• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.4
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• pp.798-805
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• 2017

This paper presents a low profile multi circular ring with different radius, patch antenna with modified feed line and slotted ground. The size of the antenna is $15{\times}12mm^2$, having electrical dimensions of $0.14{\lambda}{\times}0.12{\lambda}$ (at lower initial frequency) and footprints of $180mm^2$. The proposed antenna covers 3.1 to 12.3 GHz, reflection coefficient up to -38 dB with Bandwidth ratio of 4.13:1 and fractional Bandwidth of 122%. Bandwidth dimension ratio has been calculated (which is 6246) as a proof for compact size. Thin slots introduced on the feed line provide good impedance matching for whole frequency band. Numerical simulations of the proposed antenna are reported in terms of reflection coefficient ${\leq}-10dB$, vswr 2:1, radiation pattern and group delay (ns). The proposed antenna has advantage of very small size along with better impedance match that provides a practical approach to realize it for BW enhancement and UWB applications.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.2
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• pp.152-159
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• 2019

In general, a Doppler radar can measure only the velocity of a moving target. To measure the distance of a moving target, it is necessary to use a frequency-modulated continuous wave or pulse radar. However, the latter are very complex in terms of both hardware as well as signal processing. Moreover, the requirement of wide bandwidth necessitates the use of millimeter-wave frequency bands of 24 GHz and 77 GHz. Recently, a new kind of Doppler radar using multitone frequency has been studied to sense the distance of moving targets in addition to their speed. In this study, we show that distance sensing of moving targets is possible by adjusting only the frequency of a 2.4 GHz Doppler radar with low cost phase lock loop. In particular, we show that distance can be sensed using only alternating current information without direct current offset information. The proposed technology satisfies the Korean local standard for low power radio equipment for moving target identification in the 2.4 GHz frequency band, and enables multiple long-range sensing and radio-frequency identification applications.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.6
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• pp.60-67
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• 2008

A low-power 2.4GHz fractional-N frequency synthesizer has been designed for 2.4GHz ISM band applications such as Bluetooth, Zigbee, and WLAN. To achieve low-power characteristic, the design has been focused on the power optimization of power-hungry blocks such as VCO, prescaler, and ${\Sigma}-{\Delta}$ modulator. An NP-core type VCO is adopted to optimize both phase noise and power consumption. Dynamic D-F/Fs with no static DC current are employed in designing the low-power prescaler circuit. The ${\Sigma}-{\Delta}$ modulator is designed using a modulus mapping circuit for reducing hardware complexity and power consumption. The designed frequency synthesizer which was fabricated using a $0.18{\mu}m$ CMOS process consumes 7.9mA from a single 1.8V supply voltage. The experimental results show that a phase noise of -118dBc/Hz at 1MHz offset, the reference spur of -70dBc at 25MHz offset, and the channel switching time of $15{\mu}s$ over 25MHz transition have been achieved. The designed chip occupies an area of $1.16mm^2$ including pads where the core area is only $0.64mm^2$.

• KIEE International Transactions on Electrophysics and Applications
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• v.4C no.4
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• pp.165-169
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• 2004

This paper reports a miniaturized conductor-backed CPW (CBCPW) bandpass filter based on a thin film polyimide layer coated on CMOS-grade silicon. With a 20 ${\mu}{\textrm}{m}$-thick polyimide interface layer and back metallization on the CMOS-grade silicon, the interaction of electromagnetic fields with the lossy silicon substrate has been isolated, and as a result a low-loss and low-dispersive CBCPW line has been obtained. Measured attenuation constant at 20 GHz is below 1.2 ㏈/cm, which is compatible with the CPW on GaAs. In addition, by using the proposed CBCPW geometry, miniaturized BPF for Ku band application is designed and its measured frequency response shows excellent agreement with the predicted value with validating the performances of the proposed CBCPW geometry for RFIC interconnects and filter applications.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.5
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• pp.444-449
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• 2009

This paper presents the design of a dual band branch line hybrid coupler(BLHC) with different power division ratios at two bands. In the proposed design, transmission lines of the BLHC are transformed to $\pi$-type equivalent circuits which represent different impedances and $\lambda/4$ electrical length at two frequency bands. In order to verify the proposed method, a dual band coupler with different power division ratios is designed for 0.9 GHz and 2 GHz applications. The desired power division ratios are 1:1 and 1:3 at the two operating frequency bands. The measured results show excellent performance with an insertion loss of less than 0.33 dB, a return loss of less than -18.07 dB, and good isolation characteristics.

• ETRI Journal
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• v.32 no.1
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• pp.112-119
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• 2010

We present a useful design for a free access mat which supports two frequency bands of 2.4 GHz and 5 GHz. The free access mat is a sheet-shaped waveguide which consists of a tightly coupled double-layered microstrip resonator array. It provides easy access for devices in short-range wireless communications. Interference is a common problem with conventional applications which use free space transmission. Our proposed wireless access system uses a subsidiary waveguide, the free access mat. Wireless devices are proximately coupled to the free access mat through which the coupled electromagnetic (EM) wave transmits. The arrival domain of the EM wave of an application is therefore limited to an area close to the free access mat. Wireless devices can be coupled to the free access mat at an arbitrary position without contact. We previously presented a free access mat for a single frequency band. This paper presents a free access mat for the two frequency bands of 2.4 GHz and 5 GHz. The free access mat uses a ring patch resonator array which is easily excited by typical antennas and is resistant to interference. These characteristics are demonstrated by numerical simulation and confirmed by experiment.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.11
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• pp.2697-2702
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• 2014

In this paper, we demonstrated a Ku-band 2W MMIC power amplifier for satellite communication applications. The device technology used relies on $0.25{\mu}m$ GaAs pseudomorphic high electron mobility transistor (PHEMT) of Wireless Information Networking (WIN) Semiconductor foundry. The 2W MMIC power amplifier has gain of over 29 dB and saturation output power of over 33.4 dBm in the frequency range of 13.75 ~ 14.5 GHz. Power added efficiency (PAE) is a 29 %. To our knowledge, this is the highest power added efficiency reported for any commercial GaAs-based 2W MMIC power amplifier in the Ku-band.

• Journal of Broadcast Engineering
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• v.18 no.6
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• pp.911-918
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• 2013

The proposed print antenna using Finite Difference Time Domain(FDTD) method is analyzed in this paper. A low radiation resistance and an ultra-wide band of this antenna are also presented. The propagation process of the reflected wave and the electric field distribution in the time domain are calculated in respectively. The antenna parameters are optimized for the maximum band width, return loss, input impedance, and radiation pattern in the frequency domain using Fourier transforming. The experimental bandwidth of the antenna is 1.85GHz~6.35GHz for the VSWR less than or equal to 2.0. The measured results are relatively in good agreement with the FDTD results. The proposed antenna can be applied to various applications such as UWB, broadcasting-network system.

• KIEE International Transactions on Electrophysics and Applications
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• v.5C no.4
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• pp.176-179
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• 2005

The increasing demand for high density packaging technologies and the evolution to mixed digital and analogue devices has been the con-set of increasing research in thin film multi-layer technologies such as the passive components integration technology. In this paper, Cu and TaO thin film with RF sputtering was deposited for spiral inductor and MOM capacitor on the $SiO_2$/Si(100) substrate. MOM capacitor and spiral inductor were fabricated for L-C band pass filter by sputtering and lift-off. We are analyzed and designed thin films L-C passive components for band pass filter at 900 MHz and 1.8 GHz, important devices for mobile communication system. Based on the high-Q values of passive components, MOM capacitor and spiral inductors for L-C band pass filter, a low insertion loss of L-C passive components can be realized with a minimized chip area. The insertion loss was 3 dB for a 1.8 GHz filter, and 5 dB for a 900 MHz filter. This paper also discusses a analysis and practical design to thin-film L-C band pass filter.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.1
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• pp.43-46
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• 2018

This paper has designed a wideband bandpass filter (WBSF : Wide Band Stop Filter) using a stepped impedance resonator (SIR : Stepped Impedance Resonator) with improved performance and improved hairpin coupling structure. The SIR WBSF is small in size and has the advantage of having excellent bandstop characteristics. The designed BSF has a structure in which a quadrangular shaped hairpin of a / 4 length is arranged symmetrically on the upper and lower sides of the input and output transmission lines. The input and output terminals were terminated at 50 ohms for system applications. The center frequency of the SIR WBSF is 6.3 GHz, which is the second harmonic of 3.15 GHz. The designed filter has a 3dB bandwidth of 2.9 GHz and a transmission coefficient ($S_{21}$) of 33.2 dB. The reflection coefficient ($S_{11}$) at the center frequency is 0.106 dB. The application field is used for fixed microwave relay stations, fixed satellite and earth stations, and fixed satellite communications. The overall size is $20mm{\times}10mm$.