Transformer-Coupled Distributed Amplifier for Broadband Output Power
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Solution Overview
Problem
Existing wideband, high-power silicon-based amplifiers face limitations in output power due to narrowband frequency response and high dc current requirements, which lead to large, lossy passive structures and electromigration concerns.
Innovation Solution
A distributed amplifier design using a transformer-coupled approach with serially coupled secondary windings in the output transmission line network and differential bipolar transistor pairs, allowing for separate dc biasing and decoupling of ac and dc collector currents, enabling more manageable metal width and impedance matching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If standard L-C matching structures are used in cascode amplifiers, then maximum output power is delivered for given source and load impedance, but the circuit becomes narrowband due to resonant behavior
Solution Approach 1:
The amplifier is divided into multiple distributed stages connected by transmission line sections. Each stage contributes to the overall gain while the transmission lines provide broadband impedance transformation, eliminating the narrowband resonant behavior of single-stage L-C matching while maintaining power delivery capability.
Solution Approach 2:
The patent transitions from single-stage two-port matching to multi-stage distributed architecture with transmission line interconnects. This adds the dimension of spatial distribution and phase progression, enabling broadband operation while maintaining power transfer through coherent signal combination at the output.
2Adaptability or versatility
If all output current flows through matching inductors in distributed amplifiers, then broadband operation is achieved, but high dc current requires very wide inductors causing electromigration concerns
Solution Approach 1:
The patent extracts the dc current path from the signal path by introducing separate biasing inductors for each amplifier stage. The matching inductors only carry ac signal current, while dc bias current flows through dedicated biasing inductors, dramatically reducing the current burden on the matching network and eliminating electromigration concerns.
Solution Approach 2:
Biasing inductors serve as intermediary elements that provide separate dc current paths to each amplifier stage. These intermediaries allow the matching inductors to function solely for ac signal matching without carrying high dc currents, resolving the electromigration issue while maintaining broadband performance.
3Reliability
If dc blocking capacitors are inserted between distributed amplifier stages, then high dc current through output inductors is avoided, but additional biasing inductors are required degrading circuit performance
Solution Approach 1:
The patent merges the biasing function with the existing amplifier stage structure by using the collector inductors of each stage to provide both signal matching and dc biasing functions simultaneously. This integration eliminates the need for separate biasing inductors and capacitors, reducing component count while maintaining reliability.
4Power
If transformer coupled amplifiers are used to combine output of several amplifiers, then higher output power is achieved, but narrow band frequency response is maintained
Solution Approach 1:
The patent segments the transformer coupling into distributed stages separated by transmission line sections. Each transformer combines signals from its local amplifier stage, while the transmission lines provide broadband phase and amplitude matching across the frequency band, preventing the narrowband response inherent in direct transformer coupling.
Solution Approach 2:
The patent adds the dimension of distributed spatial arrangement with transmission line interconnects between transformer stages. This transforms the narrowband direct-coupled transformer architecture into a broadband distributed architecture where phase and amplitude are progressively adjusted across multiple stages to achieve coherent combination over a wide frequency range.
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 design achieves higher output power with improved frequency response and reduced loss in passive components, addressing the limitations of narrowband operation and high dc current issues in traditional amplifiers.
Implementation Method 1
each one of the output transformers having a primary winding, each one of the secondary windings of the output transformers being magnetically coupled to a corresponding one of the primary windings of the output transformers
Data Source
AI summary
An amplifier having an input transmission network with a plurality of input transformers having serially coupled primary windings. Each one of the input transformers has a secondary winding magnetically coupled to a corresponding one of the primary windings. The amplifier includes an output transmission network having a plurality of output transformers having serially coupled secondary windings. Each one of the output transformers has a secondary winding magnetically coupled to a corresponding one of the primary windings. The amplifier includes a plurality of amplifier sections, each one the sections having an input connected to a corresponding one of the secondary windings of the input transformers and an output connected to a corresponding one of the primary windings of the output transformers. The input and output transmission networks are arranged to combine signals passing from an input to the input transmission network through the plurality of amplifier sections combine in-phase at an output of the output transmission section.