参数资料
型号: HSP50210JI-52Z
厂商: Intersil
文件页数: 19/51页
文件大小: 0K
描述: IC DEMODULATOR COSTAS 84-PLCC
标准包装: 15
功能: 解调器
频率: 52MHz
RF 型: AM,FM
封装/外壳: 84-LCC(J 形引线)
包装: 管件
HSP50210
In applications where Phase Error terms are generated
faster than the processing rate of the Carrier Loop Filter, an
error accumulator is provided to accumulate errors until the
loop filter is ready for a new input. Phase Error terms are
generated at the rate I/Q samples are input to the Cartesian
to Polar Converter. However, the Carrier Loop Filter cannot
accept new input faster than CLK/6 since six CLK(f CLK )
clock edges are required to complete its processing cycle. If
the error accumulator is not used and the I/Q sample rate
exceeds CLK/6, error terms will be missed.
Note: The carrier Phase Error terms input to the loop filter
are only generated from the end-symbol samples when the
output of the I and D filter is selected for input to the
Cartesian-to-Polar converter.
Note: The loop filter lead gain term must be scaled
accordingly if the accumulator is used .
operation by the Control Registers described in Tables 21
through 28 beginning on page 34.
The Carrier Tracking Loop is closed by using the loop filter
output to control the NCO or VCO used to down convert the
channel of interest. In basic configurations, the frequency
correction term controls the Synthesizer NCO in the
HSP50110 Digital Quadrature Tuner via the COF and
COFSYNC pins of the HSP50210’s serial interface (see
“Serial Output Interfaces” on page 23). In applications where
the carrier tracking is performed using the NCO on board the
HSP50210, the loop filter output is fed to the on-board NCO
as a frequency control.
The gain for the lead and lag paths of the Carrier Loop Filter
are set through a programmable mantissa and exponent.
The mantissa is a 4-bit value which weights the loop filter
input from 1.0 to 1.9375. The exponent defines a shift factor
ACTUAL
CONSTELLATION
POINT
θ E
±180°
X
90°
Q
X
I
EXPECTED
CONSTELLATION
POINT
that provides additional weighting from 2 -1 to 2 -32 . Together
the loop gain mantissa and exponent provide a gain range
between 2 -32 and ~ 1.0 as given by Equation 11.
Lead/Lag Gain = (1.0+M*2 -4 )*2 -(32 -E) (EQ. 11)
X
X
DECISION
REGION
where M = a 4-bit binary number from 0 to 15, and E is
BOUNDARY
-90°
INPUT TO CARTESIAN/POLAR CONVERTER
a 5-bit binary value ranging from 0 to 31. For example, if
M = 0101 and E = 00110, the Gain = 1.3125*2 -26 . The loop
X
DECISION
REGION
BOUNDARY
±180°
θ E
90°
Q
X
45°
I
DECISION
REGION
BOUNDARY
±45°
22.5°
Q
X
θ E
I
gain mantissa and exponent are set in the Carrier Loop Gain
Control Registers (see Tables 25 through 26 on page 36).
The Phase Error input to the Carrier Loop Filter is an 8-bit
fractional two’s complement number between ~1.0 to -1.0
(Format -2 0 . 2 -1 2 -2 2 -3 2 -4 2 -5 2 -6 2 -7 ). Some LSBs are zero for
BPSK, QPSK and 8-PSK. If minimum loop gain is used, the
-90°
PHASE ROTATION BY 45°
-22.5°
MULTIPLICATION BY 4
(MODULO 2 π )
Phase Error is shifted in significance by 2 -32 . With maximum
loop gain, the Phase Error is passed almost unattenuated.
PROJECTION OF PHASE ERROR ( θ E ) ABOUT 0°
FIGURE 14. PHASE ERROR DETECTOR OPERATION (QPSK)
TABLE 8. BASIC PHASE ERROR DETECTOR SETTINGS
The output of the Carrier Loop filter is a 40-bit fractional
two’s complement number between ~1.0 and -1.0 (Format -
2 0 . 2 -1 2 -2 2 -3 ..... 2 -39 2 -40 ). In typical applications, the 32
MSBs of the loop filter output represent the frequency
MODULATION
TYPE
CW
BPSK
QPSK
8-PSK
PHASE
OFFSET
0 ° (00 HEX)
0 ° (00 HEX)
45 ° (20 HEX)
22.5 ° (10 HEX)
SHIFT
FACTOR
0 (no shift)
1 (left shift 1)
2 (left shift 2)
3 (left shift 3)
PHASE ERROR
RANGE
±180
±90
±45
±22
control word needed to adjust the down converting NCO for
phase lock. Tables 9 and 10 beginning on page 21 illustrate
the bit weighting of the Carrier Loop Filter into the NCO for
both tracking and acquisition sweep modes.
A limiter is provided on the Carrier lag accumulator output to
keep frequency tracking within a user defined range (see
Tables 23 and 24 on page 35). If the lag accumulator
exceeds either the upper or lower limit the accumulator is
Carrier Loop Filter
The Carrier Loop Filter is second order lead/lag filter as
shown in Figure 14. The loop filter is similar to the Symbol
Tracking Loop Filter except for the additional terms from the
AFC Loop Filter and the Frequency Sweep Block. The
output of the Lag Accumulator is summed with the weighted
Phase Error term on the lead path to produce a frequency
control term. The Carrier Loop Filter is configured for
19
loaded with the limit. For additional loop filter control, the
Carrier Loop Filter output can be frozen by asserting the
FZ_CT pin which nulls the Phase Error term into the loop
filter. Also, the lag accumulator can be initialized to a
particular value via the Microprocessor Interface as
described in Table 28 on page 37 and can be read via the
microprocessor interface as described in “Reading from the
Microprocessor Interface” on page 27.
FN3652.5
July 2, 2008
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