An RF front end is a device or module that incorporates all the circuitry between the antenna and at least one mixing stage of a receiver and possibly the power amplifier of the transmitter. They are used in a wide variety of RF products and applications. Examples include wireless systems and FM radio systems. They may also include the frequency generation circuitry.

5pt;">FM radio RF front end devices used in FM radios and television receivers are receiver-only front ends. They typically feature double balanced mixers (for improved intermodulation characteristics), signal limiting or clamping circuitry to prevent overloading, local oscillation buffer and impedance matching. This refers to a single device that is used in a circuit with additional filtering, power supply decoupling and matching circuitry that are impractical to implement on-chip. It can also refer to the whole circuit offered in modular form.GPS front ends are receiver RF front ends. They have an RF input to a built-in band-pass filter centered at 1575.42GHz, a low noise amplifier (LNA) and may incorporate a double balanced image rejection mixer to convert down to a lower intermediate frequency (IF). IF can be lower frequencies, for example, 16.384MHz or 4.092MHz. They usually require external circuitry like SAW filters for band pass filtering for selectivity. The LNA is usually a variable gain amplifier, and there is usually a second variable gain amplifier after the mixer to amplify the down-converted IF signal. Some GPS RF front ends even include a low precision analog to digital converter to produce a serial bit stream for subsequent digital processing, and a recovered GPS clock reference. They can include a built-in frequency synthesizer and local oscillator to produce the LO signal for the mixer. Configuration is typically by the serial interface to the processing system.Wireless LAN and Wi-Fi RF front ends are used in applications such as smart meters, intelligent lighting, routers and cellular devices. They incorporate a power amplifier (PA) for the transmitter, an LNA for the receiver and RF switches for swapping between receive and transmit. They may have a second switch to allow an auxiliary antenna to be used, baluns to perform impedance matching and balanced to unbalanced conversion are also typically incorporated. They may comply with a wireless interface standard (for example IEEE802.11g for a Wi-Fi system) and have additional antenna switching to support Wi-Fi/Bluetooth coexistence. Read more Read less