What Is a Nuller?

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  • Written By: G. Wiesen
  • Edited By: Heather Bailey
  • Last Modified Date: 05 October 2019
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A nuller is a device or piece of technology used to cancel out or reduce the strength of some type of signal or energy. One of the most common ways this is used is as a nulling interferometer, a device used with a telescope to block out a powerful signal. This is typically done when trying to observe very dim objects that are close to very bright objects, by blocking out the bright signal to better see the faint one. A nuller can also be used to overcome efforts to jam or interfere with a communications signal, by nulling the interference.

Though there are a number of different applications in which they can be used, a nuller is basically a device used to block part of a signal. This can refer to many different types of signals, though these signals are usually some form of energy wave. Visible light, for example, can be blocked out by a nuller as can various types of waves used by satellites and other telecommunications applications. This process is referred to as “nulling,” and indicates that a signal or part of a signal has been nullified by the device.


One of the most common applications of a nuller is in the design of a nulling interferometer, which is part of a telescope that can be used to nullify certain signals. The basic idea behind this is the equivalent of someone trying to see the details of a picture that is beside a very bright light. If that person uses his or her hand to block out the light, then his or her eyes adjust and can see the details on the picture, while otherwise the light overwhelms his or her vision.

A nulling interferometer works in much the same way. Telescopes can use a nuller to generate a signal that creates destructive interference between itself and another signal. This nullifies the other signal, such as the light of a bright star near a faint planet, making other signals, the light reflected by the faint planet, easier to see.

There are also ways a nuller can be used in telecommunications, typically to avoid efforts to interfere with or jam a signal. If a signal is being sent from a military station to a satellite, which then relays it to another station, then an enemy might try to create interference that distorts the original signal. A satellite can be designed with a nuller that adjusts to the interference signal and creates destructive interference with it. This nullifies the interference signal and allows the original signal to be received by the satellite.


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