ĐIỆN tử VIỄN THÔNG near field communication khotailieu

Near-Field Communication Group #31 Keshav Bansal Dan Hvala Tyler Rossi Introduction    NFC is a short-range wireless technology NFC provides unique advantages over other available wireless technologies The design includes a near-field transmitter and receiver to send data from one computer to another Benefits & Features       Not restricted to 1-to-1 communication Multiple devices in a small area can communicate with each other using the same frequency Maximum transfer bit rate of 800kbps No special software is required Operation at a frequency of 13.5 MHz No ethical concerns due to range Modulation/Demodulation Scheme  Frequency Shift Keying (FSK)   VCO produces a frequency-modulated signal at the transmitter Phase lock loop demodulates the signal at the receiver System Overview  Hardware  Transmitter      PC interface (MAX232A) Voltage-Controlled Oscillator (POS+25) Power Amplifier (LM6181) Loop Antenna Receiver     Loop Antenna Amplifier (LM6181) Phase Lock Loop (NE564) PC interface (MAX232A) System Overview Pictures System Overview (Schematic) PC Interface      Connects through serial cable Received by MAX232A to 5V square wave Voltage divider Non-inverting voltage adder PC Interface (Schematic) Power Amplifier    Accepts an input from the VCO Outputs the signal to the loop antenna Power gain of approximately 11dB Power Amplifier (Schematic) Vout Vin Amplifier Input/Output Loop Antenna    Loop Diameter = 6.5 cm Inductance = uH Capacitor used to resonate the antenna at 13.5 MHz = 45 pF Loop Antenna     Very directional Larger loop = more gain Picks up less noise Small, multi-loop turn does not radiate much Frequency Comparisons Phase Lock Loop    Tracks the frequency and phase of the input Frequency of an FSK signal changes according to the data bits; therefore, PLL can demodulate an FSK signal Output is the VCO control voltage Phase Lock Loop (Block Diagram) Phase Lock Loop Tracking Band-Pass Filters (Eliminated)    Tuned to 10MHz and 13.5MHz Pass-band of 2-3MHz Signal did not decay fast enough outside of the pass-band Difficulties     Small antenna bandwidth made us to revise our original design Drift in the frequency of VCO Amplifier oscillation Most significant bit flipping Future Hardware Development     Less power consumption More efficient loop antenna for larger range Smaller setup Two-way communication Analysis  Strengths   No interference due to decaying fields Within FCC regulation    FCC requires max E-field of 334uV/m at 30m Our max E-field at 30m is 180uV/m Weaknesses    Very small range Sensitive to distance and alignment 653mW Results     Maximum bit rate of 800kbps Text communication between two PCs Transmission range of 30cm Ability to send a text file between PCs Credits      Ethan Miller Dr Ada Y Poon Dr Christopher Schmitz Dr Steven Franke Workers in the ECE Parts Shop ... Smaller setup Two-way communication Analysis  Strengths   No interference due to decaying fields Within FCC regulation    FCC requires max E -field of 334uV/m at 30m Our max E -field at 30m is... technologies The design includes a near- field transmitter and receiver to send data from one computer to another Benefits & Features       Not restricted to 1-to-1 communication Multiple devices... range Sensitive to distance and alignment 653mW Results     Maximum bit rate of 800kbps Text communication between two PCs Transmission range of 30cm Ability to send a text file between PCs