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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