A quick google search of the product name (BG-E8 5G Signal Jammer) from the pictures in a linked article[0] indicate it costs a few hundred dollars and uses 30W, with a range of about 250m. Wonder how modified it can be, or how varied those specs may be.
These are much simpler. Usually just a 555 setup as a triangle wave generator connected to a series of voltage controlled oscillator chips with a small amp, one per antenna.
[0] https://morganhilltimes.com/police-locate-signal-jamming-dev...