SIGNALS
A signal conveys information through a medium from one place to another. The information can be in the form of data, voice, picture and so on. Information before it can be transmitted must be transformed into electromagnetic signals. This information is contained in a carrier wave or carried by a wave of the signal to be transmitted. Signals can be found in various forms such as sound waves, light waves, electrical signals and mechanical signals.
There are two types of signals; they are analog and digital signals.
Analog signals are continuous time varying signals representing physical measurement. They are generally characterized by continuous amplitude and time.
Digital signals are discrete time signals that represent information as a set or series of discrete values. They are characterized by discrete amplitude and discrete time.
A signal is characterized by the following quantities; amplitude, frequency, period, phase, wavelength and noise.
The amplitude of a signal is its magnitude or strength.
The frequency of a signal is the number of oscillations or cycles per second.
The period of a signal is the time taken for one complete oscillation or cycle.
The phase of a signal is the relative timing of the signal with respect to a reference signal.
The wavelength of a signal refers to the relationship between frequency (or period) and the propagation speed of the wave through a medium. The wavelength is the distance a signal travels in one period.
The noise is an unwanted signal that can corrupt or interfere with the desired signal.
To transmit signals the following processes are followed; filtering, amplification, modulation, demodulation and signal compression,
Signal filtering involves removing unwanted frequency components from the signal.
Signal amplification involves increasing the amplitude of the signal.
Signal modulation involves varying the amplitude, frequency or phase of a signal to encrypt or encode information.
Signal demodulation involves extracting the original information from the modulated signal.
Signal compression involves reducing the size of a signal while preserving its essential information.
The advantages of signals to the modern world cannot be overemphasized as its use enables the transmission of information. Its use also enables control systems to track, monitor and control embedded systems remotely. Signals are also used in the entertainment, telecommunication and media industries for audio and video transmission.
However the disadvantages of signals are noise and interference, attenuation or reduction and distortion of signals and the security risk it possess if attempt are not made to secure the signal using encoding or encrypting algorithm of the signal at great expense. Signal processing and deployment cost are prohibitive and signal transmission can lead to undesirable emission of electromagnetic waves with attendant health hazard.
Signals has found widespread use in the following industries; communication and control systems, medical imaging and diagnostic equipment and devices, aeronautics, space and navigation and tracking systems.
The future of signal transmission is predicated on the following trends and developments; advances in signal processing, integration of artificial intelligence (A.I) and machine learning (M.L), cyber security and new emerging technologies such as internet of things, quantum computing, augmented and virtual reality etc. in future signal networks.
SOURCES:
- Signals and systems by Alan V. Oppenheim and Allan S. Willsky.
- Signal systems and transforms by Charles L. Phillips and John M. Parr.
- Signals and systems: A fresh look by S. Unnikrishna Pillai and Augustine I. Zeki.
- Digital signal processing: A computer based approach by Sanjit K. Mitra.
- Signal processing for communication by Paolo Prandoni and Martin Vebterli.