Abstract
On-chip transformers are considered to be the primary components in many RF wireless applications. This paper provides an in-depth review of on-chip transformers, starting with a presentation on the various equivalent circuit models to represent transformer behavior and characterize their performance. Next, a comparative study on the different design and layout strategies is provided, and the fabrication techniques for on-chip implementation of transformers are discussed. The critical performance parameters to characterize on-chip transformers, such as the Q-factor, coupling factor (k), resonance frequency (fSR), and others, are discussed with reference to trade-offs in silicon chip real-estate. The performance parameters and area requirements for different types of on-chip transformers are summarized in tabular form and compared. Several techniques for performance enhancement of on-chip transformers, including the different types of micromachining and integration approaches stemming from MEMS (microelectromechanical systems) technologies are also analyzed. Lastly, the different uses and applications of on-chip transformers are discussed to highlight the evolution of on-chip transformer technology over the recent years and provide directions for future work in this field.
Highlights
With newly emerging wireless communication demands, such as 5G, the realization of fully integrated systems with on-chip components is critical to reduce production costs and overall device size
The paper is organized in seven sections as follows: After the introductory Section 1, figures-of-merit for on-chip transformers are discussed in Section 2; in Section 3, different modeling and characterization techniques of monolithic transformers and their comparison are presented; in Section 4, types of CMOS compatible monolithic transformers are described in detail; in Section 5, a performance analysis is provided, and different attempts to improve the performance of monolithic transformers are described; Section 6 discusses the applications of monolithic transformers; and in Section 7, conclusion and directions on future work are presented
In typical LC voltage-controlled oscillators (VCO) designs, AC coupling is achieved through series capacitors which interact with varactors and lower the tuning range; and varactors of LC tanks are biased through high value resistors which increase noise
Summary
With newly emerging wireless communication demands, such as 5G, the realization of fully integrated systems with on-chip components is critical to reduce production costs and overall device size. Additional to the substrate losses, there are ohmic losses, due to the thin metallization and parasitic losses between the conducting coil of the transformer and substrate, and in between the coils of the transformer Despite their lower efficiency, planar transformers are still widely preferred as they are easy to fabricate owing to their simple geometry and ease-of-compatibility with CMOS foundry processes. Noting the importance of on-chip transformers in RF systems and the multifaceted issues in their design, fabrication test cycle; this paper provides a comprehensive review and discusses the various attempts that have been proposed to realize on-chip transformers with a detailed comparison of their performance metrics. The paper is organized in seven sections as follows: After the introductory Section 1, figures-of-merit for on-chip transformers are discussed in Section 2; in Section 3, different modeling and characterization techniques of monolithic transformers and their comparison are presented; in Section 4, types of CMOS compatible monolithic transformers (either stacked or interleaved) are described in detail; in Section 5, a performance analysis is provided, and different attempts to improve the performance of monolithic transformers are described; Section 6 discusses the applications of monolithic transformers; and in Section 7, conclusion and directions on future work are presented
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
