Pulsformsdämpning

Pulsformsdämpning, often translated as pulse shaping or pulse compression in English, refers to techniques used in signal processing to alter the shape of a transmitted pulse. This alteration is typically done to improve the performance of a communication system, particularly in the context of digital modulation and radar. The primary goals of pulse shaping are to reduce intersymbol interference (ISI) and to minimize the bandwidth occupied by the signal.

In digital communications, ISI occurs when a transmitted pulse spreads out and overlaps with subsequent pulses, making it difficult for the receiver to distinguish between them. Pulse shaping aims to create pulses that have minimal side lobes and decay rapidly, thereby reducing this overlap. Common pulse shapes include the raised cosine filter and the Gaussian filter. The raised cosine filter is popular because it offers a trade-off between bandwidth efficiency and ISI.

In radar systems, pulse compression is a specific application of pulse shaping. Here, a long pulse is transmitted with a specific modulation (e.g., linear frequency modulation or phase coding). At the receiver, a matched filter or pulse compression algorithm is used to de-modulate the received signal. This process effectively compresses the energy of the long transmitted pulse into a much shorter pulse at the output of the filter. This results in improved range resolution, comparable to that of a short pulse, while maintaining the high energy of a long pulse, which enhances the detection range.