Investigating the effects of digital filtering on digital modulations

Digital filters are a basic building block of a communication system and can serve many diverse purposes such as: restricting a signal to a prescribed frequency band, separating a signal into two or more sub-bands, modifying the spectral content of a signal, modeling a communication channel, performing mathematical operations, reducing the noise content of a signal, etc. On occasion, digital filters are used to estimate the bandwidth of a digital modulation and this paper will investigate possible issues that can be encountered when using digital filters for this purpose.