For price, delivery and to place orders: Hittite Microwave Corporation, 20 Alpha Road, Chelmsford, MA 01824

Phone: 978-250-3343

Fax: 978-250-3373

Order On-line at www.hittite.com

Application Support: Phone: 978-250-3343 or apps@hittite.com

11

11 - 14

HMC909LP4E

v02.0511

RMS POWER DETECTOR

SINGLE-ENDED, DC - 5.8 GHz

Monolithic true-rMs detectors are in-effect analog calculators, calculating the rMs value of the input signal, unlike

other types of power detectors which are designed to respond to the rF signal envelope. At the core of an rMs

detector is a full-wave rectifier, log/antilog circuit, and an integrator. The RMS output signal is directly proportional

to the logarithm of the time-average of V

IN

2

. the bias block also contains temperature compensation circuits which

stabilize output accuracy over the entire operating temperature range. the Dc offset cancellation circuit actively

cancels internal offsets so that even very small input signals can be measured accurately.

Configuration For The Typical Application

The RF input can be connected in wideband single-ended configuration: see “RF Input Interface” section for details

on input configuration.

The RMS output signal is typically connected to VSET, through a resistive network providing a Pin -> RMSOUT

transfer characteristic slope of 36.9mV/dBm (at 1900 MHz), however the RMS output can be re-scaled to “magnify”

a specific portion of the input sensing range, and to fully utilize the dynamic range of the RMS output. Refer to the

section under the “log-slope and intercept” heading for details.

Due to part-to-part variations in log-slope and log-intercept, a system-level calibration is recommended to satisfy

absolute accuracy requirements: refer to the “System Calibration” section for more details.

0

0.5

1

1.5

2

2.5

3

-65 -60 -55 -50 -45 -40 -35 -30 -25 -20 -15 -10

IDEAL

MEASURED

INPUT POWER (dBm)

RMSOUT vs. PIN

Application Information

Principle of Operation

PIN = rMsoUt / [log-slope] + [log-intercept], dBm

Information furnished by Analog Devices is believed to be accurate and reliable. However, no

responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other

rights of third parties that may result from its use. Specifications subject to change without notice. No

license is granted by implication or otherwise under any patent or patent rights of Analog Devices.

Trademarks and registered trademarks are the property of their respective owners.

For price, delivery, and to place orders: Analog Devices, Inc.,

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106

Phone: 781-329-4700 • Order online at www.analog.com

Application Support: Phone: 1-800-ANALOG-D