AD831: Low Distortion Mixer Presented By, Adil Ahmed Nachiket - - PowerPoint PPT Presentation

ECE 468 Analog & Mixed-Signal VLSI Design

AD831: Low Distortion Mixer

Presented By, Adil Ahmed Nachiket Mehta Pruthav Joshi April 29, 2004

Overview

• Mixer Fundamentals
• Introduction to the Low

Distortion Mixer

• AD831
• Specifications
• Pin Description

Table

• Theory of Operation
• Schematics and

Simulation

• Applications
• End Note

Mixer Fundamentals

• Definition
• A device in which two or more input signals are

combined to give a single output signal.

• Satellite communication systems
• Non-linear device used to generate a replica of an

input signal at a higher or lower frequency

• Done by multiplying the input signal by a pure

tone of a different frequency (the "local oscillator" signal). Usually part of a frequency conversion process.

• For example, an LNB local oscillator signal at 10.6 GHz

mixed with incoming signal at 12 GHz would convert the input signal to an IF frequency of 12 -10.6 = 1.4 GHz.

Introduction to the AD831 [I]

• This is a low distortion, wide dynamic range, monolithic

mixer.

• The mixer includes an LO driver, a low-noise output

amplifier and also provides additional features.

• The AD831 improves system performance and reducing

system cost compared to passive mixers.

• Power Supply
• RF, IF and LO ports are DC or AC coupled for ±5 V
• AC coupled when using 9 V
• The mixer's IF output is available as either a differential

current output or a single-ended voltage output

Introduction to the AD831 [II]

• A low noise amplifier provides a single-ended voltage
• utput.
• The gain is set by A single resistor connected between

pins OUT and FB.

• The amplifier's low dc offset allows its use in such direct-

coupled applications.

• The AD831 has no insertion loss and does not require

an external diplexer or passive termination.

• Power consumption.
• Reduces power consumption.
• A tradeoff between dynamic range and power

consumption.

AD831 Mixer: Specifications I

AD831 Mixer: Specifications II

AD831 Mixer: Pin Description Table

AD831 Mixer: Theory of Operation

• Consists of the following:
• Mixer core
• Limiting amplifier
• Low noise output amplifier
• Bias current
• RF input is converted into differential currents by a highly

linear V/C converter

• Resulting currents drive differential pairs
• LO input converts LO input into a square wave
• Drives differential pairs and produces high level output

and a series of lower level outputs caused by odd harmonics of LO frequency mixing with RF input39

• On-chip network supplies bias current to RF and LO inputs

(ac-coupled)

AD831 Mixer: Full Schematic Diagram

Bias Current Schematic

Current Mirror Schematic

Limiting Amplifier Schematic

Full System Schematic

Simulation of Schematic

Input Values

Input Values VP/VN 5.0 V/-5.0V LOP 1.0 V LON 1.0 V RFP 1.0 V RFN

• 1.0 V

BIAS 50 µA

References

• www.analog.com/UploadedFiles/Data

_Sheets/36203455769223AD831_c.p df

• Analog Design for CMOS VLSI

Systems by Franco Maloberti

• Analysis and Design of Analog

Integrated Circuits by Grey and Meyer