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Kai Chang - One of the best experts on this subject based on the ideXlab platform.

  • Piezoelectric Transducer controlled dual mode switchable bandpass filter
    IEEE Microwave and Wireless Components Letters, 2007
    Co-Authors: Kai Chang
    Abstract:

    A Piezoelectric Transducer-controlled dual-mode switchable bandpass filter is introduced. A Piezoelectric Transducer is used to lift up or pull down the attached dielectric substrate perturbation. When the dielectric substrate is pulled down, the perturbation excites dual modes and the dual-mode filter is on. The return loss is better than 10 dB and the insertion loss is less than 3 dB from 2.92 to 3 GHz. When the dielectric substrate is lifted up, the dual-mode resonator is unperturbed and the dual-mode filter is off. The isolation is 21 dB at 3 GHz. The on-off ratio is 18 dB

  • Piezoelectric Transducer controlled multiple beam phased array using microstrip rotman lens
    IEEE Microwave and Wireless Components Letters, 2005
    Co-Authors: P Zepeda, Kai Chang
    Abstract:

    A simple and low-cost multiple beam phased array is designed using a microstrip Rotman lens and multi-line phase shifter controlled by a Piezoelectric Transducer (PET) at Ka-band. A microstrip Rotman lens with five beam ports and nine array ports is used as a feed for a multiple beam antenna array to generate five beams centered at the angles of 0/spl deg/, /spl plusmn/15/spl deg/, and /spl plusmn/30/spl deg/. The lens fed nine-element patch array shows the antenna gain of 10 dBi and sidelobe suppression of 10 dB. Each beam is steered over /spl plusmn/8/spl deg/ using two PET-controlled phase shifters, and the five beams cover /spl plusmn/38/spl deg/ from the broadside.

  • a Piezoelectric Transducer tuned microstrip ring resonator oscillator operating at the second resonant mode of the ring resonator research articles
    International Journal of Rf and Microwave Computer-aided Engineering, 2005
    Co-Authors: Lung-hwa Hsieh, Kai Chang
    Abstract:

    A microstrip open-loop resonator oscillator operating at even modes is proposed. The even mode of the ring circuit can be predicted by using a simple transmission-line model. The new oscillator has a characteristic similar to that of a push-push oscillator. In addition, in comparison with the push-push oscillator, the new oscillator with one active device can minimize the size and lower the cost. A voltage-controlled Piezoelectric Transducer (PET) is used to vary the resonant frequencies of the ring resonator, which in turn tunes the oscillator with a good tuning range of 4.9p at around 12.1 GHz. This tuned oscillator should have many applications in wireless systems. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005.

  • high efficiency Piezoelectric Transducer tuned feedback microstrip ring resonator oscillators operating at high resonant frequencies
    IEEE Transactions on Microwave Theory and Techniques, 2003
    Co-Authors: Lung-hwa Hsieh, Kai Chang
    Abstract:

    A tunable-feedback ring-resonator oscillator using a voltage-controlled Piezoelectric Transducer (PET) is introduced. The new oscillator is constructed by a ring resonator with a pair of orthogonal feed lines as a feedback structure. The ring resonator with two orthogonal feed lines can suppress odd modes and operate at even modes. This operation shows a similar characteristic of high operating oscillation frequencies as that of the push-push oscillators. The high operating resonant frequency characteristic is predicted by a simple transmission-line model. The simulated and measured results agree well with each other. At a fixed frequency of 12.09 GHz, the oscillator has a high DC-to-RF efficiency of 48.7% with an output power of 5.33 dBm. A voltage-controlled PET is used to vary the resonant frequencies of the ring resonator, which, in turn, tunes the oscillator with a good tuning rage of 4.25% around 12 GHz. This tuned oscillator operating at high oscillation frequency can be used in many wireless and sensor systems.

  • Piezoelectric Transducer controlled tunable microwave circuits
    IEEE Transactions on Microwave Theory and Techniques, 2002
    Co-Authors: Tae-yeoul Yun, Kai Chang
    Abstract:

    This paper introduces a new method to tune microwave circuits of phase shifters, filters, resonators, and oscillators, controlled by a Piezoelectric Transducer (PET) with computational and experimental results. An optimized PET-controlled phase shifter is demonstrated to operate up to 40 GHz with a maximum total loss of 4 dB and phase shift of 480/spl deg/. PET-controlled tunable bandpass filter, ring resonator, and one-dimensional photonic-bandgap resonator show a very wide tuning bandwidth of 17.5%-28.5% near 10 GHz with little performance degradation. A new PET-controlled or voltage-controlled dielectric-resonator oscillator (DRO) is demonstrated with a tuning bandwidth of 3.7% at the center frequency of 11.78 GHz. The tuning bandwidth is slightly less than that of a mechanical tuning using a micrometer-head-controlled tunable DRO with a tuning bandwidth of 4.7%. The new tuning method should have many applications in monolithic and hybrid microwave integrated circuits.

Tae-yeoul Yun - One of the best experts on this subject based on the ideXlab platform.

  • Piezoelectric Transducer controlled tunable microwave circuits
    IEEE Transactions on Microwave Theory and Techniques, 2002
    Co-Authors: Tae-yeoul Yun, Kai Chang
    Abstract:

    This paper introduces a new method to tune microwave circuits of phase shifters, filters, resonators, and oscillators, controlled by a Piezoelectric Transducer (PET) with computational and experimental results. An optimized PET-controlled phase shifter is demonstrated to operate up to 40 GHz with a maximum total loss of 4 dB and phase shift of 480/spl deg/. PET-controlled tunable bandpass filter, ring resonator, and one-dimensional photonic-bandgap resonator show a very wide tuning bandwidth of 17.5%-28.5% near 10 GHz with little performance degradation. A new PET-controlled or voltage-controlled dielectric-resonator oscillator (DRO) is demonstrated with a tuning bandwidth of 3.7% at the center frequency of 11.78 GHz. The tuning bandwidth is slightly less than that of a mechanical tuning using a micrometer-head-controlled tunable DRO with a tuning bandwidth of 4.7%. The new tuning method should have many applications in monolithic and hybrid microwave integrated circuits.

  • Analysis and optimization of a phase shifter controlled by a Piezoelectric Transducer
    IEEE Transactions on Microwave Theory and Techniques, 2002
    Co-Authors: Tae-yeoul Yun, Kai Chang
    Abstract:

    This paper introduces a method for analyzing and optimizing a phase shifter controlled by a Piezoelectric Transducer (PET). To analyze the multilayer microstrip structure of the PET-controlled phase shifter, new equivalent single-layer (ESL) equations for the phase shift and loss calculations are developed and confirmed with spectral-domain analysis (SDA) of the moment method. A parametric analysis is accomplished with ESL equations and SDA, and optimization guidelines are suggested. An optimized PET phase shifter is demonstrated to operate up to 40 GHz with a maximum total loss of 4 dB and phase shift of 480°. Measured results agree very well with calculations showing substantially smaller control voltage, size, and dispersion, as compared to previously published data. This new analysis and optimization technique for the PET-controlled phase shifter should be useful in the design of phased-array antennas and tunable microwave circuits

  • a low cost 8 to 26 5 ghz phased array antenna using a Piezoelectric Transducer controlled phase shifter
    IEEE Transactions on Antennas and Propagation, 2001
    Co-Authors: Tae-yeoul Yun, Kai Chang
    Abstract:

    A new phased array antenna of wide bandwidth and good beam scanning angle has been developed using a low cost multiline phase shifter controlled by a Piezoelectric Transducer (PET) and a stripline fed Vivaldi antenna array. The multiline progressive PET phase shifter has a low perturbation loss of less than 2 dB and a total loss of less than 4 dB up to 40 GHz with a maximum phase shift of 480/spl deg/. The proposed phased array antenna consists of four E- or H-plane Vivaldi antennas, a PET phase shifter, and a power divider. The phased array shows a wide beam scanning capability of /spl plusmn/27/spl deg/ over a wide bandwidth from 8 to 26.5 GHz covering X, Ku, and K bands.

  • a low loss time delay phase shifter controlled by Piezoelectric Transducer to perturb microstrip line
    IEEE Microwave and Guided Wave Letters, 2000
    Co-Authors: Tae-yeoul Yun, Kai Chang
    Abstract:

    This paper presents a new time-delay phase shifter using a Piezoelectric Transducer (PET) on a microstrip line with computational and experimental results. Dielectric perturbation changes the line capacitance and propagation constant of the microstrip line. The phase of the microstrip line is varied, but insertion loss is not much affected. A maximum phase shift of 460/spl deg/ with respect to the unperturbed condition has been achieved with an increased insertion loss of less than 2 dB and a total loss of less than 4 dB up to 40 GHz, using the dielectric perturbation controlled by PET. The proposed phase shifter should have many applications in antenna beam steering and in other microwave and millimeter-wave circuits.

James G Fujimoto - One of the best experts on this subject based on the ideXlab platform.

  • compact Piezoelectric Transducer fiber scanning probe for optical coherence tomography
    Optics Letters, 2014
    Co-Authors: Ning Zhang, Tsunghan Tsai, Osman O Ahsen, Kaicheng Liang, Hsiangchieh Lee, Ping Xue, James G Fujimoto
    Abstract:

    We developed a compact, optical fiber scanning Piezoelectric Transducer (PZT) probe for endoscopic and minimally invasive optical coherence tomography (OCT). Compared with previous forward-mount fiber designs, we present a reverse-mount design that achieves a shorter rigid length. The fiber was mounted at the proximal end of a quadruple PZT tube and scanned inside the hollow PZT tube to reduce the probe length. The fiber resonant frequency was 338 Hz using a 17-mm-long fiber. A 0.9 mm fiber deflection was achieved with a driving amplitude of 35 V. Using a GRIN lens-based optical design with a 1.3× magnification, a ∼6 μm spot was scanned over a 1.2 mm diameter field. The probe was encased in a metal hypodermic tube with a ∼25 mm rigid length and covered with a 3.2 mm outer diameter (OD) plastic sheath. Imaging was performed with a swept source OCT system based on a Fourier domain modelocked laser (FDML) light source at a 240 kHz axial scan rate and 8 μm axial resolution (in air). En face OCT imaging of skin in vivo and human colon ex vivo was demonstrated.

  • Piezoelectric Transducer based miniature catheter for ultrahigh speed endoscopic optical coherence tomography
    Biomedical Optics Express, 2011
    Co-Authors: Tsunghan Tsai, Benjamin Potsaid, Martin F Kraus, Chao Zhou, Yuankai K Tao, Joachim Hornegger, James G Fujimoto
    Abstract:

    We developed a Piezoelectric-Transducer- (PZT) based miniature catheter with an outer diameter of 3.5 mm for ultrahigh-speed endoscopic optical coherence tomography (OCT). A miniaturized PZT bender actuates a fiber and the beam is scanned through a GRIN lens and micro-prism to provide high-speed, side-viewing capability. The probe optics can be pulled back over a long distance to acquire three-dimensional (3D) data sets covering a large area. Imaging is performed with 11 μm axial resolution in air (8 μm in tissue) and 20 μm transverse resolution, at 960 frames per second with a Fourier domain mode-locked laser operating at 480 kHz axial scan rate. Using a high-speed data acquisition system, endoscopic OCT imaging of the rabbit esophagus and colon in vivo and human colon specimens ex vivo is demonstrated.

Kazuhiko Ogusu - One of the best experts on this subject based on the ideXlab platform.

Manuel Collet - One of the best experts on this subject based on the ideXlab platform.

  • The power output and efficiency of a negative capacitance shunt for vibration control of a flexural system
    Smart Materials and Structures, 2013
    Co-Authors: Benjamin S. Beck, Kenneth Cunefare, Manuel Collet
    Abstract:

    A negative capacitance shunt is a basic, analog, active circuit electrically connected to a Piezoelectric Transducer to control the vibrations of flexural bodies. The shunt circuit consists of a resistor and a synthetic negative capacitor to introduce a real and imaginary impedance on a vibrating mechanical system. The electrical impedance of the negative capacitance shunt modifies the effective modulus of the Piezoelectric Transducer to reduce the stiffness and increase the damping, which causes a decrease in amplitude of the vibrating structure to which the elements are bonded. To gain an insight into the electromechanical coupling and power output, the shunt and the electrical properties of the Piezoelectric Transducer are modeled using circuit modeling software. The power output of the model is validated with experimental measurements of a shunt connected to a Piezoelectric Transducer pair bonded to a vibrating aluminum cantilever beam. The model is used to select the passive components of the negative capacitance shunt to increase the efficiency and quantify the voltage output limit of the op-amp.