Design of an Audio Transmitter with Variable Frequency Modulation Parameters Using National Instruments LabVIEW 2011 and USRP-2920 for Public Address System Improvement of Asia Pacific College

摘要

The existing Public Address (PA) system at Asia Pacific College was found to be limited in transmitting beyond the range of 30 meters and susceptible to noise. The goal was to improve the system by proposing a new PA system built using LabVIEW, a platform of the National Instruments (NI). It was embedded using the Universal Radio Software Peripheral (USRP) to obtain transmission clarity, power and bandwidth efficiency, and long-range transmission. These objectives were tested by placing the transmitter at a fixed point and the receiver was placed at different distances from the transmitter. Different materials for obstructions were placed midway to interfere with the signals that propagate. Additional test for verifying how signal-to-noise ratio (SNR) is related to clarity was done using score word-a standard statistical measure of speech intelligibility. Implementing the new design, it was concluded that the prototype was able to meet the objectives. It was able to transmit signals beyond 67 meters which is classified as excellent transmission range. The average SNR measured was 16.53 dB, a power loss of - 90.98 dB, and an average bandwidth efficiency of 5.58 bits/cycle were all remarked as having excellent audio clarity, power efficiency and bandwidth efficiency.