Low‐Noise Amplifier and Frequency Converter

Abstract

This chapter is about the low‐noise amplifier (LNA) and the frequency converter, two units in the front end of the payload. It discusses their architecture, redundancy scheme, technology, and environmental considerations and provides an example of their communications‐related specification parameters. The LNA's essential features are its low noise figure and high gain. Amplifiers and frequency converters are inherently nonlinear elements, meaning that their response to a signal cannot be represented by a filter. The LNA is designed to operate in a nearly linear amplification region. A LNA without temperature compensation will exhibit higher gain and lower noise figure, the lower the temperature. There are various ways to architect the collection of frequency converters in the payload. A self‐contained receiver can consist of a single chain of LNA, reference oscillator, local oscillator (LO), and frequency converter or be without reference oscillator and LO.