Transmitter-Sided Out-of-Band-Signal Reduction Method

In the transmission of data and messages, the optimal utilization of the available frequency bands plays an important role. In frequency multiplexing, sub-frequency bands are allocated to individual communication channels, which are usually completely independent of each other. In practice, however, nonlinear signal amplification leads to cross-talk; that is, any channel also receives signals from the two adjacent channels. Thus, the received signal is composed of a useful signal and an interference signal.

The aim of the present invention is to compensate for the interfering signal component. This is particularly important when the intensity of adjacent channel signals and thus the interference signal which they contribute are greater than the actual useful signal (“adjacent channel interference problem”).

On the transmitter side, the spectral components which lie outside the dedicated communication channel (interference signal) are separately generated in a parallel signal path and are then subtracted from the transmission signal. The resulting modified signals no longer protrude into the adjacent channels, significantly improving the overall signal quality.

• Solution to mitigate cross-talk
• Developed for CPM (continuous phase modulation)
• Applicable for all types of CPM-based wireless communications, especially tactical radio applications

Simulations confirm the effectiveness of the method, as visualized in the graph above.