Linear Antenna Switch Arm Gate Configuration for Signal Linearity
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Solution Overview
Problem
Existing linear antenna switch arms introduce non-linearities in high power signal transmission due to the highly non-linear shunt capacitance of field effect transistors used in OFF arms, which affects the bias voltage and signal integrity in applications like GSM and UMTS cellular phones.
Innovation Solution
A linear antenna switch arm design featuring a field effect transistor with a plurality of gates, where at least one gate is connected to a signal path through a connection line with a node, and adjacent gates on either side are not connected, utilizing resistors in the signal and connection lines to maintain a linear signal path and control the voltage swing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple FETs are used in series in the OFF arm to handle high power signals and maintain low bias voltage, then the voltage swing is distributed across multiple junctions, but the highly non-linear shunt capacitance of each FET introduces non-linearities in the switched signal
Solution Approach 1:
The patent extracts the problematic non-linear shunt capacitance effect by selectively connecting only every second gate to the signal line while leaving adjacent gates unconnected. This extraction approach removes the source of non-linearity while preserving the voltage distribution benefit of multiple series FETs, thereby maintaining signal linearity in high power applications
Solution Approach 2:
Instead of connecting all gates to the signal line as in conventional designs, the patent inverts the approach by connecting only alternating gates and leaving others unconnected. This inversion strategy transforms the inherently non-linear multi-gate FET structure into a linear signal path, resolving the contradiction between power handling capability and signal linearity
2Ease of operation
If all gates are connected to the signal line, then the FET provides maximum control, but the non-linear shunt capacitance of each gate introduces signal distortion
Solution Approach 1:
The patent segments the gate connections by dividing them into connected and unconnected groups, specifically connecting every second gate while leaving others unconnected. This segmentation reduces the total capacitive loading on the signal line while maintaining sufficient gate control through the connected gates, thereby preserving signal integrity without sacrificing operational control
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution ensures linear signal transmission by minimizing non-linearities, allowing for efficient high power signal handling with low bias voltage, thus improving the reliability and performance of antenna switches in time division multiple access methods.
Implementation Method 1
The gate strips 8 have a rectifying effect. A change in voltage on a gate strip 8 causes a change in a depletion layer beneath the gate strip 8 so changing current flow between source 3 and drain 4 as is known.
Implementation Method 2
A change in voltage on a gate strip 8 causes a change in a depletion layer beneath the gate strip 8 so changing current flow between source 3 and drain 4 as is known.
Data Source
AI summary
A linear antenna switch arm comprising a field effect transistor comprising a source, a drain and a plurality of gates; a signal line connected between source and drain, the signal line comprising at least one signal line resistor; at least one gate being connected to the signal line by a connection line, the join between connection line and signal line comprising a node; the at least one gate being selected from the plurality of gates such that the adjacent gates on each side of the connected gates are not connected to the signal line.