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a

AD8302

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

Tel: 781/329–4700

www.analog.com

Fax: 781/326-8703

© Analog Devices, Inc., 2001

LF–2.7 GHz

RF/IF Gain and Phase Detector

FUNCTIONAL BLOCK DIAGRAM

MFLT

VMAG

MSET

PSET

VPHS

PFLT

VREF

VIDEO OUTPUT – A

INPA

OFSA

COMM

OFSB

INPB

VPOS

+

–

+

–

60dB LOG AMPS

(7 DETECTORS)

60dB LOG AMPS

(7 DETECTORS)

VIDEO OUTPUT – B

PHASE

DETECTOR

+

–

BIAS

x3

1.8V

AD8302

FEATURES

Measures Gain/Loss and Phase up to 2.7 GHz

Dual Demodulating Log Amps and Phase Detector

Input Range –60 dBm to 0 dBm in a 50

System

Accurate Gain Measurement Scaling (30 mV/dB)

Typical Nonlinearity < 0.5 dB

Accurate Phase Measurement Scaling (10 mV/Degree)

Typical Nonlinearity < 1 Degree

Measurement/Controller/Level Comparator Modes

Operates from Supply Voltages of 2.7 V–5.5 V

Stable 1.8 V Reference Voltage Output

Small Signal Envelope Bandwidth from DC to 30 MHz

APPLICATIONS

RF/IF PA Linearization

Precise RF Power Control

Remote System Monitoring and Diagnostics

Return Loss/VSWR Measurements

Log Ratio Function for AC Signals

PRODUCT DESCRIPTION

The AD8302 is an innovative, fully integrated system for mea-

suring gain/loss and phase in numerous receive, transmit, and

instrumentation applications. It requires few external compo-

nents and a single supply of 2.7 V–5.5 V. The ac-coupled input

signals can range from –60 dBm to 0 dBm in a 50

Ω system, from

low frequencies up to 2.7 GHz. The outputs provide an accu-

rate measurement of either gain or loss over a

±30 dB range

scaled to 30 mV/dB, and of phase over a 0

°–180° range scaled to

10 mV/degree. Both subsystems have an output bandwidth of

30 MHz, which may optionally be reduced by the addition of

external filter capacitors. The AD8302 can be used in direct

control mode to servo gain and phase of a signal chain toward

predetermined setpoints.

The AD8302 comprises a closely matched pair of demodulating

logarithmic amplifiers, each having a 60 dB measurement range.

By taking the difference of their outputs, a measurement of

the magnitude ratio or gain between the two input signals is

available. These signals may even be at different frequencies,

allowing the measurement of conversion gain or loss. The AD8302

may be used to determine absolute signal level by applying the

unknown signal to one input and a calibrated ac reference signal

to the other. With the output stage feedback connection dis-

abled, a comparator may be realized, using the setpoint pins

MSET and PSET to program the thresholds.

The signal inputs are single-ended, allowing them to be matched

and connected directly to a directional coupler. Their input

impedance is nominally 3 k

Ω at low frequencies.

The AD8302 includes a phase detector of the multiplier type,

but with precise phase balance, driven by the fully limited sig-

nals appearing at the outputs of the two logarithmic amplifiers.

Thus, the phase accuracy measurement is independent of signal

level over a wide range.

The phase and gain output voltages are simultaneously available

at loadable ground referenced outputs over the standard output

range of 0 V to 1.8 V. The output drivers can source or sink up

to 8 mA. A loadable, stable reference voltage of 1.8 V is avail-

able for precise repositioning of the output range by the user.

In controller applications, the connection between the gain

output pin VMAG and the setpoint control pin MSET is broken.

The desired setpoint is presented to MSET and the VMAG

control signal drives an appropriate external variable gain device.

Likewise, the feedback path between the phase output pin VPHS

and its setpoint control pin PSET may be broken, to allow

operation as a phase controller.

The AD8302 is fabricated on Analog Devices’ proprietary, high-

performance 25 GHz SOI complementary bipolar IC process. It is

available in a 14-lead TSSOP package and operates over a –40

°C

to +85

°C temperature range. An evaluation board is available.