A Brief Review on Receiver Noise Figure
Many RF front-end (RFFE) systems are unique, but the receivers are similar in many ways. In general, RF sensitivity is a key specification of all wireless radio receivers. The RF receiver's ability to pick up the required level of radio signals while ignoring the unwanted ones will enable it to operate more effectively within its application.
Some methods of measuring RF sensitivity of a receiver are:
- Noise Figure (NF) – The NF of a system is the logarithmic version of the noise factor. It specifies the noise performance of a receiver, individual components of a system, and the entire system.
- Signal to Noise Ratio (SNR) – This is a comparison ratio between the given signal power level to the noise within the system.
- Bit Error Rate (BER) – This is a form of measurement used for digital systems. As the signal level falls or the link quality degrades, the number of errors in the transmission or bit errors increases. Measuring the BER gives an indication of the SNR but in a format that is often more useful for the digital domain.
- Error Vector Magnitude (EVM) – EVM is a measure used to quantify the performance of a digital radio transmitter and receiver. A signal sent by an ideal transmitter or received by a receiver would have all EVM constellation points precisely at the ideal locations. Still, imperfections such as noise, distortion, phase noise, etc., cause the actual constellation points to deviate from the ideal locations. Ideally, the transmitter should generate the digital data to fall as close to these points as possible. The EVM is a measure of how far from the ideal positions the actual received data elements are. Additionally, the more linear an amplifier is, the better the EVM will be.