with particular direction beam-width around of 60 degree. The gain of the main lobe is greater than 5.5dBi, whereas the side lobe is kept 11dB smaller than the main lobe. Thanks to the pattern switchable ability and its simple design, the antenna can be used for the master sensors in wireless sensor networks, or for communicating devices in cognitive radios.

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