© Agilent Technologies, Inc. 2009

Printed in USA, May 25, 2009

5952-8299

Applications

These detectors can be used in a wide variety of applications ranging from lab

and production measurements to systems components. Because of their flat-

ness and match, these detectors can be used for accurately measuring trans-

mission and reflection characteristics in CW or swept-frequency measurements.

For these applications in which both flat-frequency response and square-law

characteristics are important, Option 423B, 847xB/C–001 provides a matched

pair of detectors that track each other within a few tenths of a dB, and Option

423B, 847xB/C–002 (external square-law load) extends the square-law region

up to at least 0.1 mW (10 dBm). Other common applications include use with a

coupler or power splitter to externally level a source, and to display pulsed-RF

and AM-modulated signals.

For OEM and systems applications, the broadband flatness and ruggedness of

these detectors make them particularly well suited for use in closed-loop level-

ing circuits in microwave instrumentation.

Square-law response

For many reflection and transmission measurements it is desirable to use the

detector in its square-law region where its output voltage is proportional to the

input RF power. As shown in figure 5, the LBSD typically operate within 0.5 dB

of square-law from the tangential signal sensitivity (TSS) level up to 18 dBm.

By specifying Option 423B, 847xB/C–002, a specially selected loading resistor is

provided which extends this square-law region to approximately 8 dBm with an

associated decrease in sensitivity as shown in figure 5.

Pulse response

The LBSD detectors have extremely good pulse detection characteristics when

working into low-capacitance, low-resistance loads. When loaded externally

with 50 Ω the LBSD detector can typically display 8 to 12 ns rise times. Figure 6

illustrates the equivalent circuit for the detector, as well as typical values for the

diode impedance and the RF bypass capacitor.

Ordering Information

To add options to a product, use the following ordering scheme:

Model: 847xB/C (x= 0, 2 or 3)

Example options: 8472B–001, 8473C–001

423B–001

Matched pair of detectors

847xB/C–001

423B–002

External square-law load

847xB/C–002

Product specifications and descriptions

in this document subject to change

without notice.

RF in

50

V

Video out

RF bypass

capacitor

Diode

impedance

Figure 7. Detector equivalent circuit

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