• Korean Journal of Optics and Photonics
• /
• v.4 no.1
• /
• pp.9-14
• /
• 1993

We chose Bessel beamu[$J_o(ar)}$)l in order to investigate image forming property of the optical system with combined filter of amplitude and phase(CFAP). This paper investigated numerically the influence of number of nodes of these beams on the PSF, encircled energy(E), transmission ratio(TR), gain((;) for an aberrated(1aberration-free) optical system. These results showed that the property of PSF differ considerably from the one of the existing amplitude filter and that Bessel beam has super compensating effect for an optical system with spherical aberration. Particularly, the Bessel beam has less the size of central spot than the radius of Airy disk, this result can therefore be applied to the fabrication of semiconductor device.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.17 no.1
• /
• pp.50-56
• /
• 2014

In this paper, we proposed a Ku-band antenna that can be mounted on UAV. A proposed antenna structure has small size and light weight. It is considered long distance communication environment(LOS) and equipped UAV. Proposed antenna is designed $16{\times}2$ aperture coupled microstrip patch array antenna for high gain characteristics. In the measurement results, VSWR is less than 1.5 and the gain is over 21dBi in the bandwidth. Mechanical specifications of antenna assembly are ${\phi}250{\times}200mm$ of size and 3kg of weight.

• Journal of the military operations research society of Korea
• /
• v.18 no.1
• /
• pp.61-73
• /
• 1992

Up to the present, the operating time has been studied on only a single aircraft attacking a single target or multiple targets under enemy threats. This study is to determine optimal operating time and appropriate size of aircrafts attacking multiple targets. Measures of mission effectiveness is defined through derivation of the probability of the various events associated with operating. By using these measures, the expected benefit of operating and the expected cost of operating are generated as a function of time. To formulate operating time determination model, the expected gain of operating is defined as the difference between the expected benefit of operating and the expected cost of operating. The model can be used to determine optimal operating time which maximizes the expected gain of operating, and can be used as the basis for determining the appropriate size of aircrafts.

• Proceedings of the IEEK Conference
• /
• 2000.06b
• /
• pp.84-87
• /
• 2000

In this paper, a high gain-broad bandwidth MMIC distributed amplifier was designed using cascaded single section distributed amplifier configuration. The PHEMT for this studies was fabricated at our lab The PHEMT has a 0.2 $\mu\textrm{m}$ gate length. a 80 $\mu\textrm{m}$ unit gate width and 4 gate fingers. A designed MMIC amplifier have higher S$\sub$21/ gain than the common distributed amplifier using the same number of active devices. From the simulated result, we obtained that the S$\sub$21/ gain of DC ∼ 20 GHz bandwidth was 15.6 dB and flatness was ${\pm}$0.9 dB, and input and output reflection coefficient were lower than -8 dB. The simulated gain shows an improvement 7.3 dB compared with those of conventional distributed amplifier. And the chip size is 2.0 ${\times}$ 1.2 $\textrm{mm}^2$.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
• /
• 2000.11a
• /
• pp.150-153
• /
• 2000

In this paper, we have designed a 2 stage MMIC power amplifier which has flat gains of in-band and reasonable out-band cutoff characteristics using 0.5$\mu\textrm{m}$ MESFET libra교 of ETRI. For the 1st stave, we obtaind P$_{1dB}$ of 9.2 dBm and gain 10.8 dB using 6 finger D-MESFET and P$_{1dB}$ of 18.4 dBm and gain of 10.8 dB using 14 finger D-MESFET for the 2nd stage, which is power matched using LIBRA's embedded TUNER. Also in-band gain flatness and out-band cutoff characteristics are obtained by attaching LC tank in the output matching circuit. The designed 2 stage MMIC power amplifier has bandwidth of 0.95～2.8 GHz, gain of 20 dB and P$_{1dB}$of 17.2 dBm. Especially gain flatness of $\pm$0.8dB was obtained in 1.8～2.5 GHz frequency ranges. And chip size is 1.4$\times$1.4 mm..4 mm.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.5 no.4
• /
• pp.822-828
• /
• 2001

In this paper, a high gain microstrip antenna with rectangular cavity backed is designed. A single microstrip patch is basically a low gain radiator As a ga in enhancement method, superstrate loading techniques are applied to the $2\times2$ microstrip array antenna with cavity backed. In antenna design, although the broadside gain increases as the cavity is enlarged, a cavity size of $3\times3$ wavelength is sufficient. The distance between the radiating elements is chosen as 1.5 free-space wavelength. The antenna radiation characteristics are calculated by IE3D software and compared with the experimental results. Experimental results show that the maximum gain is 18.6dBi at the frequency of 9.16GHz, which is good agreement with the calculations.

• Journal of Broadcast Engineering
• /
• v.23 no.6
• /
• pp.925-930
• /
• 2018

In this paper, we present a low profile dual-microstripline-fed double 4-arrayed meander monopole antenna with a cross-type element back by separated four-segments mesh-type reflector. The cross-type element and separated four-segments mesh-type reflector leads to enhance radiation patterns and antenna gain characteristics. The measurement value of the proposed antenna show that it has dipole-like radiation pattern characteristics. The experimental peak gain of fabricated antenna is about 2.89 dBi, which presents relatively high gain characteristics for a low profile(small-size) one. This antenna can be applied mobile RFID(radio frequency identification) readers, small medical instruments, broadcasting and home-networking operations, and other low profile high-gain systems.

• Journal of the Korean Institute of Telematics and Electronics B
• /
• v.30B no.4
• /
• pp.104-115
• /
• 1993

The motion compensated coding (MCC) technique, which exploits the temporal redundancies in the moving images with the motion estimation technique,is one of the most popular techniques currently used. Recently, a variable block size(VBS) motion estimation scheme has been utilized to improve the performance of the motion compensted coding. This scheme allows large blocks to the used when smaller blocks provide little gain, saving rates for areas containing more complex motion. Hence, a new VBS motion estimation scheme with a hierarchical structure is proposed in this paper, in order to combine the motion vector coding technique efficiently. Topmost level motion vector, which is obtained by the gain/cost motion estimation technique with selective motion prediction method, is always transmitted. Thus, the hierarchical VBS motion estimation scheme can efficiently exploit the redundancies among neighboring motion vectors, providing an efficient motion vector encoding scheme. Also, a restricted search with respect to the topmost level motion vector enables more flexible and efficient motion estimation for the remaining lower level blocks. Computer simulations on the high resolution image sequence show that, the VBS motion estimation scheme provides a performance improvement of 0.6~0.7 dB, in terms of PSNR, compared to the fixed block size motion estimation scheme.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.21 no.2
• /
• pp.152-163
• /
• 2010

In this paper, a cavity-backed high gain dual band microstrip antenna with Frequency Selective Surface space(FSS) for WLAN is proposed. The proposed antenna that operates in IEEE 802.11a/b bands with similar radiation pattern and gain is fabricated on RO4003 substrate with a dielectric constant of 3.38. The size of the antenna is $71.5{\times}42.0{\times}6.6\;mm^3$, and the FSS size is $120.0{\times}120.02\;mm^3$. The ground plane size including cavity is $150.0{\times}145.0\;mm^3$. The antenna is fed by coaxial cable. The simulated bandwidths of the antenna are 2.369~2.517 GHz and 5.608~5.833 GHz for VSWR<2. The gains are 11.23 dBi and 12.60 dBi, respectively, for the lower and upper bands.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.15 no.2
• /
• pp.175-180
• /
• 2015

In this paper, GPS / GLONASS receiving a small active antenna is proposed. A microstrip patch antenna which supports dual-band (GPS and GLONASS) was optimized. The antenna size is $13{\times}13{\times}3.6mm$. The jig was changed to confirm the proposed antenna characteristic size, was adjusted to feed gap of the patch antenna, it was confirmed by change in LNA shield case or not. The antenna jig size is $65.6{\times}13{\times}0.8mm$. The maximum gain of the GPS band is 3.78dBi, the maximum gain of the GLONASS bands is 4dBi. To amplify the Satellite reception signal level, one-stage low noise amplifier(LNA) was designed. The LNA chip was using the BGA715 N7, the LNA gain is 19.9dB. The utilization possibility of the GPS / GLONASS receiving a small active antenna could be confirmed according to compare and analyze the simulation and measurement data.