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Yayın Forward-viewing CMUT arrays for medical Imaging(IEEE-INST Electrical Electronics Engineers Inc, 2004-07) Demirci, Utkan; Ergün, Arif Sanlı; Oralkan, Ömer; Karaman, Mustafa; Khuri-Yakub, Butrus ThomasThis paper reports the design and testing of forward-viewing annular arrays fabricated using capacitive micromachined ultrasonic transducer (CMUT) technology. Recent research studies have shown that CMUTs have broad frequency bandwidth and high-transduction efficiency. One- and two-dimensional CMUT arrays of various sizes already have been fabricated, and their viability for medical imaging applications has been demonstrated. We fabricated 64-element, forward-viewing annular arrays using the standard CMUT fabrication process and carried out experiments to measure the operating frequency, bandwidth, and transmit/receive efficiency of the array elements. The annular array elements, designed for imaging applications in the 20 MHz range, had a resonance frequency of 13.5 MHz in air. The immersion pulse-echo data collected from a plane reflector showed that the devices operate in the 5-26 MHz range with a fractional bandwidth of 135%. The output pressure at the surface of the transducer was measured to be 24 kPa/V. These values translate into a dynamic range of 131.5 dB for I-V excitation in 1-Hz bandwidth with a commercial low noise receiving circuitry. The designed, forward-viewing annular CMUT array is suitable for mounting on the front surface of a cylindrical catheter probe and can provide Doppler information for measurement of blood flow and guiding information for navigation through blood vessels in intravascular ultrasound imaging.Yayın Integration of 2D CMUT arrays with front-end electronics for volumetric ultrasound imaging(IEEE-INST Electrical Electronics Engineers Inc, 2008-02) Wygant, Ira O.; Zhuang, Xuefeng; Yeh, David T.; Oralkan, Ömer; Ergün, Arif Sanlı; Karaman, Mustafa; Khuri-Yakub, Butrus ThomasFor three-dimensional (3D) ultrasound imaging, connecting elements of a two-dimensional (2D) transducer array to the imaging system's front-end electronics is a challenge because of the large number of array elements and the small element size. To compactly connect the transducer array with electronics, we flip-chip bond a 2D 16 x 16-element capacitive micromachined ultrasonic transducer (CMUT) array to a custom-designed integrated circuit (IC). Through-wafer interconnects are used to connect the CMUT elements on the top side of the array with flip-chip bond pads on the back side. The IC provides a 25-V pulser and a transimpedance preamplifier to each element of the array. For each of three characterized devices, the element yield is excellent (99 to 100% of the elements are functional). Center frequencies range from 2.6 MHz to 5.1 MHz. For pulse-echo operation, the average -6-dB fractional bandwidth is as high as 125%. Transmit pressures normalized to the face of the transducer are as high as 339 kPa and input-referred receiver noise is typically 1.2 to 2.1 mPa/root Hz. The flip-chip bonded devices were used to acquire 3D synthetic aperture images of a wire-target phantom. Combining the transducer array and IC, as shown in this paper, allows for better utilization of large arrays, improves receive sensitivity, and may lead to new imaging techniques that depend on transducer arrays that are closely coupled to IC electronics.Yayın A practical control method for single-phase input PMSM drives with small DC-Link capacitor(Institute of Electrical and Electronics Engineers Inc., 2025-03) Deshmukh, Akshay Vijayrao; Afshar, Mojtaba; Jena, Sritam; Hava, Ahmet Masum; Yu, Zhen; Akın, BilalThe primary function of the large electrolytic dc-link capacitor in the single-phase input motor drives is to enhance dc voltage stability by minimizing voltage fluctuations. Because they are both bulky and unreliable components, reducing the size of dc-link capacitors or substituting them with significantly low capacitance value film capacitors offers numerous advantages. This article introduces a method that allows using a voltage source inverter with a small film dc-link capacitor, which results in equivalent performance to high-value capacitor drives. In this approach, the effect of dc-link voltage ripple is designed as a periodic disturbance in the current loop. A proportional-integral-resonant (PIR) control strategy is implemented to eliminate the designed double-line frequency disturbance observed in motor currents, thereby ensuring a smooth motor torque response. This solution meets crucial criteria for home appliances, specifically addressing input current harmonic requirements through power factor correction while effectively reducing the adverse effects of substantial dc-link ripple on motor torque, even when employing a film capacitor (10–50 µF range). The proposed framework is experimentally tested on permanent magnet synchronous motors with fan-load and dynamometers. Experimental results demonstrate, with PIR, an 80% reduction in current and torque ripple occurring due to the use of a low-value dc-link film capacitor. This also achieves performance within ±5% of the results obtained with a drive equipped with a 1200 µF dc capacitor. In addition, the line-side power factor exceeds 0.98 for loads exceeding 8% of the rated power.
