Power Amplifiers Nonlinear Distortion — Lesson 1

This lesson covers the fundamental concepts of power amplifiers in radio communication, focusing on their role as the main source of non-linear distortion in transmitted signals. It delves into the nonlinearity distortion due to single band, single tone, and single two-tone signals. The lesson also explains the concept of multi-carrier signals and how the criteria of judging distortion changes in such cases. It further discusses the concept of adjacent channel power ratio, error vector magnitude, and the different classes of power amplifiers. The lesson also provides an understanding of the AM/AM and AM/PM conversion of power amplifiers, the concept of memory effect, and the calculation of output power back off.

Video Highlights

00:18 - Dynamic range for muti-carrier or wideband signals
04:20 - Adjacent channel power ration and error vector magnitude
07:20 - Receiver constellation error
14:58 - AM/AM or AM/PM conversion
17:57 - Power amplifier selection parameters and gain
20:57 - Signal power at the input and output
25:46 - Memory effect
27:28 - Output power back off and its relation to the carrier to third order inter modulation

Key Takeaways

- Power amplifiers are the main source of non-linear distortion in transmitted signals.
- In multi-carrier signals, distortion is measured by the adjacent channel power ratio.
- Error vector magnitude represents the deviation in the constellation diagram.
- Different classes of power amplifiers (Class A, B, AB, and C) have different profiles of gain, output power, and efficiency.
- AM/AM and AM/PM conversions represent the gain and phase modulation of power amplifiers.
- The concept of memory effect comes into play due to the heating of devices and energy storing components in the power amplifier.
- The output power back off is a method to get lesser distortion by driving the amplifier at some distance from the input power.