signalshaping

Signal shaping refers to deliberate manipulation of a signal's time-domain or frequency-domain characteristics to fit a transmission channel, minimize interference, and meet regulatory or system requirements. It is used to control bandwidth, reduce intersymbol interference, and optimize power and error performance.

Common methods include pulse shaping, where transmitter filters constrain spectral occupancy using finite impulse response filters; popular shapes are raised cosine and root raised cosine filters, which reduce out-of-band emissions and control intersymbol interference. In digital communications, probabilistic shaping adjusts the probability distribution of transmitted symbols to approach channel capacity. Pre-emphasis and equalization adjust spectral content to compensate for channel response. In optical communications, shaping may involve optical filters or modulation formats to limit bandwidth.

Design considerations include trade-offs among bandwidth efficiency, error performance, and implementation complexity; shaping also interacts with noise, nonlinearity, and regulatory spectral masks. In hardware, finite filter lengths, quantization, and clock jitter affect performance.

Applications include wireless and wired communications, fiber-optic links, audio processing, and measurement systems. Shaping is used to minimize interference with adjacent channels and to meet spectral emission limits while maintaining data integrity.