Analysis of worst-case phase quantization sidelobes in focused beamforming

Holm, Sverre; Kristoffersen, K.

doi:10.1109/58.156177

Cited by 42 publications

(33 citation statements)

References 5 publications

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“…Note that whilst the maximum tolerable phase error is expressed as a path length or phase difference, where λ is the wavelength of the center frequency of the excitation pulse in the medium, it can also be represented using the following relationships as derived from [4], [16] and [3]:…”

Section: B Phase Quantizationmentioning

confidence: 99%

“…Holm and Kristoffersen [3] combined the effect of steering with the focused case as described in [16] in order to evaluate a 'worst case' where quantization effects were most severe. It was shown that the worst case with respect to ultrasound applications would be the use of continuous wave excitation and a combination of maximum correlated error (i.e.…”

Section: B Phase Quantizationmentioning

confidence: 99%

“…A delay profile rounded or quantized to a minimum time interval results in deviation or rounding error. These deviations or errors can be classed as either correlated (periodic) or uncorrelated (random) [3]. Correlated quantization error occurs periodically across an aperture, when the minimum time increment (or integer multiple of) extends over two elements or more [13].…”

Section: B Phase Quantizationmentioning

confidence: 99%

“…A quantized delay profile is an approximation of the ideal phase delay profile, with timing inaccuracy introduced as a result of hardware implementation. The deviation from the ideal phase delay profile is described as phase quantization error [3].…”

Section: Introductionmentioning

confidence: 99%

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Ultrasound array transmitter architecture with high timing resolution using embedded phase-locked loops

Smith

Cowell

Raiton

et al. 2012

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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Abstract-Coarse time quantization of delay profiles within ultrasound array systems can produce undesirable sidelobes in the radiated beam profile. The severity of these sidelobes is dependent upon the magnitude of phase quantization error -the deviation from ideal delay profiles to the achievable quantized case. This paper describes a method to improve inter channel delay accuracy without increasing system clock frequency by utilising embedded Phase-Locked Loop (PLL) components within commercial Field Programmable Gate Arrays (FPGAs). Precise delays are achieved by shifting the relative phases of embedded PLL output clocks in 208 ps steps. The described architecture can achieve the necessary inter element timing resolution required for driving ultrasound arrays up to 50 MHz. The applicability of the proposed method at higher frequencies is demonstrated by means of extrapolating experimental results obtained using a 5 MHz array transducer. Results indicate an increase in Transmit Dynamic Range (TDR) when using accurate delay profiles generated by the embedded PLL method described, as opposed to using delay profiles quantized to the system clock.

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Section: B Phase Quantizationmentioning

confidence: 99%

Section: B Phase Quantizationmentioning

confidence: 99%

Section: B Phase Quantizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Ultrasound array transmitter architecture with high timing resolution using embedded phase-locked loops

Smith

Cowell

Raiton

et al. 2012

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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“…The focusing precision is of paramount importance for the image quality [4] and simple compression is not an option. Parametric recursive delay generators have been suggested for the case of image lines originating from the transducer [2], [14].…”

Section: Introductionmentioning

confidence: 99%

P3H-3 Parametric Beamformer for Synthetic Aperture Ultrasound Imaging

Nikolov

Tomov

Jensen

2006

2006 IEEE Ultrasonics Symposium

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Abstract-In this paper a parametric beamformer, which can handle all imaging modalities including synthetic aperture imaging, is presented. The image lines and apodization coefficients are specified parametrically, and the lines can have arbitrary orientation and starting point in 3D coordinates. The beamformer consists of a number of identical beamforming blocks, each processing data from several channels and producing part of the image. A number of these blocks can be accommodated in a modern field-programmable gate array device (FPGA), and a whole synthetic aperture system can be implemented using several FPGAs. For the current implementation, the input data is sampled at 4 times the center frequency of the excitation pulse and is match-filtered in the frequency domain. In-phase and quadrature data are beamformed with a sub-sample precision of the focusing delays of 1/16th of the sampling period. Each line is completely specified by 3 input parameters. The focusing delays are calculated iteratively in a 8-stage deep pipeline, and focusing information for 8 different lines is interleaved to produce delays at every clock cycle. The apodization is specified using piecewise linear approximation with 255 levels. A beamforming block uses input data from 4 elements and produces a set of 10 lines. Linear interpolation is used to implement sub-sample delays. The VHDL code for the beamformer has been synthesized for a Xilinx V4FX100 speed grade 11 FPGA, where it can operate at a maximum clock frequency of 167.8 MHz. Each beamformation block requires 12 multipliers, 5 buffers for parameters, 8 buffers for input data and 32 buffers for output data (I and Q). Furthermore double-buffering is used for the input data, thus simplifying the synchronization. Up to six beamforming blocks can fit in one FPGA. Clocked at 150 MHz they produce 900 × 10 6 I and Q samples/second. Assuming a pulse repetition frequency of 5000 Hz, these blocks can be configured to beamform in real time 256 B-mode lines of synthetic aperture data from 4 transducer elements, or 64 lines from 16 elements.

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