RF Circuits and Systems - Oscillators

Name: RF Circuits and Systems - Oscillators
Rating: 4.7 (23 reviews)

Course 5

Highest Rated

Created byProfessor Payam Heydari

Last updated 5/2025

English

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What you'll learn

The students will learn how to analyze and design one of the most fundamental circuits, namely, oscillators
They will learn the ring oscillators, LC oscillators, voltage-controlled oscillators, and the notion of phase noise
This course also offers basic understanding of the quadrature oscillators and the concept of injection locking
We will go through set-by-step approach of designing a cross-coupled pair LC oscillator.

Course content

22 sections • 22 lectures • 9h 30m total length

RF Circuits and Systems - Oscillators3:05
Outline of the course is as follows:
- Fundamentals of Oscillator as a Feedback Network
- An Ideal LC Circuit as an Oscillator
- Loss Compensation Circuits Used in LC Oscillators
- Voltage Controlled Oscillator (VCO)
- Ring VCOs
- LC VCOs
- Tuning Mechanism in VCOs
- Varactor Tuning
- Discrete Tuning
- Inductive Tuning
- An Overview of Phase Noise

Analysis of 3-Stage Ring Oscillator Based on Poles-Zeros of Feedback Circuit31:06
- Applying the oscillation condition, called Barkhausen Criteria, to derive the minimum required gain and the oscillation frequency of the three-stage ring oscillator, where each delay stage is a comm-source
- Investigating the oscillator's behavior for various configurations of the poles and zero of the closed-loop transfer function
- Examining the "gain-control mechanism" in an oscillator that helps producing the sustainable oscillation.
- Studying the widely used ring oscillator where each stage is a complementary NMOS-PMOS stage.
-Calculating the oscillation frequency based on the signal transition.

Closed-Loop Root-Locus Analysis of Oscillator and Circuit Realizations33:44
- Exploring the pole-zero configuration of the closed-loop system in oscillatory behavior
- Analysis of root-locus of a unity-gain feedback system in oscillation with an open-loop stage having simplest pole-zero pattern
- Calculating the minimum required gain and oscillation frequency of a closed-loop circuit having an open-loop stage with a pair of poles and a zero

Sinusoidal Oscillators Based on RLC Tank in a Closed-Loop Feedback35:34
- An overview of the root locus analysis of the closed-loop feedback network incorporating an open-loop circuit with two poles and one zero in the left half plane.
- Studying the open-loop circuit with a complexity conjugate left-half plane poles.
- Circuit realization:
1. Realization of the open-loop circuit using an RLC tank circuit
2. Building the unit-gain feedback network around the RLC tank
3. Putting them all together and using the transistor to close the loop
- Transformer-feedback LC oscillators

Requirements

The pre-requisit for this is a good understanding analog circuits and systems.

Description

This course focuses on the study and design of oscillators. As we will learn, oscillators are autonomous circuits capable of producing sustainable oscillation. The course starts by modeling the oscillator as a closed-loop feedback system. By investigating the magnitude and phase plots, the necessary conditions for oscillation are then derived. Multi-stage ring oscillator based on the feedback concepts and oscillation condition will then be designed. The large-signal study of a ring oscillator will then be presented. This will be followed by proposing several delay-stage candidates for a ring oscillator.

The course then studies the pole-zero pattern of a closed-loop feedback system to be able to generate oscillation. Looking at the LC circuits, we will learn that the passive components inevitably have losses that prevent the LC network to generate steady-state oscillation. We will then study loss-compensation networks from two perspectives, namely, (a) feedback theory and (b) active devices exhibiting negative resistance. The course then offers a ground-up approach to cross-coupled pair oscillators. We will then learn about a basic network that plays a foundational block for a class of oscillators such as Colpitts, Clapp, and Pierce topologies.

The course will then introduce voltage-controlled oscillators (VCOs). We will learn about a number of design specifications for VCO design. Next, several mechanisms and circuit techniques will be introduced that will enable tuning in a ring oscillator. This will be followed by an in-depth study of varactor-based LC VCOs. We will also learn that varactor has limited quality factors and oscillators based on varactors cannot have a wide tuning range. We will then introduce the concept of discrete tuning. Finally, we learn about the concept of inductive tuning and present two approaches based on magnetic tuning and active inductors that facilitate inductive tuning.

Since inductors are essential components in oscillators, we will review on-chip inductors and discuss a lumped electrical network that models these inductors.

The course will finally offer a general overview of phase noise. We briefly discuss a linear-time invariant approach to model the phase noise, and finally, we will discuss the widely used Leeson formula for phase noise modeling.

Who this course is for:

For all junior- and senior-level undergraduate students, graduate students, design engineers, students who are preparing for interview at a high-tech company, and engineers who are pursuing a career in RF circuits.

RF Circuits and Systems - Oscillators

What you'll learn

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