HSP50210JC-52 Intersil, HSP50210JC-52 Datasheet - Page 10

• Manufacturer Part Number: HSP50210JC-52
• Description: Digital Costas Loop 84-Pin PLCC
• Manufacturer: Intersil

Specifications of HSP50210JC-52

• Package: 84PLCC
• Power Supply Type: Analog
• Typical Supply Current: 225 mA
• Typical Operating Supply Voltage: 5 V
• Minimum Operating Supply Voltage: 4.75 V
• Maximum Operating Supply Voltage: 5.25 V

The phase conversion is equivalent to Equation 6:
where tan
conversion output is an 8-bit two’s complement output,
which ranges from -1.0 to 0.9922 (80 to 7f HEX,
respectively). The -1 to almost 1 range of the phase output
represents phase values from -π to π, respectively. An
example of the I/Q to phase mapping is shown in Figures 6A
through 6C. The phase and magnitude values may be output
via the Output Selector bits 0 through 3 (see Table 43).
Phase (I, Q)
FIGURE 6C. CARTESIAN/POLAR CONVERTER PHASE OUTPUT
FIGURE 6B. Q INPUT TO CARTESIAN/POLAR CONVERTER
FIGURE 6A. I INPUT TO CARTESIAN/POLAR CONVERTER
-0.5
-1.0
-0.5
-1.0
-0.5
-1.0
1.0
0.5
1.0
0.5
1.0
0.5
0
0
0
-π
-π
-π
-1
( ) is the arctangent function. The phase
=
tan
–
-π/2
1
-π/2
-π/2
(
Q I ⁄
),
INPUT PHASE
INPUT PHASE
INPUT PHASE
10
0
0
0
π/2
π/2
π/2
(EQ. 6)
HSP50210
π
π
π
The I/Q data path selected for input to the Cartesian-to-Polar
converter determines the input data rate of the AGC and
carrier tracking loops. If the I/Q data path out of the Integrate
and Dump Filter is selected, the AGC is fed with magnitude
values produced by the end-symbol samples. Magnitude
values produced by midsymbol samples are not used
because these samples occur on symbol transitions, resulting
in poor signal magnitude estimates. The Carrier Tracking
block is fed with phase values generated from both the end
and mid-symbol samples. The carrier tracking loop filter,
however, is only fed with Phase Error terms generated by the
end symbol samples. If the input of the I and D is selected for
input to the coordinate converter, the control loops are fed with
data at the I/Q data rate. The desired data path input to the
Cartesian to Polar converter is specified in the Data Path
Configuration Control Register, Bit 8 (see Table 15 on
page 32).
AGC
The AGC loop operates on the main data path (I and Q) and
performs three signal level adjusting functions:
The AGC Loop Block Diagram, shown in Figure 7, consists
of an Error Detector, a Loop Filter, and Signal Gain Adjusters
(multipliers). The AGC Error Detector generates an error
signal by subtracting the programmable AGC threshold from
the magnitude output of the Cartesian to Polar Converter.
This difference signal is scaled (gain adjusted via multiplier
and shifter), then filtered (integrated) by the AGC Loop Filter
to generate the gain correction to the I and Q signals at the
multipliers. If a fixed gain is desired, set the upper and lower
limits equal.
The AGC responds to the magnitude of the sum of all the
signals in the bandpass of the narrowest filter preceding the
Cartesian to Polar Coordinate Converter. This filter may be
the Integrate and Dump filter shown in Figure 7 on page 12,
the RRC filter upstream in the HSP50210 data path, or some
other filter outside the DCL chip. The magnitude signal
usually contains several components:
At high SNR’s the signal of interest is significantly greater
than the other components. At lower SNR’s, components 2
or 3 may become greater than the signal of interest.
Narrowing the filter bandwidth is the primary technique
used to mitigate magnitude contributions of component 3.
This will also improve the SNR by reducing the magnitude
contributions of element 2. Consideration of the range of
signal amplitudes expected into the HSP50210, in
conjunction with a gain distribution analysis, will provide the
1. Maximizing dynamic range
2. Compensating for SNR variations
3. Maintaining an optimal level into the Soft Decision Slicer.
1. The signal of interest component,
2. The noise component, and
3. Interfering signals component.
July 2, 2008
FN3652.5