How an RF Amplifier Boosts Signal Power Efficiently
This patent describes an RF power amplifier design that uses a main amplifier and several auxiliary amplifiers to efficiently boost radio signals over a wide power range, especially useful in wireless communication basestations.
Original patent title: “N-way RF power amplifier with increased backoff power and power added efficiency”
This patent describes an RF power amplifier design that uses a main amplifier and several auxiliary amplifiers to efficiently boost radio signals over a wide power range, especially useful in wireless communication basestations. Granted to Cree Microwave in 2004 with 11 claims and 21 forward citations, and it is now in the public domain.
Coverage
What does this patent actually cover?
This amplifier design boosts radio frequency (RF) signals efficiently across a wide range of power levels. It uses a main amplifier (ClaimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more → 1a) to handle lower power signals. When the main amplifier approaches its maximum power output, or 'saturation,' a series of auxiliary amplifiers (Claim 1b) are biased to sequentially turn on, one after another, to continue boosting the signal. An input signal splitter (Claim 1c) directs the signal to both the main and auxiliary amplifiers, with a quarter-wave transformer connected to the main amplifier's input. The amplified signals are then combined at an output, where the auxiliary amplifiers connect through quarter-wave transformers to a specific resistive load (Claim 1d, Claim 5d). For example, a cell tower could use this to amplify a weak incoming signal to a strong, broadcast-ready signal without wasting much energy, even as the required output power changes.
The gap
What does this patent NOT cover?
- Amplifiers where auxiliary amplifiers do not turn on *sequentially* after the main amplifier approaches saturation (ClaimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more → 1b).
- Amplifiers that do not use lateral DMOS transistors for both the main and auxiliary amplifier components (ClaimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more → 1a, 1b).
- Amplifiers that lack a signal splitter that includes a quarter-wave transformer connected to the input of the main amplifier (ClaimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more → 1c).
- Amplifiers where the output does not combine signals from main and auxiliary amplifiers, with auxiliary outputs connected through quarter-wave transformers (ClaimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more → 1d).
- Amplifiers that do not operate over a 'broad range of power' or where the main amplifier's saturation level is not below the maximum of that broad range (ClaimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more → 1a).
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
Key facts
What made this novel
The noveltynoveltyThe requirement that an invention be different from anything publicly known before its priority date.Read more → lies in the sequential activation of multiple auxiliary amplifiers, each precisely biased to engage only after the main amplifier nears its power limit. This, combined with the strategic use of quarter-wave transformers at both the input and output stages, allows for highly efficient power combining and extended operation over a very wide power range, significantly reducing wasted energy.
The Patent Drawing
Schematic visualization of the patent's claim structure. Hand-drawn diagrams in progress for each landmark patent.
Where you've seen this
Real-world examples
Cellular basestations
Radio transmitters
Satellite communication systems
Wireless network infrastructure
High-power radar systems
Why it matters
The bigger picture
Efficient RF power amplifiers are crucial for modern wireless communication systems. This design helps reduce energy consumption and heat generation in devices like cell tower basestations, which are always on and handling varying signal loads. By improving efficiency, it helps maintain signal quality and extend the reach of wireless networks while lowering operational costs for telecommunication providers.
Filed
January 28, 2002
Granted
March 2, 2004
Market context
Who's building on this
Companies in this space
Cree Microwave LLC, the original assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →, is now part of Wolfspeed, a leading company in silicon carbide and gallium nitride (GaN) technologies, which are essential for high-power RF applications. Other major companies like Qorvo, Broadcom, and NXP also develop advanced RF power amplifiers for various wireless infrastructure and communication systems, continuously seeking to improve efficiency and power density.
Market impact
The expansion of cellular networks (2G, 3G, and beyond) created a massive demand for more efficient RF power amplifiers. This type of technology helped reduce the operational costs and environmental footprint of basestations by significantly improving 'power added efficiency.' This improvement was crucial for the widespread and economically viable deployment of wireless communication infrastructure globally, enabling faster and more reliable connections.
Claim 1 — Plain English
What this patent covers
This amplifier design boosts radio frequency (RF) signals efficiently across a wide range of power levels. It uses a main amplifier (Claim 1a) to handle lower power signals. When the main amplifier approaches its maximum power output, or 'saturation,' a series of auxiliary amplifiers (Claim 1b) are biased to sequentially turn on, one after another, to continue boosting the signal. An input signal splitter (Claim 1c) directs the signal to both the main and auxiliary amplifiers, with a quarter-wave transformer connected to the main amplifier's input. The amplified signals are then combined at an output, where the auxiliary amplifiers connect through quarter-wave transformers to a specific resistive load (Claim 1d, Claim 5d). For example, a cell tower could use this to amplify a weak incoming signal to a strong, broadcast-ready signal without wasting much energy, even as the required output power changes.
The clever bit
The novelty lies in the sequential activation of multiple auxiliary amplifiers, each precisely biased to engage only after the main amplifier nears its power limit. This, combined with the strategic use of quarter-wave transformers at both the input and output stages, allows for highly efficient power combining and extended operation over a very wide power range, significantly reducing wasted energy.
What it does not cover
- Amplifiers where auxiliary amplifiers do not turn on *sequentially* after the main amplifier approaches saturation (Claim 1b).
- Amplifiers that do not use lateral DMOS transistors for both the main and auxiliary amplifier components (Claim 1a, 1b).
- Amplifiers that lack a signal splitter that includes a quarter-wave transformer connected to the input of the main amplifier (Claim 1c).
- Amplifiers where the output does not combine signals from main and auxiliary amplifiers, with auxiliary outputs connected through quarter-wave transformers (Claim 1d).
- Amplifiers that do not operate over a 'broad range of power' or where the main amplifier's saturation level is not below the maximum of that broad range (Claim 1a).
Patent timeline
Application submitted to the patent office
Application published, typically 18 months after filing
Patent officially issued
Patent enters public domain
This patent is in the public domain
See the Freedom to Build guide — what is free to use, what is not, and how to cite this patent.
PatentBrief Score
Impact Score
Early stage
Citation count
27/40
Moderately cited
Claim breadth
7/20
Moderate scope
Recency
0/20
Older than 20 years
Assignee scale
0/20
Independent or smaller assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →
PatentBrief Impact Score — based on citation count, claim breadth, recency, and assignee scale. Not a legal assessment.
Heuristic Value Estimate
What this patent might be worth
$19K – $60K
Midpoint $38K · expired or expiring · industry ×1.4
Heuristic only — blends forward/backward citation counts, claim scope, time remaining, litigation history, and CPC-derived industry baseline. Real valuations need a professional appraisal.
Claim text not yet imported for this patent
The original legal language
Original claims
11 claims as filed with the patent office.
Concepts involved
Citations
Patent lineage
Cite this patent
Pengelly, R. S. (2004). How an RF Amplifier Boosts Signal Power Efficiently (U.S. Patent No. 6,700,444). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/6700444/n-way-rf-power-amplifier-with-increased-backoff-power-and-power-added-efficiency
Auto-generated from the patent record. Double-check author order and the issue date against the official USPTO document before submitting.
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Common Questions
Frequently Asked Questions
What does How an RF Amplifier Boosts Signal Power Efficiently cover?
This patent describes an RF power amplifier design that uses a main amplifier and several auxiliary amplifiers to efficiently boost radio signals over a wide power range, especially useful in wireless communication basestations.
Who owns patent US 6700444?
Cree Microwave owns this patent, granted in 2004.
When does this patent expire?
This patent has expired and is now in the public domain — anyone can use the invention freely.
What is patent US 6700444 cited by?
This patent has been cited by 21 later patents that build on its ideas.
What problem does this patent solve?
Efficient RF power amplifiers are crucial for modern wireless communication systems. This design helps reduce energy consumption and heat generation in devices like cell tower basestations, which are always on and handling varying signal loads. By improving efficiency, it helps maintain signal quality and extend the reach of wireless networks while lowering operational costs for telecommunication providers.
What does this patent NOT cover?
Amplifiers where auxiliary amplifiers do not turn on *sequentially* after the main amplifier approaches saturation (Claim 1b).
Patent monitoring