• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.4
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• pp.387-392
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• 2014

In this paper, the broadband antenna design, which can be applied to USB Dongle, supporting Wibro(2.3~2.4 GHz), Wi-Fi(2.4~2.5 GHz) and LTE7(2.5~2.7 GHz) is proposed technique. The proposed antenna was designed similar to PIFA type antennas. Reactive elements were used to control the input impedance and wideband characteristics were achieved by controlling coupling between the feed structure and the radiator. As a result, the antenna printed on FR-4 PCB(${\epsilon}_r$ =4.4, tan ${\delta}$=0.02) occupying an area of $15{\times}5mm^2$ was able to achieve bandwidth of 1 GHz from 2.1 to 3.1 GHz under VSWR=2. Measured return loss characteristics, bandwidth and radiation patterns were in good agreement with the simulated results.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.1
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• pp.33-38
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• 2017

In this paper, a 4-channel common-cathode VCSEL diode driver array with 3.125 Gb/s per channel operation speed is realized. In order to achieve faster speed of the switching main driver with relatively large transistors, the transmitter array chip consists of a pre-amplifier with active inductor stage and also an input buffer with modified equalizer, which leads to bandwidth extension and reduced current consumption. The utilized VCSEL diode provides inherently 2.2 V forward bias voltage, $50{\Omega}$ resistance, and 850 fF capacitance. In addition, the main driver based upon current steering technique is designed, so that two individual current sources can provide bias currents of 3.0 mA and modulation currents of 3.3 mA to VCSEL diodes. The proposed 4-channel VCSEL driver array has been implemented by using a $0.11-{\mu}m$ CMOS technology, and the chip core occupies the area of $0.15{\times}0.18{\mu}m^2$ and dissipates 22.3 mW per channel.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.5
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• pp.513-520
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• 2003

In this paper, a novel design concept of frequency doubler using feedforward technique and DGS microstrip line is proposed. The feedforward loop plays a role of fundamental frequency suppression and DGS microstrip line suppresses over the 3rd order harmonic components. By using this new concept, the high suppression for the undesired signals could be achieved easily. The proposed technique is experimentally demonstrated in 1.87 GHz-to-3.74 GHz frequency doubler. The output power of -3 dBm at the frequency of 3.74 GHz(2f$\_$0/) is measured with 42.9 dB suppression of the fundamental frequency signal(f$\_$0/), 20.2 dB suppression of the 3rd harmonic signal(3f$\_$0/) and B9.7 dB suppression of the 4th harmonic signal(4f$\_$0/). The conversion loss of -2.34 dB ∼ -5.8 dB at the bandwidth of 100 MHz, the phase noise of -97.51 dB/Hz(＠10 kHz) were measured.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.3
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• pp.151-158
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• 2018

This paper proposes a new design method for narrow bandpass filters using two cascaded hairpin step impedance resonators (SIRs) with wideband harmonic suppression. The proposed bandpass filter utilizes a suspended strip line (SSL) to maximize the characteristic impedance ratio, thereby maximizing the harmonic suppression bandwidth. As an example of the proposed design method, the SSL bandpass filter with a center frequency of $f_0=1.4GHz$ and fractional bandwidth of 5 % was implemented, and proved to suppress harmonics up to $7.5f_0$ with a passband insertion loss of approximately -0.9 dB. This result implies that the proposed SSL narrow bandpass filter (NBPF) can suppress the harmonic bandwidth more than two times as compared with the filter design on a microstrip line (MSL).

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.6
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• pp.91-98
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• 2013

Magnetic sensor chip for measuring bio-magnetism is implemented in $0.18{\mu}m$ CMOS technology. The magnetic sensor chip consists of a small-sized high inductance coil sensor and an instrumentation amplifier (IA). High inductance coil sensor with suitable sensitivity and bandwidth for measurement of bio-magnetic signal is designed using electromagnetic field simulation. Low gm operational transconductance amplifier (OTA) using transconductance reduction techniques is designed for on-chip solution. Output signal sensitivity of magnetic sensor chip is $3.25fT/{\mu}V$ and reference noise of 21.1fT/${\surd}$Hz. Proposed IA is designed along with band pass filters(BPF) to reduce magnetic signal noise by using current feedback techniques. Proposed IA achieves a common mode rejection ratio of 117.5dB while the input noise referred is kept below $0.87{\mu}V$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.9
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• pp.826-834
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• 2004

In this paper, we fabricated thick film monopole antennas using Bi$_2$O$_3$-doped BaTi$_4$$O_{9}$ ceramics for small size and broadband intenna. In the result, the high permittivity was fixed and the quality factor was also significantly decreased by the formation of secondary phase of Bi$_4$Ti$_3$O$_{12}$ repleced by addtion Bi. The antenna property influenced by the quality value more than the permittivity. The bandwidth of antenna was increased to 33 %. On the other hand, the gain was reduced to -4.3 dBi. Also radiation patterns were showed low dBi value by increasing of dielectric loss. Specially, Measured x-y plane radiation patterns was distorted as the dispersion of wavelength and high permittivity difference. But the result is showed execellent bandwidth because of low quality value in all formation range.nge.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.4
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• pp.38-42
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• 2010

In this paper, a design method of the compact narrow band filter on the microstrip board is proposed using slot-type split spiral resonators. The design technique of this filter is based on cascading filter stages consisting of the combination of slot-type split spiral resonators, capacitive gaps between patches, and inductive grounded stubs with the meander configuration. By these means, it was possible to get the nearly symmetric frequency responses, adjustable bandwidths, compact sizes. And also excellent characteristic of the out-of-band rejection is achieved in contrast to the conventional filter design technique. The measured insertion loss shows good results about -3.47dB at the center frequency($f_0$=1GHz) and passband return loss is less than -12.62dB. The 3dB fractional bandwidth(FBW) is approximately 7.3%. The results of the frequency response measured on the fabricated band pass filter substrate show satisfactory agreement with the simulated frequency responses by the MWS(Microwave Studio) of CST in the region of interest.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.15 no.1
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• pp.21-28
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• 1990

In this paper, the effects of Intersymbol Interference(ISI) of Gaussian filtered minimum shift Keying (GMSK) with two-bit differential defection on the probability of error is analyzed theoretically in fast Rayleigh fading characterizing land mobile radio channels and a closed form for the probability of error is derived. Numerical results are presented for cased of interest, BT=0.25 to 0.4, taking fading rate $f_\rho$T as a parameter. It is shown that the probability of error taking the ISI of the only one adjacent bit into consideration is accurate enough to evaluate the performance of GMSK with two-bit differential detetion.

• Journal of Advanced Navigation Technology
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• v.17 no.6
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• pp.646-651
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• 2013

In this paper, a small inverted-F antenna with adjustable characteristics is proposed with use of lumped elements, capacitor and resistor. Capacitor is inserted between end of the antenna and ground for size reduction and tuning of resonant frequency. On the other hand, $0{\Omega}$ resistor is replaced as the short line connected to ground. The movement of short point due to use of $0{\Omega}$ resistor results in providing variation of input impedance. Therefore optimum characteristics can be obtained only by proper choice of capacitor and short point without redesign of it's geometry. In order to check the validity, the proposed antenna is designed and fabricated for 2.4 GHz frequency band, and then is applied to a product of Zigbee wireless remote controller. As a result, the size of applied antenna is $8.5{\times}4.5mm^2$ and it is observed that the measured bandwidth and antenna gain are 150 MHz and 2 dBi respectively without redesign of the antenna.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.2 s.117
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• pp.136-142
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• 2007

We present two effects of the case currents of a mobile phone on changing the radiation pattern of a PIFA and on enhancing the bandwidth of the monopole antenna. In order to change the radiation pattern, a modification of the ground plane is suggested to suppress the back radiation. The resulting gain is higher than that of a conventional PIFA by 0.5 dB. For enhancing the bandwidth, two parasitic metallic lines are added in the direction orthogonal to the monopole to induce double resonances. The impedance bandwidth of the proposed structure is 341 MHz, which is nearly twice of that of the conventional monopole.