AD9830

REV. A

–12–

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.

BANDPASS

FILTER

IFIP

IFIM

MXOP

MXOM

MIDPOINT

BIAS

GENERATOR

BIAS

CIRCUIT

LOIP

FILTER

51

Ω

51

Ω

10 BITS

1k

Ω

AD9830

AD6459

PLL

0

°

90

°

GAIN TC

COMPENSATION

IRxP

IRxN

FREF

FLTR

QRxP

QRxN

GAIN

GREF

RFHI

RFLO

VPS1

VPS2

PRUP

COM1

COM2

0.1µF

ANTENNA

Figure 24. AD9830 and AD6459 Receiver Circuit