Take a Closer Look

Diode-based sensors frequently

rely on the application of correc-

tion factors to extend their dynamic

range beyond their square-law

region, typically in the range of –70

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 aver-

age 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 19901.

The simplified block diagram shown

here illustrates this technique.

This technique ensures diodes in the

selected signal path are kept in their

square law region—with output cur-

rent and voltage proportional to input

power. The diode pair/attenuator/

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

RF in

Low Sense+

Low Sense–

High Sense+

High Sense–

diode pair assembly can then yield

the average of complex modulation

formats across a wide dynamic range,

irrespective of signal bandwidth.

The dual-range Modified Barrier

Integrated Diode (MBID)2 package

incorporates diode stacks in place of

single diodes. This further improves

measurement accuracy of high-level

signals with high crest factors with-

out incurring damage3 to the sensor.

Implementation of both techniques

in the U2000 Series USB sensors

enable effective average power mea-

surements of a wide range of signals,

including multitone and spread spec-

trum signals used in CDMA, W-CDMA

and digital television sytems.

Built-in triggering port for

synchronization with external

instruments or events

LED indicator for PC communication

Small and lightweight build

Secure locking mechanism

USB 2.0-compliant cable

for connection to PC or

other instruments

06 | Keysight | U2000 Series USB Power Sensors - Data Sheet