Browsing by Author "Karaman, Mustafa"

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Open Access
Design and implementation of a general purpose median filter unit in VLSI
(1988-10) Karaman, Mustafa
The median of a group, containing an odd number of elements, is defined as the middle element, when the elements of the group are sorted. A median filter finds the median of a number of elements at its inputs. Median filters are frequently used in many signal and image processing applications for smoothing of the noisy signals and images while at the same time preserving the edge information. The required window size, speed, and the word length of the median filters vary depending on the applications. In order to meet these changing demands a general purpose median filter unit configuration is proposed. The unit consists of two single-chip median filters. One of the chips is designed for unlimited word-length and extensibility to larger window sizes whereas the other one is for real-time video applications. The networks of the chips are based on the odd/even transposition sorting. The chips are implemented in 3-mu m MsquareCMOS by using full-custom VLSI design techniques. For physical testing of the chips, the test vectors and the corresponding outputs of the chips are generated by using software tools written for this purpose. In this thesis, the algorithms, VLSI implementations, simulation results, testing, and applications of the chips are presented.
Open Access
Design and implementation of a general purpose VLSI median filter unit and its applications
(IEEE, 1989) Karaman, Mustafa; Onural, Levent; Atalar, Abdullah
A VLSI median filter unit has been designed and implemented in 3-μ m M2 CMOS, using full-custom VLSI design techniques. The unit consists of two single-chip median filters, one extensible and one real-time. The chips are bit-level pipelined systolic structures based on odd/even transposition sorting. The extensible chip is designed for applications requiring variable window sizes and variable word-lengths, whereas the other one is for real-time applications. Various median filtering techniques are easily realized by using the designed chips together with reasonable external hardware.
Open Access
Digital beamforming techniques and VLSI circuits for medical ultrasound imaging
(1992) Karaman, Mustafa
For phased array medical ultrasound imaging, digital beamforming techniques and VLSI circuits are studied to form a fully digital receive front-end hardware. To increase the timing accuracy in beamforming, a computationally efficient upsampling schme is examined. A digital beamforming method based on receive focusing at the raster focal points is proposed. The sector images of the resolution phantom, reconstructed from the phased array experimental data by beamforming at the radial and raster focal points, are presented for comparison of the image resolution performance of the two beamforming schemes. For adaptive beamforming, a phase aberration correction technique with very low computational complexity is described. Image quality performance of the technique is examined by digitally processing the non-aberrated and aberrated phased array experimental data sets of an ultrasound resolution phantom. VLSI circuits and their implementations for the proposed techniques are presented.
Open Access
Enhancement of images corrupted with signal dependent noise: Application to ultrasonic imaging
(1993-11) Kutay, M. Alper; Karaman, Mustafa; Bozdağı, Gözde
An adaptive filter for smoothing images corrupted by signal dependent noise is presented. The filter is mainly developed for speckle suppression in medical B-scan ultrasonic imaging. The filter is based on mean filtering of the image using appropriately shaped and sized local kernels. Each filtering kernel, fitting to the local homogeneous region, is obtained through local statistics based region growing. Performance of the proposed scheme have been tested on a B-scan image of a standard tissue-mimicking ultrasound resolution phantom. The results indicate that the filter effectively reduces the speckle while preserving the resolvable details. The performance figures obtained through computer simulations on the phantom image are presented in a comparative way with some existing speckle iippression schemes.
Open Access
A general purpose VLSI median filter and its applications for image processing
(IEEE, 1989) Karaman, Mustafa; Onural, Levent; Atalar, Abdullah
A general-purpose median filter configuration consisting of two single-chip median filters is proposed. One of the chips is designed for applications requiring variable word-length and variable window size, whereas the other is for real-time applications. The architectures of the chips are based on odd/even transposition sorting. The chips are implemented in 3-μm M2CMOS using full-custom VLSI design techniques. The chips together with a reasonable external hardware can be used for the realizations of many median filtering techniques. The VLSI design procedure of the chips and their applications to different median filtering techniques for image processing are presented.
Open Access
Reduction of effects of inactive array elements in phase aberration correction
(IEEE, 1993) Karaman, Mustafa; Köymen, Hayrettin; Atalar, Abdullah; O'Donnell, M.
Phase aberration correction based on time delay estimation via minimization of sum of absolute difference (SAD) between radio frequency (RF) signals of neighboring elements is studied in the presence of missing elements. To examine the influence of inactive elements, phase estimation error is measured for various combinations of different number of missing elements, aberration level, and SNR. The measurements are performed on an experimental RF data set. Aberration delays of missing elements are interpolated using the phase estimate between the nearest active elements. The B-scan images are reconstructed for qualitative examination.
Open Access
A VLSI receive beamformer for digital ultrasound imaging
(IEEE, 1992-03) Karaman, Mustafa; Kolağasıoğlu, Ertuğrul; Atalar, Abdullah
A VLSI architecture for real-time digital receive beamforming in phased array ultrasound imaging is proposed. The architecture is an inverse binary tree like structure with N stages where N is the number of array elements. The sampled signals from the phased array channels are coherently added in a pairwise manner within the stages of the architecture in a pipelined data flow scheme. The storage requirement for the synchronization of the asynchronously received samples corresponding to a focal point is significantly reduced. The architecture is modular and has a regular communication scheme which make the VLSI implementation rather easy and straightforward.