Datasheet
Data Sheet AD9148
Rev. B | Page 53 of 72
0
–20
–40
–60
–80
–100
0 2.01.81.61.41.21.00.80.60.40.2
MAGNITUDE (dB)
(×
f
IN2
)
MODE 1
MODE 3
MODE 7
MODE 5
08910-066
Figure 67. HB2, Odd Filter Modes
As shown in Figure 66 and Figure 67, the center frequency in
each mode is offset by ¼ of the input data rate (f
IN2
) of the filter.
Mode 0 through Mode 3 do not modulate the input signal. Mode 4
through Mode 7 modulate the input signal by f
IN2
. When operating
in Mode 0 and Mode 4, the I and Q paths operate independently,
and no mixing of the data between channels occurs. When
operating in the other six modes, mixing of the data between
the I and Q paths occurs; therefore, the data input to the filter
is assumed complex. Table 21 summarizes the HB2 modes.
Table 21. 4× Interpolation Filter Modes (Register 0x1C to
Register 0x1E)
Interpolation
Factor
Filter Modes
f
CENTER
(f
DAC
)
Pre-Mod HB1 HB2 HB3
4
0
0
0
Off
0
4 1 1 1 Off f
DAC
/8
4 0 2 2 Off f
DAC
/4
4 1 3 3 Off 3f
DAC
/8
4 0 0 4 Off f
DAC
/2
4 1 1 5 Off −3f
DAC
/8
4 0 2 6 Off −f
DAC
/4
4 1 3 7 Off −f
DAC
/8
Figure 68 shows the pass-band filter response for HB2. In most
applications, the usable bandwidth of the filter is limited by the
image suppression provided by the stop-band rejection and not
by the pass-band flatness. Table 22 shows the pass-band flatness
and stop-band rejection the HB2 filter supports at different
bandwidths.
0.02
0
–0.02
–0.04
–0.06
–0.08
–0.10
0 0.320.280.240.200.160.120.080.04
MAGNITUDE (dB)
(×
f
IN2
)
08910-067
Figure 68. Pass-Band Detail of HB2
Table 22. HB2 Pass-Band and Stop-Band Performance by
Bandwidth
Bandwidth (% of f
IN2
)
Pass-Band
Flatness (dB)
Stop-Band
Rejection (dB)
50 0.001 85
50.8 0.0012 80
52.8 0.0028 70
56.0 0.0089 60
60
0.0287
50
64.8 0.1877 40
Half-Band Filter 3 (HB3)
HB3 has eight modes of operation that function the same as HB2.
The primary difference between HB2 and HB3 are the filter
bandwidths. Table 23 summarizes the filter modes for HB3.
Table 23. 8× Interpolation Filter Modes (Register 0x1C to
Register 0x1E)
Interpolation
Factor
Filter Modes
f
CENTER
(f
DAC
) Pre-Mod HB1 HB2 HB3
8 0 0 0 0 0
8 0 2 2 1 f
DAC
/8
8 0 0 4 2 f
DAC
/4
8 0 2 6 3 3f
DAC
/8
8 0 0 0 4 f
DAC
/2
8
0
2
2
5
−3f
DAC
/8
8 0 0 4 6 −f
DAC
/4
8 0 2 6 7 −f
DAC
/8