Filtreler

2009 - 20103
Filtreleri Sıfırla

Ayarlar

Bölüm: Işık University, Faculty of Engineering, Department of Electrical-Electronics Engineering × Konu: Annular array ×

Arama Sonuçları

Listeleniyor 1 - 3 / 3
  • Küçük Resim
    Yayın
    Damariçi yanal kesit görüntüleme için farklı prob yapılarının incelenmesi
    (IEEE, 2009-06-26) Şişman, Alper; Karaman, Mustafa
    Bu çalışmada dönen bir şaftın yanal yüzeyine yerleştirilmiş 8 adet içiçe halka elemanlardan oluşan yana bakan görüntüleme için yeni bir kateter yapısı incelenmiştir. Bu Katater mimarisi basit bir dizi önü alıcı verici elektroniği ile değişken odaklama olanağı sağlamaktadır. Önerilen mimari, mevcut iki farklı kateter mimarisiyle benzetim sonuçları ile karşılaştırmalı olarak incelenmiştir. Benzetimlerde görüntüleme kateter çapı 1mm alınmış, farklı derinlikler ve açılar için 3 noktasal yansıtıcı ile NDF çıkarılmıştır.
  • Küçük Resim
    Yayın
    Solid-state SL-IVUS arrays based on non-uniform aperture sampling
    (IEEE, 2010) Şişman, Alper; Karaman, Mustafa; Gürün, Gökçe; Değertekin, Fahrettin Levent
    We propose new reconfigurable ring and cylindrical array designs using non-uniform (Fresnel) aperture sampling with identical differential delays between adjacent elements which reduces the beamformer complexity. For side-looking intravascular ultrasound (SL-IVUS), the image plane is scanned through stepping the active subarray which is reformed in each step. A ring array with such sampling leads to a simplified phased array beamformer with N/2 identical differential delays. The same logic applies to a two-dimensional (2-D) array with NLNE-elements over a cylindrical patch. The 2-D beamformer becomes separable along the elevation and the lateral dimensions and possesses the delay symmetry in both dimensions. Consequently, the overall phased array beamforming can be realized by using NL elevational parallel beamformers each with (NE/2)-channel and the output of which is fed to a (NL/2)-channel lateral beamformer. We tested and compared the proposed and existing array designs through numerical PSF simulations.
  • Küçük Resim
    Yayın
    A tunable analog delay element for high-frequency dynamic beamforming
    (IEEE, 2009) Gürün, Gökçe; Şişman, Alper; Zahorian, Jaime S.; Satır, Sarp; Karaman, Mustafa; Hasler, Paul E.; Değertekin, Fahrettin Levent
    Implementing beamforming for high frequency arrays is challenging because of the accurate delay requirements at high frequencies. High frequency digital beamforming is not suitable for catheter based applications as a large number of cables is required between the array and the external beamformer. A possible solution is to perform analog beamforming on an integrated circuit adjacent or monolithically integrated to the imaging array. In this study, we introduce an improved voltage in voltage out low pass filter as an analog delay cell for high frequency dynamic beamformers. This circuit can generate three times more delay with a given bandwidth when compared to conventional low pass filters. Delay of the circuit is tunable and the gain of the cell is inherently very close to unity. The proposed delay cell operates single ended and therefore is more suitable for CMUT operation which generates single ended output. We designed a test beamformer for a 30MHz, equal area, annular array with 100% bandwidth using the proposed delay cell and the unit-delay focusing architecture. Required delays are implemented using a delay line made up of improved delay elements with tunable delays. To demonstrate functionality we designed and fabricated a custom front-end IC in a 0.5µm standard CMOS process. The IC chip consists of 8 transimpedance amplifiers, voltage-to-current converters, the analog dynamic beamformer, and two buffers. We present results of preliminary imaging experiments that demonstrate the focusing capability.