Integrated On-Chip Transformers: Recent Progress in the Design, Layout, Modeling and Fabrication

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.

Neural-Network-Based Automated Synthesis of Transformer Matching Circuits for RF Amplifier Design

“…However, in general, estimating them is beyond the capabilities of even highly experienced designers. There are other electrical parameters that can be gauged by users and represent the full two-port characteristics, such as the Q-factors (Q 1 and Q 2 ) and IL of a TF [34]…”

Comparison of Different Large Signal Measurement Setups for High Frequency Inductors

“…Equation ( 5) allows evaluating the propagation of the variation of the parameters ω i to the value of F. The function f can be nonlinear and in general is difficult to handle. In order to calculate how small variations of parameters ω i affect the measurement F, the function f is analyzed applying the first order Taylor series approximation (6) in the vicinity around a given value F 0 , considering the variations of parameters ω i around the values ω i,0 :…”

“…There has been a significant number of reports on large signal characterization of discrete passive devices. In the particular case of characterization of inductors, there is an increasing interest because of the thin film components working in Power Supply on Chip or Power Supply in Package [1][2][3][4][5][6][7][8]. These kinds of applications present two main challenges regarding the measurement: (1) the high frequency (above 10 MHz) and (2) the high Q of the component (very small resistance compared to its reactance).…”

A Survey on Microtransformers

“…Although microtransformers have been researched for decades, only a few review papers on the subject have been published until now, but all them are mainly focused on single subjects [12]- [14]. Thus, this work is aimed to provide a broad overview of microtransformers.…”