Technical details:
Many cell phones use GSM800 mobile standard to operate, thus my VCO (sweeping oscillator) is tuned to the 800MHz frequency range. It may be quite difficult to make this one to work properly without some skills and good testing tools, but in result you will have the efficient VCO.
I used clock oscillator for 45MHz as the noise generator for this jammer. It drives the local oscillator port which is located at the mixer. The signal is going out from the local oscillator and passes through the impedance matching network along its way. This helps equate the impedance of 45MHz clock oscillator with the impedance of the mixer's port.
This port acts like RF input of the signal jammer. The RF output signal passes through the amplifier on the mini-circuit. The output power is increased by additional 15-16dbm in this way. Then the output signal goes to the RF output antenna. RF input has the antenna too.
Jammer operating:
Why I chose 45MHz clock oscillator? Because GSM800 band transmitted and received signals are always separated by the exact number of frequency and it is that 45MHz. Now picture this: cell phone user dial someone and signal goes off. RF input antenna catches it and jammer modifies this signal and lets it go. This signal have a frequency of cell phone's received signal, so cell phone user would hear his or her own voice in a phone! :)
I should also mention that this particular cell phone jammer might be used to block the signal of the cell-based car tracking device which records your GPS data and sends it to some bad guys. And it probably can even jam some IED signals if they are controlled by cell phone GSM800 band.
But I hope that there be no situation in this life when that feature will be needed by me, or you, or anyone else.
