RF Linearizer Bias Switching for Low-Loss E-Band Amplifiers
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Solution Overview
Problem
Monolithic microwave integrated circuits (MMICs) require additional amplifiers due to the low gain of analog predistorters performing class-C operations, leading to increased circuit size and complexity, particularly in compensating for distortion in E-band signal amplification.
Innovation Solution
An amplifying device with a buffer circuit, linearizer, and control circuit that adjusts the operation of a transistor between class B, class AB, and class C modes based on signal levels, minimizing reflection loss and eliminating the need for additional amplifiers by achieving higher gain through combined operation modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an analog predistorter performing class-C operation is used to compensate for distortion, then distortion compensation is achieved, but gain is reduced and additional amplifiers are required
Solution Approach 1:
The patent applies dynamics by transitioning the predistorter transistor from static class-C operation to dynamic operation that switches between class-AB and class-C modes based on input signal level. The control circuit dynamically adjusts the gate voltage to maintain optimal operation mode, enabling the system to achieve both distortion compensation and sufficient gain without additional amplifiers
Solution Approach 2:
The patent changes the operational parameters of the predistorter transistor by varying its class of operation based on signal level. By switching between class-AB (for low signal levels requiring linearity) and class-C (for high signal levels where distortion compensation is sufficient), the system optimizes both gain and distortion compensation performance across different operating conditions
2Power
If additional amplifiers are added to increase gain, then gain is improved, but circuit size and complexity increase
Solution Approach 1:
The patent makes the predistorter transistor multi-functional by enabling it to operate in different classes (AB and C) depending on signal level. This single transistor performs both distortion compensation and provides sufficient gain across different operating conditions, eliminating the need for separate additional amplifier stages and reducing overall circuit complexity
Solution Approach 2:
The patent merges the functions of distortion compensation and gain provision into a single predistorter stage. By combining the operations that were previously separated into distinct functional blocks (predistorter + additional amplifier), the system achieves the same performance with reduced circuit size and complexity
3Reliability
If the transistor operates in class-C mode for distortion compensation, then distortion is reduced, but reflection loss increases
Solution Approach 1:
The patent dynamically adjusts the predistorter's operation mode based on signal level to optimize performance. At low signal levels where linearity is critical, the system operates in class-AB mode with better impedance matching and lower reflection loss. At high signal levels where distortion compensation is the primary concern, it switches to class-C mode, thus dynamically balancing distortion compensation against reflection loss
Data Source
AI summary
An amplifying device includes a radio frequency (RF) signal input terminal to which an RF signal is input, a buffer circuit, a linearizer including a transistor, a power amplifier, and a control circuit. The control circuit outputs a first gate voltage when a level of the RF signal input is a first level, the first gate voltage causing the transistor to perform a class B operation. The control circuit outputs a second gate voltage when the level of the RF signal is a second level higher than the first level, the second gate voltage causing the transistor to perform a class AB operation. Output impedance of the buffer circuit that is seen from an input side of the linearizer is set such that a reflection loss of the RF signal input from the buffer circuit to the linearizer is a predetermined level or less.