AD9856/PCB Analog Devices Inc, AD9856/PCB Datasheet - Page 24

• Manufacturer Part Number: AD9856/PCB
• Description: BOARD EVAL FOR AD9856
• Manufacturer: Analog Devices Inc
• Type: DDS Modulatorsr

Specifications of AD9856/PCB

• Rohs Status: RoHS non-compliant
• For Use With/related Products: AD9856
• Lead Free Status / RoHS Status: Not Compliant

AD9856
Table 6. CIC Interpolation Filter Insertion Loss Table
Interpolation
Rate
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
(Linear)
1.0000
0.8438
1.0000
0.9766
0.8438
0.6699
1.0000
0.7119
0.9766
0.6499
0.8438
0.5364
0.6699
0.8240
1.0000
0.5997
0.7119
0.8373
0.9766
0.5652
0.6499
0.7426
0.8438
0.9537
0.5364
0.6007
0.6699
0.7443
0.8240
0.9091
1.0000
0.5484
0.5997
0.6542
0.7119
0.7729
0.8373
0.9051
0.9766
0.5258
0.5652
0.6066
0.6499
0.6952
0.7426
0.7921
0.8438
0.8976
Default Gain
(dB)
0.000
−1.476
0.000
−0.206
−1.476
−3.480
0.000
−2.951
−0.206
−3.743
−1.476
−5.411
−3.480
−1.682
0.000
−4.441
−2.951
−1.543
−0.206
−4.955
−3.743
−2.585
−1.476
−0.412
−5.411
−4.427
−3.480
−2.565
−1.682
−0.827
0.000
−5.219
−4.441
−3.686
−2.951
−2.237
−1.543
−0.866
−0.206
−5.583
−4.955
−4.342
−3.743
−3.157
−2.585
−2.024
−1.476
−0.938
(Linear)
2.0000
1.6875
2.0000
1.9531
1.6875
1.3398
2.0000
1.4238
1.9531
1.2998
1.6875
1.0728
1.3398
1.6479
2.0000
1.1995
1.4238
1.6746
1.9531
1.1305
1.2998
1.4852
1.6875
1.9073
1.0728
1.2014
1.3398
1.4886
1.6479
1.8183
2.0000
1.0967
1.1995
1.3084
1.4238
1.5458
1.6746
1.8103
1.9531
1.0517
1.1305
1.2132
1.2998
1.3905
1.4852
1.5842
1.6875
1.7952
2 × Gain
(dB)
6.021
4.545
6.021
5.815
4.545
2.541
6.021
3.069
5.815
2.278
4.545
0.610
2.541
4.339
6.021
1.580
3.069
4.478
5.815
1.065
2.278
3.436
4.545
5.609
0.610
1.593
2.541
3.455
4.339
5.193
6.021
0.802
1.580
2.335
3.069
3.783
4.478
5.155
5.815
0.437
1.065
1.679
2.278
2.863
3.436
3.996
4.545
5.082
Rev. C | Page 24 of 36
Interpolation
Rate
50
51
52
53
54
55
56
57
58
59
60
61
62
63
INVERSE SINC FILTER (ISF)
The AD9856 is almost entirely a digital device. The input signal
is made up of a time series of digital data-words. These data-
words propagate through the device as numbers. Ultimately,
this number stream must be converted to an analog signal.
To this end, the AD9856 incorporates an integrated DAC.
The output waveform of the DAC is the familiar staircase
pattern typical of a signal that is sampled and quantized. The
staircase pattern is a result of the finite time that the DAC holds
a quantized level until the next sampling instant. This is known
as a zero-order hold function. The spectrum of the zero-order
hold function is the SIN(x)/x, or SINC, envelope.
The series of digital data-words presented at the input of the
DAC represent an impulse stream. It is the spectrum of this
impulse stream, which is the desired output signal. Due to
the zero-order hold effect of the DAC, however, the output
spectrum is the product of the zero-order hold spectrum
(the SINC envelope) and the Fourier transform of the impulse
stream. Thus, there is an intrinsic distortion in the output
spectrum, which follows the SINC response.
The SINC response is deterministic and totally predictable.
Thus, it is possible to predistort the input data stream in a
manner that compensates for the SINC envelope distortion.
This can be accomplished by means of an ISF. The ISF
incorporated on the AD9856 is a 17-tap, linear phase FIR filter.
Its frequency response characteristic is the inverse of the SINC
envelope. Data sent through the ISF is altered to correct for the
SINC envelope distortion.
Note, however, that the ISF is sampled at the same rate as
the DAC. Thus, the effective range of the SINC envelope
compensation only extends to the Nyquist frequency (1/2 of
the DAC sample rate).
(Linear)
0.9537
0.5060
0.5364
0.5679
0.6007
0.6347
0.6699
0.7065
0.7443
0.7835
0.8240
0.8659
0.9091
0.9539
Default Gain
(dB)
−0.412
−5.917
−5.411
−4.914
−4.427
−3.949
−3.480
−3.018
−2.565
−2.120
−1.682
−1.251
−0.827
−0.410
(Linear)
1.9073
1.0120
1.0728
1.1358
1.2014
1.2693
1.3398
1.4129
1.4886
1.5669
1.6479
1.7317
1.8183
1.9077
2 × Gain
(dB)
5.609
0.104
0.610
1.106
1.593
2.072
2.541
3.002
3.455
3.901
4.339
4.770
5.193
5.610