ACP Measurement according to IS 54 (NADC) using the R&S®FSE Spectrum Analyzers

In digital wireless communication systems one or multiple users are assigned to a physical RF channel. With analog systems only one user per carrier is possible. Output spectrum of the transmitter has to be restricted to the assigned channel in order to avoid interference with the neighbor channels. With the switch over to digital modulation formats more user per channel are possible. They share one channel by using only part of the time for transmission (Time Division Multiplex Access, TDMA) or by coding the transmission by orthogonal sequences for distinction to other users (Code Division Multiples Access, CDMA). Beneath the restriction of modulation spectrum with TDMA systems also time behavior of the transmitted signal is critical. One reason is that in a multi-user situation only one user is allowed to transmit within his assigned time slots. Another reason is that by switching a carrier on and off spectrum of the transmitter splatters and causes additional interference in other RF channels.