wireless sensor systems design course

Wireless Sensor Systems Design Course

A Joint Course of the University of South Florida

and Tennessee Technological University

Spring 2002

Lecture 1 - Analog and Digital Modulation Methods

(as applicable to the project)

Tennessee TechUNIVERSITY

USF EEL 4935/TTU ECE 4720SPECIAL TOPICS: WIRELESS SENSOR SYSTEMS


Weekly Lecture Topics Course Introduction Analog and Digital Modulation Methods (1/11) Fundamentals of Antennas and Propagation (1/18) Signal Detection and Processing Techniques (1/25) Microwave Systems: Communications Hardware, Noise, Linearity (2/1) System Test, Evaluation and Documentation / Effective Presentation Styles (2/8) Preliminary Design Review (student presentations*) (2/15) Microwave Sensor Technology (2/22) @ TTU TBD (3/1) TBD (3/8) Critical Design Review (student presentations*) (3/22) Microelectromechanical Systems (MEMS) Sensors (4/5) Modern Wireless Communication Systems (4/12) @ USF Review / Course Wrap-up (4/19)

* On-site internal reviews/preparation will precede inter-university presentations.



Outline

What are we trying to do in this project? Systems Approach

How do we get information sent over a wireless link?

What are some transmission options for the AW3 project?

What are some receiver options?

Wrap up / Assignment 1



AW3 - System Overview

CentralReceiver

Sensor: Temperature, Light Intensity, Humidity, Position

Sensor 1

Sensor 2

Sensor 3 Sensor 4

Sensor n



The BIG Picture

Sensor: Temperature, Light Intensity, Humidity & Location

Data for 01APR01

Time Sensor °C Intensity Humidity1532 26 24 70% 50%1533 14 25 65% 55%1544 29 30 0% 60%… … … … …… … … … …… … … … …

Historical Data:By timeBy sensorBy location

http://iweb.tntech.edu/jfrolik/sensors.html

Sensor 14: °C

Date/time

Sensor n



GPS

How are we going to get there?

Baseband

DC Power

TempIntensityHumidity

RF TX Antenna

Baseband

DC Power

SignalProcessing /

WEBRF RXAntenna

ENVIRONMENT

USER



Modulation!

Puts baseband information onto a high frequency carrier

Why? Effective wireless transmission only at higher

frequencies (dimensions proportional to λ). Signal isolation (think FM radio) More bandwidth available



General carrier

AM

FM

PM

The BIG 3

)()( tmkt fci

)cos()( ccc tAtc

)()( tmkt pi

)cos()]([)( ccAM ttmAt

))(cos()( dttmktAt fccFM

Info: m(t)

))(cos()( tmktAt pccPM



Digital Methods (time domain representation)

amplitude

phase

frequency



Nest Watch - 915 MHz Transmitter (AM example)

Battery

Oscillator: cos(ct)

Filter Amplifier

Loop Antenna

Information Signal: s(t) AM(t)=s(t) cos(ct)

Options for s(t) : AM: s(t)=A+m(t) envelope detector DSB-SC: s(t)=m(t) synchronous detector



AM (large carrier)

What is sent: What do we want? Envelope detection (i.e., simple receiver) can be used:

)cos()]([)( ttmAt cAM )(tm

1A

mp

mod index:

1. Rectify2. LP Filter3. DC Block



Last Year’s Design



Last Year’s Design

baseband

transmitterreceiver

antenna

proximitysensor



Phase and Frequency Modulation

AM is a linear function Bandwidth of modulated signal:

FM and PM are non-linear methods Bandwidth of modulated signal Power series:

mAM BB 2

)1(2 mEM BB

)sin)(!3

cos)(!2

sin)([cos)(

33

22

ttmk

ttmk

ttmktAt

cp

cp

cpcPM



Ideas for this year

Analog FM system

Digital FSK system

Digital PSK system



What are the knowns in our design?

RF section Transmitter Components

550 MHz VCO (TTU/USF interface frequency) Upconverted to 2.4 GHz (USF)

Receiver Components Direct to baseband Or to 550 MHz IF and PLL

Baseband Bandwidth: Sound card for processing (?) Signal content Bm< 20 kHz RF receiver must be match to baseband method



Key Component: VCO

Voltage Controlled Oscillator Center Frequency: 550 MHz Tuning range: 42 MHz (centered?) Tuning rate: 14 MHz/volt Tuning voltages: 0-3 volts (?)

volts

time

VCO freq

time



FM/FSK



FM Transmitter

)(tmconditioning VCO X filter

synthesizer

< 20 kHz+/- 5 Volts

centered:550 MHz 2.4 GHz

)(/ tFSKFM



PSK



PM Transmitter

)(tmconditioning

VCO Xswitch

synthesizer

Binary: 0 & 1< 20 kHz

+/- 5 Volts

fixed:550 MHz

2.4 GHz

filter

filter0°

180°

)(tPSK



Analog FM Receiver/PLL

)(tFMfilter

VCO

X filter

synthesizer

< 20 kHz

550 MHz2.4 GHz

X filter )(tm

PLL: phase locked loop



FSK Receiver

)(tFSKfilter

VCO

X filter

synthesizer

535 MHz (?)or

565 MHz (?)2.4 GHz

X

“1” filter detector

“0” filter detector

530 MHz (?)

35 MHz

5 MHz

compare

0 or 1



PSK Receiver

)(tPSKfilter

VCO

X filter

synthesizer

2.4 GHz

X 0 or 1PHASEDETECTOR



Baseband options

“Analog” Decimal data (i.e., 0-9) is encoded with baseband tones

Think touch-tone phone (see www.dtmf.info for ideas) Baseband signal drives VCO

FM modulation PLL receiver

Digital PCM encode information (i.e., analog to 0’s and 1’s) Use binary signal to FSK or PSK modulate IF Unique RF receiver for each method

However PLL could be used for FSK Baseband signal processing may be very similar



Wrap Up

Need quick answer to the following:

USF: What are the specifics of the VCO?

TTU: What are the two baseband methods to be pursued? This will influence receiver design.

TTU: Will the signal processing approach be hardware, software or a hybrid?



Assignment 1

Visit the course WebBoard site (USF students: send Frolik name and email address) DONE!

Post a short bio and hours of availability Post your bios by 1/18 TTU “reply” to TTU student board: TTU Bios USF “reply” to USF student board: USF Bios

Learn how to use NetMeeting



WebBoard

Very user friendly means of putting information on a web-site for the project.

Items that will be posted during this course Reports for peer review (.doc) Tutorial presentations (.pdf) Interim student presentations (.ppt) Any information that needs to be shared within and between

teams Link: http://webboard.tntech.edu:8080/~ee-projects

LET FROLIK KNOW ASAP IF YOU CAN’T LOG ON



Additional Notes on Assignment 1 (USF)

Download information on EE Senior Design Project requirements (http://ee.eng.usf.edu/undergraduate/seniordesign/)

Submit ½ page project proposal in electronic format Generate tentative project schedule for the semester

You must participate in the poster competition at the end of the semester. Your poster must contain 1 slide about the broader aspects of the course project (suggest you do some research on sensors)



Coming Soon!

Tutorial from USF:

Fundamentals of Antennas and Propagation (1/18)

Tutorial from TTU:

Signal Detection and Processing Techniques (1/25)

One page project description due 1/25. “Reply” TTU/USF reports: Project Descriptions



Two Month Course Schedule

January Week 1 (7-11) Week 2 (14-18)

Choose project Literature search

Week 3 (21-25) Literature search Submit project description (1 page;

references from literature search) and tentative schedule (design; fabrication; test; report)

February Week 4 (28-1)

First progress report Week 5 (4-8)

Review peer reports Week 6 (11-15)

Parts list due Preliminary Design Review

Week 7 (18-22) Weller at TTU

1. All inputs are due on Friday of the specified week - no exceptions2. Reviews of peer reports must be completed before the lecture on Friday



Format for Progress Reports

Brief project description and purpose (1-3 sentences) Objectives for the current reporting period (2-3 sentences) Progress for the current reporting period (2-3 paragraphs; use figures and

graphs where needed - they can be reused in your final project report) Plans for the upcoming project period (2-3 sentences) Revised Project Schedule

Keep in mind that the peer(s) who review your report may not be intimately familiar with your project, so you need to clearly explain the objectives and outcomes.



Peer Review Process

Grading criteria: Clarity of report Level of progress made during reporting period Clear goals for upcoming project period

You are required to turn in reviews for two peer reports that will be assigned to you. You should include brief comments/suggestions and an overall grade of G (good), P (passing), and U (unsatisfactory). Hand-in the reports with your name attached, but NOT written on the report (the reviews are anonymous). Two “U” grades from peers will result in a loss of credit for the student, unless overridden by the instructor(s).



Think about Subsystem Requirements

Functional What must the subsystem do? To what performance level must this be

accomplished? Interfaces

Electrical (DC) Signal (frequency, voltages, etc.) Dimensions Packaging



Final Comments

The success of the project (i.e., course) depends on the efforts of all students

Subsystems must work closely to ensure interface requirements are properly defined and met

Need to establish contacts in other groups, ASAP!

Schedule is aggressive: Work early and often!



Anything else?

wireless sensor systems design course

Documents

special topics

ttu ece

wireless link

microwave sensor technology

mtusf eel

projectusf eel

cdatetimeusf eel

mtsynchronous detectorusf