We use the following frequency bands as the shielding frequency band of the wifi jammer as an experiment
CDMA: 869-894MHz
Mobile phone: 935-960MHz
Mobile phone: 1805-1880MHz
PHS: 1900-1990MHz
After the working principle and circuit structure of the wifi blocker are understood, electronics enthusiasts, after understanding the working principle, they can do whatever they want, and then design and make it a try. It is very easy to use. This article is specially written. Tell interested friends about my design and production process.
The working principle is to use the sawtooth wave to control the voltage-controlled oscillator to generate a frequency sweep signal in the working frequency band. And a narrow pulse (caused by the reverse travel of the sawtooth wave), which destroys the data exchange between the mobile phone and the base station in the coverage area. The mobile phone cannot get the base station data, and can only display no signal, of course, it cannot communicate.
The frequency of the sawtooth wave used in the measured CDMA frequency band is about 30KHz, and the frequency of the sawtooth wave used in the other three frequency bands is 10KHz. According to analysis, the sawtooth wave is not used for measurement here, but it can only make the voltage-controlled oscillator work, without any precision, it can be generated by a relatively simple circuit as shown in the figure below.
The circuit is simple, the components are easy to obtain, and the precision is not high, but it can fully meet the requirements. Here, maybe a sawtooth wave with less precision and a longer return would be better. Both the voltage-controlled oscillator and the radio frequency amplifier have relatively high operating frequencies and have a lot in common.
After experiments, the four frequency bands used in mobile communication can be installed on this circuit board, and the second harmonic is used for the two high-frequency bands. Of course, two frequency bands that are close to each other can also be shared on one circuit board, but the output will be much smaller. Covering the four bands with one board is also possible, but the output is smaller because the RF energy will be more spread out.
