A project report sUbmitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Engineering. Sandtoh, 1995. / Amplitude modulation, is the oldest modulation technique used for voice communication.It is the simplest and cheapest way to modulate and demodulate voice, and as a result, it did not lose much popularity in spits of the development of other, more efficient modulation technique. This project offers a new approach for AM demodulation. The two sidebands are separated and divided into many su-bands. The signals with the lowest noise level are solected and thier levels are individually adjusted according to signal conditions. The result is reduction of over 35 dB in continuous interference and about 15 dB in whit noise level. The new detector and about out-performs the conventional detectors in all aspects and can be used in applications where top performance is required and where mone is no object.

The primary objective of this research was the investigation of position location technologies suitable for use in construction automation applications. Ground based radio frequency spread spectrum techniques were chosen due to their relatively low cost, ease of implementation, and all weather capability. Two types of spectral spreading were examined: frequency hopping and direct sequence. The error performance capabilities of spread spectrum position location systems were studied systematically through theoretical analysis, a series of experimental tests, and by the development of a computer simulation package. A small scale experimental test was conducted as a proof of concept and a test of the prototype hardware. The small scale test was also used to estimate parameters of the computer simulation program. Later, a full scale test was conducted at a site approximately the size of a typical construction project. Computer simulations of the system performance were found to be in good agreement with the experimental results. The position error performance of a frequency hopping phase Ineasurenlent type position location system was determined using theoretical, simulation, and experimental means. The primary limitation to position accuracy was found to be propagation channel induced errors. By employing nonlinear filtering methods combined with robust estimation techniques, position error distributions which exceed the performance of classic least squared error methods have been achieved. The relationship between vertical and horizontal errors for practical systems has been determined. Computer simulations have provided estimates of the position accuracy of a direct sequence system which combines time domain techniques for ambiguity resolution determination and phase measurement for fine position. For the first time, phase error distributions of hyperbolic multilateration systems in multipath environments have been studied. The computer simulation tools which have been developed and verified experimentally can be used to analyze the performance of future radio position location systems. / Ph. D.