AD8302_15 Datasheet, PDF (1/24 Pages) Analog Devices – RF/IF Gain and Phase Detector

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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
LF–2.7 GHz
RF/IF Gain and Phase Detector
AD8302
FUNCTIONAL BLOCK DIAGRAM
INPA
OFSA
AD8302
VIDEO OUTPUT – A +
+
60dB LOG AMPS
(7 DETECTORS)
–
–
COMM
PHASE
DETECTOR
MFLT
VMAG
MSET
PSET
OFSB
INPB
VPOS
60dB LOG AMPS
(7 DETECTORS)
VIDEO OUTPUT – B
BIAS
–
+
1.8V
x3
VPHS
PFLT
VREF
PRODUCT DESCRIPTION
The AD8302 is a fully integrated system for measuring gain/loss
and phase in numerous receive, transmit, and instrumentation
applications. It requires few external components 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 accurate 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 controller mode to
force the 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 kΩ at low frequencies.
The AD8302 includes a phase detector of the multiplier type,
but with precise phase balance driven by the fully limited signals
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.
REV. A
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use, nor for any infringements of patents or other rights of third parties that
may result from its use. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices.
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© Analog Devices, Inc., 2002