HMC714LP5 Datasheet, PDF (26/40 Pages) Hittite Microwave Corporation – DUAL RMS POWER DETECTOR 0.1 - 3.9 GHz

v05.0309
Application Information
Principle of Operation
HMC714LP5 / 714LP5E
DUAL RMS POWER DETECTOR
0.1 - 3.9 GHz
12
V_RMSOUT = ¹
k
ln(ßkG²âˆ«V_IN2dt)
m
V_iPAR =
ßk
V_{IN2 -1 + iREF}
∫V_IN2dt
V_RMS vs. P_IN
4
3
Measured
Ideal
Where ß is op-amp gain set via resistors on the V pin.
set
2
P = V /[log-slope]+[log-intercept], dBm
in
RMS
Monolithic true-RMS detectors are in-effect analog calculators,
1
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
0
-65 -55 -45 -35 -25 -15 -5
5
15
INPUT POWER (dBm)
time-averaged V_IN2. The bias block also contains temperature
compensation circuits which stabilize output accuracy over the
iPAR Output & Input RF Signal Envelope
entire operating temperature range. The DC offset cancellation ^{vs. Time for an Input Crest Factor of}
circuit actively cancels internal offsets so that even very small ^{9.03 dB @ 1900 MHz [2]}
input signals can be measure accurately.
2.25
1.5
IPAR Output
The iPAR feature tracks the RF envelope and provides a signal
which is directly proportional to signal power, normalized to ^1.75
1
average real power calculated by the RMS circuitry. Reading
both the iPAR and RMS output voltage signals provides a ^1.25
0.5
very informative picture of the RF input signal: peak power,
average power, peak-to-average power, and RF wave-shape. ^0.75
0
Simultaneous measurement of signal power and average
power is essential for taking full advantage of a receive signal ^0.25
-0.5
Input RF Signal Envelope
chain’s available dynamic range, while avoiding saturation, or
0
1
2
3
4
5
to maximize transmitter efficiency.
Time (usec)
For price, delivery, and to place orders, please contact Hittite Microwave Corporation:
20 Alpha Road, Chelmsford, MA 01824 Phone: [phone] Fax: [phone]
Order On-line at www.hittite.com
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