AD6652BC/PCB Analog Devices Inc, AD6652BC/PCB Datasheet - Page 40

• Manufacturer Part Number: AD6652BC/PCB
• Description: BOARD EVAL W/AD6652 & SOFTWARE
• Manufacturer: Analog Devices Inc

Specifications of AD6652BC/PCB

• Module/board Type: Evaluation Board
• For Use With/related Products: AD6652
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

AD6652
INTER
The AD6652 has two interpolating half-band FIR filters th
immediately precede the two digital AGCs a
RCF channel outputs. Each interpolating half-band takes
16-bit I and 16-bit Q data from the preceding RCF and output
16-bit I and 16-b
opera e independently of each other, so the AGC can be
bypassed
directly
operate independently of each other—eith
or disabled. The control register for Half-Band A is
0x08 and for Half-Band B is at Address 0x09.
Half-band filters also perform the function of interleaving data
from various RCF channel outputs prior to the actual function
of interpolation. Interleaving of data is allowed even when the
half-band filter is bypassed. This allows the implementation of
polyphase filter by combining the processing power of multiple
channels to act upon a single carrier. This is accomplished by
appropriate phasing of the processing channels using one o
following m
• RCF phase decimation
• Start hold-off counter
For example, if two c
one CDMA2000 carrier, RCF filters for both the channels
should be 180° out of phase. This can be done using RCF phas
decimation or an appropriate start hold-off counter followed
appropriate NCO phase offsets.
Half-band A can listen to all four channels: Channels 0, 1, 2, and
3; Channel 0 and 1; or only Channel 0. Half-band B can listen t
Channels 2 and 3, or only C
the channels specified in its control register and interpolates by
t
to the output data port. The half-band filters also
, in which case the output of the half-band is sent
POLATING HALF-BAND FILTERS
ethods:
it Q to the AGC. The half-band and AGC
hannels of the AD6652 are used to process
hannel 2. Each half-band interleaves
er one can be enabled
nd follow the four
at Address
at
f the
Rev. 0 | Page 40 of 76
by
s
e
o
a
two on the combined data from those channels. For one channel
running at twice the chip rate, the half-band can be used to
output channel data at four times the chip rate. The frequency
response of the interpolating half-band FIR is shown in
Figure 50.
The SNR of the interpolating half-band is around −149.6 dB.
The highest error spurs due to fixed-point arithmetic are
around −172.9 dB. The coefficients of the 13-tap interpolating
half-ban d FIR are given in Table 18.
Table 18. Half-Band Coefficients
0 14
–10
–20
–30
–40
–50
–60
–70
–80
0
0
Figure 50. Interpolating Half-Band Frequency Response
0 −66
0.5
1.0
0 309
SPECTRUM OF HALF-BAND
MULTIPLES OF CHIP RATE
1.5
N
i
512
3
f
CHIP
2.0
f
SAMP
2.5
309
3.0
0 −66
3.5
f
f
SAMP
CHIP
0 14
4.0
0