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BPSK RF Transmitter

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

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  1. BPSK RF Transmitter Dhaval Patel Erik Stauffer Joe Golat

  2. 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.

  3. 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

  4. 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

  5. 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

  6. 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

  7. 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

  8. 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

  9. 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

  10. IO Strobe BPSK Reset

  11. CPLD Problems • Broken Test Fixture • Out of Date Web Site • Information was for an older version of the Lattice Semiconductor Programming Software

  12. 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

  13. 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

  14. Output Spectrum

  15. Output 0-2Pi / 0 - 60MHz

  16. 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

  17. RF Stages • Output Filter: - Designed according to frequency band - FM 88-110MHz • RF Amp: - Could be used for more power. • Antenna - Pair of wires

  18. Schematic

  19. 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

  20. PCB

  21. Problems with PCB • Learning to do layout • Missing Clock trace • High mismatch factor at the output due to misplaced resistor

  22. Tests • Carrier Freq Spectrum Output Power = -25dBm @ 104.9 MHz

  23. BPSK Signal BPSK Symbol

  24. Noise Constellation

  25. BPSK Constellation

  26. QPSK Constellation

  27. 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

  28. FM Audio 104.9MHz

  29. 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

  30. Conclusion • Good experience • Fun • Learned about many different things • Dsp’s • RF • Board Layout • Digital Circuitry • Modulation Schemes

  31. Questions? • We know you have them…

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