• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.11A
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• pp.904-908
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• 2009

The PZT(lead, zirconium, titanium) based ceramics which, are reported to be ferroelectric materials have their important applications in the areas of surface acoustic waves (SAW), filters, infrared detectors, actuators, ferroelectric random acess memory, speakers, electronic switches etc. Moreover, these PZT materials possess the large electromechanical coupling factor, large spontaneous polarization, low dielectric loss and low internal stress etc. Hence, keeping in view the unique properties of PZT piezoelectric ceramics we also tried to synthesize indigenously the small sized PZT ceramic powder in the laboratory by using the modified sol-gel approach. In this paper, Propyl alcohol based sol-gel method was used for preparation of PZT piezoelectric ceramic. The powder obtained by this sol-gel process was calcined and sintering to reach a pyrochlore-free crystal phase. The characterization of synthesized material was carried out by the XRD analysis and the surface morphology was determined by high resolution scanning electron microscopy.

• Proceedings of the KIEE Conference
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• 2001.10a
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• pp.328-330
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• 2001

The construct of photovoltaic module array, main power source of photovoltaic system, is very important to the efficiency improvement of whole photovoltaic system. Photovoltaic modules are usually connected in series or parallel to meet power capacity required. Since output characteristics of a photovoltaic module are greatly fluctuated on the variation of insolation, temperature and its type, the maximum open circuit voltage and output operating voltage of photovoltaic module array must exist in the admissible input voltage range of inverter system under any operating conditions. In this paper, we present the selection and array method of photovoltaic modules through simulation for the coupling loss reduction between photovoltaic modules and a inverter.

• Journal of electromagnetic engineering and science
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• v.18 no.2
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• pp.73-77
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• 2018

This paper proposes a dual-band bandpass filter using stepped-impedance resonators (SIRs) with parallel coupled structures. The proposed filter adopts U-shaped SIRs with parallel coupled lines (PCLs) that have interdigital and comb-line shorted ends. The central PCLs build an upper passband and a transmission zero, and the two U-shaped SIRs build a lower passband. Four resonators and coupling structures are theoretically analyzed to derive its scattering parameters. A novel dual-band bandpass filter is designed and fabricated using the induced scattering characteristics. The measured results show that the fabricated dual-band bandpass filter has an insertion loss of less than 1.02 dB in the lower band of 2.45 GHz and of 3.01 dB in the upper band of 3.42 GHz, and a band-to-band isolation of more than 40 dB, from 3.14 to 3.2 GHz.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.2
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• pp.73-78
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• 2004

AIN thin film has been deposited on the $AI_2$$O_3$substrate with reactive radio frequency( RF) magnetron sputtering method. In this work, elelctromechanical coupling coefficient of AIN thin film was increased with an increase of AIN thin film thickness, and the maximum value was 0.11%. Insertion loss of SAW device was decreased with an increase of AIN thin film thickness and the minimum value was 33［㏈］. SAW velocity of IDTs/AIN/$AI_2$$O_3$structure and IDTs/AIN/$AI_2$$O_3$/Si structure were about 5480［㎧］and 5040［㎧］respectively.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.2386-2388
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• 2005

As anti-crash and pre-crash systems in vehicles become more extensively used, the need for high performance short-range radars is playing an increasing role. This paper presents the design of a micromachined, ultra-wideband beamformer centered at 24 GHz for automotive short-range radar systems. This beamformer is a Butler matrix designed using ultra-wideband transmission-line couplers, which consist of a multilayered structure that exhibits wider bandwidth compared to conventional microstrip branch-line couplers. The circuit has been designed on a quartz substrate, and to achieve the desired coupling, lines suspended on BCB layers located at specific parts of the circuit were used, achieving a three metal layered structure in form of wide microstrips, that give low loss and a wideband response. In this paper the design and fabrication procedure of the proposed beamformer are fully described.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1577-1579
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• 2003

AlN thin films are prepared on Si (111) substrate by RF magnetron sputtering. Two-step deposition method is proposed to obtain AlN thin films with high c-axis (002)-TC value and low surface roughnesses. For all the deposited AlN films, the c-axis (002)-orientation, surface mophology, and roughness are characterized in terms of deposition conditions FEAR devices with Al/AlN/Mo/Si(111) configuration are also fabricated. From the frequency response characteristics, the return loss and electromechanical coupling contant($k_t{^2}$) are estimated.

• Journal of Satellite, Information and Communications
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• v.7 no.1
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• pp.102-107
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• 2012

In this paper, we presented interference scenarios and an evaluation methodology for the co-frequency radio interference between a multi-beam mobile satellite communication system and a mobile communication system in 2.1 GHz band. Radio interferences between these systems are calculated using a minimum coupling loss method and an assesment for minimum separation distances was conducted for coexistence of a mobile satellite system and a mobile system in the same geographical area.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.317-320
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• 2003

Nowadays, the study on the ceramic components and modules used in telecommunication system is being performed. Coupler is a microwave passive component used for power coupling or dividing and directional coupler is designed to be possible optional dividing percentage. In our research, We developed 14dB and 19dB directional couplers of DCS band. The good characteristics, the target insertion loss and high isolation, of couplers is obtained by LTCC processing using a ceramic material.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.288-291
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• 2003

Nowadays, the study on the ceramic components and modules used in telecommunication system is being performed. Coupler is a microwave passive component used for power coupling or dividing and directional coupler is designed to be possible optional dividing percentage. In our research, We developed 14dB and 19dB directional couplers of EGSM band. The good characteristics, the target insertion loss and high isolation, of couplers is obtained by LTCC processing using a ceramic material.

• Journal of the Optical Society of Korea
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• v.6 no.2
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• pp.27-32
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• 2002

An integrated optical 2$\times$2 add/drop multiplexer in X-cut, Y-propagating LiNbO$_3$ has been demonstrated. The device consists of passive polarization splitters and acousto-optical mode converters with weighted coupling utilizing tapered acoustical directional couplers; their specific design and properties are discussed. The insertion loss has been measured to be about -8.16 ㏈ and -8.6 ㏈ for TE and TM polarizations, respectively. The device shows a 3 ㏈ bandwidth of 2.3 nm, a tuning rate 8.34 nm/MHz around λ = 1554 nm, and a sidelobe suppression of about 14.5 ㏈. Optimum operation is achieved with a RF drive power of about 43 ㎽. Multi-wavelength operation has been demonstrated.