ISL5416 Datasheet, PDF (11/71 Pages) Intersil Corporation – Four-Channel Wideband Programmable DownConverter

ISL5416
NCO / Mixer
After the input select/format section, the samples are
multiplied by quadrature sine wave samples from the carrier
NCO. The NCO has a 32-bit frequency control, providing
sub-hertz resolution at the maximum clock rate. The
quadrature sinusoids have exceptional purity. The purity of
the NCO should not be the determining factor for the
receiver dynamic range performance (A typical spectrum
plot is shown in Figure 20). The phase quantization to the
sine/cosine generator is 24 bits and the amplitude
quantization is 19 bits.
The carrier NCO center frequency is loaded via the uP bus. The
center frequency control is double buffered -- the input is loaded
into a holding register via the uP interface. The data is then
transferred from the holding register to the active register by a
write to a special address or by a SYNCInX signal, if enabled in
IWA = *000h. To synchronize multiple channels, the carrier
NCO phase accumulator feedback can be zeroed on loading to
restart all of the NCOs at the same phase (see IWA = *005h).
The phase of the NCO can be offset by programming IWA =
*003h. The phase offset is not double buffered.
ENA
ENB
ENC
END
ENµP
EXPA
EXPB
EXPC
EXPD
EXPµP
AMANT
BMANT
CMANT
DMANT
µPMANT
(TEST INPUT)
RR
EE
GG
MAX EXP
C
RR
L
EE
I
GG
P
RRR
EEE
GGG
RRR
EEE
GGG
R R ^0...-15
EE
GG
0...-23
RRR
EEE
GGG
0...-18
REG
REG
SIN/COS
GEN
REG
0...-23
R
DECIMATION _E
COUNTER G
BASE
SHIFT
VALUE
(from uP)
0...-23
R
E
G
34b
44b
53b
62b
69b
RRR
EEE
GGG
0...-29
0...-23
R
E
FIR ^{R R R}
G
FILTER
(COMB)
E
G
E
G
E
G
ENCOF
COF
COFSYNC
SERIAL
FREQ
OFFSET
REG
REG
REG
REG
CENTER PHASE
FREQ
OFFSET
CIC ORDER
1
2
3
4
5
FIR COEFFICIENTS
1
-1
1
-2
1
1
-3
3
-1
1
-4
6
-4
1
1
-5
10
-10
5
-1
NOTE:
BUS NUMBERING SUCH AS 0...-23 INDICATES BIT WEIGHTS
SUCH AS 2⁰ ... 2^-23
FIGURE 3. NCO, MIXER AND CIC BLOCK DIAGRAM
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