• Proceedings of the KIEE Conference
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• 1987.11a
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• pp.377-382
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• 1987

To obtain a high resolution microwave images, back scattering microwave fields from one, two, four poles on a rotating object is measured. A computation algorithm to reconstruct these poles images from measured data is programed. The program is tested for these poles on a rotating object for different frequency intervals in the X-Band. The more frequency data yield the reduction of side lobe level. The reconstructed image for the two pole objects having the diameter of 1cm and separated by 1 lamda, 2 lamda (lamda-3.75 cm) from the measured data is shown. And, the image of two objects having the different reflectivity coefficient from the measured data is also shown and it assumes that this reconstructing algorithm from the measured angular spectrum provides quite accurate images.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.1
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• pp.80-86
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• 2010

This paper describes the development result of S-band Transmitter of STSAT-3 by satellite research center(SaTReC), KAIST. STSAT-3 has two kinds of communication channels, S- band for Telemetry & Command and X-band for mission payload. S-band Transmiiter(STX) consist of modulator, frequency synthesizer, power amp and DC/DC converter. The modulation scheme of STX is FSK(Frequency Shift Keying). The interface between spacecraft OBC and STX is RS-422. The STX is based on modular design. The RF output power of STX is 1.5W(31.7dBm) and BER of STX is under 1E-5. The Test of STX is completed successfully such as functional Test and environmental(vibration, thermal vacuum) Test.

• Journal of Advanced Navigation Technology
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• v.22 no.1
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• pp.31-36
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• 2018

In this paper, we designed and implemented an ultra wideband(UWB) antenna with band rejection characteristics. The proposed antenna consists of a planar radiation patch with slots and ground planes on both sides. Due to the slots in the radiation patch, the antenna shows band rejection characteristics. U-type slot contributes for wireless local area network(WLAN, 5.15~5.825 GHz) band rejection and n-type slot contributes for X-Band(7.25~8.395 GHz) band rejection. To make voltage standing wave ratio(VSWR) less than 2.0 for UWB frequency band except rejection bands, the shapes of planar radiation patch and ground plane was modified. The Ansoft 's high frequency structure simulator(HFSS) was used for the design process and simulations of the proposed antenna. The simulated antenna showed VSWR less than 2.0 for all UWB band excepts for dual rejection bands of 5.15 ~ 5.94 GHz and 7.02 ~ 8.45 GHz. And measured VSWR for the implemented antenna is less than 2.0 for all UWB band of 3.10~10.60 GHz excluding dual rejection bands of 5.12~5.95 GHz and 7.20~8.58 GHz.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.380-381
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• 2006

A technique to control the operating frequency of microstrip antenna by using the X-cut quartz substrate has been investigated experimentally and theoretically. We consider 6, 8 and 10 GHz resonance frequency in three dimensional quartz plates. Equation of linear piezoelectricity are solved for the thickness-shear approximation of X-cut quartz plates. At X-band frequencies, the microstrip antenna was voltage-controllable using the dc electric field dependence of the piezoelectric constant of X-cut quartz. This work demonstrates advantageous application for X-cut quartz plate in microstrip antenna substrates.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.2
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• pp.152-158
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• 2004

A low phase noise frequency synthesizer at X-Band which employs the subharmonic injection locking was designed and tested. The designed frequency synthesizer consists of a 1.75 GHz master oscillator - which also operates as a harmonic generator - and a 10.5 GHz slave oscillator. A 1.75 GHz master oscillator based on PLL technique used two transistors - one constitutes the active part of VCO and the other operates as a buffer amplifier as well as harmonic generator. The first stage operates a fixed locked oscillator and using the BJT transistor whose cutoff frequency is 45 GHz, the second stage is designed, operating as a harmonic generator. The 6th harmonic which is produced from the harmonic generator is injected into the following slave oscillator which also behaves as an amplifier having about 45 dB gain. The realized frequency synthesizer has a 7.4 V/49 mA, -0.5 V/4 mA of the low DC power consumption, 4.53 dBm of output power, and a phase noise of -95.09 dBc/Hz and -108.90 dBc/Hz at the 10 kHz and 100 kHz offset frequency, respectively.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.852-854
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• 2015

In this letter, we designed and fabricated the paper-based ring-type frequency selective surface(FSSs) using inkjet printing method for practicable building wall applications to enhancement of the indoor communication environment, including low cost and ease of fabrication. Designed FSS has the band-stop characteristics at X-band, stable angle of incidence and wide bandwidth. Comparisons between measured and simulated results showed the good agreements.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.5
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• pp.943-948
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• 2018

In this paper, SSPA Module for X-band radar was designed and fabricated by using GaN MMIC. For the purpose of configuring the high power SSPA module, the drive steamers are composed of 2-layers of GaN MMIC with considering Gain Loss. In addition, the power divider and power combiner used a 4way approach by designing a 4-stage power amplifier. The power divider has a loss of -3.0dB or more, and the I/O has a loss of -0.2dB in the power combiner and the phase difference between the ports are good at $2^{\circ}$ on average. The fabricated SSPA module got the measurement results that satisfy a Gain 48dB, P(sat)=88.3W(49.46 dBm), PAE=30.3% or more efficiency in condition of frequency range 9~10GHz. The fabricated X-Band SSPA module can be applied in RF performance improvement for SSPA module whit improvement of power divider/combiner.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.49 no.8
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• pp.41-46
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• 2012

A quadrature voltage controlled oscillator(QVCO) for X-band is presented in this paper. The QVCO has fabricated in Charted $0.13{\mu}m$ CMOS process. The QVCO consists of two cross-coupled differential VCO and two differential buffers. The QVCO is controlled by 4 bit of capacitor bank and control voltage of varactor. To have a linear quality factor of varactors, voltage biases of varactors are difference. The QVCO generates frequency tuning range from 6.591 GHz to 8.012 GHz. The phase noise is -101.04 dBc/Hz at 1MHz Offset when output frequency is 7.150 GHz. The supply voltage is 1.5 V and core current 6.5-8.5 mA.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.5
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• pp.860-867
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• 2009

In this paper, we designed the array antenna for FMCW radar in X - band frequency, and we chose stacked structure for improvement of narrow bandwidth. The array antenna is implemented on the circuit board which is relative permittivity 2.33 and the stacked patchs are designed on the circuit board which is relative permittivity 4.6. A Foam which has a similar permittivity of air is added to keep the particular gap between array antenna and the stacked patch. The result of array antenna has characteristics that a half-power beam width is $10.6^{\circ}$ and antenna gain is 18.70 dBi and bandwidth is 1.25GHz at the design frequency of 9GHz. The result of the array antenna with the stacked structure has that the half power beam width is $15.17^{\circ}$ and the antenna gain is 15.85dBi and bandwidth is 2GHz. It is needed to improve the antenna gain as keeping bandwidth in same level.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.12
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• pp.22-29
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• 2009

In this paper, we developed the 200-Watts SSPA(Solid State Power Amplifier) for the X-band pulse compression solid state radar. The developed X-band SSPA is consists of 3-stage CSA(Corporate Structured Amplifier) modules in pre-amplifier stage, driver-amplifier stage and main-power amplifier stage. The main-power amplifier stage of SSPA designed by balanced type using GaN HEMT with enough power and gain to generate power more than 200-Watts in X-band. The developed SSPA has performance with more than total gain 59dB and output power 200-Watts in condition of frequency range 9.2-9.6GHz, pulse period 1msec, pulse width 100usec and duty cycle 10%. The developed SSPA in this paper can apply to high quality solid state radar system with pulse compression technique.