In this lab we have the following experiments:
Experiment one: Signal Source
The aim of this experiment is to introduce the signal source model and show how its output frequency is controlled by its voltage and the dB scale of attenuation
Lab work:
- Calibrating of the VCO
- Use of external frequency control inputs
- Calibrating the attenuator.
Experiment two : Tuned Circuit
Th aim of this experiment is to show that the parallel combination of inductance and capacitance forms a "tuned circuit" which resonates at particular frequency. It also aims to show that tuned circuits can be used to respond selectivity to signals of particular frequencies, to show that their selectivity depends on the 'damping ' or energy losses associated with the circuit.
Lab work:
- Damped Oscillation
- Frequency Response
Experiment three : Amplitude Modulation
The aim of this experiment is to see that amplitude modulation is causing the amplitude of the carrier to vary in accordance with the modulating signal, to see that AM is a multiplicative process which produces side frequencies. This experiment can also show that the original signal can be recovered by further modulation process.
Lab work:
- Multiplying action of the modulator.
- AM modulation using Balanced modulator.
- AM demodulation using Balanced modulator.
- SC AM modulation.
- Square law Detection.
Experiment four : AM Detection and Demodulation
This experiment shows that a diode may be used for detecting a normal amplitude modulated signal and that to avoid distortion of the signal, the signal level and time constants associated with the circuit must be chosen carefully. It also shows a dc component in the detected signal, dependent on the carrier amplitude, can be used for automatic gain control AGC.
Lab work:
- Diode Detector
- Automatic Gain Control (AGC)
Experiment five: Single –Sideband Transmission
This experiment helps students understand the term single-sideband transmission and demonstrates a method of producing and receiving a single-sideband transmission. It also shows the importance of synchronising the carrier signal used for modulation processes at transmitter and receiver.
Lab work :
- SSB transmitter
- The Local Oscillator
- SSB Receiver
Experiment six : FM Modulation and Demodulation
This experiment aims to show that a carrier may be modulated by changing its frequency in accordance with the signal,a frequency-modulated signal has many side bands, dependent on the amplitude as well as the frequency of the signal, FM provides improved immunity from interfering signals, with increasing bandwidth compared with AM. It also demonstrates how to adjust and use FM detector .
Lab work :
- Setting up a FM signal
- Display of the Side Frequencies
- FM detection (using the phase shift Detector)
Experiment seven: Sampling
Experiment seven is used to demonstrate what sampling is and what sample and hold is. It demonstrates the sampling theorem and aliasing frequencies and helps understand the effect of filters in eliminating aliasing, Time Division Multiplexing and Pulse Amplitude modulation and Pulse width modulation .
Lab work :
- Sample and Hold
- Aliasing
- TDM multiplexing
Experiment eight : Delta and Sigma Delta Modulation
This experiment helps explain the process of delta modulation and sigma delta modulation. It shows that each of these systems is a simple form of digital communication. The experiment also helps students to understand that digital communication has to distort the signal to some extent, in order to quantise it, but that this enables subsequent distortion noise introduced by the channel to be largely rejected
Lab work :
- Delta modulation
- Sigma-Delta Modulation
Experiment nine demonstrates how to generate Pulse Amplitude Modulation (PAM) and to demodulate (PAM), as well as how to understand sampling theorem and "sample and hold" concept, the pulse code modulation concept and the need of synchronisation in PCM.
Lab work :
- PAM(Generation of PAM, Demodulation of PAM).
- Sample and Hold ( Basic operation, Demodulation of PAM using SH).
- PCM( PCM and serial transmission, signal transmission using 4-bit PCM, voice transmission using 8-bit PCM).
Experiment ten : Data Formats and Noise in Digital systems
Experiment ten demonstrates that a binary coded waveform can be represented by a number of different data formats using either unipolar or bipolar signals and that the data format is selected to match the characteristic of the channel available for transmission. It also aims to demonstrate that there are three forms of additive noise which can be present in a communication system
Lab work :
- Examination of different data formats
- Extraction of clock signals
- Noise in digital systems.
Experiment eleven is demonstrated through an on-off ASK system the carrier wave is constant and carries no information. The modulation by a bipolar data signal produces a suppressed carrier system with a significant improvement in efficiency. A suppressed carrier system requires a locally re-generated carrier signal at the receiver.
Lab work :
- On-Off ASK
- Suppressed carrier ASK
