RF Power Combiner Matching for Low-Loss CMOS Amplifiers
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Solution Overview
Problem
Power amplifiers in wireless cellular devices face challenges in delivering high output power efficiently due to voltage scaling in nanoscale technology, requiring multiple transistors and power combiners, which are difficult to manufacture in a low-loss and compact form using CMOS processes, and suffer from power loss and leakage issues with frequency band switches.
Innovation Solution
A power combiner with multiple transformers and micro amplifiers connected in series, utilizing low voltage nanoscale CMOS transistors and series resonant capacitors to resonate out leakage inductance, allowing for high output power and efficiency with a compact, low-cost design that compensates for antenna mismatch and frequency band variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple micro power amplifiers are used to deliver high output power in nanoscale technology, then output power capability is improved, but device complexity and manufacturing difficulty increase due to the need for power combiners
Solution Approach 1:
The power amplifier is divided into multiple micro power amplifiers (first, second, third, and fourth micro PAs) that can be independently designed and manufactured using standard nanoscale CMOS processes. Each micro PA operates at lower power levels, allowing the use of available nanoscale transistors while achieving high total output power through combination.
Solution Approach 2:
Multiple micro power amplifiers are combined using a power combiner structure implemented with transformers and series-connected secondary windings. This merging approach allows the individual outputs of multiple low-power nanoscale amplifiers to be aggregated into a single high-power output, resolving the contradiction between using multiple amplifiers and maintaining manufacturing simplicity.
2Power
If a transformer network power combiner is used to combine output power from multiple micro power amplifiers, then power combination capability is improved, but manufacturing difficulty and loss increase due to requirements for high coupling factor and high inductances
Solution Approach 1:
The patent transforms the traditional transformer network requirements by changing the operational parameters. Instead of requiring high inductances and high coupling factors that are difficult to manufacture, the invention uses series-resonant capacitors to resonate out leakage inductance, allowing the use of smaller, easier-to-manufacture transformers with lower inductance values while maintaining high power combination efficiency.
Solution Approach 2:
Series-resonant capacitors are introduced as intermediary components between the micro power amplifiers and the power combiner. These capacitors resonate with the leakage inductance of the transformers at the operating frequency, effectively canceling out the harmful inductive effects and enabling efficient power combination without requiring precisely manufactured high-inductance transformers.
3Adaptability or versatility
If frequency band switches are used to select desired power amplifier output for multiple frequency bands, then frequency versatility is improved, but power loss and leakage increase due to switch resistance and finite isolation
Solution Approach 1:
The power combiner structure is designed to be universal and support multiple frequency bands without requiring separate switches for each band. The same transformer-based combiner can operate across different frequency ranges by adjusting the resonant capacitors, eliminating the need for frequency band switches and their associated power losses and leakage.
Solution Approach 2:
The frequency band switching function is extracted and eliminated from the system. Instead of using switches to select between different frequency band outputs, the invention uses a single universal power combiner that can handle multiple frequency bands directly, removing the source of power loss and leakage associated with switch resistance and finite isolation.
4Device complexity
If nanoscale CMOS transistors are used for voltage scaling, then integration capability is improved, but available power per transistor decreases due to limited voltage breakdown
Solution Approach 1:
The high-power requirement is segmented across multiple nanoscale CMOS transistors organized as micro power amplifiers. Each transistor operates within its voltage breakdown limits, but the collective output of many such transistors through the power combiner achieves the required high total power, maintaining both integration capability and power output.
Solution Approach 2:
The power outputs from multiple nanoscale transistors are merged through the transformer-based power combiner. This merging allows the aggregation of many low-power individual transistor outputs into a high-power combined output, resolving the contradiction between using low-voltage nanoscale transistors and achieving high total power output.
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 enables a high-efficiency, low-loss RF power amplifier that can deliver significant output power while minimizing power loss and leakage, effectively addressing the limitations of nanoscale technology and frequency band switching inefficiencies.
Implementation Method 1
series-resonant capacitors to resonate out leakage inductance
Data Source
AI summary
Methods to implement low cost, high efficiency, low loss power combiner with novel matching circuits are disclosed. A narrow band power combiner enables a high power and high efficiency radio frequency power amplifier to be realized using multiple low voltage CMOS transistors or micro power amplifiers. The power combiner may be printed on a package substrate and realized either using single layer substrate through edge coupling or multiple layers substrate through broadside coupling. The micro power amplifiers may be fabricated using low voltage CMOS technology and electrical connections between the outputs from the micro power amplifiers and the power combiner may be provided through stud bumps in a flip chip technology. With the tunable matching circuits, the present invention allows the narrow band power combiner to be tuned to different frequencies.