Variable Load Circuit for Quadrature Phase Error Correction
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Solution Overview
Problem
Wireless communication systems face phase errors between in-phase and quadrature components of quadrature signals due to non-symmetrical layouts and component mismatches, limiting image rejection and overall transceiver performance.
Innovation Solution
A variable load circuit with transistors and a variable current source is used to adjust the phase of differential signals, where capacitances between the transistors' terminals are controlled by a bias current based on a control signal, allowing for correction of phase errors between in-phase and quadrature components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a symmetrical design and symmetrical layout are provided to reduce phase error, then the phase error between I and Q branches is reduced, but electrical differences and component mismatches still create additional phase error that requires trial and error layout adjustments
Solution Approach 1:
The patent changes the electrical parameters (capacitance values) of existing components to correct phase error. By adjusting the capacitance values of capacitors in the I and Q branches, the phase relationship between the two branches can be precisely controlled without requiring complex layout modifications or trial-and-error design iterations.
2Manufacturing precision
If trial and error process is used to find a layout that reduces phase error, then phase error can be reduced to acceptable level, but the design process becomes time-consuming and complex
Solution Approach 1:
Instead of iteratively modifying the physical layout through trial and error, the patent enables direct adjustment of electrical parameters (capacitance values) to achieve phase error correction. This approach allows for precise phase control without the time-consuming process of repeatedly redesigning and simulating different layouts.
3Reliability
If component mismatches in I and Q branches occur due to fabrication process, then additional phase error is created, but redesigning the layout to compensate is complex and time-consuming
Solution Approach 1:
The patent compensates for fabrication-induced component mismatches by adjusting the capacitance parameters of capacitors in the I and Q branches. This electrical parameter adjustment approach corrects phase errors caused by manufacturing variations without requiring complex layout modifications or redesign iterations.
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 corrects phase errors in quadrature signals, improving the performance of transceivers by adjusting the phase of differential signals through controlled capacitances, thereby enhancing image rejection and overall system performance.
Implementation Method 1
Each of the transistors includes capacitances between the terminals of the transistor, where the capacitances are each a function of a tail current of the differential pair
Implementation Method 2
A variable current source controls the tail current of the differential pair of transistors based on a control signal, thereby controlling the capacitances and thus a phase of the differential signal
Data Source
AI summary
A variable load circuit for adjusting a phase of a differential signal including a first transistor having a first terminal adapted to receive a first component of the differential signal, a second transistor having a first terminal adapted to receive a second component of the differential signal and a second terminal coupled to a second terminal of the first transistor, and a variable current source coupled to a third terminal of both the first and second transistors. The variable current source generates a bias current based on a control signal. For each of the first and second transistors, a first capacitance is created between the first and second terminals, and a second capacitance is created between the first and third terminals. The first and second capacitances are each a function of the bias current and thus the control signal and operate to adjust the phase of the differential signal.