Distributed Amplifier Bias Resistor Grading for Uniform Gain
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Solution Overview
Problem
Distributed amplifiers and mixers face gain reduction due to non-uniform collector currents caused by voltage differences between the bias tee and input termination resistors, which also affect reflection characteristics, making it difficult to maintain optimal performance across wideband frequencies.
Innovation Solution
Setting the emitter or source resistor of each unit cell to different resistance values, with higher values closer to the bias tee and lower values closer to the input termination resistor, ensures uniform collector or drain currents, thereby improving gain and maintaining better reflection characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bias tee is used to supply bias voltage to transistors in distributed circuits, then proper biasing is achieved, but gain reduction occurs due to non-uniform collector currents caused by voltage differences between bias tee and input termination resistors
Solution Approach 1:
The patent applies local quality by setting different emitter resistor values for different unit cells based on their positions in the distributed circuit. Unit cells closer to the bias tee have larger emitter resistors, while those closer to the input termination resistor have smaller emitter resistors. This localized differentiation compensates for the voltage differences caused by current flow through the transmission line, ensuring uniform collector currents and maintaining optimal gain across all unit cells.
2Ease of manufacture
If uniform emitter resistors are used in all unit cells, then manufacturing is simplified, but non-uniform collector currents result due to voltage differences along the transmission line
Solution Approach 1:
The patent implements local quality by positioning specific resistor values at specific locations along the transmission line. Each unit cell's emitter resistor is locally optimized based on its distance from the bias tee, creating a gradient of resistor values that compensates for the cumulative voltage drop along the transmission line. This approach achieves current uniformity while maintaining reasonable manufacturing complexity.
Solution Approach 2:
The patent applies parameter changes by systematically varying the emitter resistor values across different unit cells. The resistor values are changed in a controlled manner according to position, transforming the uniform parameter set into a graded parameter set that actively compensates for the non-uniform voltage distribution along the transmission line.
3Reliability
If emitter resistors are increased to compensate for voltage drop near bias tee, then current uniformity improves, but overall circuit complexity increases
Solution Approach 1:
The patent resolves this contradiction by applying local quality - each unit cell receives a specifically tailored emitter resistor value based on its position. This localized optimization achieves current uniformity across the entire distributed circuit while keeping the overall design systematic and manageable through a clear positioning-based assignment rule.
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
This approach compensates for non-uniform collector currents, enhancing the gain of distributed circuits and maintaining optimal reflection characteristics across a wide range of frequencies, as demonstrated by simulation results showing improved gain and conversion gain performance.
Implementation Method 1
Setting the emitter or source resistor of each unit cell to different resistance values, with higher values closer to the bias tee and lower values closer to the input termination resistor, ensures uniform collector or drain currents
Implementation Method 2
a bias tee connected to the input end of the first transmission line, the bias tee configured to supply a bias voltage to an input transistor of each of the unit cells
Implementation Method 3
a first transmission line configured to receive an input signal at an input end; a second transmission line configured to output an output signal from an output end
Data Source
AI summary
A distributed amplifier includes a first transmission line for input, a second transmission line for output, an input termination resistor connecting a line end of the first transmission line and a power supply voltage, an output termination resistor connecting an input end of the second transmission line and a ground, unit cells having input terminals connected to the first transmission line and output terminals connected to the second transmission line, and a bias tee configured to supply a bias voltage to an input transistor of each of the unit cells. An emitter or source resistor of the input transistor of each of the unit cells is set to a different resistance value from each other in order for a collector or drain current flowing through the input transistor of each of the unit cells to have a uniform value.