Load Modulation Amplifier Phase Delay Bandwidth
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Solution Overview
Problem
The Doherty amplifier faces issues with maintaining high frequency characteristics over a wide bandwidth due to frequency dependence of impedance and parasitic capacitance, leading to inefficient operation and increased amplifier size.
Innovation Solution
The design incorporates a high frequency circuit board with an input distribution circuit, carrier and peak amplifiers, and an output combination circuit unit, where the carrier and peak amplifiers are directly connected to the output combination circuit without impedance conversion, and the 90-degree phase delay circuit is formed on the signal line, utilizing parasitic capacitance components to enhance load modulation and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a 1/4 wavelength phase delay line is used to provide 90-degree phase delay, then the phase delay function is achieved, but the impedance becomes frequency dependent and the bandwidth is limited
Solution Approach 1:
The patent transforms the fixed 1/4 wavelength phase delay line into a variable electrical length by introducing a switchable capacitor. This allows the electrical length to be adjusted between different states (e.g., 1/4 wavelength and other values), enabling the circuit to maintain proper phase relationships across a broader frequency range and resolve the bandwidth limitation caused by frequency-dependent impedance.
Solution Approach 2:
The patent introduces dynamic control to the phase delay circuit by adding a switchable capacitor that can change the electrical length based on operating conditions. This dynamic adjustment capability allows the circuit to adapt to different frequencies, transforming a static, frequency-dependent system into a dynamic one that can maintain performance across wide bandwidth.
2Reliability
If output matching circuits and correction lines are added to increase impedance when peak amplifier is off, then the impedance matching is improved, but the amplifier size is increased
Solution Approach 1:
The patent makes the capacitor serve multiple functions: it acts as part of the phase delay circuit, provides impedance transformation, and enables dynamic load modulation. By integrating these functions into a single component rather than adding separate matching circuits and correction lines, the patent achieves proper impedance matching without increasing amplifier size.
Solution Approach 2:
The patent combines the phase delay function and impedance matching function into a single integrated circuit structure. The switchable capacitor is part of both the phase delay path and the impedance transformation network, eliminating the need for separate matching circuits and correction lines, thereby reducing overall amplifier size while maintaining reliability.
3Reliability
If carrier amplifier and peak amplifier are connected with impedance conversion, then the impedance matching is improved, but the device complexity and size are increased
Solution Approach 1:
The patent extracts the impedance conversion function from a separate matching circuit and integrates it directly into the output combination circuit. By taking out the impedance transformation requirement and embedding it within the existing combiner structure through the switchable capacitor, the patent simplifies the overall device while maintaining proper impedance matching between amplifiers.
Data Source
AI summary
Provided is a load modulation amplifier including: a high frequency circuit board; and on the board, an input distribution circuit unit (DC) including: a distributor for dividing one input signal into two signals IS1 and IS2; and a phase delay circuit formed on a signal line for the divided IS2; a carrier amplifier (CA) including a first high frequency transistor for amplifying the IS1; a peak amplifier (PA) including a second high frequency transistor and for amplifying the IS2; and an output combination circuit (OCCU) including: a 90-degree phase delay circuit (90DC) formed on a signal line for output of the CA; a combiner for combining output of the 90DC and output of the PA; and an impedance conversion circuit for converting an output impedance of the combiner. The CA and the PA are directly connected to the OCCU without converting an output impedance.