Noise Figure and Temperature — Lesson 4

This lesson covers the concepts of noise figure and noise temperature, their relations, and how they interact with devices that amplify or lose gain. The lesson explains the difference between noise figure in dB and noise figure in ratio. It also discusses how an active device with gain G can be equivalently drawn as an input with a noise temperature and a noiseless amplifier. The lesson further explores the concept of a Lossy Device and how it can be equivalently drawn. The lesson then delves into the system noise temperature in a cascaded system and how to calculate it. The lesson concludes with a discussion on the importance of the first stage noise figure and temperature in reducing the total cascaded noise figure and temperature.

Video Highlights

00:16 - Relations between noise figure and noise temperature for active device
03:34 - Relations between noise figure and noise temperature for lossy device
06:51 - Concept of system noise temperature in cascaded system
14:59 - Example problem
24:41 - Summary

Key Takeaways

- Noise figure and noise temperature are key parameters in understanding the performance of amplifying or lossy devices.
- The noise figure can be represented in dB or in ratio, with different notations used for each.
- An active device with gain can be equivalently represented as an input with a noise temperature and a noiseless amplifier.
- In a cascaded system, the system noise temperature is calculated by considering the gain and noise temperature of each stage.
- The first stage noise figure and temperature play a crucial role in reducing the total cascaded noise figure and temperature.