AD9830 Datasheet, PDF (12/16 Pages) Analog Devices – CMOS Complete DDS

AD9830
APPLICATIONS
The AD9830 contains functions which make it suitable for
modulation applications. The part can be used to perform
simple modulation such as FSK. More complex modulation
schemes such as GMSK and QPSK can also be implemented
using the AD9830. In a FSK application, the two frequency reg-
isters of the AD9830 are loaded with different values, one fre-
quency will represent the space frequency while the other will
represent the mark frequency. The digital data stream is fed to
the FSELECT pin which will cause the AD9830 to modulate
the carrier frequency between the two values.
The AD9830 has four phase registers which enable the part to
perform PSK. With phase shift keying, the carrier frequency is
phase shifted, the phase being altered by an amount which is
related to the bit stream being input to the modulator. The
presence of four shift registers eases the interaction needed
between the DSP and the AD9830.
The frequency and phase registers can be written to continuously,
if required. The maximum update rate equals the frequency of
the MCLK. However, if a selected register is loaded with a new
word, there will be a delay of 6 MCLK cycles before the analog
output will change accordingly.
The AD9830 is also suitable for signal generator applications.
With its low current consumption, the part is suitable for
mobile applications in which it can be used as a local oscillator.
Figure 24 shows the interface between the AD9830 and AD6459
which is a down converter used on the receive side of mobile
phones or basestations.
AD9830
10 BITS
R_SET
1kΩ
FILTER
51Ω 51Ω
0.1µF
LOIP
RFHI
ANTENNA
RFLO
VPS1
VPS2
PRUP
MXOP
MXOM
MIDPOINT
BIAS
GENERATOR
BANDPASS
FILTER
AD6459
IFIP
IFIM
BIAS
CIRCUIT
0°
PLL
90°
GAIN TC
COMPENSATION
COM1 COM2
Figure 24. AD9830 and AD6459 Receiver Circuit
IRxP
IRxN
FREF
FLTR
QRxP
QRxN
GAIN
GREF
–12–
REV. A