Communications Baseband

Communications Baseband PDR

Communications Baseband

Project 05500


Members

Advisors: Dr. Joe Delorenzo Dr. Eli Saber Dr. Sohail Dianat

Team Members: Leland Smith (Team Leader) Jason Riesbeck (Chief Engineer) Jonathan Hutton


Introduction

Communications Baseband is a project created by several professors in order to stimulate student’s practical understanding of communication systems.

Sponsor: Rochester Institute of Technology Department of Electrical Engineering


Project Overview

Modulate/Demodulate using Amplitude Modulation, Frequency Modulation, and Pulse Code Modulation

Receive analog or digital transmission approximately a classrooms distance and demodulate

Output original signal to see/hear successful recovery


Team Work BreakdownSponsor

Rochester Institute of Technology Electrical

Engineering Department

AdvisorsDr. Sohail Dianat

Dr. Eli SaberDr. Joe Delorenzo

Team LeaderLeland Smith (EE)

Responsible for: PCM encoding, microprocessor

control, digital signal processing

Chief EngineerJason Riesbeck (EE)

Responsible for: FM and FSK transmission

Electrical EngineerJonathan Hutton

Responsible for: AM and Audio Processing


Fundamental Design Objectives

Specifications Weight

Can be completed in allotted time. 10

Communicates AM, FM, and PCM across a classroom 9

Suitable for evaluation in a laboratory 7

Affordable for customer. 6

Easy to Use. 4

Minimal amount of external equipment 4


Preliminary Design Concept #1

Digital data rate Not truly PCM Usefulness

FM Modulator

AM Modulator

FM Demodulator

AM DemodulatorAM or ASK Signal

FM or FSK Signal

Analog in

Digital in Digital out

Analog out

Universal AM/FM/ASK/FSK System

Versatile

• Two distanced RF channels

• Digital and analog signals utilize common modulators



Not a PCM solution Requires extra lab equipment Duplex communication

Analog Voice and Wireless RS232

Reasonable Bandwidth

• Analog AM and FM maintained

• Serial link establishedFM Modulator/Demodulator

AM Modulator

FM Modulator/Demodulator

AM DemodulatorAM or ASK Signal

FM or FSK Signal

Analog in

RS232

Analog out

FM or FSK Signal

PC PCRS232



Difficult to implement Requires extra lab equipment Duplex communication

Analog Voice and Wireless USB

Impressive Bandwidth 1.5 - 450 Mbps

•Analog AM and FM maintained•USB link established

USB

FSK SignalPC PCUSB

FSK Signal

FSK Transmitter/Receiver

FSK Transmitter/Receiver


Preliminary Design Concept #4Analog Voice and Streaming PCM Audio

◦Impressive Bandwidth

◦Comparison of modulation schemes

◦No external equipment

•All modulations have independent communication systems

•All schemes have a common audio source

FM Modulator

AM Modulator

FM Demodulator

AM DemodulatorAM Signal

FM Signal

Analog in Analog out

FSK Signal FSK ReceiverFSK TransmitterAnalog to Digital

ConverterDigital to Analog

Converter


Concept Analysis


System Development

FM Transmitter

AM Transmitter

FM Reciever

AM Receiver

Analog in Analog out

FSK ReceiverFSK Transmitter Digital Control and PCM Encoding

Digital Control and PCM Encoding

Audio Processing Audio Processing

Power Supply Power Supply

1 23 4

5 6

7 89 10

1112

Transmitter Receiver

•Divided into 12 subsystems

•Specification developed for each


Feasibility

Assessed at a subsystem level. Depends on the resources available

To maintain feasibility, subsystems should: Satisfy design objectives Economical Comply with time constraints


FCC Considerations

Country Frequency Notes Standards

US 2.400-2.483.5 GHz ISM Band 1W 802.11/11b

902-928 MHz ISM Band (Used by GSM in most countries)

5.800-5.925 GHz ISM Band

5.15-5.25 GHz U-NII (Unlicensed - National Information Infrastructure) max. 200 mw EIRP

802.11a

5.25-5.35 GHz U-NII max. 1w EIRP 802.11a

5.725-5.825 GHz U-NII max. 4w EIRP 802.11a

Unlicensed Bands (FCC 15.247.b.4)

All other bands

100mW or less

Antenna gain can be as much as 6dB.


Audio Subsystem

Block Diagram

Analog Input

Gain BlockAnti-Aliasing

Filter

Gain AM

Gain FM

Gain PCM

Low-PassFilter

Gain Block SpeakerDemodulated Signal

TX Side

RX Side


Anti-Aliasing Filter

Specifications: 0-5V Input Pass-band 20 kHz Stop-band 22 kHz Attenuation 20 dB

Butterworth Filter Elliptical Filter


Low Pass FilterR 5

1 0 k

R 8

1 0 k

+3

-2

V+

7V

-4

O U T6

O S 11

O S 25

U 3

L M 7 4 1

+3

-2

V+

7V

-4

O U T6

O S 11

O S 25

U 4

L M 7 4 1

C 4

. 6 2 n

C 51 n

C 6. 3 9 n

R 9

1 2 0 k

R 1 0

8 . 2 k

R 1 1

8 . 2 k

R 1 2

8 . 2 k

R 1 33 3 0 k

R 1 41 2 0 k

V 61 2 V d c

V 71 2 V d c

V 81 2 V d c

0

V 91 2 V d c

0

0

0

+3

-2

V+

7V

-4

O U T6

O S 11

O S 25

U 1

L M 7 4 1

+3

-2

V+

7V

-4

O U T6

O S 11

O S 25

U 2

L M 7 4 1

C 1

. 7 5 n

C 21 n

C 3. 2 2 n

R 1

1 5 k

R 2

8 . 2 k

R 3

8 . 2 k

R 4

8 . 2 k

R 63 3 0 k

R 71 5 k

V 11 2 V d c

V 21 2 V d c

V 31 2 V d c

V 41 2 V d c

0

0

0

0

0V 55 V a c0 V d c

0

V

V

V

Frequency

1.0KHz 3.0KHz 10KHz 30KHz 100KHzV(V18:+) V(R19:2)

0V

1.0V

2.0V

3.0V

4.0V

(20.434K,1.6498)

(22.103K,289.562m)

-17dB

22.1 kHz


AM Modulation

Concept Development Discrete Parts IC Transceiver IC

Feasibility Assessment

+

-

OUT

U1

OPAMP

+

-

OUT

U2

OPAMP

1 2

U3

INV

Vn

Vp

MessageInput

Carrier Input

AD835

Z

V112Vdc

V212Vdc

0

0

+

-

OUT

U4

OPAMP

R110k

R2

10k

AD8055

V312Vdc

V412Vdc

0

3

2

Pins 1, 5, 8 are NC

43

2

1

7

6

4

6

8

5

7


Design Objectives and Synthesis

Clock Oscillator 1 MHz Sine Wave RLC Filter

R1

620

1 2

L1

100uH

C1270p

V1

TD = 0

TF = 10nPW = 500nPER = 1u

V1 = 0.4

TR = 10n

V2 = 2.4

0

Clock Oscillator

V

V


Clock Oscillator

Time

40us 41us 42us 43us 44us 45us 46us 47us 48us 49us 50usV(R1:2) V(L1:2)

0V

0.5V

1.0V

1.5V

2.0V

2.5V

3.0V


AM Receiver

AM Receiver Demodulates Signal Amplifies the Signal by 18 dB


FM Systems

Complicated to engineer Could take months in industry

Modulator RF AmplifierPre emphasisAudio In RF Out

Local Oscilator

Mixer

Band-pass Filter RF Amplifier

Local Oscilator

Demodulator AmplifierRF In Audio Out

Mixer

Transmitter

Receiver


Radio IC’s

A simple and effective solution


Choosing an FM ICObjectives Weight

Part availability 10

Comprehensive design resources 8

Application examples 7

Performance 6

Price 5

Low parts count 5


FM Feasibility

Task Time in Hours

Schematic Creation 15

Performance Analysis 5

Specification Formation 13

Parts List 8

General Documentation 10

Board Layout 12

Board assembly 7

Functional Test 12

Integration 4

Tweaking and Repair 20

Total 106

Completed 51

Remaining 55

•Meets design requirements

•Able to be complete in allotted time

•Low cost


FSK Systems

Similar to analog FM systems Also very complicated


FSK Feasibility

Nordic NRF2401

•Transmits data at 1Mbps

•2.4GHz ISM band


FSK Link Analysis

NRF2401 Specification○ 0dBm output power

○ -80dBm receiver sensitivity

Link Budget Analysis○ 60dB of attenuation at 10m

(with 0dB antenna gain)


Task Time in Hours

Part Research 8

Schematic Creation 7

Performance Analysis 5

Specification Formation 8

Parts List 8

Timing Information 10

Board Layout 12

Board assembly 7

Functional Test 13

Integration 15

Tweaking and Repair 20

Total 113

Completed 46

Remaining 67

FSK Feasibility

•Meets project needs

•Only $4 with few external parts

•Reasonable time budget


PCM and Control Subassembly

Transmit Side Conversion of Analog to Digital Apply Protocol to Digital Data Manage Memory and Data Flow to FSK Chip

Receive Side Provide Control to FSK Chip Receive and Manage FSK Chip Data Control and Send Data to DAC


Interface Specifications

Rail to rail (0-3.3V) analog signal input Desire ~44 kHz Sample Rate 1 Mbps transmit rate to FSK chip Send samples to Digital to Analog

Converter at sample rate


Microcontroller Specifications

At least 10 I/O pins UART (clocked serial data transfer) Support 1 Mbps


Solutions

PICmicro Microcontroller

Analog Devices DAC 10-bit No overhead bits Serial

Price Prog Memory Data Memory EEPROM Max Speed I/O PackagePIC16F870 $2.81 2k X 14 128 bytes 64 bytes 20 MHz 22 28-DIPPIC18F1320 $3.15 4096x16 256 bytes 256 bytes 40 MHz 16 18-DIPPIC18C242 $5.12 8192x16 768 bytes 0 40 MHz 23 28-DIPPIC18C252 $5.57 16384x16 1536 bytes 0 40 MHz 23 28-DIP


Capabilities

PIC offers 10-bit AD PIC provides I/O ports

USART (Synchronous/Asynchronous Communications)

Many I/O Ports for control lines Provides 1MHz USART

Data storage and management


System Diagram

PICmicro Microcontroller(PIC18Cx)

Analog Signal FSK Transceiver

Transmit Side

Receive Side

Control Lines

Data Line

PICmicro Microcontroller(PIC18Cx)

FSK Transceiver

Control Lines

Data Line

DACControl Lines

and Data

Analog Signal

Digital Processing and

Control


Communications Protocol

PIC must manage data from 10-bit samples to exact 1 Mbps output

USART sends 8-bit words Start and Stop bit Must hold at least 2 samples in PIC

memory to transfer


IN PIC OUT

Known: What goes in must come out – and at the same rate.

Therefore: The rate the PIC can sample at is governed by the FSK communications protocol.

Sampling rate must be some integer number of the outgoing packet rate


Protocol Options

Protocol Type FSK Chip Mode

Synchronous ShockBurst

Asynchronous Direct


Synchronous Option

18us

Get 20 Samples

t=0

194us

224 bits @ 1Mbps

Require next sample!

t=440usFs=44kHz

1) FSK Transceiver in Shockburst Mode Frame Size = 200 bits 20 10-bit Samples

208us

Send 208 bits @ 1Mbpsto FSK chip

Wait timefor FSK chip

FSK Chip Transmits

224us

204us OVER time requirement!

t=644usFs=31kHz


Asynchronous Option 1

2) FSK Transceiver in Direct Mode Option 1 - Undersample

Start

USART Start @ 1Mbps8-bits at a time

t=0

Stop8 Data Start Stop8 Data Start Stop4 Data

t=10us

USART TX @ 1Mbps

10-bit Frame

t=20us t=30usFs=33.3kHz

2 Samples

4 Junk


Asynchronous Option 2

3) FSK Transceiver in Direct Mode Option 2 - Oversample

Start

USART Start @ 1Mbps8-bits at a time

t=0

Stop8 Data Start Stop2 Data

t=10us

USART TX @ 1Mbps

10-bit Frame

t=20usFs=50kHz

1 Sample

6 Junk


Choice Protocol

Asynchronous – 1 Sample per 2 Frames

FSK Chip Mode Frame Size Necessary Sample Rate Memory Shockburst 20 samples 31 kHz 200 bytesDirect 2 samples 33.3 kHz 2 bytesDirect 1 sample 50 kHz 1 byte


The Plan for May

Purchase all components Build systems to spec Test individual systems Integrate Systems


Preliminary Cost AnalysisItem Price ($)

Board Layout 100

FM Transmitter Parts 40

FM Receiver Parts 30

GFSK Transceiver Parts 30

Audio Section parts 25

AM Receiver Parts 30

AM Transmitter Parts 30

PIC Implementations 15

Power Supply 15

RF Cables 30

Misc. Prototype Materials 20

Total 365


Possible Upgrades


Questions?


Preliminary System Design

Amp LPF

PIC Microcontroller

FSK Transceiver

FM Transmitter

AM Transmitter

AmpLPF

PIC Microcontroller

FSK Transceiver

FM Receiver

AM Receiver

DAC

Audio In

Audio Out

Transmitter

Receiver

Documents

Communications Baseband