AD9139 View Datasheet(PDF) - Analog Devices
Part Name
Description
Manufacturer
AD9139 Datasheet PDF : 56 Pages
| |||
Data Sheet
DIGITAL DATAPATH
The block diagram in Figure 35 shows the functionality of the
digital datapath. The digital processing includes
• One half-band interpolation filter
• An inverse sinc filter
• A gain and offset adjustment block
DIGITAL GAIN
HB1
INV
SINC
AND OFFSET
ADJUSTMENT
Figure 35. Block Diagram of Digital Datapath
INTERPOLATION FILTERS
The transmit path contains a half-band interpolation filter. The
interpolation filters provides a 2× increase in output data rate and a
low-pass function.
The AD9139 provides two interpolation modes. Each mode offers
a different usable signal bandwidth in an operating mode. Which
mode to select depends on the required signal bandwidth and the
DAC update rate. Refer to Table 5 for the maximum speed and
signal bandwidth of each interpolation mode.
The usable bandwidth in 1× interpolation is the DCI rate or half
of the input data rate. The usable bandwidth in 2× interpolation
is 0.8 times the DCI rate or 0.4 times the input data rate. It is
defined as the frequency band over which the filters have a
pass-band ripple of less than ±0.001 dB and a stop-band
rejection of greater than 85 dB.
2× Interpolation Mode
Figure 36 and Figure 37 show the pass-band and all-band filter
response for 2× mode. Note that the transition from the
transition band to the stop band is much sharper than the tran-
sition from the pass band to the transition band. Therefore, when
the desired output signal moves out of the defined pass band,
the signal image, which is supposed to be suppressed by the stop
band, grows faster than the droop of the signal itself due to the
degraded pass-band flatness. In cases where the degraded image
rejection is acceptable or can be compensated by the analog
low-pass filter at the DAC output, it is possible to let the output
signal extend beyond the specified usable signal bandwidth.
AD9139
0.02
0
–0.02
–0.04
–0.06
–0.08
–0.10
0
10
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
0
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45
FREQUENCY (Hz)
Figure 36. Pass-Band Detail of 2× Mode
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
FREQUENCY (Hz)
Figure 37. All-Band Response of 2× Mode
Rev. A | Page 27 of 56
Share Link: 