In
telecommunications
Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that fe ...
, desensitization (also known as receiver blocking) is a form of
electromagnetic interference
Interference is the act of interfering, invading, or poaching. Interference may also refer to:
Communications
* Interference (communication), anything which alters, modifies, or disrupts a message
* Adjacent-channel interference, caused by extra ...
where a radio receiver is unable to receive a weak radio signal that it might otherwise be able to receive when there is no interference. This is caused by a nearby transmitter with a strong signal on a close
frequency
Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...
, which overloads the receiver and makes it unable to fully receive the desired signal.
Typical receiver operation is such that the Minimum Detectable Signal (MDS) level is determined by the thermal noise of its electronic components. When a signal is received, additional spurious signals are produced within the receiver because it is not truly a linear device. When these spurious signals have a power level that is less than the thermal noise power level, then the receiver is operating normally. When these spurious signals have a power level that is higher than the thermal noise floor, then the receiver is desensitized. This is because the MDS has risen due to the level of the spurious signals. Spurious signals increase in level when the received signal strength increases.
When an interfering signal is present, it can contribute to the level of the spurious signals. Stronger interference generates stronger spurious signals. The interference may be at a different frequency than the signal of interest, but the spurious signals caused by that interference can show up at the same frequency as the signal of interest. It is these spurious signals that degrade the ability of the receiver by raising the MDS.
Consider the case of a
repeater station, a station consisting of a transmitter and receiver, both operating at the same time, but on separate frequencies, and in some cases, separate
antennas. Elevated MDS can be experienced in this case as well.
One way to correct this condition is adding a
duplexer
A duplexer is an electronic device that allows bi-directional ( duplex) communication over a single path. In radar and radio communications systems, it isolates the receiver from the transmitter while permitting them to share a common antenna. M ...
to the station. This is common in
Land Mobile Radio
A land mobile radio system (LMRS) is a person-to-person voice communication system consisting of two-way radio transceivers (an audio transmitter and receiver in one unit) which can be stationary ( base station units), mobile (installed in vehicl ...
services such as police, fire, various commercial and
amateur service
Amateur radio, also known as ham radio, is the use of the radio frequency spectrum for purposes of non-commercial exchange of messages, wireless experimentation, self-training, private recreation, radiosport, contesting, and emergency communic ...
.
See also
*
Receiver (radio)
In radio communications, a radio receiver, also known as a receiver, a wireless, or simply a radio, is an electronic device that receives radio waves and converts the information carried by them to a usable form. It is used with an antenna. T ...
*
Sensitivity (electronics)
*
Minimum detectable signal
A minimum detectable signal is a signal at the input of a system whose power allows it to be detected over the background electronic noise of the detector system. It can alternately be defined as a signal that produces a signal-to-noise ratio of ...
References
{{Reflist
Electromagnetic compatibility
Interference
Noise (electronics)
Radio communications