Circular RF Transistor Layout for Precise Digital Power Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing digital RF amplifiers face challenges in reducing Ohmic losses and resistance, and achieving high gain and efficiency due to electromagnetic coupling between transistor inputs and shared drain regions, which complicates individual control of transistor cells.
Innovation Solution
The use of circular transistor cells with concentrically arranged control and output terminals, along with identical or varying widths of control terminals, helps mitigate coupling and improve performance by allowing separate control of transistor cells, thereby enhancing power output resolution and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional transistor layouts with shared drain regions are used, then device complexity is reduced, but electromagnetic coupling between transistor inputs occurs which worsens control precision and increases Ohmic losses
Solution Approach 1:
The transistor is divided into multiple independently controllable transistor cells, each with its own drain region. This segmentation eliminates the electromagnetic coupling problem inherent in shared drain configurations while maintaining device integration. Each cell can be individually controlled by separate control signals, enabling precise power output regulation.
Solution Approach 2:
Each transistor cell is designed with locally optimized characteristics, including dedicated drain regions and appropriately sized control terminals. The local quality of each cell can be tailored to specific control requirements, with control terminal widths adjusted to achieve desired saturation characteristics and minimize coupling effects.
2Loss of energy
If control terminal widths are increased to reduce Ohmic losses, then electrical resistance decreases, but electromagnetic coupling between adjacent transistor inputs increases
Solution Approach 1:
By segmenting the transistor into cells with individual drain regions, the patent allows control terminals to be optimized for low resistance without the harmful effect of coupling to adjacent cells. The segmentation physically isolates the electromagnetic fields of each cell while maintaining electrical connectivity where needed.
Solution Approach 2:
The patent introduces intermediate structures such as via connections and metal layers that mediate between the control terminals and upper-lying metal layers. These intermediaries provide low-resistance pathways while maintaining proper spacing to prevent electromagnetic coupling between adjacent transistor inputs.
3Measurement precision
If more transistor cells are used to increase power output resolution, then the number of controllable power values increases, but device complexity and control difficulty increase
Solution Approach 1:
The transistor is segmented into a manageable number of cells (e.g., 6 cells providing 64 power values), which balances power output resolution with device complexity. This segmentation enables precise control without requiring excessive numbers of cells that would make the device unwieldy.
Solution Approach 2:
The patent implements a control scheme where not all transistor cells need to be fully independently controlled in all operating conditions. The control logic can activate subsets of cells based on required power levels, reducing the effective control complexity while maintaining the capability for fine power resolution when needed.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The present invention is related to a digital RF amplifier. The present invention is particularly related to a digital transmitter in which the digital amplifier is used. The digital RF amplifier comprises a driver having a plurality of outputs and is configured to individually set a signal level at the outputs either to an inactive level or to an active level in response to a digital input signal. The digital RF amplifier further comprises a transistor configured to output an analog RF signal. The transistor comprises a plurality of transistor cells and a plurality of transistor inputs, each transistor input being electrically connected to the control terminal of at least one transistor cell, and wherein each transistor input is connected to a different output of the driver. According to the present invention, the transistor is a circular transistor of which the control terminal and the output terminal of each transistor cell have a circular geometry and are concentrically arranged.