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Communications Baseband

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.

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Communications Baseband

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  1. Communications Baseband Project 05500

  2. Members • Advisors: • Dr. Joe Delorenzo • Dr. Eli Saber • Dr. Sohail Dianat • Team Members: • Leland Smith (Team Leader) • Jason Riesbeck (Chief Engineer) • Jonathan Hutton

  3. 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

  4. 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

  5. Team Work Breakdown

  6. Fundamental Design Objectives

  7. Preliminary Design Concept #1 Universal AM/FM/ASK/FSK System • Digital data rate • Not truly PCM • Usefulness • Two distanced RF channels • Digital and analog signals utilize common modulators   • Versatile

  8. Preliminary Design Concept #2 Analog Voice and Wireless RS232 • Not a PCM solution • Requires extra lab equipment • Duplex communication • Analog AM and FM maintained • Serial link established   • Reasonable Bandwidth

  9. Preliminary Design Concept #3 Analog Voice and Wireless USB • Difficult to implement • Requires extra lab equipment • Duplex communication • Analog AM and FM maintained • USB link established   • Impressive Bandwidth • 1.5 - 450 Mbps

  10. Preliminary Design Concept #4 Analog Voice and Streaming PCM Audio •All modulations have independent communication systems •All schemes have a common audio source ◦Impressive Bandwidth ◦Comparison of modulation schemes ◦No external equipment 

  11. Concept Analysis

  12. System Development •Divided into 12 subsystems •Specification developed for each

  13. Feasibility • Assessed at a subsystem level. • Depends on the resources available • To maintain feasibility, subsystems should: • Satisfy design objectives • Economical • Comply with time constraints

  14. FCC Considerations Unlicensed Bands (FCC 15.247.b.4) Antenna gain can be as much as 6dB. All other bands 100mW or less

  15. Audio Subsystem • Block Diagram

  16. Anti-Aliasing Filter • Specifications: • 0-5V Input • Pass-band 20 kHz • Stop-band 22 kHz • Attenuation 20 dB • Butterworth Filter • Elliptical Filter

  17. Low Pass Filter -17dB 22.1 kHz

  18. AM Modulation • Concept Development • Discrete Parts • IC • Transceiver IC • Feasibility Assessment

  19. Design Objectives and Synthesis • Clock Oscillator • 1 MHz Sine Wave • RLC Filter

  20. Clock Oscillator

  21. AM Receiver • AM Receiver • Demodulates Signal • Amplifies the Signal by 18 dB

  22. FM Systems • Complicated to engineer • Could take months in industry Transmitter Receiver

  23. Radio IC’s • A simple and effective solution

  24. Choosing an FM IC

  25. FM Feasibility • Meets design requirements • •Able to be complete in allotted time • •Low cost

  26. FSK Systems • Similar to analog FM systems • Also very complicated

  27. FSK Feasibility • Nordic NRF2401 • Transmits data at 1Mbps • 2.4GHz ISM band

  28. FSK Link Analysis • NRF2401 Specification ○ 0dBm output power ○ -80dBm receiver sensitivity • Link Budget Analysis ○ 60dB of attenuation at 10m (with 0dB antenna gain)

  29. FSK Feasibility •Meets project needs •Only $4 with few external parts •Reasonable time budget

  30. 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

  31. 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

  32. Microcontroller Specifications • At least 10 I/O pins • UART (clocked serial data transfer) • Support 1 Mbps

  33. Solutions • PICmicro Microcontroller • Analog Devices DAC • 10-bit • No overhead bits • Serial

  34. 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

  35. System Diagram

  36. 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

  37. 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

  38. Protocol Options

  39. Synchronous Option

  40. Asynchronous Option 1

  41. Asynchronous Option 2

  42. Choice Protocol • Asynchronous – 1 Sample per 2 Frames

  43. The Plan for May • Purchase all components • Build systems to spec • Test individual systems • Integrate Systems

  44. Preliminary Cost Analysis

  45. Possible Upgrades

  46. Questions?

  47. Preliminary System Design

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