• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.3
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• pp.270-277
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• 2013

In this paper, we propose a wideband ridge SIW(Ridge Substrate Integrated Waveguide)-to-SIW(Substrate Integrated Waveguide) transition. The proposed transition structure is designed to acquire a wide bandwidth by inserting through via holes at the regular interval for an impedance matching and an E-field mode matching method. The measurement results show a fractional bandwidth is 29.1 % at 20 dB return loss from the center frequency(11 GHz). The maximum insertion loss is 0.49 dB from 9.21 GHz to 12.41 GHz.

• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.2
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• pp.301-306
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• 2015

An ultra-compact and wideband low noise amplifier (LNA) in a quad flat non-leaded (QFN) package is presented. The LNA monolithic microwave integrated circuit (MMIC) is implemented in a $0.25{\mu}m$ GaN IC technology on a Silicon Carbide (SiC) substrate provided by Triquint. A source degeneration inductor and a gate inductor are used to obtain the noise and input matching simultaneously. The resistive feedback and inductor peaking techniques are employed to achieve a wideband characteristic. The LNA chip is mounted in the $3{\times}3-mm^2$ QFN package and measured. The supply voltages for the first and second stages are 14 V and 7 V, respectively, and the total current is 70 mA. The highest gain is 13.5 dB around the mid-band, and -3 dB frequencies are observed at 0.7 and 12 GHz. Input and output return losses ($S_{11}$ and $S_{22}$) of less than -10 dB measure from 1 to 12 GHz; there is an absolute bandwidth of 11 GHz and a fractional bandwidth of 169%. Across the bandwidth, the noise figures (NFs) are between 3 and 5 dB, while the output-referred third-order intercept points (OIP3s) are between 26 and 28 dBm. The overall chip size with all bonding pads is $1.1{\times}0.9mm^2$. To the best of our knowledge, this LNA shows the best figure-of-merit (FoM) compared with other published GaN LNAs with the same gate length.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.5
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• pp.944-949
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• 2015

This study proposed a patch antenna with a MIMO structure which is applicable for wireless communication equipment by combining a single patch antenna with a multi port. The proposed MIMO patch antenna was designed through the TRF-45 substrate with a relative permittivity of 4.5, loss tangent equal to 0.0035 and dielectric high of 1.6 mm, and the center frequency of the antenna was 2.45 GHz in the ISM (Industrial Scientific and Medical) band. The proposed MIMO patch antenna had a 500 MHz bandwidth from 2.16 ~ 2.66 GHz and 24.1% fractional bandwidth. The return loss and VSWR were -62.05 dB, 1.01 at the ISM bandwidth of 2.45 GHz. The Wibro band of 2.3 GHz was -17.43 dB, 1.33, the WiFi band of 2.4 GHz was -31.89 dB, 1.05, and the WiMax band of 2.5 GHz was -36.47 dB, 1.03. The radiation patterns included in the bandwidth were directional, and the WiBro band of 2.3 GHzhad a gain of 4.22 dBi, the WiFi band of 2.4 GHz had a gain of 4.12 dBi, the ISM band of 2.45 GHz had a gain of 4.06dBi, and the WiMax band of 2.5 GHz had a gain of 3.9 6dBi.

• ETRI Journal
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• v.41 no.2
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• pp.167-175
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• 2019

A wideband dual-polarized antenna coupling cross resonator is proposed for LTE700/GSM850/GSM900 base stations. An additional resonance is introduced to obtain strong coupling between the dipole and resonator. Moreover, the input impedance of the proposed antenna is steadily close to $50{\Omega}$, which results in better impedance matching. Therefore, a wide bandwidth can be achieved with multiresonance. A prototype is fabricated to verify the proposed design. The measured results show that the antenna has a fractional bandwidth of 35.7% from 690 MHz to 990 MHz for ${\mid}S_{11}{\mid}$ < -15 dB. Stable radiation patterns as well as gain are also obtained over the entire operating band. Moreover, a five-element antenna array with an electrical downtilt of $0^{\circ}$to $14^{\circ}$ is developed for modern base station applications. Measurement shows that a wide impedance bandwidth of 34.7% (690 MHz to 980 MHz), stable HPBW (3-dB beamwidth) of $65{\pm}5^{\circ}$, and high gain of $13.8{\pm}0.6dBi$ are achieved with electrical downtilts of $0^{\circ}$, $7^{\circ}$, and $14^{\circ}$.

• Journal of electromagnetic engineering and science
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• v.13 no.2
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• pp.93-103
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• 2013

This paper presented a novel approach for the design of a tunable dual-band bandpass filter (BPF) with independently tunable passband center frequencies and bandwidths. The newly proposed dual-band filter principally comprised two dual-mode single band filters using common input/output lines. Each single BPF was realized using a varactor-loaded transmission line resonator. To suppress the harmonics over a broad bandwidth, a defected ground structure was used at the input/output feeding lines. From the experimental results, it was found that the proposed filter exhibited the first passband center frequency tunable range from 1.48 to 1.8 GHz with a 3-dB fractional bandwidth (FBW) variation from 5.76% to 8.55%, while the second passband center's frequency tunable range was 2.40 to 2.88 GHz with a 3-dB FBW variation from 8.28% to 12.42%. The measured results of the proposed filters showed a rejection level of 19 dB up to more than 10 times the highest center frequency of the first passband.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.5
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• pp.23-31
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• 2001

A very compact narrowband high-temperature superconducting microstrip filter using multiple coupled line resonators is designed and fabricated to effectively use the limited space of the wafer. The fabricated 12 pole filter has a center frequency of 1.79 GHz and a 3dB bandwidth of 7.63 MHz(0.43% fractional bandwidth). The filter also shows sharp skirt characteristics of 71 dB/MHz and 41dB/MHz blow and above the passband, respectively, and has an insertion loss of less than 0.5dB and a return loss of more than 15dB in the passband.

• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.3
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• pp.342-348
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• 2015

This paper presents a 1.9-GHz digital ${{\Delta}{\Sigma}}$ fractional-N PLL with a finite impulse response (FIR) filter embedded for noise suppression. The proposed digital implementation of FIR provides a simple method of increasing the number of taps without complicated calculation for gain matching. This work demonstrates 32 tap FIR filtering for the first time and successfully filtered the in-band phase noise generated from delta-sigma modulator (DSM). Design considerations are also addressed to find the optimum number of taps when the resolution of time-to-digital converter (TDC) is given. The PLL, fabricated in $0.11-{\mu}m$ CMOS, achieves a well-regulated in-band phase noise of less than -100 dBc/Hz for the entire range inside the bandwidth of 3 MHz. Compared with the conventional dual-modulus division, the proposed PLL shows an overall noise suppression of about 15dB both at in-band and out-of-band region.

• The KIPS Transactions:PartC
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• v.11C no.3
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• pp.395-400
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• 2004

Being aware of growing needs for wireless communication led to the development of UWB systems, this study proposed an impulse for single band UWB systems which does not count a carrier; analyzed the characteristics and the problems of pulses suggested by the existing poise of the Un system; finally, proposed TDMG(Time Delay Multiple Gaussian) pulse that generates signals of UWB without attenuation of pulse width. The hardware structure of the TDMC pulse for the single band UWB system was modelled after describing the pulse in a mathematical method in an attempt to compare with performances of the existing pulses through computer simulation. The outcome of the test unveiled the fact that each center frequency of the TDMG pulse rose approximately 1GHz, and also each l0dB fractional bandwidth of the TDMG pulse was widened over 1GHz. In the case of derivative, center frequencies of the TDMG pulse rose over 1GHz each. As a consequence, the TDMG pulse appeared to have better quality frequency, satisfying the characteristics of spectrum and the band of frequency recommended by the FCC and decreasing interference with other wireless communication systems.

• Journal of Electrical Engineering and Technology
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• v.13 no.2
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• pp.858-867
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• 2018

Analytical modeling equations are proposed for the conventional and modified three-section branch-line couplers. The analytical equations are explicit and capable of determining the characteristic impedance of each branch line for the coupler at desired coupling level as well as the suitability of broadband S-parameters analysis. In addition, a bandwidth extension and miniaturization of three-section branch-line coupler using slow-wave and meandering line structures were designed. The modified coupler, which is able to operate within frequencies from 1.5 to 3.32 GHz has been fabricated, tested and compared. A bandwidth extension of 600 MHz and 53% reduced size of the modified coupler have been achieved compared to a conventional coupler. The modified coupler has roughly insertion loss and coupling of -4 dB and -3.2 dB, while the isolation and return loss, respectively less than -14 dB with fractional bandwidth of 77 %, as well as phase imbalances less than $2^{\circ}$ over the operating bandwidth. Overall, the derived analytical model, simulation and measurement results demonstrated a good agreement.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.3
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• pp.68-73
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• 2011

In this paper, a compact-narrow open stub band-pass filter with parasitic-signal of low frequency range and second harmonics rejected using the parallel coupled line and FLCLM(Frquency Locked Controlled Length Method) is proposed. The characteristic of the parallel coupled line can be rejection for parasitic-signal of low frequency range and second harmonics. In last filter of experimental results show that insertion loss is 1.2 dB and return loss is 14.8 dB, and the fractional bandwidth is 10 % at the center frequency of 5.8 GHz. In additional, the rejection for parasitic-signal of low frequency range and second harmonics are 28.9 dB and 28.8 dB, respectively.