6.02 Fall 2010Lecture #2• Samples and Bits• Real Wires• Models• Linearity and Superposition6.02 Lecture 2 – Wires and Models• Wires, Samples, and Bits• Non-Ideal Transmission– Example wires and signal impact– Intersymbol Interference and Eye Diagrams• Modeling Wires– Causality– Time-invariance– Linearity• SUPERPOSITION– Demonstrating why it is so superTypes of Real “Wires”http://materials.usask.ca/images/photos/SEMof3LevelCuInterconP98.GIFIC Interconnecthttp://www.gpv-pcb.com/Files/Billeder/fabrikker/chemitalic/Chem_pcb_hdi.jpgPrinted Circuit Boardhttp://www.satamerica.com/imagens/4a27897r1.jpgTransatlantic CableSlow Response RingingMay also have long delays (Receiver does NOT know)Transmission Setup and NotationXmit RcvrBits inBits outChannelSample Rates:4 million Samples/Second (IR Transceiver) Up to gigaSamples/Second (Fastest)Samples, Bit Period, Bit Rate• Our Hardware – Updates transmitter output voltage every ¼ microsecond (4 million times a second).– Remeasures receiver voltage every ¼ microsecond (4 million times a second).• Bit Period and Bit Rate– BP = Samples/bit * ¼ microsecond– BR = Bits transmitted per second – BR = (4 million) / (Samples/bit)• Slower Bit Rate = Longer Bit Period– More time to propagate through channelSending 0101110, 2.5 microseconds/bitReceived Voltage has not “settled”10 samples/bit, 400,000 bits/secSending 0101110, 5 microseconds/bitReceived Voltage is more “settled”.20 samples/bit, 200,000 bits/secSending 0101110, 7.5 microseconds/bitReceived Voltage much more “settled”30 samples/bit, 133,333 bits/secThe 6.02 Infrared Transceiver400 Samples/bitXmit RcvrBits outLoopback SetupIR IR xmitterIR rcvrThe 6.02 IR Tranceiver – Bounce off ceiling40 Samples/bitBits sent = [1011010111]Dark RoomLights On200 Samples/bitBits sent = [10110001000111]Intersymbol InterferenceLong Bit Period (slow rate)Short Bit Period (Fast Rate)Received Data – Noisy Channel, 24 sample/bitDigitizingThresholdAny Bit Errors?Eye Diagram-Overlay 3 Period SectionsEyes for Ringing versus Slow SystemMedium Bit Period(33 samples)Short Bit Period(20 samples)RingSlowEye Diagram for IR DetectorEye Diagram 40 Samples per bit, dark roomEye Diagram 40 Samples per bit, lights on!SuperpositionEdgeSuperpositionStep Response and results from superpositionStep Response For Another Example Channel0 01 1 1 0Rising Edge add step responseFalling Edge, subtract step responseRising Edge add step responseFalling Edge, subtract step responseXmitDataTime shifted and sign adjusted channel step reponsesSummed responses = Rcv’d dataEdgeSuperpositionSending 0101110, 1.25 microseconds/bit 5 samples/bit, 800,000 bits/secEye Diagram for 1.25 microsecond bit periodSending 0101110, 2.25 microseconds/bitEye Diagram for 2.25 microsecond bit periodSending 0101110, 3.25 microseconds/bitEye Diagram for 3.25 microsecond bit periodStep Response for Slow ChannelSlow Channel ResponseSlow Channel Eye DiagramSlow Channel ResponseSlow Channel Eye DiagramSlow Channel ResponseSlow Channel Eye DiagramSlow Channel ResponseSlow Channel Eye DiagramSlow Channel ResponseSlow Channel Eye DiagramStep Response for Ringing ChannelRinging Channel ResponseRinging Channel Eye DiagramRinging Channel ResponseRinging Channel Eye DiagramRinging Channel ResponseRinging Channel Eye DiagramRinging Channel ResponseRinging Channel Eye DiagramStraight Rise Step ResponseStraight Rise ResponseStriaght Rise Eye DiagramStraight Rise ResponseStriaght Rise Eye DiagramStraight Rise ResponseStriaght Rise Eye DiagramStraight Rise ResponseStriaght Rise Eye