volume33-number1(1).pdf

About Analog Dialogue

Analog Dialogue is the free technical magazine of Analog Devices, Inc., published

continuously for thirty-three years, starting in 1967. It discusses products, applications,

technology and techniques for analog, digital, and mixed-signal processing.

Volume 33, the current issue, incorporates all articles published during 1999 in the

World Wide Web 1 editions. All recent issues, starting with Volume 29, Number 2

(1995) have been archived on that website.

As one of the many informative Analog Devices publications, Analog Dialogue ’s

objectives are to inform engineers, scientists, and electronic technicians about new

ADI products and technologies, and to help them understand and competently

apply our products.

The monthly Web editions have at least three further objectives:

• Provide timely digests that alert readers to upcoming and available products.

• Provide a set of links to important and rapidly proliferating sources

of information and activity fermenting within the ADI Web site 2

• Listen to reader suggestions and help find sources of aid to answer

their questions.

Thus, Analog Dialogue is more than a magazine: its links and tendrils to all

parts of our website (and some outside sites) make its bookmark a favorite

“high-pass-filtered” point of entry to the analog.com site—the world of

Analog Devices.

Our hope is that readers will think of ADI publications as “Great Stuff ” and the

Analog Dialogue bookmark on their web browser as a favorite alternative path to

answer the question, “What’s new at ADI?”

Welcome! Read and enjoy!

Dan Sheingold

dan.sheingold@analog.com

Editor, Analog Dialogue

1 www.analog.com/analogdialogue/

2 www.analog.com

IN THIS ISSUE

Analog Dialogue Volume 33, 1999

Page

Editor’s Notes, Authors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Othello: A new direct-conversion radio chip set eliminates IF stages . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

DSPs enhance flexible third-generation (3G) base station design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Phase-locked loops for high-frequency receivers and transmitters, Part 1 . . . . . . . . . . . . . . . . . . . . . . . . 9

Phase-locked loops for high-frequency receivers and transmitters, Part 2 . . . . . . . . . . . . . . . . . . . . . . . 13

Phase-locked loops for high-frequency receivers and transmitters, Part 3 . . . . . . . . . . . . . . . . . . . . . . . 18

Dual-axis, low-g, fully integrated accelerometers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Accelerometers—fantasy and reality (Ask The Applications Engineer—29) . . . . . . . . . . . . . . . . . . . . 25

ADXL105: A lower-noise, wider-bandwidth accelerometer, rivals performance of

more expensive sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Logarithmic amplifiers explained (Ask The Applications Engineer—28) . . . . . . . . . . . . . . . . . . . . . . 30

Analog-to-Digital converter architectures and choices for system design . . . . . . . . . . . . . . . . . . . . . . . . 35

New-Product Brief: AD9814 Low Power 14-Bit, 3-Channel CCD Signal Processor . . . . . . . . . 38

New-Product Brief: AD9884 8-bit, 140 MSPS Flat Panel Display Interface . . . . . . . . . . . . . . . 38

New TxDAC ® Generation: 125 MSPS 10-, 12-, and 14-bit high-performance DACs

for wideband multitone communication Transmit channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

New-Product Brief: AD9772 14-bit, 300 MSPS TxDAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Ultrasound analog electronics primer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

New-Product Brief: ADP3421 Geyserville-Enabled DC/DC Converter Controller . . . . . . . . . 43

A chip you can use to monitor environmental conditions on PC motherboard designs . . . . . . . . . . . . . . 44

Measuring Temperatures on Computer Chips with Speed and Accuracy: A new approach using

silicon sensors and off-chip processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

New-Product Brief: AD1881 AC’97 SoundMAX ® Audio Codec . . . . . . . . . . . . . . . . . . . . . . . 53

Compensate for loading effects on power lines with a DSP-controlled active shunt filter . . . . . . . . . . . . . 54

Signal corruption in industrial measurement (Ask The Applications Enginee—27) . . . . . . . . . . . . . . . 58

New-Product Brief: AD8551/2/4 Zero-Drift, Single-Supply, Rail-to-Rail Op Amps . . . . . . . . . 59

Process signals from millivolts to

10 V directly with a versatile single-supply 3/5V

charge-balancing A/D converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

New-Product Brief: ADuC812 12-bit MicroConverter Data Acquisition System . . . . . . . . . . . 61

Microcontroller-based energy metering using the AD7755 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

New-Product Brief: ADMC401 DSP-Based High-Performance Motor Controller . . . . . . . . . . 63

All-electronic power and energy meters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

New-Product Brief: AD7751 Fault-Tolerant Energy Metering IC . . . . . . . . . . . . . . . . . . . . . . 66

Make vs. Buy: When should I re-invent the wheel? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

New ADI Fellows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

Authors (continued from page 2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

Worth Reading: An authoritative, practical, readable new DSP book. Read it FREE on-line. . . . . 72

Cover: The cover illustration was designed and executed by Kristine Chmiel-Lafleur, of Communications Services, Analog Devices, Inc.

Analog Dialogue Volume 33 (1999)

Editor’s Notes

1999: THE YEAR THAT WAS

In 1999, with the aid of the World

Wide Web, Analog Dialogue has

increased its value to its readers and

simultaneously increased its value to

its sponsor, Analog Devices, Inc.

With a target of monthly publica-

tion, ten issues were published in

1999, more than three times as many

as the yearly average over its prior 32 years in print. The greater

frequency of publication made it possible for readers to read about

new products in timely fashion, and the ease of publishing on the

Web allowed us to literally “turn on a dime”. More importantly,

though, it allowed readers immediately to link to extensive further

information on products and topics of interest on the vast Analog

Devices Web Site and to promptly print usable data sheets. This

essentially eliminated the need for Business Reply cards and the

lengthy “circle and wait” cycle.

The one downside and source of anguish to many faithful readers

was that, in order to read Analog Dialogue , they had to access the

Web (a task that day by day is nevertheless becoming easier with

the help of some ADI broadband and DSL products). This issue,

Volume 33, divorced from the quest for immediacy that energizes

our Web version, is our answer to the need for a “permanent”

version of Analog Dialogue that you can hold in your hand. It

contains all the technical articles (and a few worthy New-Product

Briefs) that have been published during 1999. You can carry it,

read it wherever you are (except in the dark), and stack it in a

binder with previous issues to complete your set. And, in between

this edition and Volume 34, in December, 2000, you can still get up-

to-date information from the monthly editions of ADI’s technical

magazine on the Web. 1 Surely this is the best of both worlds!

monolithic technologies. In June of 1999, Scott transferred out of

Design, and into Corporate Marketing, where he is ADI’s Senior

Technical Editor.

Scott has written articles and design ideas that have appeared in

the trade press, and he was a contributor to the 1986 edition of

the Analog-Digital Conversion Handbook . He holds a patent for a

precision switched-capacitor-ratio system and has a second patent

pending. He has presented several times at the Analog Devices

General Technical Conference.

In his free time, Scott enjoys sailing, hiking, golf, bicycling,

watching Boston’s Red Sox and Bruins, and hanging out with his

“Little Brother,” Gary.

Dan.Sheingold@analog.com b

THE AUTHORS

Brian Black (page 35), who joined

Analog Devices in 1998, is Product

Manager, high-resolution data

converters, for the General-Purpose

Converter group, in Wilmington, MA.

He has a BSEE from Brigham Young

University (1991), and MS degrees

from MIT (1996) in both EE and

Management (Sloan School).

Michael Curtin (pages 9-22) is a Staff

Applications Engineer at our Limerick,

Ireland facility, providing application

support for the frequency-synthesis

products. Mike was graduated from the

University of Limerick with a BSc. He

is the author of several technical

articles on high-resolution A/D and D/

A converters and is the holder of two

patents. For relaxation, he enjoys

playing snooker, reading, and walking the family dog.

Robert De Robertis (page 6)

manages the Wireless Infrastructure

Business Group in ADI’s DSP division,

which includes applications of

products such as TigerSHARC and the

ADSP-219x. His activities in the past

decade have centered on leveraging

DSP technologies into emerging digital

wireless markets. In his various

engineering, marketing, and product-

line management positions at Analog Devices, Cadence Design

Systems, Lucent Technologies, and Harris Semiconductor, Rob

has experienced many aspects of the wireless revolution.

Paul Daigle (page 64) joined Analog

Devices in 1997 as a Product Manager

in the Standard Linear Products divi-

sion. He holds an MSEE and BSEE

from Syracuse University. Paul has

been participating in the semiconduc-

tor industry since 1989. He thoroughly

enjoys life as father to a 1-year-old son

and a 3-year-old daughter. Mountain

hikes and seaside walks are his family’s

favorites.

SCOTT WAYNE

Contributing Editor

We’re pleased to welcome Scott

Wayne to the staff of Analog Dialogue

in the role of Contributing Editor.

Scott is the newest addition to the

Corporate Technical Communica-

tions group at Analog Devices.

Besides contributing counsel and

articles to this publication, Scott

works with engineers at all levels and locations within Analog

Devices, with editors of trade publications, and with a wide range

of technical people throughout the world to develop interesting

and useful stories about designs, technologies, and applications

of Analog Devices products. He also has a role in one of the more

important aspects of professional development—encouraging,

stimulating, and helping engineers to overcome their reticence to

write technical articles.

Scott has an SBEE from MIT. He interned with Analog Devices

in 1978, and came back after graduating in 1979. Since then, he

has designed high-resolution analog-to-digital converters, digital-

to-analog converters, sample-and-hold amplifiers, instrumentation

amplifiers, isolation amplifiers, and an iontophoretic drug-delivery

system using modular, hybrid, compound-monolithic, and

[ more authors on Page 71]

1 http://www.analog.com/analogdialogue/

ISSN 0161–3626

Analog Dialogue Volume 33 © Analog Devices, Inc. 1999

Othello: A New Direct-

Conversion Radio Chip

Set Eliminates IF Stages

by Dan Fague

Today’s typical GSM handset (or handy) will have 2-W output

power and is required to receive signals as low as –102 dBm (less

than 1/10 of a picowatt). The handy includes a powerful digital

signal processor (DSP) core (equivalent to an ADSP-218x) to

encode, encrypt, interleave, packetize, transmit, receive, de-

packetize, de-interleave, de-encrypt, and de-encode the data going

to and coming from the voiceband A/D and D/A converters. An

equally powerful microcontroller (ARM or Hitachi H8), combined

with a hardware burst processor, controls the timing necessary to

implement the time-division multiple-access (TDMA) and

frequency hopping functions to keep the phone call on a specific

time and frequency channel. The microcontroller also implements

the man-machine interface, and operates all the necessary protocols

for communication to the base stations.

INTRODUCTION

Analog Devices recently announced the revolutionary Othello

direct-conversion radio for mobile applications. By eliminating

intermediate-frequency (IF) stages, this chip set will permit the

mobile electronics industry to reduce the size and cost of radio

sections and enable flexible, multistandard, multimode operation.

The radio consists of two integrated circuits, the AD6523 Zero-

IF Transceiver and the AD6524 Multiband Synthesizer. The

AD6523 contains the main functions necessary for both a direct-

conversion receiver and a direct VCO transmitter, known as the

Virtual-IF™ transmitter. It also includes the local-oscillator

generation block and a complete on-chip regulator that supplies

power to all active circuitry for the radio. The AD6524 is a

fractional- N synthesizer that features extremely fast lock times to

enable advanced data services over cellular telephones—such as

high-speed circuit-switched data (HSCSD) and general packet

radio services (GPRS).

Together, the two ICs supply the main functions necessary for

implementing dual- or triple-band radios for GSM cellular phones.

The direct conversion technology, combined with a new twist on

the translation loop (or direct VCO) modulator, reduces the

amount of external filtering needed in the radio to an absolute

minimum.

RADIO ARCHITECTURE DESIGN

Most digital cellular phones today include at least one

“downconversion” in their signal chain. This frequency conversion

shifts the desired signal from the allocated RF band for the standard

(say, at 900 MHz) to some lower intermediate frequency (IF),

where channel selection is performed with a narrow channel-select

filter (usually a surface acoustic-wave (SAW) or a ceramic type).

The now-filtered signal is then further down-converted to either a

second IF or directly to baseband, where it is digitized and

demodulated in a digital signal processor (DSP).

The idea of using direct-conversion for receivers has long been of

interest in RF design. The reason is obvious: in consumer

equipment conversion stages add cost, bulk, and weight. Each

conversion stage requires a local oscillator, (often including a

frequency synthesizer to lock the LO onto a given frequency), a

mixer, a filter, and (possibly) an amplifier. No wonder, then, that

direct conversion receivers would be attractive. All intermediate

stages are eliminated, reducing the cost, volume, and weight of

the receiver.

The first Othello radio reduces the component count even more

by integrating the front-end GSM low-noise amplifier (LNA). This

eliminates an RF filter (the “image” filter) that is necessary to

eliminate the image, or unwanted mixing product of a mixer and

the off chip LNA. This stage, normally implemented with a discrete

transistor, plus biasing and matching networks, accounts for a total

of about 12 components. Integrating the LNA saves a total of about

15 to 17 components, depending on the amount of matching called

for by the (now-eliminated) filter.

THE GSM STANDARD

The Global System for Mobiles (GSM) was officially launched in

1992, after over five years of standards writing by the European

Telecommunications Standards Institute (ETSI). The goal of GSM

was to unite a Babel of European communications under one digital

cellular standard. Before GSM, Europe maintained in effect one

separate cellular network for each country, making international

roaming on the continent virtually impossible. With GSM, a citizen

of any of the original seventeen countries could roam to any other

country using a single cellular handset. The standard, which was

written with future expansion to data services and other

applications in mind, soon became popular around the world. It is

now accepted in more than 140 countries, with over 200 networks

running.

The frequency bands originally allocated to GSM were 890 to

915 MHz for mobile transmitting and 935 to 960 MHz for mobile

receiving. That band was expanded to the so-called E-GSM bands

of 880 to 915 MHz and 925 to 960 MHz. Another frequency

allocation was made to further expand GSM capacity. This band,

allocated to digital communications services (DCS), was 1710 to

1785 MHz and 1805 to 1880 MHz. All countries adopting GSM

use one of these two pairs of frequency bands, except the United

States, where both bands were already allocated by the FCC. The

Personal Communications Services (PCS) frequency auctions in

the mid-1990s made available a set of bands for GSM in the U.S.—

1850 to 1910 MHz and 1930 to 1990 MHz.

SUPERHOMODYNE™ DIRECT-CONVERSION RECEIVER

A functional block diagram of the Othello dual band GSM radio’s

architecture is shown in Figure 1. The receive section is at the top

of the figure. From the antenna connector, the desired signal enters

the transmit/receive switch and exits on the appropriate path, either

925-960 MHz for the GSM band or 1805-1880 MHz for DCS.

The signal then passes through an RF band filter (a so-called

“roofing filter”) that serves to pass the entire desired frequency

band while attenuating all other out-of-band frequencies

(blockers—including frequencies in the transmission band) to

prevent them from saturating the active components in the radio

front end. The roofing filter is followed by the low-noise amplifier

(LNA). This is the first gain element in the system, effectively

reducing the contribution of all following stages to system noise.

After the LNA, the direct-conversion mixer translates the desired

signal from radio frequency (RF) all the way to baseband by

Othello, Superhomodyne and Virtual-IF are trademarks of Analog Devices, Inc.

Analog Dialogue 33-10 (1999)

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