Doherty Peaking Amplifier Load Impedance for Maximum Output
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Solution Overview
Problem
Doherty amplifiers suffer from reduced maximum output and deteriorated high drain efficiency due to the peaking amplifier's inability to reach maximum output when using the same output load as the carrier amplifier, leading to suboptimal performance.
Innovation Solution
The solution involves creating a Doherty amplifier apparatus and method where the load impedance of the peaking amplifiers is made less than that of the carrier amplifier, using a splitter to split the input signal into multiple power signals, and employing a Doherty combiner to form load impedance such that the peaking amplifiers operate with a lower DC bias, allowing both amplifiers to reach maximum output simultaneously.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the peaking amplifier uses the same output load as the carrier amplifier, then the structure is simple, but the peaking amplifier cannot reach maximum output
Solution Approach 1:
The patent applies local quality by providing different load impedances to different parts of the system - specifically, the peaking amplifier is given a different load impedance (Zp) than the carrier amplifier (Zc). This allows each amplifier to operate at its optimal load condition, enabling the peaking amplifier to reach maximum output while maintaining overall system simplicity.
2Adaptability or versatility
If the peaking amplifier uses lower DC bias than the carrier amplifier, then the amplifiers operate at different input signal ranges, but the peaking amplifier cannot reach maximum output
Solution Approach 1:
The patent provides different load impedances to different amplifiers based on their specific operating characteristics. The peaking amplifier operating at lower DC bias is given a specifically optimized load impedance that allows it to reach maximum output despite its different operating range, while the carrier amplifier receives a different load impedance suited to its higher bias operation.
3Device complexity
If both amplifiers use the same load impedance, then the design is straightforward, but the high drain efficiency operating region deteriorates
Solution Approach 1:
The patent optimizes energy efficiency by providing different load impedances tailored to each amplifier's operating characteristics. The peaking amplifier receives a load impedance specifically optimized for its lower DC bias operation, maximizing its drain efficiency in its operating region, while the carrier amplifier receives a different load impedance optimized for its higher bias operation.
Data Source
AI summary
An apparatus and method for maximizing the performance of a peaking amplifier in a Doherty amplifier are provided. The apparatus includes a splitter, a carrier amplifier, an (N−1) number of peaking amplifiers, a Doherty combiner, and an output load. The splitter splits an input signal into an ‘N’ number of power signals. The carrier amplifier amplifies the signal provided from the splitter using a first Direct Current (DC) bias. The peaking amplifiers amplify the signals provided from the splitter using a second DC bias, which is lower than the first DC bias. When the carrier amplifier and the peaking amplifiers are all operating, the Doherty combiner forms a load impedance of the respective amplifiers such that the load impedance of the peaking amplifiers are less than the load impedance of the carrier amplifier. The output load outputs the signals amplified by the carrier amplifier and the peaking amplifiers.