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Method for 2-D varactor waffle structures

IP.com Disclosure Number: IPCOM000021502D
Publication Date: 2004-Jan-21
Document File: 3 page(s) / 133K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for two-dimensional (2-D) varactor waffle structures. Benefits include improved performance.

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Method for 2-D varactor waffle structures

Disclosed is a method for two-dimensional (2-D) varactor waffle structures. Benefits include improved performance.

General description

         The disclosed method is a waffle structure used to implement differential and single-ended voltage-controlled capacitors. The key characteristics facilitated by these structures are as follows: high capacitive density, high quality factor, and a large signal-frequency bandwidth. These characteristics are key to the realization of high-performance voltage-controlled oscillators (VCOs). High performance here is low phase noise and low power consumption.

Advantages

         The disclosed method provides advantages, including:

•         Improved performance due to a large fill factor, at least 2x that of its conventional counterpart

•         Improved performance due to a larger capacitive density

•         Improved performance due to a high signal bandwidth

•         Improved performance due to a high level of matching because of a high degree of symmetry

•         Improved performance due to a larger pull-in range in VCO applications

Detailed description

         The disclosed method includes a waffle structure that is inherently compact and lends itself to efficient layout implementations (see Figure 1). The cross shapes represent poly-Silicon while the open areas are diffusion openings with contacts or without contacts. As stated earlier, differential and single-ended varactors can be realized with such structures. For example, assume the following statement is true:

0 £ f £ a

         A single-ended structure can be realized by setting f equal to 0. Differential structures are realized when f > 0. Alternating positive and negative potential cells, checkerboard or interlaced columns or rows form these structures. They are completely symmetric in nature, with or without diffusion between the poly islands. One possible implementation of a var...