AD831 Datasheet, PDF (1/16 Pages) Analog Devices – Low Distortion Mixer

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Low Distortion Mixer
AD831
FEATURES
Doubly-Balanced Mixer
Low Distortion
+24 dBm Third Order Intercept (IP3)
+10 dBm 1 dB Compression Point
Low LO Drive Required: –10 dBm
Bandwidth
500 MHz RF and LO Input Bandwidths
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 Lower Frequency Limit—Operation to DC
User-Programmable Power Consumption
APPLICATIONS
High Performance RF/IF Mixer
Direct to Baseband Conversion
Image-Reject Mixers
I/Q Modulators and Demodulators
PRODUCT DESCRIPTION
The 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. The mixer includes an LO driver
and a low-noise output amplifier and provides both user-pro-
grammable power consumption and 3rd-order intercept point.
The 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.
The 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. The mixer operates
with RF and LO inputs as high as 500 MHz.
The mixer’s IF output is available as either a differential current
output or a single-ended voltage output. The 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
REV. B
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
FUNCTIONAL BLOCK DIAGRAM
GND 4
VN 5
RFP 6
RFN 7
VN 8
3
2
50Ω
1 20 19
50Ω
18 COM
17 VFB
16 OUT
AD831
15 VN
14 BIAS
9 10 11 12 13
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.
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. The amplifier’s low dc offset allows
its use in such direct-coupled applications as direct-to-baseband
conversion and quadrature-amplitude demodulation.
The 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.
A programmable-bias feature allows the user to reduce power
consumption, with a reduction in the 1 dB compression point
and third-order intercept. This 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.
PRODUCT HIGHLIGHTS
1. –10 dBm LO Drive for a +24 dBm Output Referred Third
Order Intercept Point
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
© Analog Devices, Inc., 1995
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