GC5018_06 Datasheet, PDF (24/134 Pages) Texas Instruments – 8-CHANNEL WIDEBAND RECEIVER

GC5018
8-CHANNEL WIDEBAND RECEIVER
SLWS169A – MAY 2005 – REVISED NOVEMBER 2005
MPU control
interface
read data
write data
write pointer
COEF
RAM
32x18
mpu
ram_read
read pointer
MUX
complex
input
samples
DATA
RAM
64x36
COEF
RAM
32x18
DATA
RAM
64x36
www.ti.com
complex
reg
output
samples
crastarttap
write
pointer
read
pointer
State Machine
Figure 3-24. DDC CFIR Block Diagram
output
sample
valid
The maximum CFIR filter length is a function of GC5018 clock rate, output sample rate and the number of
coefficient memory registers. The maximum number of taps is 64 and the minimum number is 14. Lengths
between these limits can be specified in increments of 2.
Subject to the above minimum and maximum values, in the general case, the number of taps available is:
UMTS Mode: 2 x (rxclk ÷ output sample rate)
CDMA Mode if cic_decim is even (decimating by an odd number): 2 x (cic_decim)
CDMA Mode if cic_decim is odd (decimating by an even number): 2 x (cic_decim + 1)
Example CFIR filter lengths available based on mode and rxclk frequency:
Mode
UMTS
UMTS
CDMA
CDMA
CDMA
CDMA
CDMA
CDMA
rxclk
(MHz)
153.60
122.88
157.2864
122.88
78.6432
153.60
81.92
76.80
CIC
DECIMATION
10
8
32
25
16
30
16
15
cic_decim
9
7
31
24
15
29
15
14
CFIR
CFIR
MAX LENGTH MIN LENGTH
COMMENTS
40
14
UMTS
32
14
UMTS
64
14
CDMA2000
48
14
CDMA2000
32
14
CDMA2000 low power configuration
60
14
TD-SCDMA
32
14
TD-SCDMA
28
14
TD-SCDMA low power configuration
24
RECEIVE DIGITAL SIGNAL PROCESSING