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Communications Baseband PDR
Members
Advisors: Dr. Joe Delorenzo Dr. Eli Saber Dr. Sohail Dianat
Team Members: Leland Smith (Team Leader) Jason Riesbeck (Chief Engineer) Jonathan Hutton
Communications Baseband PDR
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
Communications Baseband PDR
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
Communications Baseband PDR
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
Communications Baseband PDR
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
Communications Baseband PDR
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
Communications Baseband PDR
Preliminary Design Concept #2
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
Communications Baseband PDR
Preliminary Design Concept #3
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
Communications Baseband PDR
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
Communications Baseband PDR
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
Communications Baseband PDR
Feasibility
Assessed at a subsystem level. Depends on the resources available
To maintain feasibility, subsystems should: Satisfy design objectives Economical Comply with time constraints
Communications Baseband PDR
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.
Communications Baseband PDR
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
Communications Baseband PDR
Anti-Aliasing Filter
Specifications: 0-5V Input Pass-band 20 kHz Stop-band 22 kHz Attenuation 20 dB
Butterworth Filter Elliptical Filter
Communications Baseband PDR
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
Communications Baseband PDR
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
Communications Baseband PDR
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
Communications Baseband PDR
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
Communications Baseband PDR
AM Receiver
AM Receiver Demodulates Signal Amplifies the Signal by 18 dB
Communications Baseband PDR
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
Communications Baseband PDR
Choosing an FM ICObjectives Weight
Part availability 10
Comprehensive design resources 8
Application examples 7
Performance 6
Price 5
Low parts count 5
Communications Baseband PDR
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
Communications Baseband PDR
FSK Feasibility
Nordic NRF2401
•Transmits data at 1Mbps
•2.4GHz ISM band
Communications Baseband PDR
FSK Link Analysis
NRF2401 Specification○ 0dBm output power
○ -80dBm receiver sensitivity
Link Budget Analysis○ 60dB of attenuation at 10m
(with 0dB antenna gain)
Communications Baseband PDR
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
Communications Baseband PDR
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
Communications Baseband PDR
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
Communications Baseband PDR
Microcontroller Specifications
At least 10 I/O pins UART (clocked serial data transfer) Support 1 Mbps
Communications Baseband PDR
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
Communications Baseband PDR
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
Communications Baseband PDR
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 Baseband PDR
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
Communications Baseband PDR
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
Communications Baseband PDR
Protocol Options
Protocol Type FSK Chip Mode
Synchronous ShockBurst
Asynchronous Direct
Communications Baseband PDR
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
Communications Baseband PDR
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
Communications Baseband PDR
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
Communications Baseband PDR
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
Communications Baseband PDR
The Plan for May
Purchase all components Build systems to spec Test individual systems Integrate Systems
Communications Baseband PDR
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