R&S^®ABFS Baseband Fading Simulator

Flexible concept

The basic model of the R&S® ABFS comes with two independent channels for six-path fading. The two channels can be interconnected as follows:

• Distribution of an input to two outputs (e.g. with different fading profiles). This feature makes it possible to simulate the signal of two antennas with different characteristics or frequency diversity methods.
• Simulation of two channels with individual profiles and addition at the output. Cell change or superposition of interferers can be tested with this configuration.
• Coupling of two channels so that a channel with 12 propagation paths is obtained

High versatility through options

The Noise Generator R&S® ABFS-B1 adds a noise source to the output of the fi rst channel (see Fig. 4) so that noise can be simulated in the frequency band used. The noise generator can be switched on or off irrespective of the operating modes of the basic version.

The optional Second Fading Simulator R&S® ABFS-B2 offers two extra channels with the same characteristics in addition to the two channels of the basic model.

The optional Second Noise Generator R&S® ABFS-B3 provides an additional noise source for a further output. This second noise generator is either assigned to the second channel of the basic R&S® ABFS (with the first Noise Generator R&S® ABFS-B1 for the first channel) or to the first channel of the Second Fading Simulator R&S® ABFS-B2.

Fading profi les such as Rayleigh, Rician, pure Doppler, Lognormal or Suzuki can be assigned to each of the propagation paths irrespective of the selected circuit. In addition to the fading profiles mentioned, the following parameters can be defi ned for each propagation path:

• Path attenuation
• Delay time
• Doppler frequency or speed between transmitter and receiver
• Coupling to another channel

Preprogrammed fading models

Many fading models have already been programmed in ABFS. The user can quickly recall these default settings and also modify the parameters.

Enhanced fading functions for 3GPP WCDMA

The R&S® ABFS-B49 option extends the functionality of the Baseband Fading Simulator R&S® ABFS to include 3GPP WCDMA channel simulation. It adds three new modes to the fading simulator so that all scenarios defined in 3GPP Release 99 can be simulated:

• In fine delay mode, the fading simulator resolution is increased to 1 ns with up to four paths being available.
• In moving delay mode, two paths are simulated: the delay for one path remains constant, whereas the delay for the other path varies continuously.
• In birth/death mode, there are two paths where the delay changes in steps in accordance with the 3GPP channel model. The option R&S® ABFS-B50 enables the enhanced fading functions for 3GPP WCDMA for the second fading simulator.