62
4430-V & VN BPSK/QPSK VME Demodulator & Optional Modulator User’s Manual
Doc: 4430_V,VN.fm, © 11 Jul 2005, 14:55
Figure 3.5.21: Register 39h Bit Assignments
Table 3.5.27: High Pass Filter Tuning Register Definition
To program this register, follow the procedure below.
1.
Determine the filter range by evaluating the following:
Filter Range (f
h
) = Demod f
c
- (2 x Symbol Rate)
2.
Using the results of Step 1, select the coefficients K
0
, K
1
, K
2,
and K
3
from the
table below.
Table 3.5.28: Input High Pass Filter Tuning Ranges
3.
Using the coefficients selected in Step 2, evaluate the following equation:
HP Filter = (K
0
x f
h
3
) + (K
1
x f
h
2
) + (K
2
x f
h
) + K
3
4.
Round the value from Step 3 and limit it to the range of 0 to 255.
5.
Convert the number to a hexadecimal value and write the value to register
39h.
Programming
Example
For the programming example given, the following steps apply:
7
6
5
4
3
2
1
0
0/1
0/1 0/1
0/1
0/1
0/1
0/1
0/1
HP Filter Select [Bit weight = 1] LSB
HP Filter Select [Bit weight = 2]
HP Filter Select [Bit weight = 4]
HP Filter Select [Bit weight = 8]
HP Filter Select [Bit weight = 16]
HP Filter Select [Bit weight = 32]
HP Filter Select [Bit weight = 64]
HP Filter Select [Bit weight = 128] MSB
Bit No.
Bit Name(s)
Functional Description
07-00
High Pass Filter Tuning
(See steps below)
Input High Pass Filter Range
Step
K
0
K
1
K
2
K
3
500 kHZ
≤
f
h
≤
5MHz
00b
0
-7.1
x
10
-13
6.12
x
10
-5
-25.26
55kHZ
≤
f
h
< 500kHz
01b
-8.99
x
10
-16
8.4
x
10
-10
2.91
x
10
-4
-15.27
5kHz
≤
f
h
< 55kHz
11b
-1.01
x
10
-12
7.17
x
10
-8
3.9
x
10
-3
-16
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