Power Amplifier Input Matching to Reduce Lower-Band Power Loss
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Solution Overview
Problem
Existing power amplifier circuits experience power efficiency degradation due to high frequency signal attenuation near the lower limit frequency, leading to increased power loss and consumption as the signal progresses through multiple stages, particularly in posterior stages.
Innovation Solution
Incorporating a high pass filter as an input matching circuit and an automatic transformer or transmission line transformer as an inter-stage matching circuit between amplifiers, along with an impedance circuit to block DC components and pass AC components, to minimize power loss and maintain linear amplitude characteristics across the signal band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a high pass filter is used as an inter-stage matching circuit to flatten gain in the signal band, then the signal level is stabilized across frequency, but power loss increases near the lower limit frequency and power efficiency degrades
Solution Approach 1:
The patent introduces an impedance circuit as an intermediary component between the high pass filter and the amplifier. This impedance circuit includes a capacitor connected in parallel with a resistor, which acts as a mediator to recover the attenuated low frequency components near the cutoff frequency. The capacitor passes AC components while the resistor provides a DC path, together reducing the power loss caused by the high pass filter without compromising the gain flattening effect.
2Power
If multiple amplifiers are connected in series with increasing transistor sizes to handle higher power requirements, then the output power capability increases, but power loss accumulates in posterior stages and overall power efficiency degrades
Solution Approach 1:
The patent applies preliminary action by placing the impedance circuit at the input stage, before the signal enters the multi-stage amplifier chain. By recovering the attenuated low frequency components early in the signal path, the impedance circuit prevents power loss from accumulating in subsequent amplifier stages. This preliminary recovery action ensures that all downstream amplifiers receive a signal with restored power content, thereby improving overall power efficiency while maintaining the required output power capability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively suppresses power efficiency degradation by reducing power loss near the lower limit frequency, improving overall power added efficiency and maintaining linear amplitude characteristics across the signal band.
Implementation Method 1
a high pass filter as an inter-stage matching circuit... attenuates low frequency components by the high pass filter... flattening a signal level of the high frequency signal
Implementation Method 2
an automatic transformer that is electrically connected between the first amplifier and the second amplifier and performs impedance matching between the first amplifier and the second amplifier
Implementation Method 3
an impedance circuit... that outputs the high frequency input signal, outputted from the other end of the high pass filter, to the bias circuit
Data Source
AI summary
A power amplifier circuit includes: a high pass filter that has one end into which a high frequency input signal is inputted; a first amplifier that amplifies the high frequency input signal outputted from the other end of the high pass filter and outputs a high frequency signal obtained through the first amplification; a second amplifier that amplifies the high frequency signal and outputs a high frequency output signal obtained through the second amplification; an automatic transformer that performs impedance matching between the first amplifier and the second amplifier; and an impedance circuit, one end of which is electrically connected with the other end of the high pass filter, the other end of which is electrically connected with an output terminal of a bias circuit outputting bias voltage or bias current to the first amplifier, and that outputs the high frequency input signal to the bias circuit.