• Journal of the Korean Society for Precision Engineering
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• v.22 no.9 s.174
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• pp.69-76
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• 2005

The laser interferometer system such as HP5529A is one of the most powerful equipment fur measurement of the straightness error in precision stages. The straightness measurement system, HP5529A is composed of a Wollaston prism and a reflector. In this system, the straightness error is defined as relative lateral motion change between the prism and the reflector and computed from optical path difference of two polarized laser beams between these optics. However, rotating motion of the prism or the reflector used as a moving optic causes unwanted straightness error. In this paper, a compensation method is proposed for removing the unwanted straightness error generated by rotating the moving optic and an experiment is carried out for theoretical verification. The result shows that the unwanted straightness error becomes very large when the reflector is used as the moving optic and the distance between the reflector and the prism is far. Therefore, the prism must be generally used as the moving optic instead of the reflector so as to reduce the measurement error. Nevertheless, the measurement error must be compensated because it's not a negligible error if a rotating angle of the prism is large. In case the reflector must be used as the moving optic, which is unavoidable when the squareness error is measured between two axes, this compensation method can be applied and produces a better result.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.7A
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• pp.511-519
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• 2003

In this paper, to achieve a broad-band and high-gain antenna, we thus designed and analyzed the CRLPDA(Corner Reflector Antenna feeding by Log-Periodic Dipole Antenna) made up of 90$^{\circ}$corner reflector, which is trough-reflector type installed a planar reflector at the folded line. CRLPDA for operating frequency band of 1,400 MHB ~ 2,400 MHz was designed and radiation characteristics of the designed antenna were analyzed by moment method. To verify the analysis results, CRLPDA was fabricated and the calculated results were compared with the measured results. The measured results showed good agreement with the calculated results. As the result of measurements, bandwidth(VSWR＞2) for 1,000 MHz was achieved and gain was 13 dBi.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.5
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• pp.429-436
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• 2012

In concert halls and auditoriums, acoustic reflector and stage enclosure is one of the main factors on the room and stage acoustic characteristics. As a stage enclosure and acoustic reflector honey comb based light-weight reflector is widely used, because it is easy to install. However, there was not enough research on the surface density effect on room and stage acoustics. In this study, sound absorption coefficient tests on three kinds of wooden acoustic reflectors with different surface density were conducted. Surface density of acoustic reflector was changed from 11 kg/$m^2$ to 41 kg/$m^2$. For the low frequency excitation, sub-woofer was used with omnidirectional loud-speaker simultaneously. From the experiments, it was found that sound absorption coefficient below 250 Hz band was decrease by the increment of surface density. In order to check the influence of the surface density on room and stage acoustic parameters, room acoustic simulation was conducted with sound absorption coefficients, which were tested in reverberation chamber. By the increment of surface density of acoustic reflector, RT(reverberation time) and EDT(early decay time) were increased. Also, ST(stage support) was improved in low frequency bands.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.8
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• pp.563-569
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• 2008

Radiative, heating is suitable for outdoor heating system in windy and cold seasons. Optimal design of the reflector is very important to maximize heat transfer to a specific target area in the open space. The geometrical optical theory can be applied to analyze efficiency of the reflector. Commercial ray tracing computer programs are available only for limited geometries of the reflector. Alternatively, it may be designed and analyzed through an approximated simple lens theory. Two types of reflectors are analyzed using either of these methods. The key issue in this paper is to propose a new illumination experimental method for determination of the radiative efficiency. Optical light source and illuminometer are employed. The calculated efficiency of the reflector is compared with experimental one for checking the reliability. The relative errors between the experimental and analytical results are less than 5%, which proves the validity of this method. Based on these methodologies, a practical reflector and heating lamp unit is developed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.3
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• pp.340-350
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• 1999

In this paper, W-type reflector antennas modified from corner reflector antenna structure were proposed and the radiation characteristics were analyzed using the method of moments. The analysis results such as gain, F/B, half power beamwidth, and radiation pattern are presented as functions of dipole height h and back edge spacing d. Also, the proposed antenna was compared with corner reflector antennas in the same size of side reflectors, W-type reflector antenna was found to exhibit somewhat higher gain and larger F/B than corner reflector antennas. To verify the analysis results, W-type reflector antenna was fabricated and the radiation characteristics were measured. The measured results show good agreement with the calculated results.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.392-393
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• 2009

The study is aimed at studying a weakly relativistic oversized BWO with a Bragg reflector entrance of SWS. The Bragg reflector reflects microwaves, while it is open for beam propagations. By changing the boundary condition at the beam entrance, the effect of the Bragg reflector on the BWO performance is examined.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.4
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• pp.451-460
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• 2008

Gregorian offset dual-shaped reflector antennas have been widely used in the satellite communication systems for their high gain and low sidelobe characteristics. However, in this paper, it is designed as the CATR(Compact Antenna Test Range) reflector system, and its near-field characteristics are investigated. The CATR facility needs to provide an uniform plane wave with the minimum amplitude and phase ripple and the low cross polarization to the test region. Therefore, the reflector near-field patterns are calculated and presented with the variations of the aperture power distribution, the feed horn pattern, and the distance from the aperture to the test zone. Also, the offset dual-shaped reflector is fabricated at 30 GHz, and its near-field patterns are measured. The measured results are in good agreement with the calculated results. From theses results, we confirm that the designed offset dual-shaped reflector can be used as the reflector system for the compact antenna test range.

• Journal of Satellite, Information and Communications
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• v.7 no.2
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• pp.67-71
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• 2012

This paper represents the impact analysis results of antenna reflector for the UHF-band antenna of Space Launch Vehicle. Three types of UHF-band antenna reflector model have been proposed and simulated to compare their characteristics such as resonance frequency, reflection loss and radiation pattern etc. Simulation results showed that resonance frequency and return loss of each reflector models were rarely affected even if reflector sizes are changed. The antenna gain and 3dB bandwidth were slightly changed to the worse directions as the reflector sizes are smaller.

• Journal of Navigation and Port Research
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• v.27 no.3
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• pp.267-272
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• 2003

This paper describes design method of Passive-type Radar Reflector (PRR) which is to provide the requirement of newly revised 2000 SOLAS regulations on the Radar Reflector. The main target of this work is to find the optimum shape of a radar target having large Radar Cross Section (RCS). Through the RCS analysis based on the theoretical approach, two kinds of PRR models, RRR-F model for use in fisheries and PRR-S model for use in small sized ship, are designed and discussed their RCS performance. RCS measurement tests for the various sized samples are carried out in an anechoic chamber. As evaluation results it was clearly shown that the conventional sphere-type shows optimum shape in case of PRR-S, while the cylinder-type which consists of large sized corner clusters or zig-zag flat plats gives best performance in case of PRR-F.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.40.2-40.2
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• 2010

The Solar Daylighting Technology is considered with the plan that will be able to embody the energy technology which is possible to continue. Daylighting has an considerable advantage of the high effectiveness and the various use because daylighting can use the infrared ray, the visible ray and the ultraviolet rays without energy transformation. In this study, the experiment is tried of making the shape and an arrangement of the reflector different After establishing the reflector in the height(10m) which is fixed. It's also researched on the shape of the efficient reflector using the program(Trace Pro) at the time of the autumnal equinox and the winter solstice at fixed hours.