PDSP16350_96 Datasheet, PDF (7/12 Pages) Mitel Networks Corporation – I/Q Splitter/NCO

PDSP16350
Fig. 4 shows the operation of the device when loading the
It can also be used to generate the in-phase and quadra-
phase increment directly from the DIN bus. First the device ture components of an analog waveform, which has been
must be reset then data is presented on each clock cycle. The digitized and which is to be processed using complex tech-
amplitude modulation value is presented on the most signifi- niques. Such a quadrature heterodyning system, alternatively
cant 16 bits while the phase increment is presented on the known as an IQ splitter, is shown in Fig. 5.
least significant 18 bits. The first valid result is obtained after
The output from an A/D converter drives the D33:18 inputs
31 cycles. (In this mode the least significant 16 bits of the of the PDSP16350. If all sixteen inputs are not required, the
phase increment register remain low).
unused least significant bits should be tied to ground, and the
Fig.6 shows the operation of the device when using the full more significant inputs connected to the A/D converter. Multi-
34 bits of the phase increment register. First the device must plying an input signal with a local oscillator in this manner
be reset, then the full 34 bits of the phase increment register produces both sum and difference components. The former
are loaded from the DIN bus by taking signal JUMP high can be removed by using the PDSP16256 Programmable FIR
before the rising edge of the clock. Following this new data can Filter.
be presented on each cycle of the clock. The amplitude
modulation value is presented on the most significant 16 bits
while the phase increment is presented on the least significant
18 bits. The least significant 16
bits of the phase increment reg-
ister remain fixed at the value
loaded using JUMP. The first
valid result is obtained after 31
cycles. When using JUMP to
Analog
Data
load the phase increment regis-
ter, normal operation cannot be
maintained. This is because the
amplitude modulation value
Phase
Increment
Value
A/D
Converter
EPROM
normally presented on the most
significant 16 bits of the DIN bus
D17:0
D33:18
are replaced by part of the new
I
phase increment value.
The AM mode is useful in
systems requiring frequency
sweeps. By varying the ampli-
tudes at different frequencies, it
16 bit
Cordic
Sin / Cos
Generator
PDSP
16350
Q
PDSP16256
O/P
DATA
is possible to compensate for
the analog gain characteristics
of amplifiers further along in the
system.
Fig. 5 IQ Split Function
CLK
MODE
RESET
JUMP
DATA IN
RESULT
12345
PI A B
32 33 34 35 36 37
ABCD
Device Reset Apply phase Apply first data
increment
First Result Available
Fig. 6 Amplitude Modulation (34bit frequency accuracy)
7