20-11-2012, 03:17 PM
RF Jamming on Multiple Frequencies
[attachment=40343]
Importance of Jamming
Many IED’s are controlled by simple wireless devices
IED’s account for 32.5% of US fatalities in Iraq
Threat continues to evolve as terrorists find ways to overcome current jamming systems
Project Goals
Simultaneously jam RC cars at 27 and 49 MHz
Design a shielding method to allow friendly cars to use the entire frequency spectrum while denying that ability to enemy cars
Building Process
Waveform from car controller measured
4 large pulses followed by set number of small pulses
0111 0111 0111 0111 01 01 … 01 0111 0111 0111 ..
Carrier frequency runs during high periods
Carriers are 27.14 MHz and 50.04 MHz
Switches at 3 kHz
Building Process
SOT-23 Resistor Set Oscillator
5 Volt Square Wave
590 kOhms sets to 3kHz
Silver conductive pens used to make contacts due to small size of component
Fosc = 10MHz(10000)
(N)(Rset)
Friendly Modification Overview
Jamming slightly off controller frequency
Controller frequency mixed to 10.7 MHz so that 10.7 MHz filter attenuates jamming signal
Desired signal mixed back to controller after filter
[attachment=40343]
Importance of Jamming
Many IED’s are controlled by simple wireless devices
IED’s account for 32.5% of US fatalities in Iraq
Threat continues to evolve as terrorists find ways to overcome current jamming systems
Project Goals
Simultaneously jam RC cars at 27 and 49 MHz
Design a shielding method to allow friendly cars to use the entire frequency spectrum while denying that ability to enemy cars
Building Process
Waveform from car controller measured
4 large pulses followed by set number of small pulses
0111 0111 0111 0111 01 01 … 01 0111 0111 0111 ..
Carrier frequency runs during high periods
Carriers are 27.14 MHz and 50.04 MHz
Switches at 3 kHz
Building Process
SOT-23 Resistor Set Oscillator
5 Volt Square Wave
590 kOhms sets to 3kHz
Silver conductive pens used to make contacts due to small size of component
Fosc = 10MHz(10000)
(N)(Rset)
Friendly Modification Overview
Jamming slightly off controller frequency
Controller frequency mixed to 10.7 MHz so that 10.7 MHz filter attenuates jamming signal
Desired signal mixed back to controller after filter