Adding software radio functions to smartphones

• Main Author: Ho, Larry Rui Hao
• Other Authors: Guan Yong Liang
• Format: Final Year Project
• Language: English
• Published: 2016
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/68127
• Institution: Nanyang Technological University

Frequency modulation, invented by Edwin H Armstrong, has played a major role in communication such as communications between NASA and the Apollo program astronauts. As such, this project will demonstrate the process of demodulation on a smartphone at an undergraduate level. This project will showcase situations such as ineffective filtering and effect of frequency deviation. Moreover, wideband and narrowband transmissions were done on different platforms, namely Gnuradio on Ubantu Linux and RF Analyzer on Android. The received waveform was observed and analyzed on Gnuradio when demonstrating ineffective filtering as it provides more functionality. Thereafter, it was used to transmit a known sound clip over air to the RF analyzer for demodulation. It was found that with a low pass filter between 400-500kHz, distortion could be heard due to aliasing effect from ineffective filtering. On top of that, at 30kHz, it was found that the sound quality has degraded significantly. In addition, distortion could be heard when frequency deviation was below 10kHz and above 90Khz during the transmission between the Gnuradio and RF analyzer. As frequency deviation decreases, its function goes from wideband towards the function narrowband transmission. Hence, these results from the experiments will provide a deeper understanding of the modulation and demodulation process.