a
Low Distortion Mixer
AD831
FUNCTIO NAL BLO CK D IAGRAM
FEATURES
Doubly-Balanced Mixer
Low Distortion
3
2
1
20
50Ω
19
+24 dBm Third Order Intercept (IP3)
+10 dBm 1 dB Com pression Point
Low LO Drive Required: –10 dBm
Bandw idth
500 MHz RF and LO Input Bandw idths
250 MHz Differential Current IF Output
DC to >200 MHz Single-Ended Voltage IF Output
Single or Dual Supply Operation
DC Coupled Using Dual Supplies
All Ports May Be DC Coupled
No Low er Frequency Lim it—Operation to DC
User-Program m able Pow er Consum ption
50Ω
GND
VN
4
5
6
7
8
18
17
16
15
14
COM
VFB
OUT
VN
RFP
RFN
VN
AD831
BIAS
9
10
11
12
13
APPLICATIONS
High Perform ance RF/ IF Mixer
Direct to Baseband Conversion
Im age-Reject Mixers
filtering. When building a quadrature-amplitude modulator or
image reject mixer, the differential current outputs of two
AD831s may be summed by connecting them together.
I/ Q Modulators and Dem odulators
An integral low noise amplifier provides a single-ended voltage
output and can drive such low impedance loads as filters, 50 Ω
amplifier inputs, and A/D converters. Its small signal bandwidth
exceeds 200 MHz. A single resistor connected between pins
OUT and FB sets its gain. T he amplifier’s low dc offset allows
its use in such direct-coupled applications as direct-to-baseband
conversion and quadrature-amplitude demodulation.
P RO D UCT D ESCRIP TIO N
T he AD831 is a low distortion, wide dynamic range, monolithic
mixer for use in such applications as RF to IF down conversion
in HF and VHF receivers, the second mixer in DMR base sta-
tions, direct-to-baseband conversion, quadrature modula-
tion and demodulation, and doppler-shift detection in ultra-
sound imaging applications. T he mixer includes an LO driver
and a low-noise output amplifier and provides both user-pro-
grammable power consumption and 3rd-order intercept point.
T he mixer’s SSB noise figure is 10.3 dB at 70 MHz using its
output amplifier and optimum source impedance. Unlike pas-
sive mixers, the AD831 has no insertion loss and does not re-
quire an external diplexer or passive termination.
T he AD831 provides a +24 dBm third-order intercept point for
–10 dBm LO power, thus improving system performance and
reducing system cost compared to passive mixers, by eliminating
the need for a high power LO driver and its attendant shielding
and isolation problems.
A programmable-bias feature allows the user to reduce power
consumption, with a reduction in the 1 dB compression point
and third-order intercept. T his permits a tradeoff between dy-
namic range and power consumption. For example, the AD831
may be used as a second mixer in cellular and two-way radio
base stations at reduced power while still providing a substantial
performance improvement over passive solutions.
T he RF, IF, and LO ports may be dc or ac coupled when the
mixer is operating from ±5 V supplies or ac coupled when oper-
ating from a single supply of 9 V minimum. T he mixer operates
with RF and LO inputs as high as 500 MHz.
P RO D UCT H IGH LIGH TS
1. –10 dBm LO Drive for a +24 dBm Output Referred T hird
Order Intercept Point
T he mixer’s IF output is available as either a differential current
output or a single-ended voltage output. T he differential output
is from a pair of open collectors and may be ac coupled via a
transformer or capacitor to provide a 250 MHz output band-
width. In down-conversion applications, a single capacitor con-
nected across these outputs implements a low-pass filter to
reduce harmonics directly at the mixer core, simplifying output
2. Single-Ended Voltage Output
3. High Port-to-Port Isolation
4. No Insertion Loss
5. Single or Dual Supply Operation
6. 10.3 dB Noise Figure
REV. B
Inform ation furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assum ed by Analog Devices for its
use, nor for any infringem ents of patents or other rights of third parties
which m ay result from its use. No license is granted by im plication or
otherwise under any patent or patent rights of Analog Devices.
© Analog Devices, Inc., 1995
One Technology Way, P.O. Box 9106, Norw ood. MA 02062-9106, U.S.A.
Tel: 617/ 329-4700
Fax: 617/ 326-8703
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