Quantitative asset managment laboratory - Coursework Example

The QAM obtains its name from its two components of out of phase which are 90 degrees. Aim of the experiment The primary concern of the experiment is to design and implement a Quadrature Amplitude Modulation transmitter. The experiment aims at the student being able to understand the representation of baseband signals in constellations and to have a better knowledge of differential encoding. The experiment also aims at reviewing the Quadrature Amplitude Modulation in digital communication, as this will help in generation of signals and demodulation.

Because of the close relationship between AM and QAM, the experiment should also demonstrate modulation and demodulation in AM signals and examine the sensitivity of QAM phase errors (Ho, 2005). Equipment required The plugs in modules that will be needed for a complete run of the experiment include: An audio oscillator An adder and an multiplier Quadrature utilities Phase shifter and the associated utilities Dual analog switch Quadrature phase shifter Sequence generator Two tunable low pass filters Procedure The first step is to set up a QAM modulator using the equipments provided.

Basically, a QAM modulator uses an analog circuit arrangement with emphasis on avoiding overload. Overload on the modulator must be eliminated as a way of avoiding crosstalk between channels when a common path is being shared between the adder and the multiplier. Make sure a filter is put between the paths as a way of ensuring that unwanted components are kept away from the multiplier (Hsueh-Ming, 1995). By using the Quadrature utilities which basically consist of two multipliers and one adder, several steps are taken into account.

The upper multiplier is used to generate the first message while the lower multiplier is used to generate the second message by feeding message 1 to the channel 1 of the speech module, feeding message 2 to the channel 2 of the speech module, and preparation of a carrier of 9 kHz sinusoid by using the audio oscillator. The in-phase component of the oscillator and the cos are then used as the carrier to message 1 while the quad phase and the sin components are used as the carriers to message 2 (William, 1994).

The two data control signals are also set to two thirds of the full scale while the IQ modulator is controlled to half scale. The noise amplitude that is associated with the transmission block should be set to the minimum level. The phase scope is then opened and by using the variable phase shift control, the IQ carrier phase is set to 90 degrees. The phasescope signal probe is then moved to the noise channel output and set to costelaltion mode with the persistence and hi persist on. At this point, the phase scope should indicate 16 constellations and by using the phi offset control on the phase scope, the pattern is rotated to line up with the square phase scope gratitude.

The data signal level control is then adjusted with the aim of achieving perfect and an equal sided square. The pattern can be centralizing through further adjustment of the lower balance control on each side of the IQ modulator (Lajos, 2000). Several adjustments are made on the QAM. The button on the block diagram is used to adjust to 64 QAM demonstrated by 64 symbols. Again, by using the button, adjustment is made to 256 QAM. The Oscilloscope is opened and the button adjusted to 16 QAM with observations noted.

Since the QAM works through a combination of