Quadrature Modulator Feedback for LO Leakage and Sideband Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Low-cost two-way wireless communication systems often suffer from deleterious effects due to L-band synthesizer (LO leakage) and opposite side band signals, which can interfere with system performance and user operations.
Innovation Solution
An apparatus and method that measures LO leakage and side band signals, adjusting input processing signals to a quadrature modulator to minimize these unwanted signals, utilizing digital signal processing and adaptive control signals to optimize in-phase and quadrature channel settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If low-cost modulator devices are used, then device complexity and cost are reduced, but LO leakage and side band signals increase causing harmful interference
Solution Approach 1:
The patent implements feedback control by measuring the LO leakage and side band signals at the modulator output, then using these measurements to generate control signals that adjust the in-phase and quadrature baseband input signals to minimize the harmful outputs. This closed-loop feedback system enables low-cost modulators to achieve performance comparable to expensive devices.
Solution Approach 2:
The system performs self-adjustment by automatically measuring its own harmful outputs (LO leakage and side band signals) and correcting its own input signals accordingly. The modulator system serves itself by generating control signals based on its own performance measurements, eliminating the need for external manual calibration or complex hardware modifications.
2Object-generated harmful factors
If proper adjustment of in-phase and quadrature input signals is made, then LO leakage and side band signals are minimized, but measurement and control complexity increases
Solution Approach 1:
The patent makes the baseband signal controller perform multiple functions: it generates the normal in-phase and quadrature baseband signals for modulation, and simultaneously generates control signals to minimize LO leakage and side band signals. This multi-functionality eliminates the need for separate measurement and control hardware, reducing overall system complexity while achieving the desired signal minimization.
Solution Approach 2:
The patent combines the signal generation function and the harmful signal minimization function into a single baseband signal controller. By merging these functions, the system avoids adding separate complex measurement and control subsystems, achieving minimization of LO leakage and side band signals through an integrated approach that uses the existing baseband controller resources.
3Reliability
If LO leakage signal is reduced, then system performance improves, but in-phase and quadrature signal balance requirements increase
Solution Approach 1:
The patent changes the parameters of the in-phase and quadrature baseband signals dynamically by adjusting their amplitudes and phases based on feedback from LO leakage measurements. The baseband signal controller modifies these signal parameters in real-time to minimize harmful outputs, compensating for imbalances without requiring precise manufacturing tolerances in the hardware.
Data Source
AI summary
In a communication device, the LO leakage and opposite side band signals are measured at an output signal. Input processing signals to a modulator are adjusted in response to the measured values to minimize the LO leakage and maximize side band suppression.