Electrical Communications Systems
Course No. 0909-331-01
Spring 2005
Laboratory Project 4
Digital Baseband Communications
Objectives
In this project, you are required to implement a m-law
companded PCM transceiver system for analog VF signals using a CODEC.
In
addition, you are required characterize the performance of the CODEC by
obtaining its transfer characteristics and by introducing noise into
the
analog signal input.
Equipment and Software
- HP
33120A Function Generator/Arbitrary Waveform Generator
- HP
54645A Oscilloscope, HP Infinium Oscilloscope /HP
54657A FFT Module.
- HP 1663C Logic Analyzer
- TP3054 Serial Interface CODEC
(Download
datasheet here)
- SG-531P 1.544 MHz Crystal Oscillator (Download datasheet here)
- CD74HCT93 4-Bit Binary Ripple Counter (Download datasheet here)
- Assorted resistors and capacitors (based on design)
- PC sound card and speakers
- MATLAB
- Agilent IntuiLink Suite, HPVEE or Matlab Instrument Control
Toolbox
- Audio Player Software on PC
- CDs with your favorite music!
Project Requirements
- The circuit you are required to implement is shown in the figure.
The
SG-531P
Crystal Oscillator generates a a pulse train at 1.544 MHz that is
used both as a Transmit/Receive Master Clock and a Bit Clock for
shifting
digital data out of and into the TP3054 CODEC. The CD74HCT93 4-Bit
Binary
Ripple Counter is used to divide the Master Clock frequency by a factor
of 16; this is used to generate the frame synchronization pulses for
the
CODEC. Print out and study the data sheets
for
all of the chips before starting on this lab project.
- As soon as you power on the circuit, check if the transmit master
clock
(MCLKX), bit clock (BCLKX) and frame sync (FSX)
inputs are being fed accurately.
- Feed a 1 kHz sine wave into the non-inverting input of the
transmit
input
amplifier (VFXI+). Observe the bitstream at the PCM data
output
pin (Dx). Vary the input signal amplitude and verify that
the
output bitstream also varies.
- Test whether your CODEC system is working by feeding the output
bitstream
into the receive data input pin (DR). The input analog
signal
must be resynthesized at the analog output pin (VFRO). What
is the quantization error?
- Repeat the experiment using multi-tone audio-frequency signals
obtained
from the PC's sound card.
- Design and conduct an experiment to determine the input-output
transfer
characteristics of the CODEC. You are required to generate a table that
contains the input analog voltage and the corresponding output
bitstream.
- Design and conduct an experiment to characterize the system
performance
in the presence of additive noise in the audio input signal. Experiment
with various SNRs.
- Bonus Exercise: Design and conduct an experiment
that
introduces
random bit-flips in the digital input bitstream of the CODEC -
characterize
its performance as the bit error rate is varied.
Required Reading