AD9148BPCZ AD [Analog Devices], AD9148BPCZ Datasheet - Page 51

• Manufacturer Part Number: AD9148BPCZ
• Description: Quad 16-Bit,1 GSPS, TxDAC+ Digital-to-Analog Converter
• Manufacturer: AD [Analog Devices]

Preliminary Technical Data
Table 17. Programmable Inverse Sinc Filter Coefficient Widths and Ranges
Coefficient
c
c
c
c
c
c
c
c
c
c
The real and imaginary filters are implemented using the
structure described in Figure 61 and Figure 62.
The AD9148 evaluation tools provide software that allow for
the processing of the filter coefficients based on the DAC
sampling frequency, the amount of interpolation used
(combination of HB1, HB2 and HB3), and the desired center
frequency. This center frequency is limited to
where INT is the interpolation rate.
INPUT
INPUT
0
0
1
1
2
2
3
3
4
4
in-phase (real)
quadrature (imaginary)
in-phase (real)
quadrature (imaginary)
in-phase (real)
quadrature (imaginary)
in-phase (real)
quadrature (imaginary)
in-phase (real)
quadrature (imaginary)
n
+
+
n
+
–
[−( f
c
c
0REAL
DAC
0IMG
z
z
z
z
–1
–1
–1
–1
/2, f
+
+
+
–
Figure 62. Imaginary Filter implementation
c
DAC
c
1REAL
1IMG
z
z
Figure 61. Real Filter implementation
z
z
+
+
–1
–1
–1
–1
+
+
/2/ INT ); f
+
+
+
–
c
c
2REAL
z
z
z
z
2IMG
+
+
–1
–1
–1
–1
+
+
+
+
+
–
DAC
c
c
/2, f
z
3REAL
z
z
z
3IMG
–1
–1
–1
–1
+
+
+
+
DAC
+
+
+
–
/2/ INT ]
c
z
z
c
4REAL
–1
–1
4IMG
+
+
+
+
Width
3
3
4
4
5
5
7
7
10
10
c
5REAL
c
5IMG
+
+
+
+
OUTPUT
OUTPUT
Rev. PrA | Page 51 of 73
n
n
Minimum
100b
−4
0100b
−4
1000b
−8
1000b
−8
10000b
−16
10000b
−16
1000000b
−64
1000000b
−64
1000000000b
−1024
1000000000b
−1024
When there is no interpolation used, the real filter coefficients
can be fixed at (no imaginary coefficients):
C
C
C
C
C
INTERPOLATION FILTERS
The transmit path contains three interpolation filters. Each of
the three interpolation filters provides a 2× increase in output
data rate. The filters can be cascaded to provide 2×, 4×, or 8×
interpolation ratios. Each of the half-band filter stages offers a
different combination of bandwidths and operating modes.
The bandwidth of the three half-band filters with respect to the
data rate at the filter input is as follows:
•
•
•
The usable bandwidth is defined as the frequency over which
the filters have a pass-band ripple of less than ±0.001 dB and an
image rejection of greater than +85 dB. As is discussed in the
Half-Band Filter 1 (HB1) section, the image rejection usually sets
the usable bandwidth of the filter, not the pass-band flatness.
The half-band filters operate in several modes, providing
programmable pass-band center frequencies as well as signal
modulation. The HB1 filter has four modes of operation, and
the HB2 and HB3 filters each have eight modes of operation.
0
1
2
3
4
= 2
= −4
= 10
= −35
= 401
Bandwidth of HB1 = 0.8 × f
Bandwidth of HB2 = 0.5 × f
Bandwidth of HB3 = 0.4 × f
Maximum
011b
3
011b
3
0111b
7
0111b
7
01111b
15
01111b
15
0111111b
63
0111111b
63
0111111111b
1023
0111111111b
1023
;
;
;
;
IN1
IN2
IN3
C
C
C
C
8
7
6
5
= 2
= −4
= 10
= −35
AD9148