• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.5
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• pp.528-536
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• 2010

A monopulse feeder gives the most important impact upon the radiation pattern characteristics of a multi-function radar or a tracking radar which uses the space feed. It is described that the triple-mode type monopulse feeder which possesses the optimum aperture illumination for three monopulse channels is designed and measured in this paper. The measured results show that the designed feeder has not only the characteristics of the optimum aperture illimination in each channel and also very low return loss over the 10 % of fractional bandwidth at X-band. This means that the feeder provides the antenna system with low sidelobe level and high monopulse slope characteristics.

• Smart Structures and Systems
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• v.2 no.1
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• pp.1-24
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• 2006

The optimal design of multiple tuned mass dampers (multiple TMD's) to suppress multi-mode structural response of beams and floor structures was investigated. A new method using a numerical optimizer, which can effectively handle a large number of design variables, was employed to search for both optimal placement and tuning of TMD's for these structures under wide-band loading. The first design problem considered was vibration control of a simple beam using 10 TMD's. The results confirmed that for structures with widelyspaced natural frequencies, multiple TMD's can be adequately designed by treating each structural vibration mode as an equivalent SDOF system. Next, the control of a beam structure with two closely-spaced natural frequencies was investigated. The results showed that the most effective multiple TMD's have their natural frequencies distributed over a range covering the two controlled structural frequencies and have low damping ratios. Moreover, a single TMD can also be made effective in controlling two modes with closely spaced frequencies by a newly identified control mechanism, but the effectiveness can be greatly impaired when the loading position changes. Finally, a realistic problem of a large floor structure with 5 closely spaced frequencies was presented. The acceleration responses at 5 positions on the floor excited by 3 wide-band forces were simultaneously suppressed using 10 TMD's. The obtained multiple TMD's were shown to be very effective and robust.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.4
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• pp.651-658
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• 2001

A novel multi-section power divider configuration is proposed to obtain wide-band frequency performance up to microwave frequency region. Design procedures for the proposed microwave broadband power divider are composed of a planar multi-section three-ports hybrid and a waveguide transformer design procedures. The multi-section power divider is based on design theory of the optimum quarter-wave transformer. Furthermore, in order to obtain the broadband isolation performance between the two adjacent output ports, the odd mode equivalent circuit should be matched by using the lossy element such as resistor. The derived design formula for calculating these odd mode matching elements is based on the singly terminated filter design theory. The waveguide transformer section is designed to suppress the propagation of the higher order modes such as waveguide modes due to employing the metallic electric wall. Thus, each section of the designed waveguide transformer should be operated with evanescent mode over the whole design frequency band of the proposed microwave broadband power divider. This paper presents several simulations and experimental results of multi-section power divider to show validity of the proposed microwave broadband power divider configuration. Simulation and experiment show excellent performance of multi section power divider.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.3
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• pp.292-300
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• 2010

In this paper, we propose a RF front-end architecture based on hybrid conversion which is available to receive both broadband and multiband DVB-H receiver, and a multi-function circuit for implementing the RF front-end is fabricated. A multi-function circuit is operated as a sub-harmonic mixer mode in the case of receiving a broadband VHF/UHF band, which show a conversion loss of -10.0 dB, noise figure of 7.0 dB and IIP3 of 2.0 dBm. On the other hand, it is performed as a attenuation mode with a insertion loss of -10.0 dB in receiving a multiband, L-band.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.9
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• pp.1027-1034
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• 2014

We present the Low Power Broadband Low noise amplifier(LNA) that can be applied a whole bandwidth from 3G to 4G LTE. This multi input LNA was designed to steadily amplify through a multi input method regardless the size of the input signal and operate on a wide range of frequency band from a standard 3G CDMA band 1.2GHz to LTE band 2.5GHz. The designed LNA consumes an average of 6mA on a 1.2V power supply and this was affirmed using computer simulation tests. The amplification which was corresponded to the lowest input signal is at a maximum of 20dB and was able to obtain the minimum value of the gain of -10dB. The Noise figure is less than 3dB at a High-gain mode and is less than 15dB at a Low-gain mode.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.12
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• pp.1343-1350
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• 2012

This paper presents a new method for designing a dual-band WIFI antenna using the third-order harmonic mode of a monopole antenna whose first-order mode operates at the low frequency band of WIFI. As analysing the current distribution of the third-order mode of this monopole antenna, the strongest point of electric field can be found. Then by attaching a stub at this point, the resonant frequency of the stub radiator can be adjusted from the third-order mode of the monopole antenna into the high frequency band of WIFI and the input impedance at this resonant frequency can be controlled with the width of the branch, without affecting the low frequency band of WIFI (the first-order mode of the monopole antenna). The compact dual-band antenna is designed at the size of an USB(universal serial bus) dongle and the bandwidth covers 600 MHz(2.3~3 GHz) at 2 GHz and 1 GHz(4.9~5.9 GHz) at 5 GHz under -10 dB which is satisfied with WLAN frequency. Efficiency of proposed antenna achieves over 50 % at WLAN frequency.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.5
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• pp.598-605
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• 2012

In this paper, a multi-layer dual-band bandpass filter using aperture-coupling is proposed. Two coupling paths are formed with the two apertures which exist between two dual-mode resonators. The coupling coefficients can be adjusted without changing the shape of resonators. The bandwidth of the second passband can be adjusted without affecting the bandwidth of the first passband using the size of an aperture between stubs of the dual-mode resonator. The aperture coupling mechanism is theoretically analysed. The dual-mode bandpass filter for the 2.4 GHz WLAN, 3.5 GHz WiMax was designed and fabricated. The fabricated filter shows centered 2.45 GHz and 3.5 GHz with 9 % and 8 % of the bandwidth.

• Journal of IKEEE
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• v.16 no.4
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• pp.297-303
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• 2012

This paper proposes the effective design procedure for a broadband, double-ridged horn antenna for evaluating the performance of the RF energy harvesting system with a multi-band rectenna. Using multi-mode network analysis, the higher-mode scattering parameters of the transition and horn were acquired and applied to the antenna design, respectively. As a result, the computing time could be reduced and the calculated VSWR(voltage standing wave ratio) of the antenna was very similar to the analyzed result using fully electromagnetic simulation. And there was also good agreement between the simulated and measured results. The designed broadband antenna has a bandwidth of 660~6360 MHz and 6~13.7 dBi peak radiation gain.

• Korean Journal of Optics and Photonics
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• v.17 no.2
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• pp.191-197
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• 2006

We analyze the self-pulsation(SP) characteristics due to mode beating of two modes emitted in a multi-section complex-coupled (CC) DFB laser composed of two DFB sections and a phase control section between them. SP frequency due to mode beating of the two modes is determined by the difference of grating periods in the two CC DFB regions. As the difference of grating periods in the two CC DFB regions increases, the SP frequency increases from very low frequency to the THz region. In the case of a mode which is not located in the stop band of the other DFB region, the mode propagates into the other DFB region without a high reflection, so that output powers emitted in a multi-section CC DFB laser have high modulation indexes due to the large interaction between the two modes.

• 한국ITS학회:학술대회논문집
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• 2008.11a
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• pp.625-628
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• 2008