This section goes into detail on various system files that may be interesting from the researcher’s perspective. All of these files can be modified by the user as to add filters and transmit shapes, or change parameter ranges.
Digital RF Filters (Exam 5.7)
There is a file that defines all of the RF filters used by the system called filters.txt which is located in the folder: C:\Program Files\Ultrasonix\Exam\config An entry into the file has the following format:
|Filter ID||Identifies the filter. The file has been set up so that the filter ID is equal to the filter frequency multiplied by 10 plus an index to the type and length|
|Name||The name of the filter|
|Description||A brief description of the filter.|
|Length||The number of coefficients.|
|Coefficents||The coefficient list.|
|Shift||Shift value used to increase or decrease the coefficient amplitude before being applied to the data.|
: <43> : Cardiac1 : Band-pass filter at 4MHz with 15 taps : 15 : -20 -63 -84 -72 -29 31 81 101 81 31 -29 -72 -84 -63 -20 : 1
The filters are chosen through the parameters:
- RF FIR A
- RF FIR B
- RF FIR C
There is a file that defines all of the transmit shapes that the system can use called pulses.txt which is located in the folder: C:\Program Files\Ultrasonix\Exam\config. An excitation is defined as a series of +,–,0 characters, with the maximum length being 96. Each excitation is placed on a new line. The first line is identified as index 0 from the Pulse A/B/C parameters, the second line is identified as index 1, and so on. Combining similar characters does not bring the signal down, but rather stays high to allow the combination of frequencies. For more information, see Transmit Control.
Element masking allows elements to be turned off or on for transmit and receive. There is a file mask.txt which is located in the folder: C:\Program Files\Ultrasonix\Exam\config. This file is comprised of lines of 128 0's and 1's which correspond to element on (1) and element off (0). To select a mask from the interface, adjust the 'Element Mask' parameter. When this is set to 0, it will select the first line in the file, setting to 1, selects the second line, and so on. Note that setting the mask affects both transmit and receive, these cannot be adjusted individually at this time.