This online article is an excerpt from Chapter 8 from a new edition of the book, RF Circuit Design, 2e by Christopher Bowick. The main idea is:
The RF front end is generally defined as everything between the antenna and the digital baseband system. For a receiver, this “between” area includes all the filters, low-noise amplifiers (LNAs), and down-conversion mixer(s) needed to process the modulated signals received at the antenna into signals suitable for input into the baseband analog-to-digital converter (ADC). For this reason, the RF front end is often called the analog-to-digital or RF-to-baseband portion of a receiver.
Of course, this is for most modern radios, including digital cell phones. Lots of older ham gear is strictly analog. For these radios, the front end is all the circuitry up to, and including, the IF stage.
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