Datasheet

AD9125
Rev. 0 | Page 36 of 56
HB1, HB2, AND HB3
f
OUT
/f
DATA
BANDWIDTH/f
DATA
0.25
0.8
0.6
0.5
1.000.750.50
0.1 0.90.60.4
09016-029
DETERMINING INTERPOLATION FILTER MODES
Table 21 shows the recommended interpolation filter settings
for a variety of filter interpolation factors, filter center frequencies,
and signal modulation. The interpolation modes were chosen
based on the final center frequency of the signal and by
determining the frequency shift of the signal required. When
these are known and put in terms of the input data rate (f
DATA
),
the filter configuration that comes closest to matching should
be chosen from Tabl e 21.
Figure 59. Signal Bandwidth vs. Center Frequency of the Output Signal,
8× Interpolation
Table 21. Recommended Interpolation Filter Modes (Register 0x1C through Register 0x1E)
Filter Modes
Interpolation Factor HB1[1:0] HB2[5:0] HB3[5:0] f
SIGNAL
Modulation f
CENTER
Shift
8 00 (0) 000000 000000 DC 0
8 01 (1) 001001 000000 DC
1
f
DATA
/2
8
2
10 (2) 010010 001001 f
DATA
f
DATA
8 11 (3) 011011 001001 f
DATA
1
3 × f
DATA
/2
8 00 (0) 100100 010010 2 × f
DATA
2 × f
DATA
8 01 (1) 101101 010010 2 × f
DATA
1
5 × f
DATA
/2
8 10 (2) 110110 011011 3 × f
DATA
3 × f
DATA
8 11 (3) 111111 011011 3 × f
DATA
1
7 × f
DATA
/2
8 00 (0) 000000 100100 4 × f
DATA
4 × f
DATA
8 01 (1) 001001 100100 4 × f
DATA
1
9 × f
DATA
/2
8 10 (2) 010010 101101 5 × f
DATA
5 × f
DATA
8 11 (3) 011011 101101 5 × f
DATA
1
11 × f
DATA
/2
8 00 (0) 100100 110110 6 × f
DATA
6 × f
DATA
8 01 (1) 101101 110110 6 × f
DATA
1
13 × f
DATA
/2
8 10 (2) 110110 111111 7 × f
DATA
7 × f
DATA
8 11 (3) 111111 111111 7 × f
DATA
1
15 × f
DATA
/2
4 00 (0) 000000 Bypass DC 0
4
3
01 (1) 001001 Bypass DC
1
f
DATA
/2
4 10 (2) 010010 Bypass f
DATA
f
DATA
4 11 (3) 011011 Bypass f
DATA
1
3 × f
DATA
/2
4 00 (0) 100100 Bypass 2 × f
DATA
2 × f
DATA
4 01 (1) 101101 Bypass 2 × f
DATA
1
5 × f
DATA
/2
4 10 (2) 110110 Bypass 3 × f
DATA
3 × f
DATA
4 11 (3) 111111 Bypass 3 × f
DATA
1
7 × f
DATA
/2
2 00 (0) Bypass Bypass DC 0
2 01 (1) Bypass Bypass DC
1
f
DATA
/2
2 10 (2) Bypass Bypass f
DATA
f
DATA
2 11 (3) Bypass Bypass f
DATA
1
3 × f
DATA
/2
1
When HB1 Mode 1 or Mode 3 is used, enabling premodulation provides an addition frequency translation of the input signal by f
DATA
/2, which centers a baseband
input signal in the filter pass band.
2
This configuration was used in the 8× interpolation without NCO example. In addition, see the 8× Interpolation Without NCO section.
3
This configuration was used in the 4× interpolation with NCO example. In addition, see the 4× Interpolation with NCO section