In a radio receiver circuit, the RF front end, short for radio frequency front end, is a generic term for all the circuitry between a receiver's antenna input up to and including the mixer stage.[1] It consists of all the components in the receiver that process the signal at the original incoming radio frequency (RF), before it is converted to a lower intermediate frequency (IF). In microwave and satellite receivers it is often called the low-noise block downconverter (LNB) and is often located at the antenna, so that the signal from the antenna can be transferred to the rest of the receiver at the more easily handled intermediate frequency.
For most superheterodyne architectures, the RF front end consists of:[2]
In digital receivers, particularly those in wireless devices such as cell phones and Wifi receivers, the intermediate frequency is digitized; sampled and converted to a binary digital form, and the rest of the processing – IF filtering and demodulation – is done by digital filters (digital signal processing, DSP), as these are smaller, use less power and can have more selectivity.[3] In this type of receiver the RF front end is defined as everything from the antenna to the analog-to-digital converter (ADC) which digitizes the signal.[3] The general trend is to do as much of the signal processing in digital form as possible, and some receivers digitize the RF signal directly, without down-conversion to an IF, so here the front end is merely an RF filter in the simple receiver path/chain.
