Transmitter Harmonic Calibration Using Common-Mode Signal Injection
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Solution Overview
Problem
In wireless communication chip transmitters, the power amplifier's non-linear operation generates second harmonics in the output signal, degrading signal quality and requiring reduced transmission power to mitigate harmonic intensity, which affects overall transmission efficiency.
Innovation Solution
A transmitter circuit comprising a power amplifier, transformer, first and second adjusting circuits, coupling circuit, control circuit, and harmonic intensity calculation circuit, which adjusts phase and amplitude of common mode signals to generate coupled signals that eliminate second harmonics in the output signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the power amplifier operates in a non-linear region to amplify the signal, then the transmission power of the output signal is improved, but second harmonic or higher-order harmonics will appear in the output signal which will affect the signal quality
Solution Approach 1:
The patent converts the harmful second harmonic into a useful component by injecting a calibrated second harmonic signal into the power amplifier's input. This injected harmonic interacts with the amplifier's non-linear characteristics to cancel out the unwanted harmonics generated during amplification, thereby maintaining high transmission power while improving signal quality.
Solution Approach 2:
The patent applies preliminary anti-action by pre-calculating and injecting a compensating second harmonic signal before the power amplification process. The control circuit determines the optimal harmonic injection level based on the power amplifier's characteristics, and this pre-applied harmonic counteracts the harmful harmonics that would otherwise be generated during normal operation.
2Object-affected harmful factors
If the intensity of the second harmonic generated by the power amplifier is too high, then the transmission power of the output signal needs to be reduced, but this will affect the transmission of the output signal
Solution Approach 1:
The patent implements a feedback mechanism where the control circuit continuously monitors the power amplifier's operating characteristics and dynamically adjusts the second harmonic injection level. Based on the measured output signal quality and power amplifier state, the control circuit optimizes the harmonic compensation in real-time, ensuring maximum transmission power is maintained while keeping second harmonic interference within acceptable limits.
Solution Approach 2:
The patent changes the operating parameters of the power amplifier by injecting a second harmonic signal with specific amplitude and phase characteristics. The control circuit adjusts the injection level parameter to optimize the balance between transmission power and harmonic suppression, effectively transforming the amplifier's harmonic generation behavior through parameter modification rather than reducing overall power.
3Device complexity
If the current transmitter does not have relevant circuit or parameters to adjust the intensity of the second harmonic, then the circuit structure is simple, but the intensity of the second harmonic generated by the power amplifier depends on its own circuit characteristics which cannot be optimized
Solution Approach 1:
The patent introduces a second harmonic injection circuit as an intermediary component between the signal source and the power amplifier. This intermediary circuit generates and injects a calibrated second harmonic signal that mediates the interaction between the input signal and the power amplifier's non-linear characteristics, enabling optimization of harmonic content without fundamentally redesigning the entire transmitter architecture.
Solution Approach 2:
The control circuit in the patent serves multiple functions: it characterizes the power amplifier's harmonic generation properties, calculates the optimal second harmonic injection level, controls the harmonic injection circuit, and monitors output signal quality. This multi-functional approach adds harmonic optimization capability without requiring completely separate dedicated circuits for each function.
Data Source
AI summary
The present invention provides a calibration method of a transmitter, wherein the transmitter includes a power amplifier, a transformer, an adjusting circuit and a coupling circuit, wherein the power amplifier receives an input signal to generate an amplified input signal, the transformer receives the amplified input signal to generate an output signal, the adjusting circuit adjusts phase and amplitude of a common mode signal of the amplified input signal to generate a first signal, and the coupling circuit generates a coupled signal to the output signal according to the first signal. In addition, the calibration method includes: controlling the adjusting circuit to have a specific setting of the phase and amplitude adjustment for the common mode signal, to effectively eliminate a second harmonic generated due to the power amplifier, to improve electromagnetic interference and signal quality.