Data Transmission Filters are similar to Raised Cosine Filters, but are easier to build: they do not require a delay equalizer, but are less effective in removing Inter-Symbol Interference (ISI). The data transmission solution offered by FilterSolutions eliminates only post-cursor ISI (ISI following the impulse response peak), or all ISI, if the passband frequency is doubled.
Examples of impulse responses for 7th order filters are shown below.
The Data Transmission Filter only has one point of significant pre-cursor ISI. If the passband frequency is doubled, the pre-cursor ISI disappears or is insignificant. The result is that Data Transmission Filters are less effective in removing ISI, or require twice the bandwidth.
FilterSolutions creates Data Transmission Filters by removing the delay equalizer from the Raised Cosine Filter, and employing numerical methods to remove the pre-cursor ISI.
Other solutions for Data Transmission Filters are known to exist, such as those found in The CRC Handbook of Electrical Filters. The use of FilterSolutions provides the advantage of offering the user flexibility in designing for accuracy vs. bandwidth by selecting different Alpha values.