Power amplifier and radio transmitter
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Solution Overview
Problem
Doherty amplifiers face challenges in widening their bandwidth due to the effects of output capacitance from transistors, which limit the impedance matching and efficiency, especially when dealing with signals having large Peak to Average Power Ratio (PAPR) in wireless communication.
Innovation Solution
The implementation of a power amplifier configuration that includes a carrier amplifier, a peak amplifier, a phase adjusting circuit, and an impedance transforming line, along with series and parallel resonant circuits using inductances and capacitances to reduce the effect of output capacitance, ensuring optimal load impedance across varying signal levels, thereby enhancing bandwidth and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the output power of the power amplifier is increased to expand transmission range, then the transmission coverage is improved, but the power consumption increases significantly
Solution Approach 1:
The patent implements dynamic load impedance adjustment by switching between different impedance values (50Ω and 200Ω) based on the operating mode. The load impedance is dynamically changed to match the optimal value for each operating condition, enabling the amplifier to maintain high efficiency across different power levels and transmission ranges.
Solution Approach 2:
The patent changes the load impedance parameter from a fixed value to a variable parameter that can take different values (50Ω or 200Ω) depending on the operating mode. This parameter change allows the amplifier to optimize its efficiency by selecting the appropriate impedance for each operating condition, thereby reducing power consumption while maintaining transmission coverage.
2Device complexity
If the load impedance of the carrier amplifier is fixed at 50Ω, then the impedance matching is simple, but the bandwidth is limited and cannot achieve wideband characteristics
Solution Approach 1:
The patent makes the load impedance dynamic by switching between 50Ω and 200Ω based on the operating mode. This dynamic adjustment enables the amplifier to achieve wideband characteristics while maintaining relatively simple impedance matching circuits, as each impedance value is optimized for specific operating conditions.
Solution Approach 2:
The patent makes the load impedance multi-functional by implementing two different impedance values (50Ω and 200Ω) that serve different purposes. The 50Ω impedance is used for maximum power output, while the 200Ω impedance is used for maximum power efficiency. This multi-functionality allows a single amplifier to achieve wideband characteristics across different operating modes.
3Reliability
If the power amplifier operates at average power much smaller than saturation power to handle large PAPR signals, then the signal distortion is suppressed, but the efficiency becomes very low
Solution Approach 1:
The patent changes the load impedance parameter based on the operating mode to optimize efficiency. When the peak amplifier is off, the load impedance is set to 200Ω for maximum power efficiency, allowing the carrier amplifier to operate efficiently even at lower power levels. This parameter change enables the system to maintain both signal quality and efficiency across different power levels.
Solution Approach 2:
The patent dynamically adjusts the load impedance to match the optimal value for each operating mode. By switching between 50Ω and 200Ω impedance values, the system can maintain high efficiency regardless of whether the peak amplifier is on or off, thereby improving overall energy utilization while maintaining signal quality.
4Power
If the load impedance is optimized for maximum power output, then the output power is maximized, but the power efficiency decreases
Solution Approach 1:
The patent implements a multi-functional load impedance system that can operate at two different impedance values (50Ω for maximum power output, 200Ω for maximum power efficiency). This allows the amplifier to achieve both high output power and high efficiency by selecting the appropriate impedance for each operating condition, thereby resolving the trade-off between power and efficiency.
Solution Approach 2:
The patent dynamically switches the load impedance between 50Ω and 200Ω based on the operating mode. When maximum power output is needed, the impedance is set to 50Ω; when efficiency is prioritized, the impedance is set to 200Ω. This dynamic adjustment enables the system to optimize both power output and efficiency according to the specific operating requirements.
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
This configuration effectively reduces the impact of output capacitance across a wider band, allowing for improved impedance matching and higher efficiency in the Doherty amplifier, even at low signal levels, thus supporting multiple frequency bands and achieving high-performance wideband characteristics.
Implementation Method 1
an impedance transforming line that transforms a load of the carrier amplifier when the signal level of the input signal is lower than the predetermined level
Implementation Method 2
a serial resonant circuit in which a second inductance and a first capacitance are coupled in series between the output of the first transistor and the impedance transforming line
Implementation Method 3
a phase adjusting circuit that adjusts phases of an output of the carrier amplifier and an output of the peak amplifier
Data Source
AI summary
A power amplifier includes a carrier amplifier that operates from when an input signal is small, a peak amplifier that starts to operate when the input signal becomes large, a phase adjusting circuit that adjusts phases of an output of the carrier amplifier and an output of the peak amplifier, an impedance transforming line that transforms a load of the carrier amplifier when the input signal is small, and has a characteristic impedance close to an optimum load impedance of the carrier amplifier, and a circuit that is arranged between the output of the carrier amplifier and the impedance transforming line and reduces an output capacitance of the carrier amplifier.