DBc

The signal level difference is the difference between the level of a signal and the level of a support ( Sheet Carrier) or a reference signal. The signal level difference describes the logarithmic ratio of signal power to the power of the reference signal.

The specification in dBc (dB Carrier) takes place in communication engineering in intermodulation products and spurious signals from a carrier. In communication systems, the boundaries of noise are shown in both maximum absolute levels, as well as in dBc levels. Too large noise level, equivalent to a large dBc level can lead to disturbances in the signal transmission.

How big is the signal to noise ratio, in this case the level difference between noise signal and carrier, must be at least to have no influence on the transmission depends on the used wireless technology and especially on the receiver sensitivity and its analog input and possibly used digital signal filtering. A default value is about -10 dBc. Are the filters of the receiver sharp and the frequency spacing between support and interference signal large enough noise in the receiver can be suppressed to the extent that even with a - no influence of the transmission channel is greater signal strength - in comparison with the carrier power.

The term dBc / Hz ( difference in level relative to 1 Hz bandwidth) is used in particular in the phase noise to indicate the noise power density.

Example

A carrier has a transmission capacity of C = 0.1 mW, an interfering signal power S = 10 uW.

The carrier thus having a signal level of

If the level of the interference signal

Thus, the signal level difference between noise signal and carrier calculated

The signal level difference can be calculated directly from the logarithmic ratio of the two signal powers ( interference signal based on the carrier ):