• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.12
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• pp.1706-1711
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• 2013

This paper presents the filter of a resonator comprising a shorted open gap ring(SOGR) and interdigital lines. The proposed filter has the ultra wideband characteristic operating from 3 GHz to 10.5 GHz. In order to achieve the remarkable improvement in the size-reduction of the overall filter structure, only one cell of the SOGR with the inter-digital lines is adopted. It is shown that this filter has the size of $18mm{\times}15mm$ using a metamaterial, the fractional bandwidth over 100%, the insertion loss much less than 1dB, an acceptable return loss performance in the results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.9
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• pp.1050-1055
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• 2010

In this paper, the K band $3{\times}6$ array antenna having unequal input is presented. To control the input impedance of the patch antenna, the length of inset feed is adjusted. Also, the same current in each element is excited by Kirchhoff's law. The proposed unequal impedance array antenna is a nonuniform amplitude array. The bandwidth of the proposed unequal impedance array antenna is wider by 1.5 times than that of the equal array antenna. This broad bandwidth is thought to be due to multiple resonances of patches. The unequal impedance array antennas have fractional bandwidths of 5.07 % and gains of 18.32 dBi.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.10A
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• pp.847-852
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• 2003

Apertures and PBG(Photonic Band Gap) has been employed on the ground plane in the coupled line filter simultaneously. In order to observe the maximum bandwidth, we used the line gap 0.2mm which is can be made in our lab. Band-pass filter type is four-stage coupled strip line filter. Teflon has been used for the substrate ($\varepsilon$$\sub$r/=3.2). The center frequency and the bandwidth are 2.18GHz and 230MHz, respectively. The bandwidth is broaden from 230MHz to 310MHz (80Mhz, about 34.7%) by aperture effect and harmonic frequencies are suppressed to 20-30dB by PBG effect. So the harmonic frequencies have been suppressed by the PBG effect and the bandwidth are broaden by aperture effect.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.1
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• pp.76-80
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• 2011

This paper has proposed a 3~5 GHz low-power and wideband LNA(Low Noise Amplifier), which has been implemented in a 0.18-${\mu}m$ CMOS technology. The proposed LNA has basically the noise-cancelling topology to achieve a balun-function, wideband input matching, and relative low noise figure. In addition, it has utilized a 2nd-order LC-band-pass filter(BPF) as its output load to achieve higher power gain and lower noise figure with the lowest dc power consumption among previously reported works. The proposed amplifier consumes only 3.94 mA from a 1.8 V supply voltage. The simulation results show a power gain of more than +17 dB, a noise figure of less than +4 dB, and an input IP3 of -15.5 dBm.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.5
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• pp.249-254
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• 2014

In this paper, minimizing of a parabolic edge planar monopole antenna by scaling method is presented. With the aid of a matching step and discontinuous CPW, the antenna easily adjusts the impedance matching. We used an FR4 dielectric substrate with a dielectric constant of 4.4. The dimensions of the antenna are $26mm{\times}31mm{\times}1.6mm$. A return loss value of more than 10dB was found in the 2.37GHz to 10.52GHz (8.15GHz) range of the antenna fed by the discontinuous CPW. The radiation pattern is about the same as that of the dipole antenna at all frequencies. Configuration elements of the antenna except feed part were reduced into the same rate. So, the size of the antenna was decreased and a broadband property was maintained. Therefore, the self-complementary characteristic of the antenna was confirmed. While satisfying the UWB band, having the smallest size in the antenna miniaturized by scaling;when scale was 0.6. The dimensions of the antenna are $15.6mm{\times}18.6mm{\times}1.6mm$. The return loss was more than 10 dB of the measured result in the range of 3.07GHz to 12.59GHz (9.52GHz).

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.2
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• pp.136-142
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• 2010

In this paper, the microstrip antenna for penta-band service is proposed. It is designed for a wide band characteristic based on a monopole line combined with a triangular patch structure which has two slits. Total antenna size is $35\;mm{\times}20\;mm$ and it was fabricated on FR-4 substrate($\varepsilon_r=4.4$) which has $35\;mm{\times}75\;mm{\times}1\;mm$ size and a microstrip line with impedance 50 ohm is used. Experimental result shows the impedance bandwidth($VSWR{\leq}3$) of the proposed antenna operated within GSM/DCS/USPCS/UMTS/Bluetooth frequency band. The resonance frequency of the proposed antenna is 0.92, 1.97, 2.45 GHz and the average gain is -2.18, -0.66, -0.58 dBi. Also, the radiation efficiency is 60, 85, 87%. The fabricated antenna is satisfied with the aimed impedance bandwidth ($VSWR{\leq}3$) in GSM/DCS/ USPCS/UMTS/Bluetooth frequency band.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.2
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• pp.1-5
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• 2017

In this paper, we propose a wideband band-stop filter (BSF) in order to extend the stopband of the band-stop filter using a symmetric dual spurline and the coupled open stub. First, we know that the symmetric dual spurline structure is advantageous in widening the stopband, as compared to the asymmetric dual spurline structure. So we designed a band-stop filter that combines the electrically coupled open stub (ECOS) band-stop filter with a symmetric dual spurline. We can greatly extend the stopband, when it is combined with the dual spurline and electrically coupled open stub on a microstrip transmission line, without any size increment. The stopband of the proposed band-stop filter is extended by approximately 244% (rejection depth: -20 dB) compared with a band-stop filter without a dual spurline.

• Journal of electromagnetic engineering and science
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• v.8 no.3
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• pp.134-137
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• 2008

This paper proposes a novel quadrature VCO(QVCO) based on direct back-gate second harmonic coupling. The QVCO directly couples the current sources of the conventional LC VCOs through the back-gate instead of front-gate to generate quadrature signals. By the second harmonic injection locking, the two LC VCOs can generate quadrature signals without using on-chip transformer, or stability problem that is inherent in the direct front-gate second harmonic coupling. The proposed QVCO is implemented in $0.18{\mu}m$ CMOS technology operating at 2 GHz with 5.0 mA core current consumption from 1.8 V power supply. The measured phase noise of the proposed QVCO is - 63 dBc/Hz at 10 kHz offset, -95 dBc/Hz at 100 kHz offset, and -116 dBc/Hz at 1 MHz offset from the 2 GHz output frequency, respectively. The calculated figure of merit(FOM) is about -174 dBc/Hz at 1 MHz offset. The measured image band rejection is 46 dB which corresponds to the phase error of $0.6^{\circ}$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.4 s.119
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• pp.372-378
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• 2007

This paper presents an improvement of field uniformity in a reverberation chamber with QRDs(Quadratic Residue Diffuser) and also shows the optimal dimension of the QRDs. The QRD is designed for $1{\sim}3\;GHz$ frequency band and the FDTD(finite-Difference Time-Domain) method is used to analyze the field characteristics. At 2 GHz, the standard deviation of test volume in the reverberation chamber is the smallest when the QRD has $30{\sim}60\;%$ coverage of one side of the reverberation chamber and the field uniformity is worsened when the coverage of the QRD is either below 20 % or above 70 % of the area of the side wall. Particularly, the standard deviation of test volume in the reverberation chamber with 30 % coverage of QRD is improved by 1.53 dB compared to that of the reference chamber with no QRDs.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.1
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• pp.53-60
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• 2010

This paper presents a novel gain control system composed of a feedback circuit, Two stage Low Noise Amplifier (LNA) using 0.18 um CMOS technology for 5.2 GHz. The feedback circuit consists of the seven function blocks: peak detector, comparator, ADC, IVE(Initial Voltage Elimination) circuit, switch, storage, and current controller. We focus on detecting signal and designing storage circuit that store the previous state. The power consumption of the feedback circuit in the system can be reduced without sacrificing the gain by inserting the storage circuit. The adaptive front-end system with the feedback circuit exhibits 11.39~22.74 dB gain, and has excellent noise performance at high gain mode. Variable gain LNA consumes 5.68~6.75 mW from a 1.8 V supply voltage.