Parallel RF Power Amplifier With Impedance Inversion for Power Modes
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Solution Overview
Problem
RF transmitters, such as those used in WLAN and cellular communication, face inefficiencies in power amplifier operation due to sub-optimal load impedance in different power modes, leading to reduced efficiency and bandwidth when switching between power modes, especially with the use of switches in the signal path that introduce insertion losses and parasitic capacitance.
Innovation Solution
The RF power amplifier design includes a phase adjuster and impedance inverters to modulate the load impedance of parallel amplifier stages based on operation modes, eliminating the need for switches in the signal path by ensuring optimal load impedance for each power mode, thereby enhancing efficiency and maintaining bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If switches are used in the signal path to selectively switch amplifier stages on or off for different power modes, then power mode switching is enabled, but insertion losses and parasitic capacitance are introduced reducing efficiency and bandwidth
Solution Approach 1:
The patent removes switches from the signal path entirely. Instead of using switches to select between parallel amplifier stages, the invention uses a single continuously operating amplifier whose load impedance is dynamically adjusted through impedance inverting networks. This extraction of the switching element eliminates insertion losses and parasitic capacitance while maintaining power mode switching capability through continuous impedance transformation.
Solution Approach 2:
The patent replaces the mechanical/electronic switching mechanism with a continuous impedance transformation system. Rather than mechanically or electronically opening/closing circuit paths with switches, the invention uses impedance inverting networks that continuously transform the load impedance seen by the amplifier, substituting a smooth electrical transformation for discrete switching action.
2Adaptability or versatility
If switches are used in the signal path to selectively switch amplifier stages on or off for different power modes, then power mode switching is enabled, but bandwidth is reduced due to parasitic capacitance
Solution Approach 1:
By removing switches from the signal path, the patent eliminates the parasitic capacitance inherent in switching elements. This extraction of the switching mechanism removes the bandwidth-limiting factor while preserving the ability to switch between power modes through continuous impedance adjustment in the RF signal path.
Solution Approach 2:
The patent substitutes continuous impedance transformation for discrete switching, replacing a mechanism that introduces parasitic capacitance with one that maintains smooth RF signal flow. The impedance inverting networks provide continuous adaptation without the abrupt transitions and parasitic effects of switching, thereby preserving bandwidth.
3Power
If parallel amplifier stages are used with selective switching for different power modes, then power level adjustment is achieved, but load impedance becomes sub-optimal reducing amplifier efficiency
Solution Approach 1:
The patent implements dynamic load impedance adjustment through impedance inverting networks that continuously adapt the load impedance seen by the amplifier based on the desired power level. Instead of using fixed parallel stages with static impedance characteristics, the system dynamically transforms the load impedance to maintain optimal operating conditions across different power output levels, thereby maximizing amplifier efficiency throughout the power range.
Solution Approach 2:
The patent changes the load impedance parameter dynamically to maintain optimal amplifier efficiency. By using impedance inverting networks that transform the load impedance according to the desired power level, the system maintains the amplifier's optimal operating point across different power modes, preventing the sub-optimal impedance conditions that would otherwise reduce efficiency.
Data Source
AI summary
An RF power amplifier is described including a first amplifier and a second amplifier arranged in parallel between an RF power amplifier input and an RF power amplifier output. A phase adjuster adjusts the phase of a signal on at least one of the first amplifier signal path and the second amplifier signal path. A first impedance inverter has a first impedance inverter input coupled to an output of the second amplifier and a first impedance inverter output coupled to the RF power amplifier output. The RF power amplifier is configured to enable at least one of the first amplifier and the second amplifier dependent on an operation mode and the first impedance inverter is configured to modulate the load impedance of the second amplifier in response to the operation mode changing.