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- Bipolar square wave harmonics code#
- Bipolar square wave harmonics series#
- Bipolar square wave harmonics download#
- Bipolar square wave harmonics windows#
N2 - Optimal transmit phasing has been proposed to increase contrast-to-tissue ratio (CTR) by relatively phasing the tissue and leakage harmonic components to cancel each other out for tissue-background suppression in harmonic imaging. T1 - Optimal transmit phasing for harmonic-background suppression with bipolar square-wave pulser. It should be noted, however, that the abrupt harmonic magnitude with transmit phasing could pose difficulties in the selection of the optimal suppression phase and thus limit the clinical applicability of optimal transmit phasing. Based on in-vivo images of seven consecutive cardiac cycles, a bipolar transmit waveform with the optimal suppression phase generally improves the CTR by 4.9 dB (p < 10(-8)). Our results indicate that although the harmonic magnitude becomes abrupt with the transmit phasing when a bipolar waveform is utilized in optimal transmit phasing, effective harmonic suppression is still achievable in the tissue background. In-vivo cardiac imaging of a rabbit model was also established in the clinical ultrasound system to test the efficacy of a bipolar waveform in optimal transmit phasing. Measurements of echoes from a wire phantom were performed to investigate the difference in harmonic suppression between the original transmit waveform and its bipolar counterpart.
Bipolar square wave harmonics code#
In this study, sigma-delta modulation is combined with code tuning to achieve this goal. Since most clinical systems are only equipped with a bipolar square-wave pulser, effective procedures for binary conversion of continuous transmit signals become essential in optimal transmit phasing to generate arbitrarily-phased bipolar waveforms. The zero ohm resistor simply creates two unique port labels two terminations connected to one another would cause overlapping ports and is not allowed.Optimal transmit phasing has been proposed to increase contrast-to-tissue ratio (CTR) by relatively phasing the tissue and leakage harmonic components to cancel each other out for tissue-background suppression in harmonic imaging. The fifty ohm termination port impedance matches the fifty ohm source impedance of the PORT_SQR port. If you check all of these settings you will see that they are set accordingly to get the results seen in the graphs.Įach schematic has three elements, the square wave voltage source PORT_SQR, a zero ohm resistor, and a termination port. You then select the "APLAC Sim" tab to see that you can set the number of harmonics locally here.
Bipolar square wave harmonics windows#
To see this, select one of the schematics (with a left mouse click), lets say "square_wave_1harmonic" in the project tree (left side of project windows when "Proj" tab is selected on the bottom). For this simulation the number of harmonics for each schematic is locally. You can set the number of harmonics globally from "Options > Default Circuit Options > APLAC Sim". Therefore, it is important in a simulation to distinguish between rise and fall time due to limiting harmonics, and rise and fall time due to actual circuit performance. The importance is that if the rise and fall time for each harmonic content were to be measured on the graphs, each would be different. As the number of harmonics is increased, the rise and fall times can be displayed in the response. Notice that there was a zero rise time and fall time set for the source for each square wave. The graph "Square wave time all" shows all the different harmonic settings in one graph. Note the extremes, 1 harmonic will produce a pure sine wave while 64 harmonics is very close to an ideal square wave. The graphs labels relate to the number of harmonics set in the corresponding schematic. The square wave results for each schematic with varying harmonic content can be seen the graphs. Each schematic has a different harmonic content specified, from one harmonic to 64 harmonics.
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Bipolar square wave harmonics series#
There is a series of similar schematics containing the square wave voltage source PORT_SQR. This project is a collection of square wave sources with different harmonic content, to illustrate the principles of harmonic balance circuit simulation.
Bipolar square wave harmonics download#
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