AD8302 datasheet(22/24 Pages) AD

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AD8302

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CHARACTERIZATION SETUPS AND METHODS

The general hardware configuration used for most of the AD8302

characterization is shown in Figure 16. The characterization board

is similar to the Customer Evaluation Board. Two reference-locked

R & S SMT03 signal generators are used as the inputs to INPA

and INPB, while the Gain and Phase outputs are monitored using

both a TDS 744A oscilloscope with 10

× high impedances probes and

Agilent 34401A multimeters.

Gain

The basic technique used to evaluate the static gain (VMAG)

performance was to set one source to a fixed level and sweep the

amplitude of the other source, while measuring the VMAG output

with the DMM. In practice the two sources were run at 100 kHz

frequency offset and average output measured with the DMM to

alleviate errors that might be induced by gain/phase modulation

due to phase jitter between the two sources.

The errors stated are the difference between a best fit line calcu-

lated by a linear regression and the actual measured data divided

by the slope of the line to give an error in V/dB. The “referred to

°C error” uses this same method, while always using the slope

and intercept calculated for that device at 25

°C.

Response measurement made of the VMAG output used the

configuration shown in Figure 17. The variable attenuator,

Alpha AD260, is driven with a HP8112A pulse generator pro-

ducing a change in RF level within 10 ns.

Noise spectral density measurements were made using a

HP3589A with the inputs delivered through a Narda 4032C

° phase splitter.

To measure the modulation of VMAG due to phase variation

again the sources were run at a frequency offset, fOS, effectively

creating a continuous linear change in phase going through 360

once every 1/fOS seconds. The VMAG output is then measured

with a DSO. When perceivable, only at high frequencies and

large input magnitude differences, the linearly ramping phase

creates a near sinusoid output riding on the expected VMAG

DC output level. The curves in TPC 24 show the peak-to-peak

output level measured with averaging.

Phase

The majority of the VPHS output data was collected by generat-

ing phase change, again by operating the two input sources with

a small frequency offset (normally 100 kHz) using the same

configuration shown in Figure 16. Although this method gives

excellent linear phase change, good for measurement of slope

and linearity, it lacks an absolute phase reference point. In the

curves showing swept phase the phase at which the VPHS is the

same as VPHS with no input signal is taken to be –90

° and all

other angles are references to there. Typical Performance Curves

show two figures of merit; instantaneous slope and error. Instan-

taneous slope, as shown in TPCs 43, 44, and 45 was calculated

simply by taking the delta in VPHS over angular change for adjacent

measurement points.

TEKTRONIX

TDS 744A

OSCILLOSCOPE

MULTIMETER/

OSCILLOSCOPE

INPA

INPB

VMAG

VREF

VPHS

EVB

3dB

R & S

SIGNAL GENERATOR

SMTO3

TEKTRONIX

VX1410A

3dB

R & S

SIGNAL GENERATOR

SMTO3

HP 34401A

MULTIMETER

SAME SETUP AS

VMAG

Figure 16. Primary Characterization Setup

INPA

INPB

VMAG

VREF

VPHS

EVB

3dB

R & S

SIGNAL

GENERATOR

SMTO3

SPLITTER

VARIABLE

ATTEN

FIXED

ATTEN

TEKTRONIX

VX1410A

3dB

TEKTRONIX

TDS 744A

OSCILLOSCOPE

PULSE

GENERATOR

Figure 17. VMAG Dynamic Performance Measurement Setup

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