Introductory Digital Communications

zoom

The CT02 teaching set comprises four boards and provides a basic platform to introduce modern digital communications by firstly considering how analogue signals can be sampled and then transmitted as a series of pulses before being converted back into an analogue signal. By understanding this process, known as Pulse Amplitude Modulation (PAM), students gain an insight into the starting point for many modern digital communications systems.

Using a multi channel PAM system students are introduced to the concept of multiplexing channels transmitted through a single transmission line. The teaching set uses Time Division Multiplexed (TDM) PAM signals to explore synchronisation and clock recovery.

The work on PAM and TDM is extended to include a two channel Pulse Code Modulation (PCM) system. This PCM system can be run in real time (as a practical system) or single step mode (allowing data flow to be observed on LEDs). Techniques for word and clock synchronisation are fully explored along with error code checking and correction techniques. This part of the system comprises two boards, a transmitter and a receiver. The modulator and demodulator boards of CT05 can also be connected between these two boards for extended study.

Because all sampled waveforms and the sample clock circuits are synchronised, textbook waveforms can be easily demonstrated on a laboratory oscilloscope. A comprehensive workbook is included to guide students through practical tasks.

Typical topic areas include:

• Introduction to Pulse Modulation.
• Waveform Sampling.
• Low Pass Filters.
• A Pulse Amplitude Modulated System.
• Introduction to Time Division Multiplexing.
• Time Division Multiplex Transmitter.
• Synchronization.
• The Demultiplexer and the Demodulator.
• The Complete PAM-TDM System.
• Introduction to Pulse Code Modulation.
• Synchronization in PCM Systems.
• Error Detection and Correction.
• System Troubleshooting.

Typical activities include:

• Investigate the characteristics of first, second and fourth order filters.
• Compare the performance of sample amplifiers and sample & hold amplifiers.
• Recognize the separate PAM signals in
  a TDM waveform.
• Investigate the use of a Phase Locked Loop (PLL) timing circuit in providing circuit timing signals.
• Compare the transmission links
  required by PAM-TDM systems operating in different configurations.
• Identify the cause of quantization noise.
• Investigate the importance of system timing in a PCM receiver.
• Interpret and use a fault diagnosis algorithm to assist in the location of faults in a PCM transmission system.

This resource includes:

• Signal Sampling and Reconstruction Board
• Time Division Multiplexed PAM Board
• PCM Transmitter Board
• PCM Receiver Board
• Curriculum Manual Set
• Instructor Manual Set
• Power Supply
• 4mm Connection Lead Set