AD9852ASQ Analog Devices Inc, AD9852ASQ Datasheet - Page 20

• Manufacturer Part Number: AD9852ASQ
• Manufacturer: Analog Devices Inc

Specifications of AD9852ASQ

• Lead Free Status / RoHS Status: Not Compliant

AD9852
Table 6. Function Availability vs. Mode of Operation
Function
Phase Adjust 1
Phase Adjust 2
Single-Pin FSK/BPSK or HOLD
Single-Pin Shaped Keying
Phase Offset or Modulation
Amplitude Control or Modulation
Inverse Sinc Filter
Frequency Tuning Word 1
Frequency Tuning Word 2
Automatic Frequency Sweep
UNRAMPED FSK (MODE 001)
When selected, the output frequency of the DDS is a function
of the values loaded into Frequency Tuning Word Register 1
and Frequency Tuning Word Register 2 and the logic level of
Pin 29 (FSK/BPSK/HOLD). A logic low on Pin 29 chooses F1
(Frequency Tuning Word 1, Parallel Address 4 hex to Parallel
Address 9 hex), and a logic high chooses F2 (Frequency Tuning
Word 2, Parallel Register Address A hex to Parallel Register
Address F hex). Changes in frequency are phase-continuous
and are internally coincident with the FSK data pin (29);
however, there is deterministic pipeline delay between the FSK
data signal and the DAC output (see Table 1).
The unramped FSK mode (see Figure 33) is representative of
traditional FSK, radio teletype (RTTY), or teletype (TTY)
transmission of digital data. FSK is a very reliable means of
digital communication; however, it makes inefficient use of the
bandwidth in the RF spectrum. Ramped FSK, shown in
Figure 34, is a method of conserving the bandwidth.
FSK DATA (PIN 29)
I/O UD CLK
MODE
TW1
TW2
FREQUENCY
000 (DEFAULT)
F2
F1
0
0
0
Single-Tone Mode
●
●
●
●
●
●
Figure 33. Traditional FSK Mode
Rev. D | Page 20 of 52
FSK Mode
●
●
●
●
●
●
●
●
001 (FSK NO RAMP)
RAMPED FSK (MODE 010)
In this method of FSK, changes from F1 to F2 are not
instantaneous but are accomplished in a frequency sweep or
ramped fashion. The ramped notation implies the sweep is
linear. While linear sweeping, or frequency ramping, is easily
and automatically accomplished, it is only one of many
possibilities. Other frequency transition schemes may be
implemented by changing the ramp rate and ramp step size at
any time during operation.
Frequency ramping, whether linear or nonlinear, necessitates
that many intermediate frequencies between F1 and F2 are
output in addition to the primary F1 and F2 frequencies.
Figure 34 and Figure 35 graphically depict the frequency vs.
time characteristics of a linear ramped FSK signal.
In ramped FSK mode, the delta frequency word (DFW) is
required to be programmed as a positive twos complement
value. Another requirement is that the lowest frequency (F1) be
programmed in the Frequency Tuning Word 1 registers.
F1
F2
Ramped FSK Mode
●
●
●
●
●
●
●
●
●
Chirp Mode
●
●
●
●
●
●
●
●
BPSK Mode
●
●
●
●
●
●
●