Cascode Power Amplifier Output Switching Without Band Select Loss
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Solution Overview
Problem
Modern communication front-ends face challenges with broadband power amplifiers followed by band select switches, which introduce additional insertion loss and pose difficulties in meeting high power handling, minimum insertion loss, and linearity requirements, particularly due to harmonic generation and intermodulation issues.
Innovation Solution
The proposed solution employs a cascode power amplifier with a shared common cascode input stage and parallelly connected cascode output stages, where selective application of voltages activates or deactivates amplification paths, eliminating the need for a band select switch by providing separate amplification paths for different frequency bands without impedance transformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a band select switch is used to direct transmit signal to different filter RF paths, then signal routing for different frequency bands is achieved, but insertion loss increases and power handling capability decreases
Solution Approach 1:
The power amplifier is segmented into multiple parallel cascode output stages, each optimized for specific frequency bands. Each stage includes its own output transistor and associated circuitry, allowing direct connection to band-specific filters without requiring a central band select switch. This segmentation eliminates the insertion loss associated with switching while maintaining the ability to route signals to different frequency bands.
Solution Approach 2:
The invention transitions from a single-dimensional switching architecture to a multi-dimensional parallel architecture. Instead of using a switch to select between bands sequentially, multiple amplification paths operate in parallel simultaneously, with each path dedicated to a specific frequency band. This dimensional change from sequential switching to parallel processing eliminates the need for band select switches and their associated losses.
2Adaptability or versatility
If a band select switch is employed to manage different frequency bands, then frequency band selection is achieved, but device complexity and component count increase
Solution Approach 1:
The invention merges the frequency band selection function directly into the power amplifier structure itself. Rather than adding a separate band select switch as an external component, the amplifier integrates multiple cascode output stages with different frequency responses directly within the amplifier circuit. This merging eliminates the need for separate switching components and reduces overall device complexity.
Solution Approach 2:
The power amplifier is designed with multi-functionality by incorporating multiple cascode output stages that can each handle different frequency bands. The amplifier structure itself serves both the amplification function and the frequency band selection function simultaneously, eliminating the need for separate dedicated components for each function and thereby reducing overall system complexity.
3Adaptability or versatility
If broadband power amplifier is used to cover multiple frequency bands, then frequency coverage is improved, but power handling capability and linearity deteriorate
Solution Approach 1:
Each cascode output stage is designed with local quality optimization for its specific frequency band. The output transistors, biasing circuits, and matching networks in each stage are tailored to the specific requirements of their assigned frequency band, ensuring optimal power handling capability and linearity for that band. This local optimization allows each stage to perform at its peak within its designated frequency range.
Solution Approach 2:
The broadband amplification function is segmented into multiple narrowband cascode output stages, each optimized for a specific frequency range. Rather than using a single broadband stage that compromises performance across all bands, the segmentation allows each stage to be independently optimized for its specific band, maintaining high power handling capability and linearity while achieving broad overall frequency coverage through the parallel combination of stages.
Data Source
AI summary
A power amplification system may include a shared common cascode input stage. A power amplification system may include a plurality of cascode output stages parallelly connected to the shared common cascode input stage, each cascode output stage associated with a frequency band.