hsp50214 Intersil Corporation, hsp50214 Datasheet - Page 23

• Manufacturer Part Number: hsp50214
• Description: Programmable Downconverter
• Manufacturer: Intersil Corporation

FIGURE 24A. POLYPHASE RESAMPLER FILTER BROADBAND
FIGURE 24B. POLYPHASE RESAMPLER FILTER PASS BAND
FIGURE 24C. POLYPHASE RESAMPLER FILTER EXPANDED
-10
-20
-30
-40
-50
-60
-70
-80
-100
-120
-10
10
-20
-40
-60
-80
-1
-2
-3
-4
-5
-6
-7
-8
-9
0
2
1
0
0
0
1
2
FREQUENCY RESPONSE
FREQUENCY RESPONSE
RESOLUTION PASSBAND FREQUENCY
RESPONSE
3
FREQUENCY (RELATIVE TO f
FREQUENCY (RELATIVE TO f
FREQUENCY (RELATIVE TO f
4
5
6
7
8
9 10 11 12 13 14 15 16
IN
IN
IN
)
)
)
HSP50214
23
TABLE 10. POLYPHASE AND INTERPOLATING HALFBAND
In burst systems (such as TDMA), time resolution is needed
for quickly identifying the optimum sample point. The timing
is adjusted by shifting the decimation in the DSP P to the
closest sample. Use of timing error rate in this way may yield
a faster acquisition than a phase-locked loop coherent bit
synchronization. Finding the optimum sample point mini-
mizes intersymbol interference.
Fine time resolution is needed in CDMA systems to resolve
different multipath rays. In CDMA systems, the demands on
the programmable FIR can only be relieved by the Resam-
pler/interpolation halfband filters. Assume the chip rate for a
baseband CDMA system is 1.2288MHz and PROCCLK is lim-
ited to 35MHz. Using the symmetric filter pre-sum approach,
PROCCLK limits the programmable FIR to 70MIPS (millions
Bypass
Polyphase Filter
Polyphase and
1 Halfband Filter
Polyphase and
2 Halfband Filters
1 Halfband Filter
2 Halfband Filters
FIGURE 25. GENERATING DATA READY PULSES FOR OUTPUT
PROCCLK
NV = INVALAID MODE
MODE
RESAMPLER
POLYPHASE
THIS BLOCK GENERATES EXTRA
DATA READY PULSES FOR THE
NEW OUTPUTS FROM THE
INTERPOLATION PROCESS.
RESAMPLER
FILTER MAXIMUM CLOCKING RATES
FILTER
DATA
NCO
PROCCLK/N
CYCLES
CLOCK
13
23
17
0
6
7
HALFBAND
FILTER #1
RESAM-
= 2.059
INPUT
RATE
(MHz)
= 5.83
= 2.69
= 1.52
= 5.00
PLER
35.00
35/13
35/23
35/17
35/6
35/7
PULSE DELAY
COUNTER
PULSE
DELAY
POLATION
INTER-
RATE
HALFBAND
FILTER #2
2
4
2
4
-
-
0
0
0
0
1
1
1
1
0 0
0
1
1
0
0
1
1
1
0
1
0
1
0
1
NCO
NCO
NCO
OUTPUT
# EXTRA
0 BYPASS
0
1
1
3 (NV)
3
3
PULSES
RATE
(MHz)
28.00
10.00
8.24
5.83
5.38
6.09