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VHDL/FPGA Applications in Signal Processing and Communications

VHDL/FPGA Applications in Signal Processing and Communications. By: Robert Patterson and Ismail Jouny. Overview of Presentation. Description of an FPGA Description of VHDL Applications Error Control Coding CDMA Communications Master/Slave And Token Ring Networks

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VHDL/FPGA Applications in Signal Processing and Communications

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  1. VHDL/FPGA Applications in Signal Processing and Communications By: Robert Patterson and Ismail Jouny D6A

  2. Overview of Presentation • Description of an FPGA • Description of VHDL • Applications • Error Control Coding • CDMA Communications • Master/Slave And Token Ring Networks • Pattern Classification With A Hopfield Neural Net

  3. Design Options • TTL logic chips • Difficult for large designs • Customized board • PLD • Limited by power consumption and time delay • ASIC/MPGA • Custom masks required for wiring • Expensive • Long turnaround time

  4. What is an FPGA? • Field Programmable Gate Array • Consists of: • An array of configurable logic blocks • Programmable I/O blocks • Programmable interconnects

  5. Benefits of Using an FPGA • Programmed by users at their site using programming hardware • Can implement tens of thousands of gates of logic on a single IC • Can be programmed many times • Short development time • Low cost

  6. What is VHDL? • VHSIC Hardware Definition Language • Common Language for Designers (> 50%) • High-Level Language • Simulation and Synthesis Tools are Available

  7. Error Control System Overview Introduction of Error A/Dconverter D/A converter Encoder Decoder

  8. Error Control Coding Overview • By adding redundancy in the signal, errors can be detected and corrected • Signals are broken up into blocks of data • Parity calculations add extra bits to signal • Receiver tries to detect and correct the error through the use of the parity bits

  9. (7,4) Hamming Code • 4 data bits => 7-bit code word • Minimum distance between codes is 3 • All single bit errors can be corrected - or - • All single and double bit errors can be detected B A

  10. What is CDMA? • Code Division Multiple Access • Multiple users can use a wide slice of the bandwidth • A unique code accesses the user’s information • Codes are made orthogonal as much as possible to reduce cross correlation

  11. CDMA Design Overview Pn1 Pn1 Encoder Decoder Encoder Decoder Pn2 Pn2

  12. Spectrum Spreading • Data signal • PN-code • Coded signal Received signal at Decoder #1 = (M1•Pn1 + M2•Pn2)•Pn1 = M1•Pn1•Pn1 + M2•Pn1•Pn2 = M1 + M2•Pn1•Pn2 = M1

  13. Master/Slave Network Overview

  14. Token Ring Network Overview

  15. Hopfield Neural Net • An artificial network that is capable of recalling certain stored patterns from a set of inputs

  16. Hopfield Neural Net (cont.) • The weight matrix is formed from exemplars

  17. Problems Encountered • VHDL  Synthesis/Implementation • Memory in FPGA • Speed of computer in the synthesis of design

  18. Conclusions • VHDL/FPGA combination is a very powerful design tool • Versatile • Adaptable • Efficient • Economic

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