Agilent Technologies ESG series, User And Programming Manual, Page: 56 / 446

2-28 Real-Time I/Q Baseband Generator User’s and Programming Guide
Using Functions HP ESG Family Signal Generators
Creating User-Defined FIR Filters Options UN8 and 202
Duplicating the First 16 Coefficients using Mirror Table
In a windowed sinc function filter, the second half of the coefficients are identical to the
first half in reverse order. The signal generator provides a mirror table function that
automatically duplicates the existing coefficient values in the reverse order.
1. Press the
Mirror Table
softkey. The last 16 coefficients are automatically generated and
the first of these coefficients (number 16) is highlighted. The following illustration
shows the display at this point in the process.
Setting the Oversample Ratio
The oversample ratio (OSR) is the number of filter taps per symbol. Acceptable values
range from 1 through 32, where the maximum combination of symbols and oversampling
ratio allowed by the table editor is 1024. The instrument hardware, however, is actually
limited to 32 symbols, an oversample ratio between 4 and 16, and 256 coefficients. If you
enter more than 256 coefficients (but no more than 32 symbols) the instrument will
resample to filter within the OSR limits. If the oversample ratio is different from the
internal, optimally selected one, then the filter will be resampled to the most optimal
oversample ratio.
For this example, the desired OSR is 4, which is the default, so no action is necessary.