• Proceedings of the IEEK Conference
• /
• 2003.11c
• /
• pp.32-36
• /
• 2003

In this work, we have designed a fully integrated 2.4GHz LC-tuned voltage-controlled oscillator (VCO) with multiple tuning inputs for a 0.25-$\mu\textrm{m}$ standard CMOS process. The design of voltage-controlled oscillator is based on an LC-resonator with a spiral inductor of octagonal type and pMOS-varactors. Only two metal layer have been used in the designed inductor. The frequency tuning is achieved by using parallel pMOS transistors as varactors and back-gate tuned pMOS transistors in an active region. Coarse tuning is achieved by using 3-bit pMOS-varactors and fine tuning is performed by using back-gate tuned pMOS transistors in the active region. When 3-bit digital and analog inputs are applied to the designed circuits, voltage-controlled oscillator shows the tuning feature of frequency range between 2.3 GHz and 2.64 GHz. At the power supply voltage of 2.5 V, phase noise is -128dBc/Hz at 3MHz offset from the carrier. Total power dissipation is 7.5 mW.

• Current Optics and Photonics
• /
• v.5 no.4
• /
• pp.466-476
• /
• 2021

Frequency-multiplication technology based on microwave photonic principles can be used to generate microwave and millimeter wave signals with a wide frequency tuning range. However, the existing cascaded external modulation frequency-tupling scheme needs to ensure the phase coherence of the modulated Radio Frequency (RF) signal, while the phase modulation directly limits the frequency tuning range of the external modulation frequency multiplication. In this paper, a novel approach for generating an incoherent frequency 12-tupling signal with cascade modulation is proposed. The structure of cascaded dual-parallel Mach-Zehnder modulators can generate a frequency 12-tupling signal. The proposed structure uses no filter or phase control of the RF driving signal. Microwave photonic frequency-tupling was realized under incoherent conditions. Software simulations and experiments validated the proposed structure and proved that it can generate frequency 12-tupling microwave signals under incoherent conditions. Both the frequency range and reliability of the frequency-tupling system has been improved by the proposed structure.

• Structural Engineering and Mechanics
• /
• v.20 no.5
• /
• pp.543-558
• /
• 2005

The natural frequencies of a long span bridge vary during its construction and it is thus difficult to apply traditional tuned liquid column dampers (TLCD) with a fixed configuration to reduce bridge vibration. The restriction of TLCD imposed by frequency tuning requirement also make it difficult to be applied to structure with either very low or high natural frequency. A semi-active tuned liquid column damper (SATLCD), whose natural frequency can be altered by active control of liquid column pressure, is studied in this paper. The principle of SATLCD with adaptive tuning capacity is first introduced. The analytical models are then developed for lateral vibration of a structure with SATLCD and torsional vibration of a structure with SATLCD, respectively, under either harmonic or white noise excitation. The non-linear damping property of SATLCD is linearized by an equivalent linearization technique. Extensive parametric studies are finally carried out in the frequency domain to find the beneficial parameters by which the maximum vibration reduction can be achieved. The key parameters investigated include the distance from the centre line of SATLCD to the rotational axis of a structure, the ratio of horizontal length to the total length of liquid column, head loss coefficient, and frequency offset ratio. The investigations demonstrate that SATLCD can provide a greater flexibility for its application in practice and achieve a high degree of vibration reduction. The sensitivity of SATLCD to the frequency offset between the damper and structure can be improved by adapting its frequency precisely to the measured structural frequency.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.16 no.3
• /
• pp.285-294
• /
• 2013

In this paper, we present a tunable BPF with a novel structure. The filter is very useful to optimization of low frequency filter performance, because the fiilter has air-coils and tuning screws. This filter also has the merits of light weight and small size in comparison with conventional tunable filter at low frequency. This type filters are especially suitable for switched filter bank due to tuning structure. We designed 4 channel filter bank with two SP4Ts and 4 BPFs using novel structure. Tuning processes were subsequently executed. We obtained satisfactory performances as a result; consequently, the validity of our proposal was proved.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.33A no.2
• /
• pp.78-86
• /
• 1996

Solid-state devices can be directly integrated with a planar antenna to form active antenna elements. In this paper, the voltage controlled oscillator (VCO) is designed and fabricated at 2.4 to 2.5 GHz using a microstrip patch antenna. A varactor diode is used as avariable reactance. The predicted frequency tuning range of the VCO is 2.448 to 2.498 GHz in the design procedure and the fabricated VCO has 2.446 to 2.498 GHz frequency tuning range when the varactor tuning voltage is varied from 0 to 11V. Transmitted power output of the patch antenna which serves both as a rsonator and a radiating element for VCO is about 18 mW over this tuning range.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.57 no.9
• /
• pp.1618-1623
• /
• 2008

In this paper, a new design method for IMC-PID that adds a phase scaling factor of system identifications to the standard IMC-PID controller as a control parameter is proposed. Based on analytically derived frequency properties such as gain and phase margins, this tuning rule is an optimal control method determining the optimum values of controlling factors to minimize the cost function, integral error criterion of the step response in time domain, in the constraints of design parameters to guarantee qualified frequency design specifications. The proposed controller improves existing single-parameter design methods of IMC-PID in the inflexibility problem to be able to consider various design specifications. Its effectiveness is examined by a simulation example, where a comparison of the performances obtained with the proposed tuning rule and with other common tuning rules is shown.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.11a
• /
• pp.401.2-401
• /
• 2002

An unconstrained tuning fork with a 3-D model has been numerically analyzed by Finite Element Method (FEM) and Boundary Element Method (BEM). The first three natural frequencies were calculated by the FEM modal analysis. Then the change of the modal frequencies was examined with the variation of the tuning fork length and width. (omitted)

• The Transactions of the Korean Institute of Electrical Engineers A
• /
• v.52 no.5
• /
• pp.241-249
• /
• 2003

This paper describes a novel approach for performing eigenvalue analysis and frequency domain analysis of multi-machine power system. The salient feature of this approach is a direct approach for constructing the state matrix equations of linearized power systems about its operating point using modular technique. These state matrix equations are then used to obtain eigenvalues and mode shapes of the system, and frequency response, or Bode, plots of selected transfer functions. The proposed program provides a flexible tool for systematic analyses of tuning PSS's parameters. The paper also presents its application to the analyses of a single-machine infinite bus system and two-area system with 4 machines.

• Journal of KSNVE
• /
• v.9 no.4
• /
• pp.761-768
• /
• 1999

This paper presents an NVH test of Automotive power steering system performed at a half-car Test-rig. The test was done for neutral and full turn(or relief) conditions in steering wheel at a fixed rpm first, then followed by the same conditions for the rpm run-up. The sound intensity measurement verified the results from the frequency and order analysis, especially about the identification of major noise sources and their dominant frequencies. The results from thie study can be utilized in the system noise tuning when a new steering component is installed. In particular, the noise and vibration reduction at the relief condition will be accomplished through the knowledge obtained from this study and from the on-going research on the hose tuning techniques usign silencers and tuning cable inserted in the pressure hose.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.16 no.5
• /
• pp.650-656
• /
• 2016

Voltage controlled oscillator (VCO) is widely used circuit component in high-performance microprocessors and modern communication systems as a frequency source. In present work, VCO designs using the different combination of NAND gates with three transistors and CMOS inverter are reported. Three, five and seven stages ring VCO circuits are designed. Coarse and fine tuning have been done using two different supply sources. The frequency with coarse tuning varies from 3.31 GHz to 5.60 GHz in three stages, 1.77 GHz to 3.26 GHz in five stages and 1.27 GHz to 2.32 GHz in seven stages VCO respectively. Moreover, for fine tuning frequency varies from 3.70 GHz to 3.94 GHz in three stages, 2.04 GHz to 2.18 GHz in five stages and 1.43 GHz to 1.58 GHz in seven stages VCO respectively. Results of power consumption and phase noise for the VCO circuits are also been reported. Results of proposed VCO circuits have been compared with previously reported circuits and present circuit approach show significant improvement.