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AD831

Low Distortion Mixer

FUNCTIONAL BLOCK DIAGRAM

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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 downconversion

in HF and VHF receivers, the second mixer in DMR base sta-

tions, direct-to-baseband conversion, quadrature modulation and

demodulation, and doppler shift detection in ultrasound imaging

applications. The mixer includes an LO driver and a low noise

output amplifier and provides both user-programmable power

consumption and third 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 trans-

former or capacitor to provide a 250 MHz output bandwidth. In

downconversion applications, a single capacitor connected across

these outputs implements a low-pass filter to reduce harmonics

directly at the mixer core, simplifying output 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 

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 passive

mixers, the AD831 has no insertion loss and does not require 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 dynamic

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

REV. C