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 designHardware circuit to

generate In-phase and Quadrature

Multi-functionalityVoice based to text

basedSoftware Design

Software System DiagramTransmit Receive

EncodingThe 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 2,97,4Text Text to ASCII

equivalent

0000010 (2)1100001 (97)0000100 (4)

ASCII to binary equivalent

ModulateEncoded message is modulated to

on-off keying at low frequency

0000010 (2)1100001 (97)0000100 (4)binary equivalent

(0100000) (1000011) (001000)

TransmitModulated signal converted from

digital to analog and sent to PC’s audio output

Antenna is in audio output Transmitting

Antenna

Get DataRadio signal received from other

PC and specifically PowerSDRPowerSDR: Signal Modulation

software for SDR’sSignal converted to vectors

containing values for each data element of signal

SDR

Receiving Antenna

Signal ProcessingSignal processing is applied to

sampled data from radio signalDC offset removed, passed

through low pass filter and envelope generated.

DecodeEnvelope of sampled signal used

to generate binary numbers from original signal

From binary converted back to text

a2,97,4

Text ASCII equivalent

0000010 (2)1100001 (97)0000100 (4) binary

equivalent

SDR

Transmitting Antenna

Receiving Antenna

InputText

Message

OutputText

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

ReflectionA 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