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Date of Award

1993

Document Type

Thesis - Pacific Access Restricted

Degree Name

Master of Science (M.S.)

Department

Graduate Studies

First Advisor

George Schroeder

First Committee Member

Thuan Van Nguyen

Second Committee Member

Andres Rodriguez

Abstract

A prototype communication system has been designed, built and tested. The system is a digital communication system that uses near infrared radiation transmitted through the atmosphere. The prototype system consists of two transceivers, each with associated electronics and power supplies. Each transceiver is capable of simultaneously transmitting and receiving light at a wavelength of 830 nm . The transmitter emits light in a 0.3 degree (full angle) cone through the atmosphere , while the receiver accepts light within its 0.33 degree field of view. For the purpose of alignment, each receiver also has an eyepiece and alignment reticle with a field-of-view of approximately 1.5 degrees.

The system is capable of transmitting and receiving digital data at a rate of up to 72 thousand bits per second (kbps) over a distance of 0 . 2 km on a clear day with an average transmitted power of less than 100 MW. Data is encoded for transmission using Pulse Position Modulation (PPM). The transmitting electronics include a pulse code modulation (PCM) voice digitizer, PPM modulator, and infrared emitter driver circuitry. The receiving circuitry includes a photodiode with bias supply and preamplifier, PPM automatic gain control, PPM demodulator, and PCM digital to analog converter

Finally, a model has been developed which describes system performance. The model may be used for investigating the performance of other similar systems which may need t o meet specific design criteria or restrictions.

Pages

171

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