AD9870EB datasheet(17/20 Pages) AD

17 / 20 page

REV. 0

AD9870

–17–

–20

–40

–60

–80

–100

10–4

10–3

10–2

10–1

BASEBAND FREQUENCY – Relative to

fCLK

Figure 13b. Decimator Frequency Response

–20

–40

–60

–80

–100

0.50

0.25

NORMALIZED FREQUENCY – Relative to

fOUT

Figure 13c. Folded Decimator Frequency Response

As Figure 13d shows, the gain variation across the passband

is approximately 0.4 dB. Normalization of full-scale is accurate

to within 0.4 dB across all decimation modes.

NORMALIZED FREQUENCY – Relative to

fOUT

–40

–100

–20

–60

–80

0.25

Figure 13d. Passband Frequency Response of the

Decimator

Evaluation Board and Software

The evaluation board along with its accompanying software

provide a simple means to evaluate the AD9870. The block

diagram in Figure 14 shows the major blocks of the evaluation

board. The evaluation board is designed to be flexible allowing

the user to configure it for different potential applications. The

power supply distribution block provides filtered, adjustable

voltages to the various supply pins of the AD9870. In the IF

Input signal path, component pads are available to implement

different IF impedance matching networks. The LO and CLK

signals can be externally applied or internally derived from a

user-supplied VCO Module interface daughter board. The refer-

ence for the on-chip LO and CLK synthesizers can be applied

via the external FREF input or an on-board crystal oscillator.

MIXER

OUTPUT

INPUT

AD9870

AD9874

VCO

MODULE

INTERFACE

CRYSTAL

OSCILLATOR

IDT

FIFO

(OPTIONAL)

AD9870/AD9874

POWER SUPPLY

DISTRIBUTION

EPROM

CLK

INPUT

FREF

INPUT

NIDAQ

68-PIN

CONNECTOR

XILINX

SPARTON

FPGA

Figure 14. Evaluation Board Platform

The evaluation board is designed to interface to a PC via a

National Instruments PCI-DIO-32HS digital IO card. A XILINX

FPGA formats the data between the AD987x and digital I/O

board. Software developed using National Instruments LabVIEW™

and provided as MS Windows™ executable programs is supplied

for the configuration of the SPI port registers and evaluation

of the AD9870 output data. These programs have a convenient

graphical user interface allowing for easy access to the various

SPI port configuration registers and real time frequency analysis

of output data.

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