• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.18 no.6 s.121
• /
• pp.591-601
• /
• 2007

In this paper, the miniaturized radio frequency identification(RFID) tag antennas used in UHF band$(908.5{\sim}914MHz)$ are designed and fabricated by using the circular loop antenna(CLA). Miniaturization of CLA was possible to transform the structure of circular loop into the structure of meander line. In the case of double meander line CLA is reduced up to 83% compared with the general type CLA. The $S_{11}$, -10 dB bandwidth, and gain of double meander line CLA were -11.9 dB, 12 MHz(1.3%), and -1.18 dBd. Also, a small half-wavelength CLA using double meander line is designed and fabricated for flat snack bag coated aluminum. The antenna is reduced up to 92.1% except ground. It shows the $S_{11}$ of -16.5 dB, -10 dB bandwidth of 48 MHz(5%) and gain of -0.58 dBd. The radiation pattern shows omni-directional pattern in z-y plane(x-axis pol.). Through this result, we can confirm that miniaturized type CLAs using meander lines are suitable for miniaturized RFIB tag antennas with the UHF band.

• Radiation Oncology Journal
• /
• v.14 no.1
• /
• pp.77-85
• /
• 1996

Purpose : Multileaf collimator(MLC) is very suitable tool for conformal radio-therapy and commissioning measurements for a multileaf collimator installed on a dual energy accelerator with 6 and 10MV photons are required, For modeling the collimator with treament planning software, detailed dosimetric characterization of the multileaf collimator including the penumbra width, leaf transmission between leaf leakage and localization of the leaf ends and sides is an essential requirement. materials and Methods : Measurement of characteristic data of the MLC with 26 pair block leaves installed on CLINAC 2100C linear accelerator was performed. Low sensitive radiographic film(X-omatV) was used for the penumbra measurement and separate experiments using radiographic film and thermoluminescent dosimeters were performed to verify the dose distribution, Measured films were analized with a photodensitometer of WP700i scanner. Results : For 6 & 10 MV x-ray energies, approximately $2.0\%$ of photons incident on the multileaf collimator were transmitted and an additional $0.5\%$ leakage occurs between the leaves. Localizing the physical end of the leaves showed less than 1mm deviation from the $50\%$ decrement line and this difference is attributed to the curved shaped end on the leaves One side of a sin히e leaf corresponded to the $50\%$ decrement line, but the opposite face was aligned with a lower value. This difference is due to the tongue and groove used to decrease between leaf leakage. Alignment of the leaves to form a straight edge resulted larger penumbra at far position from isocenter as compare with divergent alloy blocks. When the MLC edge is stepped by sloping field, the isodose lines follow the leaf pattern and Produce scalloping isodose curves in tissue. The effective penumbra by 45 degree stepped MLC is about 10mm at 10cm depth for 6MV x-ray. The difference of effective penumbra in deep tissue between MLC and divergent alloy blocks is small (5mm). Conclusion : Using the characteristic data of MLC, the MLC has the clinlical acceptability and suitability for 3-D conformal radiotherapy except small field size.