Harmonic Rejection in Multiphase Receiver Signals
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing receiver circuits face challenges in reducing harmonic distortion in multiphase in-phase I and quadrature Q signals, which affects receiver fidelity performance, particularly due to imperfections in phase mismatch and harmonic cancellation.
Innovation Solution
The implementation of a variable gain circuit with programmable amplifiers having gains ai, bi, aq, and bq, which are calibrated to specifically cancel or reduce harmonic distortions, including the 2nd harmonic, by generating and processing multiphase baseband signals using a combination of amplifiers, combiners, and differential transconductance amplifiers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If down conversion process is used to extract low frequency information signal, then the information signal can be recovered, but harmonic distortion is generated which harms receiver fidelity performance
Solution Approach 1:
The patent applies preliminary anti-action by generating anti-phase signals before the harmful harmonic distortion affects the output. The circuit generates multiphase signals (I0, Q0, I90, Q90) that are combined with specific phase relationships to preemptively cancel harmonic components at the mixer output, preventing rather than correcting the distortion.
Solution Approach 2:
The patent employs asymmetry by introducing deliberate phase mismatches between the I and Q signal paths. By using different phase shift amounts (α and β) in the I and Q channels, the patent creates an asymmetric signal combination that enables harmonic cancellation while preserving the desired fundamental frequency components.
2Reliability
If phase mismatch calibration is performed to improve harmonic rejection, then harmonic distortion is reduced, but device complexity increases due to additional calibration circuitry
Solution Approach 1:
The patent merges the calibration function with the normal signal processing path by using the same multiphase signals (I0, Q0, I90, Q90) for both harmonic cancellation during operation and for calibration. The calibration process adjusts the phase shift amounts α and β using the existing signal paths without requiring separate calibration hardware, thus reducing overall device complexity.
3Object-generated harmful factors
If multiple multiphase signals are combined to cancel harmonics, then harmonic distortion is reduced, but signal processing complexity increases
Solution Approach 1:
The patent segments the signal processing into distinct multiphase components (I0, Q0, I90, Q90) that can be independently processed and combined. By dividing the harmonic cancellation function into separate phase-shifted signal paths, the patent simplifies the overall processing complexity compared to attempting to cancel harmonics in a single unified path.
Data Source
Figure 1A~1B
Figure 2~3
Figure 4~5
AI summary
A receiver circuit includes a mixer receiving an RF signal encoding an information signal. The mixer receives a number of multiphase oscillator signals and generates multiphase baseband signals. The receiver circuit also includes a variable gain circuit receives the multiphase baseband signals, generates a first output signal having a first distortion, and a second output signal having a second distortion. The variable gain circuit is configured to generate a reduced distortion output signal based on the first and second output signals.