• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.9
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• pp.1014-1020
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• 2009

In this paper, a novel UWB(Ultra Wide-band) antenna with suppressed band of IEEE 802.11a($5.15{\sim}5.825\;GHz$) WLAN was designed and fabricated by using SRR(Split Ring Resonator) with band rejection property. MWS(Micro-wave Studio) of CST company was utilized in the design stage. The antenna was fabricated on a substrate, Rogers 4003, with the thickness of 0.8 mm and relative permittivity of 3.38. The measured result shows that the proposed antenna has a good return loss below -10 dB and group delay below 1nsec over UWB communication band($3.1{\sim}10.6\;GHz$) except WLAN band. It also shows the omni-directional radiation pattern.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.6
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• pp.8-12
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• 2008

A ring resonator based band-pass filter enabling enhanced sideband suppression was proposed and demonstrated. It is composed of a single-ring based band-pass section combined with a band-rejection section based on two different coupled rings. The sideband region of the transfer characteristics of the first band-pass filter section was selectively suppressed by means of the band-rejection section without causing any excessive insertion loss. As a result, the overall transfer characteristics of the proposed filter was unproved so that its sideband suppression was elevated to allow for sharper roll-off and narrower bandwidth. In this work, a conventional single-ring band-pass filter and a proposed filter including the band-rejection section were designed and fabricated. As for the achieved device performance, with the center frequency at about 4 GHz, the sideband suppression ratio was increased as much as 8 dB and the 3-dB bandwidth was reduced from 98 MHz to 48 MHz by about 51% with no remarkable excessive insertion loss as expected. And the quality factor of the device was increased by about 105%.

• ETRI Journal
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• v.36 no.3
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• pp.510-513
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• 2014

A Q-band pHEMT image-rejection low-noise amplifier (IR-LNA) is presented using inter-stage tunable resonators. The inter-stage L-C resonators can maximize an image rejection by functioning as inter-stage matching circuits at an operating frequency ($F_{OP}$) and short circuits at an image frequency ($F_{IM}$). In addition, it also brings more wideband image rejection than conventional notch filters. Moreover, tunable varactors in L-C resonators not only compensate for the mismatch of an image frequency induced by the process variation or model error but can also change the image frequency according to a required RF frequency. The implemented pHEMT IR-LNA shows 54.3 dB maximum image rejection ratio (IRR). By changing the varactor bias, the image frequency shifts from 27 GHz to 37 GHz with over 40 dB IRR, a 19.1 dB to 17.6 dB peak gain, and 3.2 dB to 4.3 dB noise figure. To the best of the authors' knowledge, it shows the highest IRR and $F_{IM}/F_{OP}$ of the reported millimeter/quasi-millimeter wave IR-LNAs.

• Journal of electromagnetic engineering and science
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• v.11 no.3
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• pp.186-191
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• 2011

This paper presents a simple and effective method for improving stopband rejection characteristics of previously studied dual-band filters. Small electric couplings were applied to the symmetrically positioned shunt resonators, which divided each transmission zero into two transmission zeros without any effect on passbands. We were able to achieve improved stopband rejection characteristics by these additional transmission zeros. For the filter application, we designed a dual-band filter with improved stopband characteristics using microstrip quasi-lumped elements. The electric couplings that control the location of transmission zeros are controlled by the distance between symmetric open stubs of the filter. The filter was fabricated with a relative dielectric constant of 3.5 and a thickness of 0.76 mm. The fabricated filter has a small size ($14.6{\times}13.2{\times}0.76$ mm) and a low insertion loss when compared with conventional filters.

• ETRI Journal
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• v.33 no.6
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• pp.981-984
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• 2011

A novel lowpass filter with a very sharp transition band and wide stopband is proposed. The proposed filter is based on T-shaped patches which are etched in symmetrical structures and folded open stub. To obtain a wide stopband, we have used stub loaded semi-circle stepped-impedance structures. By designing the resonator with high inductance and capacitance, a very sharp transition band is achieved. The proposed filter has a 3-dB cutoff frequency at 2.37 GHz and a 40-dB rejection at 2.44 GHz. The stopband with an attenuation level better than -13.2 dB is up from 2.4 GHz to 16 GHz, and consequently we have reached the high and wide rejection in stopband with compact size. Good agreements between the simulated and the measured results are presented.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.5
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• pp.516-521
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• 2011

In this paper, an inverted-triangle patch UWB antenna with an uneven ground planes and an inverted T-slot for 5 GHz WLAN band rejection is presented. The operating bandwidth of the proposed antenna fed with the CPW line is expanded from 3.1 GHz to 10.6 GHz for about -10 dB return loss using three angular parameters correlated to the main patch and the ground plane. The fabricated antenna on Taconic RF-60A substrate with 6.16 relative dielectric constant and 0.64 mm thickness has a main antenna patch size of 36 mm${\times}$19.5 mm. The measured results show return losses of about -10 dB and nearly omni-directional radiation patterns. The proposed UWB antenna has advantages of easily adjustable impedance characteristics by the three angular parameters and easily accomplishable band rejection characteristics by the inverted T-slot.

• Transactions on Electrical and Electronic Materials
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• v.7 no.4
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• pp.196-203
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• 2006

An air-gap type FBAR was designed using Leach equivalent model for analyzing a vertical structure of the FBAR. For the top electrode, Pt, and the bottom electrode, Au, of $1.2{\mu}m$ thickness and the piezoelectric of 0.8,urn thickness, the resonance and anti-resonance occurred at 2.401 GHz and 2.460 GHz, respectively. $S_{11}$ was increased and $S_{21}$ was decreased as the resonance area of FBAR was widened. We observed the characteristics of insertion loss, bandwidth and out-of-band rejection of ladder-type FBAR BPF by changing resonance areas of series and shunt resonators and by adding stages. As the resonance area of series resonator was increased, insertion loss was improved but out-of-band rejection was degraded. And as the resonance area of shunt resonator was increased, insertion loss was degraded a little but out-of-band rejection was improved even without adding stages. We, also, changed the shape of the resonance area from square shape to rectangle shape to examine the effects of the resonator shape on the characteristics of the BPF. The best performances were observed when the sizes of series and shunt resonator are $150{\mu}m{\times}l50{\mu}m\;and\;5{\mu}m{\times}50{\mu}m$, respectively. Out-of-band rejection was improved about 10dB and bandwidth was broadened from 30MHz to 100MHz utilizing inductor tuning on $2{\times}2\;and\; 4{\times}2$ ladder-type BPFs.

• Journal of IKEEE
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• v.12 no.4
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• pp.225-233
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• 2008

This paper presents a compact, low insertion loss, sharp rejection and wide band microstrip band pass filter that is composed rectangular loop resonator and step-impedance-open-stub(SIOS) for wireless data communication. The SIOS can be reduce length about 30% more than general 0.25${\lambda}$ stub. And stubs can have the advantage of tuning impedance magnitude. In order to demonstrate agrement of this paper prove, the optimized wide band pass filters are realized and experimented. A transmission line model used to calculate the frequency response of the new filters shows good agreement with measurements. The filter with perturbation stubs has four poles at rejection band, the poles are excited 3.610GHz, 4.265GHz at low frequency band, 8.494GHz, 9.056GHz at high frequency band. And the filter has 3dB fractional bandwidth of 57%(3.695GHz), an insertion loss of better than 0.37dB from 4.549GHz to 8.244GHz, and two rejection of greater than 30dB within 237MHz(4.312GHz${\sim}$ 4.549GHz) at low frequency band, 234MHz(8.244GHz-8.491GHz) at high frequency band.

• 한국정보통신설비학회:학술대회논문집
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• 2006.08a
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• pp.208-211
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• 2006

In this paper, a tunable image rejection filter using two varactors is developed for mobile convergence. The filter is fabricated on a 0.25um substrate. ESD Pad is embedded to prevent damage caused by electrostatic discharge(ESD). Bias voltages are at WCDMA(2.1GHz). WiBro(2.3GHz), and WLAN(2.45) are 0.5V, 0.95V and 1.8V respectively. And the image rejection rations are more than 28dB at each band and insertion losses are less than 2dB at each band.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.1
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• pp.245-252
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• 2018

In this paper, the dual band circular polarization patch antenna was designed by using band rejection characteristics of CSRR structure for geostationary satellites. A quadrangular CSRR structure was etched on the ground at the rear of the patch antenna's feed to obtain band rejection characteristics in between the receiving frequency band(1525~1559MHz) and transmission band(1626.5~1660.5MHz), and the corner of the patch antenna was truncated to enable circular polarization. It was confirmed that the resonant frequency of the patch antenna differs according to the size anc location of the CSRR and cirular polarization characteristics with simulation and measurement results. Measurement results shows the gain of about 0.2dB and 1.5dB in the TX and RX band.