The RF receiver's ability to reject unwanted signal is called

Selectivity:

• The ability of a radio receiver to respond only to the radio signal it is tuned to and reject other signals nearby is termed as Selectivity.
• Selectivity is the ability of a receiver to reject the unwanted frequency signal.
• This function is performed by the tuned circuits ahead of the detector stage.

Sensitivity:

• Sensitivity is the ability to amplify weak signals.
• Radio receivers should have reasonably high sensitivity so that it may have a good response to the desired signal.
• It should not have excessively high sensitivity, otherwise, it will pick up all the undesired noise signals.

Fidelity:

• The fidelity of a receiver is the ability to reproduce all the modulating frequencies equally, i.e. the fundamental frequency and the harmonics of the fundamental frequency.
• The radio receiver should have high fidelity or accuracy without introducing any distortion.
• Ex- In an AM broadcast the maximum audio frequency is 5 kHz. Hence the receiver with high fidelity must produce the entire frequency up to 5 kHz.

SNR:

The signal to noise ratio (SNR) is defined as the ratio of the signal power to the noise power, i.e.

\(SNR=\frac{{Signal\;power}}{{Noise\;power}}\)

In dB, the SNR is expressed as:

SNR(dB) = 10log10(SNR)