EE 345S Real-Time Digital Signal Processing Lab Spring 2009 Lab #5.1 Pulse Amplitude Modulation Akshaya Srivatsa

Outline Block Diagram of Transmitter Expressions for Transmitter Block Diagram of Receiver Expressions for Receiver Inter Symbol Interference Nyquist Criteria for ISI Raised Cosine Filter Interpolation Filters Task List for Lab #3.1

Block Diagram of Transmitter Bit Rate: Rd bits/sec Symbol Rate: Rd/J bits/sec Courtesy: Steven Tretters Chapter 11 Recitation Slides Example of 2J Mapping

Expressions for Transmitter An Impulse Modulator is Output of Transmit Filter it

Block Diagram of Receiver Removes out of band noise Forms perfect pulse shape with Tx Courtesy: Steven Tretters Chapter 11 Recitation Slides

Expressions for Receiver Let us define g(t) as Output of transmit filter it

Inter Symbol Interference The received filter output: (Assuming no AWGN) We can rewrite this as: Worst case ISI:

Inter Symbol Interference Binary PSK with ISI Binary PSK without ISI Courtesy: http://www.answers.com/topic/intersymbol-interference Courtesy: http://www.answers.com/topic/intersymbol-interference

Nyquist Criteria for ISI The condition on g(t) that needs to be satisfied for no ISI is The filter we will use is called the Raised Cosine Filter given by

Raised Cosine Filter In frequency domain, Frequency Domain Time Domain Courtesy: http://en.wikipedia.org/wiki/Raised-cosine_filter

Square Root Raised Cosine Filter The system should be designed in such a manner that the combined effect of Tx filter and Rx filter should be an RC filter.

Interpolation Sub Filters Put We get Now we can define an interpolation subfilter as

Interpolation Sub Filters Courtesy: Steven Tretters Chapter 11 Recitation Slides Block Diagram for Interpolation Filter

Task List Tasks for Lab 5.1 are 4 level PN sequence generator Simulation of block diagram (Tasks 2 to 4) Raised Cosine Filter using the EXE files (Task 5 & 6) Important Points Download the rascos.exe from Dr. Evans website The task list can be found at the following link http://users.ece.utexas.edu/~bevans/courses/realtime/lectures/laboratory/c6713/lab5/Lab_5_Task_List.doc

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