Keysight Signal Generators Programming Guide 361
Creating and Downloading User–Data Files
FIR Filter Coefficient Downloads (N5162A, N5182A, E4438C and E8267D)
Data Limitations
NOTE Modulation filters are real and have an oversample ratio (OSR) of two or greater.
On the N5162A/N5182A with Options 651, 652, 654 only, equalization filters are typically
complex and must have an OSR of one (refer to “Using the Equalization Filter (N5162A and
N5182A with Options 651, 652, 654 Only)” on page 364 and to the User’s Guide).
The MXG supports both Real and Complex filters. Complex filters can only be used with equalization
filters. Refer to Table 6-16 and to Table 6-17. For more on equalization filters, refer to “Using the
Equalization Filter (N5162A and N5182A with Options 651, 652, 654 Only)” on page 364.
Filter lengths of up to 1024 taps are allowed. The oversample ratio (OSR) is the number of filter taps
per symbol. Oversample ratios from 1 through 32 are possible.
The sampling period (Δt) is equal to the inverse of the sampling rate (FS). For modulation filters, the
sampling rate is equal to the symbol rate multiplied by the oversample ratio. For example, the GSM
symbol rate is 270.83 ksps. With an oversample ratio of 4, the sampling rate is 1083.32 kHz and Δt
(inverse of FS) is 923.088 nsec.
Ta bl e 6- 16
Type of
Filter
Description
Real The I and Q samples are independently filtered by a single set of real coefficients.
Complex The samples are treated as complex (I + jQ) and convolved with the filter coefficients which
are specified as (I + jQ) in the time domain.
Ta bl e 6- 17
Filter Type Oversampling Ratio
(OSR)
Number of Taps
(Maximum)
Symbols/Coefficients
(Maximum)
Equalization
a
a
When I/Q timing skew, I/Q delay, or the ACP internal I/Q channel optimization features are active, the
effective number of taps for the equalization filter are reduced.
1 256 - -
ARB Custom
Modulation
b
b
The filter may be sampled to a higher or lower OSR.
≥ 2 - - 512/1024
Dual ARB
Real- Time
Modulation
c
c
The filter will be decimated to a 16 or lower OSR depending on the symbol rate.
≥ 2 - - 32/1024
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