Cascode Power Splitter Biasing for Multi-Band RF Amplification

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Solution Overview

Problem

Multiband power amplification systems face inefficiencies due to the use of band switches or passive splitters, which introduce loss and require additional semiconductor dies, increasing size, cost, and current drain.

Innovation Solution

A power amplification system utilizing a cascode power amplifier with multiple common base cascode stages that switches between frequency bands without a band switch, sharing a common RF gain path and achieving band selection through selective biasing, thereby eliminating the need for additional process technology complexity or semiconductor dies.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a band switch is used to switch between frequency bands, then band selection is achieved, but additional semiconductor die is required and system loss increases

Engineering Contradiction:

Improveband selection capabilityVSAvoidsemiconductor die quantity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent merges the band switching function with the power amplifier function by integrating multiple cascode stages directly into the amplifier circuit. The common emitter stage is paired with selectable common base cascode stages, eliminating the need for a separate band switch die while maintaining multi-band operation capability.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The power amplifier circuit is designed to perform both amplification and band selection functions simultaneously. The same transistor stages that provide gain also enable frequency band switching through selective biasing, making the amplifier multi-functional and eliminating dedicated switching components.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Adaptability or versatility

If a passive splitter is used to split RF signals, then multiple frequency bands are supported, but system loss increases and efficiency decreases

Engineering Contradiction:

Improvemulti-band supportVSAvoidsignal loss

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The patent replaces the passive mechanical/electrical splitter with an active electronic switching mechanism using transistor biasing. Instead of using passive components that inherently lose signal, the invention uses active transistor stages that can be selectively enabled through bias control, substituting a lossy passive system with an active one.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Adaptability or versatility

If a band switch or passive splitter is used, then band selection is achieved, but current drain increases

Engineering Contradiction:

Improveband switching capabilityVSAvoidcurrent drain

Core Design Contradiction:

Adaptability or versatilityVSUse of energy by moving object

Solution Approach 1:

The patent maintains continuous useful action by keeping the power amplifier stages actively biased and ready across all frequency bands. Instead of switching between active and inactive states (which causes transient current draws), the common emitter stage remains continuously active while only the specific common base cascode stage needed for the current band is actively biased, reducing unnecessary current drain.

Inventive Principle:

Principle #20Continuity of useful action

Data Source

PatentUS10778161B2Power splitter with cascode stage selection

Publication Date: 2020.09.15 SKYWORKS SOLUTIONS INC

AI summary

A power splitter that amplifies an input radio-frequency (RF) signal. The power splitter uses a single transistor in a common emitter stage of a cascode amplifier and two or more common base stages of the cascode amplifier to amplify and to split the input RF signal. A common base biasing signal can be used to simultaneously enable two or more of the common base stages to generate two or more amplified RF output signals.