Chainarong Kittiyanpunya

Beam-Scanning Reflectometer for Detecting Granulated Fruits

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

Pattern reconfigurable printed Yagi-Uda antenna

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A reflectometer using antenna mixers

-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.

A reflectometer with beam switching capability

This paper presents a pattern reconfigurable antenna which is based on Yagi-Uda dipole antenna. The antenna can operate at ISM band of 2.45 GHz. It consists of microstrip-to-coplanar stripline (CPS) transition, driven elements and parasitic elements. The switch of driven element can be controlled by using PIN diodes while parasitic element function can be either reflector or director with different PIN diode states. The maximum of radiation patterns are in azimuth plane with four directions around the antenna to the directions of Ø = 40°, 120°, 220° and 320°.

WIRELESS COMMUNICATIONS IN A TREE CANOPY

This paper presents a sensor for monitoring moisture content of paper. The reflection coefficient of paper at various moisture contents are measured and used for determining humidity of paper. The resultant IF output of 50 MHz from the reflectometer operating at the frequency of 2.40 GHz and 2.45 GHz shows an obvious difference in reflection coefficient for dry and wet paper depicting the feasibility to design a moisture content sensor.

Dual-band unidirectional cross dipole antenna

This paper presents a reflectometer using pattern reconfigurable antenna. A system based on the free-space technique is developed for measuring reflected wave from a material under test. The pattern reconfigurable antenna can be implemented through alteration of switches (On/Off). The proposed antenna is capable of re-directing the main beam toward intended material. It is able to minimize installation cost. The experiments were performed on a conductor plate, paper with different moisture content. The obvious different results show the usefulness in quality control of the product in industrial processes.

Dual-band conical-scanning Yagi-Uda antenna

The wireless communications in a tree canopy is essential for pre-harvesting control of fruit productions. To e-ciently communicate between a sensor node and a sink node, channel characteristics in a tree canopy must be well-established. In this paper, propagation channel characteristics at the frequencies of 2.45 and 5.2GHz have been estimated for designing a wireless communication system in a tree canopy. The proposed solution is based on measured path loss, time-varying signal strength and Angle of Arrival (AoA) for various paths in a tree canopy to estimate the channel. Since the waves re∞ect, refract, difiract and scatter from the foliage, it is complicated to flnd the true travelling path between a transmitter and a receiver at the nodes. The AoA estimator is used for physical interpretation of the channel. The experimental results demonstrate the channels in a tree canopy are mostly matched with the General Extreme Value model. The measured path gains illustrate that the appropriate antenna patterns must be selected to enhance the reliability of the system.

Dual beam Yagi patch antenna

This paper presents a dual-band unidirectional antenna based on a straight dipole shunted with a meander line dipole antenna. This antenna is fed with a wide band Balun and equipped with reflectors to generate unidirectional patterns. The low and high frequency reflectors are plane and box reflectors, respectively. The antenna is well matched at the designed frequencies of 1 and 2 GHz. The unidirectional patterns are obtained at both frequencies with gain higher than 5.7 dBi. This antenna is used for illuminating microwave signal to an object under-test in a dual-band reflectometer.

Design of Pattern Reconfigurable Printed Yagi-Uda Antenna

A dual-band conical-scanning Yagi-Uda antenna is presented. The proposed antenna is composed of dual-band director elements, dual-band driven elements, and planar reflectors which the alignment of each element is not on the same plane of the dual-band driven elements. The PIN diodes are used in order to change position of driven elements and directors. The patterns can be switched in four directions that main beams are in the zenith angle of 30°. It is shown that the dual-band antenna for 1 and 2 GHz operation achieves an impedance bandwidth of 8.5% and 12.5%, respectively. The front-to-back ratio of conical beams is higher than 8 dB. The antenna gain is around 6 dBi.

A switch-beam circular array antenna using pattern reconfigurable Yagi-Uda antenna for space communications

This paper presents a dual beam Yagi patch antenna. The antenna operates in the ISM band of 2.41 and 2.45 GHz. It consists of rectangular patch fed at two different probe positions. The patch has two reflectors each provides directional pattern in two perpendicular directions. The isolation is better than 20 dB and directivity is more than 3 dBi. This antenna can be applied for receiving video signals from wireless cameras.