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APPENDIX B
87
S
AMPLE
R
ATES AND
N
OMINAL
S
PANS
The sample rate is the data rate that user gets after decimation. While the Nyquist frequency is
<sample rate>/2, the usable frequency range after the decimation filter, without alias error, is the
nominal span. The nominal spans are calculated as <sample rate>/2.56. The frequency region above
the pass-band (Span) can be alias contaminated. It is called guard-band.
Model
EMX-4350/4380
EMX-4250/4251
Clock Freq
409600 Hz*
524288 Hz*
625000 Hz*
131072 Hz**
204800Hz**
Top Span
160000***
204800***
244140.625***
51200***
80000***
1/5
32000
40960
48828.13
10240
16000
½- Stage1
80000
16000 102400 20480.00
122070.3
24414.06
25600
5120
40000
8000
Stage2
40000
8000
51200 10240.00
61035.16
12207.03
12800
2560
20000
4000
Stage3
20000
4000
25600
5120.00
30517.58
6103.52
6400
1280
10000
2000
Stage4
10000
2000
12800
2560.00
15258.79
3051.76
3200
640
5000
1000
Stage5
5000
1000
6400
1280.00
7629.40
1525.88
1600
320
2500
500
Stage6
2500
500
3200
640.00
3814.70
762.94
800
160
1250
250
Stage7
1250
250
1600
320.00
1907.34
381.47
400
80
625
125
Stage8
625
125
800
160.00
953.67
190.73
200
40
312.5
62.5
Stage9
312.5
62.5
400
80.00
476.83
95.37
100
20
156.25
31.25
Stage10
156.25
31.25
200.00
40.00
238.42
47.68
50.00
10.00
78.13
15.63
Stage11
78.13
15.63
100.00
20.00
119.21
23.84
25.00
5.00
39.06
7.81
Stage12
39.06
7.81
50.00
10.00
59.60
11.92
12.50
2.50
19.53
3.91
Stage13
19.53
3.91
25.00
5.00
29.80
5.96
6.25
1.25
9.77
1.95
Stage14
9.77
1.95
12.50
2.50
14.90
2.98
3.13
0.63
4.88
0.98
Stage15
4.88
0.98
6.25
1.25
7.45
1.49
1.56
0.31
2.44
0.49
Stage16
2.44
0.49
3.13
0.63
0.37
0.07
0.78
0.16
1.22
0.24
*EMX-4350/4380 clock frequencies can be divided by 2, 4, or 8 to obtain lower spans.
**EMX-4250 clock frequencies can be divided by 2 or 4 to obtain lower spans
***While the programming API defines nominal span = sample rate/2.56(0.39fs), the actual pass-band at the top span is
0.424 fs for 4350/4380, 0.4545fs for 4250/51.
Table A-1: Nominal Span (Sample Rate / 2.56)
G
ROUP
D
ELAYS
With EMX-4250/51, a filter in A/D converter introduces 39 samples group delay, and with for
EMX-4350/4380 it is 28 samples. This delay is about 45 µs at 625000 Hz.
