GC5018 Datasheet, PDF (24/115 Pages) Texas Instruments – 8-CHANNEL WIDEBAND RECEIVER

GC5018
8-CHANNEL WIDEBAND RECEIVER
SLWS169 – MAY 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
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
CFIR
MAX LENGTH
40
32
64
48
32
60
32
28
CFIR
MIN LENGTH
14
14
14
14
14
14
14
14
COMMENTS
UMTS
UMTS
CDMA2000
CDMA2000
CDMA2000 low power configuration
TD-SCDMA
TD-SCDMA
TD-SCDMA low power configuration
24
RECEIVE DIGITAL SIGNAL PROCESSING