What are the key components in an RF front-end?

An RF front-end is the interface between the antenna and the baseband processor. Key components: Antenna for radiating/receiving RF signals. Duplexer/switch separates Tx and Rx paths (FDD) or switches between them (TDD). LNA (Low Noise Amplifier) amplifies weak received signals with low noise figure (typically 1-2 dB). PA (Power Amplifier) amplifies transmitted signals to required power level. Filters (bandpass, SAW, BAW) select desired frequency band and reject out-of-band signals. Mixer converts between RF and IF or baseband frequencies. VCO/PLL generates local oscillator frequencies. Modern smartphones integrate many components into FEMs (Front-End Modules) to save space.