hsp50210 Intersil Corporation, hsp50210 Datasheet - Page 8

• Manufacturer Part Number: hsp50210
• Description: Digital Costas Loop
• Manufacturer: Intersil Corporation

FIGURE 5. PASSBAND RIPPLE OF RRC FILTER IN HSP50210
-0.18
-0.36
-0.54
-0.72
-0.90
-100
-0.07
-0.14
-0.21
-0.28
-0.35
-20
-40
-60
-80
0
0
0
0
0
0
FREQUENCY (NORMALIZED TO INPUT SAMPLE RATE)
FREQUENCY (NORMALIZED TO INPUT SAMPLE RATE)
FIGURE 4. RRC FILTER IN HSP50210
f
CLK
40
f
f
CLK
CLK
10
25
SHOWN BELOW
ENLARGED FOR CLARITY
f
CLK
20
2f
2f
CLK
10
CLK
25
3f
3-8
40
CLK
3f
3f
f
CLK
25
10
CLK
CLK
10
5f
40
CLK
4f
4f
10
25
CLK
CLK
3f
CLK
20
f
f
CLK
CLK
2
5
HSP50210
The I&D filter consists of an accumulator, a programmable
shifter and a two sample summer as shown in Figure 3. The
programmable shifter is provided to compensate for the gain
introduced by the accumulator (see Table 14). The
accumulator provides Integrate and Dump Filtering for
decimation factors up to 16. The two sample summer
provides the moving average required for an additional
decimation factor of 2. A decimation factor of 1 (bypass), 2,
4, 8, 16, or 32 may be selected. At the maximum decimation
rate, a baseband signal sampled at 32 times the symbol rate
can be filtered.
The output of the two sample summer is demultiplexed into
two sample streams at the symbol rate. The demultiplexed
data streams from the I and Q processing paths are fed to
the Symbol Tracking Block and Soft decision slicer. The
multiplexed data streams on I and Q are provided as one of
the selectable inputs for the Cartesian to Polar Converter.
Cartesian/Polar Converter
The Cartesian/Polar Converter maps samples on the I and Q
processing paths to their equivalent phase/magnitude
representation. The magnitude conversion is equivalent to:
where 0.81 is the gain of the conversion process. The
magnitude output is an 8-bit unsigned value ranging from 0.0
to 1.9922.
Mag (I, Q)
COEFFICIENT INDEX
TABLE 1. ROOT RAISED COSINE COEFFICIENTS
=
0.81
10
11
12
13
14
0
1
2
3
4
5
6
7
8
9
I
2
+
Q
2
,
COEFFICIENT
160
-16
-14
-14
-16
86
86
-2
-2
2
1
8
8
1
2
(EQ. 5)