Microwave Forum

richy_64 · Administrator Beiträge: 198

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For a jammer you need just a sawtooth generator, which tunes a voltage controlled oscillator (like POS1060 or MAX2622) continusly from lower frequencies to higher frequencies.

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If you want to jam the complete the gsm downlink band (920-960MHz), you have to disturb it with a carrier that sweeps around, because the bandwith of our carrier is too small to cover the whole band. To get the vco sweeping, we have to feed it with a changing signal, the best signal for this task is sawtooth signal.

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The POS1060 is a vco that produces frequencies from 750...1060MHz.
The tuning voltage is 1...20V.
So we may say: 750MHz comes out we the tuning voltage is 1V,
and 1060MHz comes out when the tuning voltage is 20V.

So what tuning range do we need for 920-950MHz?
Calculate it, and you get 10,9...13.55V ---> or better 10...15V to be sure

We have to adjust the sawtooth generator to let him produce that voltage range we need.

I´ve made 3 pictures of my sawtooth generator, for example:

http://homepages.compuserve.de/richardkotte/1.jpg
What we see: 12V DC and 4V AC=> 10...14V
This waveform would be suitable for our jammer!!

http://homepages.compuserve.de/richardkotte/2.jpg
1,5...4,5V, just for example

http://homepages.compuserve.de/richardkotte/3.jpg
17,5V DC and 5V AC (noticed the voltage button at the oscilloscope?), so we get 15...20V.

At all these pictures we have a sweep frequency of 12,5kHz.
That means that the vco moves 12500 times per second from the lower to the higher frequency.
The vco sweeps over the gsm band, and so gsm will be jammed...

Any questions?