Specifications

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SLWS142J − JANUARY 2003 − REVISED AUGUST 2007
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81
18 5016 − CONFIGURATION SOFTWARE
18.1 CDMA2000
This section describes an example of the down-conversion filter response for CDMA2000 1X. The GC5016
configuration values were input sample rate of 78.643 MSPS, CIC decimation of eight, and PFIR decimation of four
for an overall decimation of 32, output rate of 2.4576 MSPS (2x chip rate), and 255 PFIR taps. The overall filter
response, including both the CIC and PFIR filters, is shown in Figure 33 and Figure 34. As seen in Figure 34 of the
transition region, the filter response meets the CDMA2000 1X stop-band rejection requirements of −50 dB at 750
kHz and −87 dB at 900 kHz.
−120
−100
−80
−60
−40
−20
0
−5−4−3−2−1012345
Frequency − MHz
Filter Response − dB
FILTER RESPONSE
vs
FREQUENCY
Figure 33. CDMA2000 1X Filter Response
−120
−100
−80
−60
−40
−20
0
0.0 0.2 0.4 0.6 0.8 1.0
Frequency − MHz
Filter Response − dB
FILTER RESPONSE
vs
FREQUENCY
−87
dBc
−50 dbc
Figure 34. CDMA2000 1X Filter Response Transition Region with Spectral Mask
In transmit the input is presumed to operate at one sample per chip (1.2288 MHz), the PFIR interpolates by four and
uses a 192 tap filter that applies the phase predistortion, pulse shaping, adjacent channel rejection, and CIC roll-off
compensation. This is followed by a six stage CIC filter. The cmd5016 configuration file and filter taps are available
on the web.