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Diode-based sensors frequently rely on the

application of correction factors to extend their

dynamic range beyond their square-law region,

typically in the range of –70 dBm to –20 dBm.

While this technique achieves measurement

of CW signals over a wide dynamic range, it

fails to do so for modulated signals when the

signal level is above the square-law region.

Modulated signals must be padded down, with

their average and peak power levels within

the diode square-law region, for accurate

average power measurement.

The U2000 Series USB power sensors are true-

average, wide-dynamic-range RF/microwave

power sensors, based on a dual-sensor diode

pair/attenuator/diode pair topology as

proposed by Szente et. al. in 1990

. The

simpliﬁed block diagram shown here illustrates

this technique.

The dual-range Modiﬁed Barrier Integrated

Diode (MBID)

package incorporates diode

stacks in place of single diodes. This further

improves measurement accuracy of high-level

signals with high crest factors without

incurring damage

to the sensor.

Implementation of both techniques in the

U2000 Series USB sensors enable effective

average power measurements of a wide range

of signals, including multitone and spread

spectrum signals used in CDMA, W-CDMA

and digital television sytems.

This technique ensures diodes in the selected

signal path are kept in their square law

region—with output current and voltage

proportional to input power. The diode

pair/attenuator/diode pair assembly can then

yield the average of complex modulation

formats across a wide dynamic range,

irrespective of signal bandwidth.

1. US Patent #4943764, assigned to Hewlett-Packard Company.

2. November 1986 Hewlett-Packard Journal pages 14-2, “Diode Integrated Circuits for Millimeter-Wave Applications.”

3. Refer to “Maximum Power” on page 9 for maximum power handling speciﬁcations.

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