RF Power Amplifier Diode Linearizer for Lower Intermodulation
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Solution Overview
Problem
RF power amplifiers in wireless communications face challenges in achieving high efficiency with minimal distortion, particularly in CMOS technology, where gain and phase deviations lead to non-linear performance and increased intermodulation distortion, especially in MIMO systems.
Innovation Solution
A diode-based linearizer network is introduced to control biasing voltage and resistance, reducing asymmetry and intermodulation products by incorporating feedback and feed-forward diode networks at the gate of the RF power amplifier transistor, which compensates for gain and phase deviations and minimizes third-order intermodulation distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high efficiency power amplifier classes (F, inverse F, E, Doherty) are used in CMOS technology, then power efficiency is improved, but linearity deteriorates due to non-linear performance from lower gate bias voltages
Solution Approach 1:
A diode-based linearizer network is introduced as an intermediary component between the power amplifier and the signal path. The network includes a feedback diode connected to the drain and a feed-forward diode connected to the gate, which act as mediators to compensate for non-linearities without requiring changes to the core power amplifier design
Solution Approach 2:
The diode linearizer dynamically adjusts biasing voltage and bias resistance parameters at the gate of the power amplifier transistor. By changing these parameters in real-time based on the operating conditions, the system maintains optimal linearity across varying power levels while preserving the high efficiency characteristics of class F and related amplifier topologies
2Use of energy by moving object
If class F power amplifier is used to achieve high efficiency, then power efficiency is improved, but distortion increases due to positive gain and negative phase deviation
Solution Approach 1:
The feedback diode in the linearizer network is connected to the drain terminal of the power amplifier transistor and provides a feedback path that senses the output signal. This feedback mechanism detects gain and phase deviations and automatically adjusts the biasing conditions to compensate for distortion, reducing third-order intermodulation products by 3 to 6 dB
Solution Approach 2:
The feed-forward diode network acts as an intermediary that pre-distorts the input signal by controlling the biasing voltage at the gate. This pre-distortion compensates for the anticipated positive gain and negative phase deviation that occur in class F amplifiers, thereby reducing overall distortion before the signal is amplified
3Manufacturing precision
If linearizer networks are added to compensate for gain and phase deviation, then linearity is improved, but device complexity increases
Solution Approach 1:
The patent employs simple diode components rather than complex active devices for the linearizer network. These passive diode elements are inexpensive, easy to integrate into existing CMOS processes, and require minimal biasing circuitry, thereby achieving linearity improvement without proportionally increasing device complexity or manufacturing cost
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 diode linearizer network achieves a significant reduction in intermodulation distortion by up to 5 dB across a wide frequency band and power range, enhancing the efficiency and linearity of RF power amplifiers without increasing quiescent current, suitable for CMOS technology.
Implementation Method 1
The linearizer circuit may have a non-linear current-voltage curve as well as a non-linear capacitance
Implementation Method 2
The linearizer circuit may have a non-linear current-voltage curve as well as a non-linear capacitance
Data Source
AI summary
A radio frequency (RF) power amplifier circuit with a diode linearizer circuit. The power amplifier circuit has an input and an output, as well as a power amplifier transistor with a first terminal connected to the input, a second terminal connected to the output, and a third terminal. The linearizer circuit is connected to the third terminal and to ground, and has a non-linear current-voltage curve as well as a non-linear capacitance. The linearizer circuit reduces inter-modulation products in a current through the power amplifier transistor from the second terminal to the third terminal that corresponds to an input signal applied to the input.