Category:Signals

Background

Multicomputer for signal processing, 1974

Electrical signals are everywhere, since they are used in communications, in entertainment devices, in measuring instruments, in imaging devices, in control systems, and in computers. Such signals are of two types: analog, where the signals are carried by continuously varying quantities, and digital, where the signals are restricted to a finite set of discrete values (often just two, symbolized by 0 and 1). The traditional telephone uses analog signals, since the continuously varying pressure associated with sound waves is converted into continuously varying voltages of an electrical signal. Computers, by contrast, usually deal with so-called binary signals, sequences of zeros and ones.

Early uses of mechanical signals are naval flag signalling and railway semaphores, whereas the early theoretical basis of processing analog and digital signals lies in numerical analysis. Early devices which utilize analog signals include the telephone, the phonograph, the radio and television, whereas digital signals became prominent after the advent of the digital computer. Foundational work in digital signal processing was done by Claude Shannon, Harry Nyquist, John Tukey and James Cooley.

Formed in 1948, the IEEE Signal Processing Society is the IEEE's first society and is the world’s premier professional society for signal processing scientist and professionals. The Signal Processing Society is an international organization whose purpose is to: advance and disseminate state-of-the-art scientific information and resources; educate the signal processing community; and provide a venue for people to interact and exchange ideas. The Signal Processing Society's publications include the IEEE Signal Processing Magazine, which is ranked first in popularity among all of IEEE's publications.

Subcategories

• Acoustics - The science of waves, subcategories include acoustic propagation, biomedical acoustics and nonlinear acoustics
• Amplitude - The magnitude of a waveform, topics include those related to amplification and attenuation
• Dispersion - The relationship between wave velocity and frequency described by the laws of physics
• Filters - Systems which remove unwanted frequencies including digital filters, nonlinear filters and superconducting filters
• Loops - Electronic control systems whose output signal is related to their input signal
• Noise - Unwanted or unintentional interference in a signal
• Pulse compression methods - Various methods of pulse compression including optical pulse compression
• Pulse shaping methods - Methods of changing a waveform into transmittable pulses
• Quantization - Converting larger numbers into more manageable smaller numbers
• Signal analysis - Various methods of analyzing signals including harmonic analysis and spectral analysis
• Signal detection - Devices and methods which detect different kinds of signals such as acoustic signal detection, phase detection and radar direction
• Signal generation & recording - The generation and recording of various signals including audio recording, digital recording and noise generators
• Signal processing - The modification and analysis of signals
• Signal reconstruction & restoration - Methods of reconstructing and restoring signals including signal denoising and signal error correction
• Signal resolution - Topics pertaining to signal resolution such as diversity reception
• Signal sampling - The process of converting an analog signal to a digital one