Balun-Coupled Differential Output Circuit With Calibrated Harmonic Suppression
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Solution Overview
Problem
Power amplifiers with differential outputs often produce significant second harmonic energy, which can exceed regulatory limits and be radiated into the environment, posing challenges in compliance with electromagnetic emission regulations.
Innovation Solution
A configurable harmonic reduction circuit with unequal calibrated capacitance values for each shunt capacitance circuit is implemented to minimize second harmonic signal energy by compensating for offsets and mismatches in the differential output circuit, using a calibration process to determine optimal capacitance settings for each instance of the electronic system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a power amplifier with differential output is used to amplify radio frequency signals, then signal amplification is achieved, but significant second harmonic energy is generated that may exceed regulatory emission limits
Solution Approach 1:
The patent converts the harmful second harmonic energy into a useful signal by rectifying it to extract baseband information, then using this extracted signal to adjust the amplifier's operating point dynamically, thereby reducing the harmful harmonic emissions while maintaining amplification function
Solution Approach 2:
The patent implements a feedback mechanism where the second harmonic signal is detected, rectified, and fed back to adjust the amplifier's bias point. This closed-loop feedback continuously reduces the harmful second harmonic emissions by dynamically optimizing the amplifier's operating conditions
2Object-generated harmful factors
If configurable shunt capacitance circuits are added to reduce second harmonic energy, then harmonic emission compliance is improved, but circuit complexity increases
Solution Approach 1:
The patent makes the shunt capacitance circuits configurable and controllable, allowing them to serve multiple functions: filtering second harmonic emissions, adjusting impedance matching, and adapting to different operating conditions. This multi-functionality reduces the need for separate dedicated circuits for each function
Solution Approach 2:
The patent introduces dynamic control of the shunt capacitance values, allowing the circuit to adapt its characteristics in real-time based on operating conditions. This dynamic adjustment optimizes harmonic reduction across different frequency ranges and power levels without requiring multiple fixed circuits
3Object-generated harmful factors
If asymmetric capacitance values are used in shunt capacitance circuits to minimize second harmonic energy, then harmonic reduction effectiveness is improved, but manufacturing precision requirements increase due to instance-specific calibration
Solution Approach 1:
The patent changes the capacitance values asymmetrically in the shunt capacitance circuits based on instance-specific calibration data. By storing and applying calibrated capacitance values for each individual device, the system achieves optimal harmonic reduction while accommodating manufacturing variations without requiring tight precision controls
4Object-generated harmful factors
If a calibration process is implemented to determine optimal capacitance settings for each device instance, then harmonic reduction performance is improved, but manufacturing time and complexity increase
Solution Approach 1:
The patent performs calibration during the manufacturing process to determine optimal capacitance settings for each device instance before deployment. By completing the calibration upfront and storing the results, the system eliminates the need for time-consuming field calibration and ensures optimal harmonic reduction performance from the start
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 reduces electromagnetic emissions at or near the second harmonic frequency, ensuring compliance with regulatory limits by optimizing the harmonic reduction circuit for each manufactured instance of the electronic system.
Implementation Method 1
A configurable harmonic reduction circuit includes first and second configurable shunt capacitance circuits coupled between the first differential output terminal or the second differential output terminal, respectively, and a ground reference node
Data Source
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AI summary
An electronic circuit includes a differential output circuit that produces a differential output signal at a differential output. A primary winding of a balun has a first balun terminal coupled to a first differential output terminal, and a second balun terminal coupled to a second differential output terminal. A configurable harmonic reduction circuit includes first and second configurable shunt capacitance circuits coupled between the first differential output terminal or the second differential output terminal, respectively, and a ground reference node. A control circuit receives tuning data associated with a calibrated tuning state. The tuning data indicates a first and second calibrated capacitance values, which are unequal, for the first and second configurable shunt capacitance circuits, respectively. The control circuit controls the first configurable shunt capacitance circuit to have the first calibrated capacitance value, and controls the second configurable shunt capacitance circuit to have the second calibrated capacitance value.