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BPSK RF Transmitter. Dhaval Patel Erik Stauffer Joe Golat. Objective: Software Transmitter. Provide an inexpensive implementation for wireless data transfer. Various Carrier Frequencies, from 0 to 1GHz Capable of several different modulation schemes

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bpsk rf transmitter

BPSK RF Transmitter

Dhaval Patel

Erik Stauffer

Joe Golat

objective software transmitter
Objective: Software Transmitter
  • Provide an inexpensive implementation for wireless data transfer.
  • Various Carrier Frequencies, from 0 to 1GHz
  • Capable of several different modulation schemes
  • Software radio: Nearly everything is reprogramable.
user benefits
User Benefits
  • Quick and easy module which is ready to go on “air”
  • Flexible, capable of FM, AM, BPSK, QPSK…
  • Possible Uses:
    • Digital Data Transfer
    • FM / AM radio
    • Long Range with the addition of a Power Amplifier
original design
Original Design

Data

RS232

A/D

RF Stages

Digital Stages

DDS – (Analog Devices)

DSP (TI)

CPLD (Lattice)

Output Filter

Data and Address Bus

Data and Control Signals

Clock

50 or 60 MHz

Vector Signal Analyzer

RF amp

Antenna

dsp ti
DSP - TI
  • TMS320C54 Evaluation Board (Spectrum Digital)
    • TMS320549 TI DSP Processor
  • Controls configuration and handles data flow
  • Easily reprogramable for different modulation schemes
  • Room for expansion
    • Powerful processor
    • Large amount of memory
dsp problems
DSP Problems
  • Different version of Spectrum Digital’s evaluation board than ECE320
    • Incompatible PC driver software
    • Available sample / test code didn’t work
  • Poor support from Spectrum Digital
    • Incorrect driver, software, and information on web site
  • DSP IO Ports
    • A/D sample code from Spectrum Digital didn’t work.
    • RS-232 echo code didn’t work
final dsp code
Final DSP Code
  • Initializes DDS
    • Resets DDS on program start
    • Configures DDS into proper operation mode
  • Handles communication I/O ports
  • Prepares input data for output to DDS
  • Streams data to frequency, phase, or amplitude registers
slide8
CPLD

Data

RS232

A/D

RF Stages

Digital Stages

DDS – (Analog Devices)

DSP (TI)

CPLD (Lattice)

Output Filter

Data and Address Bus

Data and Control Signals

Clock

50 or 60 MHz

Vector Signal Analyzer

RF amp

Antenna

slide9
CPLD
  • Purpose:
    • To provide an easy means to reconfigure and rewire the PCB.
    • Translates Address from the DSP
    • Contains several state machines that drive control pins on the DDS
    • Only allows DDS to latch data at the correct time.
    • “Soft” configuration of DDS
slide10
IO Strobe

BPSK

Reset

cpld problems
CPLD Problems
  • Broken Test Fixture
  • Out of Date Web Site
    • Information was for an older version of the Lattice Semiconductor Programming Software
slide12
DDS

Data

RS232

A/D

RF Stages

Digital Stages

DDS – (Analog Devices)

DSP (TI)

CPLD (Lattice)

Output Filter

Data and Address Bus

Data and Control Signals

Clock

50 or 60 MHz

Vector Signal Analyzer

RF amp

Antenna

slide13
DDS
  • AD 9854 – Direct Digital Synthesizer
  • Large Amount of Functionality
    • Quadrature DAC’s
    • Programmable Clock Multiplier
    • 48 bit frequency register
    • 14 bit phase register
    • 12 bit amplitude register
    • Ramped FSK and FM CHIRP modes
block diagram
Block Diagram

Data

RS232

A/D

RF Stages

Digital Stages

DDS – (Analog Devices)

DSP (TI)

CPLD (Lattice)

Output Filter

Data and Address Bus

Data and Control Signals

Clock

50 or 60 MHz

Vector Signal Analyzer

RF amp

Antenna

rf stages
RF Stages
  • Output Filter:

- Designed according to frequency band

- FM 88-110MHz

  • RF Amp:

- Could be used for more power.

  • Antenna

- Pair of wires

evolution into a pcb
Evolution into a PCB
  • Proto-board was unreliable
  • Used schematic to generate a Netlist
  • Systematically created footprints for the different chips
  • Individually added all traces according to Netlist
  • Created Power, Ground and two trace planes
problems with pcb
Problems with PCB
  • Learning to do layout
  • Missing Clock trace
  • High mismatch factor at the output due to misplaced resistor
tests
Tests
  • Carrier Freq Spectrum

Output Power = -25dBm

@ 104.9 MHz

bpsk signal
BPSK Signal

BPSK Symbol

fm radio modulation
FM Radio Modulation
  • Wanted to actually send a radio signal
  • We needed a modulation scheme for which there was already a receiver for
  • FM Audio
    • DSP has an A/D
    • FM radio already in the lab
fm audio
FM Audio

104.9MHz

future development
Future Development
  • Finish Producing other 3 boards
  • Give transmitter cards to 320 TA’s
  • Boost output power via Power Amp.
  • Build receiver on same board to enable two-way communications
  • Package and sell
    • Wireless Modem
    • Broadcast Radio
    • Radar
    • Amateur Radio
conclusion
Conclusion
  • Good experience
  • Fun
  • Learned about many different things
    • Dsp’s
    • RF
    • Board Layout
    • Digital Circuitry
    • Modulation Schemes
questions
Questions?
  • We know you have them…
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