Software Defined Radio Architectures - Part III — Lesson 5

This lesson covers the fundamentals of software defined radio architectures, focusing on Homodyne and Heterodyne structures. It delves into the advantages of Heterodyne structures over Homodyne, the problem of image signal at higher frequencies, and the practical constraints of Local Oscillator (LO) and Intermediate Frequency (IF) values. The lesson also explores solutions to these issues, such as increasing the IF or using a digital IF-based architecture. It further discusses the role of numerically controlled oscillators, the precision of digital systems, and the application of these concepts in modern communication systems. For instance, the lesson explains how a multichannel frontend can support multiple frequencies in a handset.

Video Highlights

00:18 - Dual conversion superheterodyne architecture
05:21 - Digital IF homodyne architecture
06:54 - Numerically controlled oscillators
14:49 - How to control the frequency of sinusoids?
17:49 - Digital IF for multiband processing
22:14 - Architectures with multirate processing

Key Takeaways

- Homodyne and Heterodyne are two primary software defined radio architectures.
- Heterodyne structures have selectivity advantages over Homodyne but face the issue of image signal at higher frequencies.
- The LO and IF values are typically fixed and not meant to be changed in practical scenarios.
- Increasing the IF or using a digital IF-based architecture can solve the problem of image signal.
- Numerically controlled oscillators play a crucial role in digital IF-based architecture.
- Digital systems offer precision and ease of reconfiguration, making them advantageous over their analog counterparts.
- Modern communication systems often deal with multiple channels, requiring a frontend that can support multiple frequencies.