In the world of physics, interference means two or more waves meeting in space, creating a pattern dictated by each wave’s frequency and direction.
The simplest way to understand wave interference is to imagine two rocks thrown to a lake. Each rock creates a circular wave pattern in the water, and when the two waves meet – they merge.
Here’s a short animation of wave interference in action:
According to classical physics, pretty much the same thing happens when three-dimentional waves meet, such as sound waves, electromagnetic waves, etc.
What is a wave?
In classical physics, a wave is a disturbance that transfers energy. Each wave has a frequency – which means the number of times it”pulsates” – and from that frequency also derive the wave’s wavelength. If one wave peak move through a given unit of space each second, the wave’s frequency is 1 hertz. If 10 wave peaks do that – we have a 10 Hz wave.
When a wave peak meets with another exact wave peak (“in-phase”), they enhance each other to create constructive interference. The end product of which is a new wave of greater amplitude (see image, left). When a wave trough meet another exact wave trough (“out of phase”) – they cancel each other out to create destructive interference (see image, right).
Here’s an animation of a dynamic interference. The green and blue waves pass across each other, and create a constructive or
destructive interderence resulting in the red wave.
Signal Jamming Is Interference-Based
Now, that we understand how waves propagate in space and what happens when they meet – we can really appreciate how signal jamming works.
Let’s say we own a smartphone. These devices usually operate in a frequency range of hundreds of mega hertz to a few giga hertz (meaning their waves oscillate millions to billions of times per second, making them radio waves).
In order to jam any cellphone / mobile phone, one must create a destructive interference pattern with that cell phone’s radio waves. RF jamming devices actually saturate space in a given radius, with a radio wave that exactly fits the mobile phone’s frequency. The only difference between the two waves, is that they are out of phase (reverse wave – see again above images).
The product of this activity is a “white noise” RF wave, which destructively interfere with the mobile phone’s waves. Hence any mobile phone in the affected radius, will show a “no signal” announcement.