Now showing items 1-20 of 74

    • 100-GHz resonant cavity enhanced Schottky photodiodes 

      Onat, B. M.; Gökkavas, M.; Özbay, Ekmel; Ata, E. P.; Towe, E.; Ünlü, M. S. (Institute of Electrical and Electronics Engineers, 1998)
      Resonant cavity enhanced (RCE) photodiodes are promising candidates for applications in optical communications and interconnects where ultrafast high-efficiency detection is desirable. We have designed and fabricated RCE ...
    • 45 GHz bandwidth-efficiency resonant cavity enhanced ITO-Schottky photodiodes 

      Bıyıklı, Necmi; Kimukin, İbrahim; Aytür, Orhan; Özbay, Ekmel; Gökkavas, M.; Ünlü, M. S. (OSA, 2001)
      We demonstrated high-performance resonant cavity enhanced ITO-Schottky photodiodes. We achieved a peak efficiency of 75% around 820 nm with a 3-dB bandwidth of 60 GHz resulting in a bandwidth-efficiency product of 45 GHz.
    • Adaptive polyphase subband decomposition structures for image compression 

      Gerek, Ö. N.; Çetin, A. Enis (IEEE, 2000)
      Subband decomposition techniques have been extensively used for data coding and analysis. In most filter banks, the goal is to obtain subsampled signals corresponding to different spectral regions of the original data. ...
    • Adaptive schemes for location update generation in execution location-dependent continuous queries 

      Lam, Kam-Yiu; Ulusoy, Özgür (Elsevier Inc., 2006-04)
      An important feature that is expected to be owned by today's mobile computing systems is the ability of processing location-dependent continuous queries on moving objects. The result of a location-dependent query depends ...
    • An approach to manage connectionless services in connection-oriented networks 

      Abdelatı, Muhammed; Arıkan, Erdal (IEEE, 1996)
      In this work we propose a pricing scheme which serves as an instrument for managing connectionless services in connection-oriented communication networks. The scheme is able to allocate network bandwidth in a Pareto-optimal ...
    • Bandwidth improvement in a cMUT array with mixed sized elements 

      Bayram, Can; Olcum, Selim; Şenlik, Muhammed N.; Atalar, Abdullah (IEEE, 2005-09)
      A capacitive micromachined ultrasonic transducer (cMUT) is typically fabricated by concatenation of several cMUT cells with identical physical dimensions. If the membrane thickness is kept fixed, the radius of the cMUT ...
    • Bandwidth selection for kernel density estimation using fourier domain constraints 

      Suhre, A.; Arıkan, Orhan; Çetin, A. Enis (Institution of Engineering and Technology, 2016)
      Kernel density estimation (KDE) is widely-used for non-parametric estimation of an underlying density from data. The performance of KDE is mainly dependent on the bandwidth parameter of the kernel. This study presents an ...
    • Bandwidth, power and noise considerations in airborne cMUTs 

      Şenlik, Muhammed N.; Olcum, Selim; Köymen, Hayrettin; Atalar, Abdullah (IEEE, 2009-09)
      Capacitive micromachined ultrasonic transducers (cMUTs) offer wider bandwidth in air due to their low mechanical impedances. The impedance mismatch between the air and transducer decreases with the smaller device dimensions ...
    • Broadband quarter-wave plates at near-infrared using high-contrast gratings 

      Mutlu, M.; Akosman, A.E.; Kurt G.; Gokkavas, M.; Özbay, Ekmel (2013)
      In this paper, we report the theoretical and experimental possibility of achieving a quarter-wave plate regime by using high-contrast gratings, which are binary, vertical, periodic, near-wavelength, and two-dimensional ...
    • Capacity bounds for an ultra-wideband channel model 

      Arıkan, Erdal (IEEE, 2004-10)
      There is an ongoing effort by the IEEE 802.15.3a subcommittee to reach a UWB personal area network standard. We estimate the achievable rates for such networks using a channel model specified by the same group. The analysis ...
    • Cartesian partitioning models for 2D and 3D parallel SpGEMM algorithms 

      Demirci, Gündüz Vehbi; Aykanat, Cevdet (IEEE, 2020)
      The focus is distributed-memory parallelization of sparse-general-matrix-multiplication (SpGEMM). Parallel SpGEMM algorithms are classified under one-dimensional (1D), 2D, and 3D categories denoting the number of dimensions ...
    • Characterization and imaging with lamb wave lens at gigahertz frequencies 

      Bozkurt, Ayhan; Yaralıoğlu, Göksenin; Atalar, Abdullah; Köymen, Hayrettin; Kramer, K. (IEEE, 1994-10-11)
      Lamb wave lenses with conical refracting surfaces are fabricated for use at 400 MHz and 1 GHz. The conical surfaces are ground and polished with mechanical means and they are sufficiently smooth for the frequencies of ...
    • Compressive sensing-based robust off-the-grid stretch processing 

      Ilhan, I.; Gurbuz, A. C.; Arıkan, Orhan (Institution of Engineering and Technology, 2017)
      Classical stretch processing (SP) obtains high range resolution by compressing large bandwidth signals with narrowband receivers using lower rate analogue-to-digital converters. SP achieves the resolution of the large ...
    • Deep-collapse operation of capacitive micromachined ultrasonic transducers 

      Olcum, S.; Yamaner F. Y.; Bozkurt, A.; Atalar, Abdullah (IEEE, 2011)
      Capacitive micromachined ultrasonic transducers (CMUTs) have been introduced as a promising technology for ultrasound imaging and therapeutic ultrasound applications which require high transmitted pressures for increased ...
    • Design charts to maximize the gain-bandwidth product of capacitive micromachined ultrasonic transducers 

      Ölçüm, Selim; Şenlik, Muhammed Niyazi; Bayram, Can; Atalar, Abdullah (IEEE, 2005)
      In this work we define a performance measure for capacitive micromachined ultrasonic transducers (cMUT) in the form of a gain-bandwidth product to investigate the conditions that optimize the gain and bandwidth with respect ...
    • The design of a wideband and widebeam piston transducer in a finite closed circular baffle 

      Şahin, Z.; Köymen, Hayrettin (2008-06-07)
      The design of a high power piezoelectric underwater transducer operating at frequency range 40 kHz-80 kHz with acoustic power capability in excess of 250W is described. The transducer consists of two back-toback elements. ...
    • Design, fabrication and characterization of high-performance solarblind AlGaN photodetectors 

      Özbay, Ekmel (SPIE, 2005)
      Design, fabrication, and characterization of high-performance AlxGal-xN-based photodetectors for solar-blind applications are reported. AlxGal-xN heterostructures were designed for Schottky, p-i-n, and metal-semiconductor-metal ...
    • Designing efficient CMUT cells for airborne applications 

      Ünlügedik, Aslı; Taşdelen, Akif Sinan; Atalar, Abdullah; Köymen, Hayrettin (IEEE, 2014)
      In this work, we study airborne CMUT cells with vacuum gap where silicon plate is operated both in elastically linear and nonlinear regimes. We report the results of a new mode of operation where the plate center swings ...
    • Digital computation of the fractional Fourier transform 

      Özaktaş, Haldun M.; Arıkan, Orhan; Kutay, M. A.; Bozdağı, G. (Institute of Electrical and Electronics Engineers, 1996-09)
      An algorithm for efficient and accurate computation of the fractional Fourier transform is given. For signals with time-bandwidth product N, the presented algorithm computes the fractional transform in O(NlogN) time. A ...
    • Discriminative fine-grained mixing for adaptive compression of data streams 

      Gedik, B. (Institute of Electrical and Electronics Engineers, 2014)
      This paper introduces an adaptive compression algorithm for transfer of data streams across operators in stream processing systems. The algorithm is adaptive in the sense that it can adjust the amount of compression applied ...