• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 A
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• pp.251-253
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• 1993

This paper proposes an automatic tuning fuzzy controller for frequency control of a hydro power plant (HPP). The proposed automatic tuning fuzzy controller consists of fuzzy control part and scaling factor calculation part. Scaling factor tuning is based on the concept of conventional tuning rules for the PI controller. The proposed controller was evaluated by simulation. Good results have been obtained for the 5kW model HHP.

• 대한전자공학회논문지SD
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• 제43권9호
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• pp.10-16
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• 2006

본 논문에서는 PHS 어플리케이션에서 새로운 Coarse Toning 기법을 사용한 빠른 스위칭의 CMOS 주파수 합성기를 기술하였다. 제안한 Coarse Tuning 방법은 Phase Noise와 Lock-Time을 최적화하기 위해 LC-VCO의 적절한 Tuning Capacitances를 선택하는 것이다. 이를 바탕으로 측정된 Lock-Time은 약 $20{\mu}s$ 이고, Phase Noise는 600kHz의 offset에서 -121dBc/Hz이다. 칩은 $0.25{\mu}m$ CMOS 공정으로 제작하였고, 면적은 $0.7mm{\times}2.1mm$ 이다. 소비전력은 2.7V 공급 전압 하에서 54mW 이다.

• ETRI Journal
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• 제33권2호
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• pp.201-209
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• 2011

This paper presents a wide-band fine-resolution digitally controlled oscillator (DCO) with an active inductor using an automatic three-step coarse and gain tuning loop. To control the frequency of the DCO, the transconductance of the active inductor is tuned digitally. To cover the wide tuning range, a three-step coarse tuning scheme is used. In addition, the DCO gain needs to be calibrated digitally to compensate for gain variations. The DCO tuning range is 58% at 2.4 GHz, and the power consumption is 6.6 mW from a 1.2 V supply voltage. An effective frequency resolution is 0.14 kHz. The phase noise of the DCO output at 2.4 GHz is -120.67 dBc/Hz at 1 MHz offset.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권2호
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• pp.601-617
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• 2014

In digital radio broadcasting systems, long delays are incurred in service start time when tuning to a particular frequency because several synchronization steps, such as symbol timing synchronization, frame synchronization, and carrier frequency offset and sampling frequency offset compensation are necessary. Therefore, the operation of the synchronization blocks causes delays ranging from several hundred milliseconds to a few seconds until the start of the radio service after frequency tuning. Furthermore, if spectrum inversed signals are transmitted in digital radio broadcasting systems, the receivers are unable to decode them, even though most receivers can demodulate the spectral inversed signals in analog radio broadcasting systems. Accordingly, fast synchronization techniques and a method for spectral inversion detection are required in digital radio broadcasting systems that are to replace the analog radio systems. This paper presents a joint detection method of frame, integer carrier frequency offset, and spectrum inversion for DRM Plus digital broadcasting systems. The proposed scheme can detect the frame and determine whether the signal is normal or spectral inversed without any carrier frequency offset and sampling frequency offset compensation, enabling fast frame synchronization. The proposed method shows outstanding performance in environments where symbol timing offsets and sampling frequency offsets exist.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2009년도 춘계학술대회 논문집
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• pp.281-284
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• 2009

로켓엔진 연소기의 연소 불안정 억제를 위해 연소 상황에서의 1/4파장 공명기의 주파수 동조를 수치적으로 연구하였다. 상온 음향 시험을 통해 도출된 최적 감쇠 조건을 충족시키는 사양의 1/4파장 공명기를 채택하였다. 먼저, 실규모 연소실의 조건을 모사한 모형 연소실에서의 연소장을 수치해석하여 기본 음향파 응답 특성을 분석하였다. 다음으로, 이 연소실에 음향 공명기를 장착하여 공명기 내부 물성치를 예측하였다. 이러한 기본 데이터를 토대로 특정 음향 모드를 감쇠시킬 수 있는 주파수 동조 방안을 연구하였다. 각 공명기 내부의 물성치를 토대로 공명기를 개별 공명기의 최적 동조 길이로 설계할 경우에 충분한 감쇠 성능을 얻을 수 있었다. 설계의 편의를 위해 모든 공명기를 동일길이로 설정한 경우, 길이에 따른 감쇠성능을 비교하여 제시하였다. 이를 토대로 최적의 동조길이를 찾을 수 있었다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2008년도 춘계학술대회 논문집
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• pp.591-592
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• 2008

• Journal of Mechanical Science and Technology
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• 제19권9호
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• pp.1711-1719
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• 2005

In an electro statically actuated nanoelectromechanical system (NEMS) resonator, it is shown that both the resonance frequency and the resonance quality (Q) factor can be manipulated. How much the frequency and quality factor can be tuned by excitation voltage and resistance on a doubly-clamped beam resonator is addressed. A mathematical model for investigating the tuning effects is presented. All results are shown based on the feasible dimension of the nanoresonator and appropriate external driving voltage, yielding up to 20 MHz resonance frequency. Such parameter tuning could prove to be a very convenient scheme to actively control the response of NEMS for a variety of applications.

• 한국통신학회논문지
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• 제35권5A호
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• pp.513-518
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• 2010

전압제어 발진기의 위상잡음 특성을 개선하기 위해 결합 마이크로스트립라인을 이용하여 공진주파수를 동조하는 변형된 구조의 주파수 동조회로를 제안한다. 위상잡음 특성이 개선됨을 실험적으로 입증하기 위해 주파수 동조회로를 제외하면 같은 구조를 갖는 2개의 9.8GHz HEMT 전압제어 발진기를 설계 및 제작하였다. 측정결과 결합마이크로스트립라인의 주파수 동조회로를 갖는 제안된 구조의 전압제어 발진기가 일반적인 전압제어 발진기에 비해 100KHz 오프셋 지점에서 8dBc/Hz 이상의 위상잡음 특성 개선효과를 나타내었다.

• Journal of information and communication convergence engineering
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• 제13권2호
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• pp.139-143
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• 2015

A push-push voltage controlled dielectric resonator oscillator (VCDRO) with a modified frequency tuning structure using broadside couplers is investigated. The push-push VCDRO designed at 16 GHz is manufactured using a low temperature co-fired ceramic (LTCC) technology to reduce the circuit size. The frequency tuning structure using a broadside coupler is embedded in a layer of the A6 substrate by using the LTCC process. Experimental results show that the fundamental and third harmonics are suppressed above 15 dBc and 30 dBc, respectively, and the phase noise of push-push VCDRO is -97.5 dBc/Hz at an offset frequency of 100 kHz from the carrier. The proposed frequency tuning structure has a tuning range of 4.46 MHz over a control voltage of 1-11 V. This push-push VCDRO has a miniature size of 15 mm×15 mm. The proposed design and fabrication techniques for a push-push oscillator seem to be applicable in many space and commercial VCDRO products.

• 센서학회지
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• 제23권3호
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• pp.202-206
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• 2014

The common vibration energy harvester effectively converts mechanical vibration to electric power at a specific resonance frequency that must match the ambient excitation frequency. The resonance frequencies of energy harvesters are fixed during the design process and could not be changed after fabrication. In this paper, we proposed the new frequency tuning which uses the rotatable spring in order to adjust the spring constants. By this tuning method, the resonance frequency of the system can simply be manipulated using spring rotation. The proposed energy harvester has been successfully tuned to a resonance frequency between 23 and 32 Hz. The experimental results demonstrated that the proposed energy harvester could generate a maximum output power of $60{\mu}W$ with an acceleration of 0.5 g ($1g=9.81m/s^2$), and that the resonance frequency of the harvester was able to tune approximately 31.4%. When the proposed harvester was attached to an automobile engine, the maximum open circuit voltage of 1.78 Vpp was produced at 700 rpm.