Emergency Mine Radio Daniel Weller, Adam Jozwick, David West

Problem Statement: To build a device for miners to use in the case of an emergency in a mine. The solution we decided to pursue was to build a Software Defined Radio (SDR) with an Induction Loop antenna to communicate using low frequencies that pass through solid earth.

Software Defined Radio A SDR is a radio that swaps out the use of many hardware components(mixers, filters, detectors) and instead uses software and a PC to implement the same thing. The boards used are called Janus and Magister. Janus: A/D, D,A Converter Magister: USB interface

Changes from original design Hardware circuit to generate In-phase and Quadrature Multi-functionality Voice based to text based Software Design

Software System Diagram TransmitReceive

Encoding The user defined text message is transformed into binary using the ASCII equivalent of letters. A start(2 in ASCII) and stop (4 in ASCII) bit are also added to help decode the message later. MATLAB used a 2,97,4 Text Text to ASCII equivalent (2) (97) (4) ASCII to binary equivalent

Modulate Encoded message is modulated to on-off keying at low frequency (2) (97) (4) binary equivalent ( ) ( ) (001000)

Transmit Modulated signal converted from digital to analog and sent to PC’s audio output Antenna is in audio output Transmitting Antenna

Get Data Radio signal received from other PC and specifically PowerSDR PowerSDR: Signal Modulation software for SDR’s Signal converted to vectors containing values for each data element of signal SDR Receiving Antenna

Signal Processing Signal processing is applied to sampled data from radio signal DC offset removed, passed through low pass filter and envelope generated.

Decode Envelope of sampled signal used to generate binary numbers from original signal From binary converted back to text a 2,97,4 Text ASCII equivalent (2) (97) (4) binary equivalent

SDR Transmitting Antenna Receiving Antenna Input Text Message Output Text Message

Testing Interface testing –Test used to check communications from Magister to PC Radio Frequency test -Check if RF signal can be picked up In-Phase/Quadrature tests – to test the A/D and D/A converters in Janus Multiple Audio Signals test ASCII Signal Tests – Final text based test with antenna

Reflection A major difficulty was in understanding of data transmission via radio waves and there limitations Understanding of SDRs and I and Q were a challenge Future groups should consider: ◦ Re-sampling of data ◦ Other modulation schemes