• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.9
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• pp.853-861
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• 2009

In this paper, we propose the architecture of a multi-band receiver which can receive X-band, Ku-band, K-band and Ka-band signals. For implementing this architecture, we designed a wideband and high power VCO with a buffer stage. In order that a buffer does not affect the characteristic of a oscillation in steady state condition, output impedance of a oscillation part and input impedance of a buffer are orthogonally crossed. The fabricated VCO meets the performance parameter of the multi-band receiver which has a $14.00{\sim}15.20\;GHz$ bandwidth with respect to the tuning voltage, $0.0{\sim}8.0\;V$, and output power of $12{\sim}13\;dBm$.

• Journal of IKEEE
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• v.15 no.4
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• pp.299-304
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• 2011

In this paper, the circular polarized horn antenna composed of circular polarizer and impedance transformer is designed, and fabricated. For the circular polarizer, two types of the polarizer are designed and the electrical performance of them is compared; rectangular waveguide polarizer with $45^{\circ}$-inclined dielectric slab and oval shaped one. Straight type mode converter has a stepped impedance structure and plays a role of converting waveguide TE mode into coaxial TEM mode, and the proposed antenna is designed to directly connect with active components using the feed-through in the input port of the mode converter. Fabricated antenna has the wideband performance, VSWR<1.5 and Axial ratio < 1.0dB, ranging from 30.085 to 30.885 GHz, and the antenna gain is 6.7~7.0 dBi.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.7
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• pp.1218-1224
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• 2000

A half-height waveguide power combiner is designed and analyzed for Ka-band satellite application. The branch line directional coupler is utilized as a power combiner to achieve high port-to-port isolation and low insertion loss. The half height waveguide is adopted to reduce the volume and mass of a power combiner. In this paper a half height waveguide power combiner is designed and analyzed by FDTD and its performance is compared with that of a full-height waveguide power combiner. The designed half-height combiner having optimum order is manufactured and tested. The measurement shows that the designed half-height power combiner satisfies all the performance requirements (insertion loss less than 0.3 dB, reflection loss more than 20dB, port to port isolation more than 20 dB, and port to port phase difference within 5$^{\circ}$) in the satellite communication frequency band of 20.255 GHz to 21.255 GHz.

• Journal of Satellite, Information and Communications
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• v.3 no.1
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• pp.8-14
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• 2008

In this paper, we analyze throughput performance of MF-TDMA scheme and QS MC-DS/CDMA(quasi-synchronous MC-DS/CDMA) scheme based on scrambling on WH sequence and PPGC sequence in early frequency offset caused by high speed transfer terminal. QS MC-DS/CDMA scheme with scrambled WH sequence shows 5.7% higher throughput than MF-TDMA scheme and 8% higher throughput than QS MC-DS/CDMA with PPGC sequence in high speed transfer terminal environment such as maximum 1000Km/h speed with high frequency of Ka-band. Finally, we show that QS MC-DS/CDMA scheme with scrambled WH sequence is more efficient than traditional MF-TDMA scheme at the aspect of throughput in DVB-RCS system with Ka frequency band.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.8
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• pp.854-861
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• 2007

In this paper, a compact L-shaped shorted pin patch to be used at local oscillator port in radar detector is proposed. Shorted pin patch operates as short-open cavity while conventional patch operates as open-open cavity. Shorted pins are L-shaped to obtain quarter wave length and three-quarter wave length resonance for the fundamental(X-band) and $2^{nd}(3^{rd})$(K- and Ka-band) mode resonance frequency, respectively. Thus, the proposed patch can be compact. It is also possible to operate at triple band(X-, K-, Ka-band) with small return loss in radar detector, It is expected that shorted pin patch could improve radar detector sensitivity.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.6
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• pp.552-559
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• 2002

The EM(Engineering Model) LO(Local Oscillator) is designed for Ka-band satellite transponder. The VCO(Voltage Controlled Oscillator) is implemented using a high impedance inverter coupled with dielectric resonator to improve the phase noise performance out of the loop bandwidth. The phase of VCO is locked to that of a stable OCXO(Oven Controlled Crystal Oscillator) by using a SPD(Sampling Phase detector) to improve phase noise performance in the loop bandwidth. This LO exhibits the harmonic rejection characteristics above 43.83 dBc and requires 15 V and 160 mA. The phase noise characteristics are performed as -102.5 dBc/Hz at 10 KHz offset frequency and -104.0 dBc/Hz at 100 KHz offset frequency, respectively, with the output power of 13.50 dBm$\pm$0.33 dB over the temperature range of -20~+7$0^{\circ}C$.

• Journal of IKEEE
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• v.17 no.2
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• pp.135-139
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• 2013

This paper presents the 8-channel active module operated in Ka-band. The module is designed for the mobile satellite communication antenna systems, and the module structure has the merit to minimize the size and weight of the antenna systems by 30% compared with the conventional systems using the active module composed of single channel. This module was designed to be optimally operated by prohibiting the electrical interference among the individual channels. From the test results of the fabricated 8-channel active module, it can be confirmed that the maximum channel gain error is ${\pm}1.3dB$, the minimum channel output power is 21.5dBm, and the maximum gain variation by phase control is ${\pm}1.0dB$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.10
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• pp.926-934
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• 2016

In this paper, we designed a compact frequency synthesizer with multi-function for Ka-band seeker. DDS(Direct Digital Synthesizer) is applied to generate various waveform and to cover high-speed frequency sweep. In order to reduce size, waveform generator and frequency up-converter are integrated in one module. Proposed frequency synthesizer provides precise detection and tracking waveform for low and high speed targets. It is observed that fabricated synthesizer performs $0.45{\mu}sec$ frequency switching time and -93.69 dBc/Hz phase noise at offset 1 kHz. The size of the synthesizer is kept within 120 mm width, 120 mm length and 22 mm height.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.2
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• pp.173-176
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• 2019

In this study, a Ka-band waveguide rotary joint that can be applied to a millimeter-wave seeker is designed and fabricated. The proposed rotary joint maintains a low standing-wave ratio and low-loss characteristics, and has two rotary axes designed to enable azimuth and elevation rotation. The rotary joint is designed as a ridge-waveguide-type mode converter and a ${\lambda}/4$ choke structure to match the electromagnetic wave propagation mode between the spherical and circular waveguides. A performance test using a network analyzer and a high-power transmitter to assess vibration and shock were conducted. Results showed that the rotary joint had a very low standing-wave ratio of less than the maximum of 1.19:1 and an insertion loss of less than 0.80 dB at $F_C{\pm}500MHz$.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.6
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• pp.149-154
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• 2022

Due to high power capabilities and high linearity of GaN devices, GaN Low-Noise Amplifiers (LNAs) without a limiter can be implemented in order to improve noise figure and reduce chip area in radar receivers. In this paper, a GaN LNA is presented for Ka-band radar receivers. The designed LNA was realized in a 150-nm GaN HEMT process and measurement results show that the voltage gain of >23 dB and the noise figure of <6.5 dB including packaging loss in the target frequency range. Under the high-power stress test, measured gain and noise figure of the GaN LNA is degraded after the first stress test, but no more degradation is observed under multiple stress tests. Through post-stress noise and s-parameter measurements, we verified that the GaN LNA is resilient to pulsed input power of ~40 dBm.