Open AccessThird‐order tunable‐phase asymmetric cross‐coupled oscillator
Author(s) -
Maundy Brent,
Elwakil Ahmed
Publication year - 2019
Publication title -
iet circuits, devices and systems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.251
H-Index - 49
ISSN - 1751-8598
DOI - 10.1049/iet-cds.2018.5494
Subject(s) - oscillation (cell signaling) , biasing , correctness , transistor , phase (matter) , voltage controlled oscillator , vackář oscillator , voltage , cmos , control theory (sociology) , physics , computer science , optoelectronics , quantum mechanics , algorithm , genetics , control (management) , artificial intelligence , biology
Here, the authors show that an asymmetric cross‐coupled oscillator can be used to achieve independent‐phase tunable outputs. In particular, a third‐order cross‐coupled oscillator, with non‐balanced loads, is studied and expressions for its start‐up condition, oscillation frequency, phase‐shift between its two outputs as well as their amplitude ratio are derived. From these expressions, it is found that independent tuning of these design specifications is possible and a voltage‐controlled phase‐tunable oscillator can be achieved. As a consequence of the non‐balanced loads, the tail biasing current is not equally split between the two cross‐coupled transistors. However, a design procedure that enables the equal splitting of the current is proposed and validated. Simulations of a prototype in a 0.18μ m CMOS process are given and experimental results with discrete transistors verify the correctness of the theory.