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AD8370

Rev. 0 | Page 24 of 28

APPENDIX

CHARACTERIZATION EQUIPMENT

An Agilent N4441A Balanced Measurement System was used to

obtain the gain, phase, group delay, reverse isolation, CMRR,

and s-parameter information contained in this data sheet. With

the exception for the s-parameter information, T-attenuator

pads were used to match the 50 Ω impedance of this instrument’s

ports to the AD8370. An Agilent 4795A Spectrum Analyzer was

used to obtain nonlinear measurements IMD, IP3, and P1dB

through matching baluns and/or attenuator networks. Various

other measurements were taken with setups shown in this

section.

COMPOSITE WAVEFORM ASSUMPTION

The nonlinear two-tone measurements made for this data sheet,

i.e., IMD and IP3, are based on the assumption of a fixed value

composite waveform at the output, generally 1 V p-p. The fre-

quencies of interest dictate the use of RF test equipment, and

because this equipment is generally not designed to work in

units of volts, but rather watts and dBm, an assumption was

made to facilitate equipment setup and operation. Two sinusoidal

tones can be represented as

V1 = V sin (2∏f1t)

V2 = V sin (2∏f2t)

The RMS average voltage of one tone is

)

(

∫ dt

where T is the period of the waveform. The RMS average

voltage of the two-tone composite signal is

)

(

∫

It can be shown that the average power of this composite

waveform is twice (3 dB) that of the single tone. This also means

that the composite peak-to-peak voltage is twice (6 dB) that of a

single tone. This principle can be used to set correct input

amplitudes from generators scaled in dBm and is correct if the

two tones are of equal amplitude and are reasonably close in

frequency.

DEFINITIONS OF SELECTED PARAMETERS

Common-mode rejection ratio (Figure 26) has been defined for

this characterization effort as

Gain

Mode

Common

Gain

Mode

Differenti

where the numerator is the gain into a differential load at the

output due to a differential source at the input, and the

denominator is the gain into a differential-mode load at the

output due to a common-mode source at the input. In terms of

mixed-mode s-parameters, this equates to

SDC21

SDD21

More information on mixed-mode s-parameters can be

obtained in a reference by Bockelman, D.E. and Eisenstadt,

W.R., Combined Differential and Common-Mode Scattering

Parameters: Theory and Simulation. IEEE Transactions on

Microwave Theory and Techniques, v 43, n 7, 1530 (July 1995).

Reverse isolation (Figure 24) is defined as SDD12.

Power supply rejection ratio (PSRR) has been defined as

where Adm is the differential mode forward gain (SDD21), and

As is the gain from the power supply pins (VCCI and VCCO,

taken together) to the output (OPLO and OPHI, taken differen-

tially), corrected for impedance mismatch. The following

reference provides more information: Gray, P.R., Hurst, P.J.,

Lewis, S.H. and Meyer, R.G., Analysis and Design of Analog

Integrated Circuits, 4th Edition, John Wiley & Sons, Inc., page 422.

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