Interference Analysis Methods | Power Spectral Density and Spectral Filtering

Calculating Interference for the CommSystem

Use the Basic Interference page to specify:

Whether to calculate the effect of interference emanating from sources identified on the IF Sources page. Enable this calculation by selecting Calculate Interference.
How interference is to be calculated by selecting the Reference Bandwidth value to be used in reporting power flux density.

For more detailed information regarding Power Flux Density, see Technical Notes.

Interference Analysis Methods

When working in the ITU (International Telecommunications Union) framework, the key figures of interest is the equivalent power flux density (epfd) at the receivers. Currently epfd_down is measured on the ground on the basis of the contribution of the interference sources and includes the gain discrimination of the receiver. The epfd_up is measured at the satellite and includes the receiver gain discrimination.

The interference analysis gives the power flux density relative to a reference bandwidth, typically 4 kHz, 40 kHz or 1 MHz, when reporting or graphing the results. The interference analysis method takes into account the bandwidth of the receiver as well as that of the interfering transmitter and includes only the overlap (if any exists) between these two in the denominator when calculating carrier-to-noise ratio. The difference is illustrated in the following graph showing power, frequency and bandwidth for a receiver R and an interfering transmitter T.

Interference analysis methods

The ITU method uses only the overlap between the transmitter and receiver bandwidths (the shaded area in the figure).

Power Spectral Density and Spectral Filtering

The Power Spectral Density (PSD) option allows the scenario to model the actual spectral shape of the transmitted signal based on the modulation, data rate, etc. The use of Spectral Filters on transmitters modifies the spectral shape. The use of Spectral Filters on the receiver helps reduce the impact of out of band signals from jammers and other sources.

Example Illustration of 8th Order Butterworth Filter with 5 MHz Cutoff Centered at 14.5 GHz