Doherty Combiner Circuit Without 1/4-Wavelength Lines
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Solution Overview
Problem
The Doherty amplifier requires a combiner circuit that achieves broader bandwidth without using a ¼ wavelength line, as traditional designs with ¼ wavelength lines are not suitable for miniaturization and broader bandwidth characteristics.
Innovation Solution
A combiner circuit is designed with a combiner section that combines signals from a carrier amplifier and a peak amplifier, and a matching section with a negative variation coefficient for the imaginary part of impedance, allowing impedance matching between the combiner section and a load, thereby achieving broader bandwidth without the need for a ¼ wavelength line.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a 1/4 wavelength line is used for the combiner, then the combiner can be implemented with a simple structure, but the bandwidth is limited and miniaturization is difficult
Solution Approach 1:
The patent changes the electrical parameters of the combiner by introducing a series capacitor and parallel inductor, transforming the impedance characteristics across the frequency band. This allows the combiner to achieve broad bandwidth performance without relying on the frequency-dependent 1/4 wavelength line, thereby resolving the contradiction between structural simplicity and bandwidth adaptability
Solution Approach 2:
The patent introduces reactive components (capacitor and inductor) as intermediary elements that mediate the impedance matching between the combiner and load. These intermediaries compensate for impedance variations across frequency, enabling broad bandwidth operation while maintaining a compact structure that does not require long 1/4 wavelength transmission lines
2Device complexity
If a 1/4 wavelength line is used for the combiner, then the design is simpler, but the circuit size increases
Solution Approach 1:
The patent transforms the combiner's impedance parameters using reactive components, allowing the use of short transmission line sections instead of long 1/4 wavelength lines. This parameter transformation achieves the same combining function in a much smaller physical space, resolving the contradiction between structural simplicity and circuit size
Solution Approach 2:
The patent nests the reactive components (capacitor and inductor) within the combiner structure, creating a compact integrated design. The series capacitor and parallel inductor are embedded in the signal path, allowing the combiner to achieve broad bandwidth performance in a miniaturized form factor without requiring external 1/4 wavelength transmission lines
Data Source
AI summary
A combiner circuit includes: a combiner section that outputs a combined signal by combining a first signal output from a carrier amplifier circuit and a second signal output from a peak amplifier circuit, the first signal being generated by amplifying a first distribution signal distributed from an input signal, the second signal being generated by amplifying a second distribution signal distributed from the input signal; and a matching section connected in series with the combiner section to receive the combined signal, wherein a variation coefficient of an imaginary part of impedance associated with an increase in frequency of the input signal indicates a negative value, and the matching section matches impedance between the combiner section and a load.