HSP50210 datasheet(9/51 Pages) INTERSIL

9 / 51 page

FN3652.5

July 2, 2008

The I and 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 15). 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 32x 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

Equation 5:

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.

-20

-40

-60

-80

-100

fCLK

FREQUENCY (NORMALIZED TO INPUT SAMPLE RATE)

FIGURE 4. RRC FILTER IN HSP50210

2fCLK

3fCLK

4fCLK

fCLK

-0.18

-0.36

-0.54

-0.72

-0.90

-0.07

-0.14

-0.21

-0.28

-0.35

FREQUENCY (NORMALIZED TO INPUT SAMPLE RATE)

fCLK

2fCLK

3fCLK

4fCLK

fCLK

FIGURE 5. PASSBAND RIPPLE OF RRC FILTER IN HSP50210

SHOWN BELOW

ENLARGED FOR CLARITY

fCLK

3fCLK

fCLK

3fCLK

5fCLK

TABLE 1. ROOT RAISED COSINE COEFFICIENTS

COEFFICIENT INDEX

COEFFICIENT

1-2

4-16

5-14

686

160

886

9-14

-16

-2

Mag (I, Q)

0.81

()∗ I

()

(EQ. 5)

HSP50210

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