Waveform generator

Wefers M M and Nelson K A 1995 Analysis of programmable ultrashort waveform generation using liquid-crystal spatial light modulators J. Opt. Soc. Am. B 12 1343-62... 

Figure 20. Photograph and schematic diagram of the Keck dye laser waveform generator.

Figure 2.2.11 shows a typical block diagram of the MRI transceiver used for the compact MRI system. The waveform generator can be replaced by the DA converter on the DSP board described in the previous section. Because the typical input/ output power level for the transmitter and from the preamplifier is about 1 mW, a commercially available transmitter and preamplifier are directly connected. 

Figure 2.15 Schematic representation of the equipment necessary to perform linear sweep voltammetry LSV) or cyclic voltammetry CV). WFG waveform generator, P potentiostat, CR chart recorder, EC electrochemical cell, WE working electrode, CE counter electrode, RE...

Fig. 5.5 Experimental setup. The diode laser is frequency scanned by one waveform generator, while the other controls the modulation. The light couples from a tapered fiber into and back out of microsphere WGMs, and the throughput is detected. A polarizing beamsplitter (PBS) separates throughput of the two polarizations. A diode pumped solid state laser can be used as an external heat source for the microsphere, and the vacuum chamber allows control over the ambient pressure. Reprinted from Ref. 5 with permission. 2008 International Society for Optical Engineering...

The idea of using phase increment to achieve frequency-shifted excitation can be extended virtually to any sort of RF pulses, including the most complicated adiabatic inversion pulses where a non-linear phase increment has already been applied. Using the phase increment, double or multiple pulses can be constructed with only a single waveform generator in order to excite different regions of a NMR spectrum or to compensate the BSFS, BSPS, as well as BSOS. 

When using the waveform generator to create the shaped pulses, the tmncation level should be kept low to reduce the spurious excitation due to the discontinuity. Usually, a 1% tmncation level (compared to the maximum amplitude of the shaped pulse) is recommended and is generally used. 

Verify that the time step provides an appropriate resolution. The time step must be small enough to provide appropriate resolution of the switching waveforms generated by the simulation. The time step should be assigned to an order of magnitude smaller than the shortest period in the simulation. For example, in a 100 kHz oscillator, the period is 10 /is. The time step should be set to 1 /is. 

Analogue control of the electrode potential or current is achieved by a function generator there are now very expensive waveform generators on the market which enable any potential on current waveform to be applied. 

PCII/IIA interface board, and an IEEE-488 General Purpose Interface Bus may be used for communication. The internal command set of the PAR Model 276 interface allows for waveform generation to circumvent the requirement for analog programming. 

The sinusoidal speech model for the single-voice case is easily generalized to the two-voice case. A waveform generated by two simultaneous voices can be represented by a sum of two sets of sine waves each with time-varying amplitudes, frequencies, and... 

Fujita, 1996] Fujita, Y. (1996). Waveform generating apparatus for musical instrument. U. S. Patent 5,553,011. 

Hartmann, 1987] Hartmann, W. M. (1987). Digital waveform generation by fractional addressing. J. Acoustical Society of America, 82(6) 1883—1891. 

Time-domain waveforms generated from a constant-phase Initial spectrum by the SWIFT procedure just described have been successfully applied to broad-band excitation, windowed excitation, and multiple-ion monitoring (11), and to mult1ple-1on ejection for enhancement of FT/ICR dynamic range (21) as described below. 

Stored waveform inverse Fourier transform (SWIFT) pulses [17] have been applied as a means of broadband ejection of matrix ions generated by Cs+ desorption [18]. These pulses are generated by taking the inverse Fourier transform of the desired frequency domain spectrum and applying the stored time domain waveform to the endcap electrodes via an arbitrary waveform generator. The magnitude of the SWIFT pulse determines the degree of excitation for ions of specific secular frequencies. 

Shaped pulses are created from text files that have a line-by-line description of the amplitude and phase of each of the component rectangular pulses. These files are created by software that calculates from a mathematical shape and a frequency shift (to create the phase ramp). There are hundreds of shapes available, with names like Wurst , Sneeze , Iburp , and so on, specialized for all sorts of applications (inversion, excitation, broadband, selective, decoupling, peak suppression, band selective, etc.). The software sets the maximum RF power level of the shape at the top of the curve, so that the area under the curve will correspond to the approximately correct pulse rotation desired (90°, 180°, etc.). When an experiment is started, this list is loaded into the memory of the waveform generator (Varian) or amplitude setting unit (Bruker), and when a shaped pulse is called for in the pulse sequence, the amplitudes and phases are set in real time as the individual rectangular pulses are executed. 

---