RF Switch Nonlinearity Cancellation for Lower IMD3
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Solution Overview
Problem
RF switches in radio frequency circuitry suffer from inherent nonlinearity, leading to undesirable third-order intermodulation distortion (IMD3), which degrades performance and is challenging to address without complex and costly fabrication processes.
Innovation Solution
Incorporating built-in nonlinearity cancellation circuitry in RF switch circuitry, which generates a nonlinear signal with adjusted amplitude and phase to offset the nonlinearity, using MOS devices and a shunt path with signal adjustment and nonlinearity generation circuitry to minimize IMD3, and employing adjustable nonlinearity generation circuitry for optimal cancellation across variations in device characteristics and temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional RF switch circuitry is used, then device complexity and fabrication cost are reduced, but nonlinearity distortion and third-order intermodulation distortion increase
Solution Approach 1:
The patent generates additional nonlinearity through dedicated circuitry that, when combined with the original nonlinearity, creates cancellation effects. The harmful nonlinearity is converted into a beneficial cancellation mechanism by generating a nonlinear signal that opposes and reduces the overall distortion, including third-order intermodulation distortion.
Solution Approach 2:
The patent applies preliminary anti-action by generating a nonlinear signal in advance that is specifically designed to counteract the nonlinearity produced by the RF switch circuitry. This preemptive cancellation signal is injected into the signal path before the distortion fully manifests, reducing the net nonlinearity and intermodulation distortion.
2Manufacturing precision
If complex fabrication processes are used to reduce nonlinearity, then linearity improves, but manufacturing cost and complexity increase
Solution Approach 1:
The patent achieves improved linearity by changing circuit parameters through added nonlinearity cancellation circuitry rather than modifying fabrication processes. By adjusting circuit elements and adding functional blocks, the patent attains better linearity performance using standard fabrication processes, avoiding the need for complex manufacturing changes.
3Reliability
If nonlinearity cancellation circuitry is added, then third-order intercept point increases, but device complexity increases
Solution Approach 1:
The patent introduces an intermediary nonlinearity cancellation circuit that acts as a mediator between the input signal and the RF switch circuitry. This intermediary generates a cancellation signal that reduces third-order intermodulation distortion, effectively raising the third-order intercept point while maintaining a modular architecture that manages complexity.
4Adaptability or versatility
If fixed nonlinearity cancellation is used, then circuit simplicity is maintained, but adaptability to device variations and temperature changes decreases
Solution Approach 1:
The patent implements dynamic adaptability by making the nonlinearity cancellation circuit adjustable rather than fixed. The circuit can be calibrated and tuned to adapt to device variations and temperature changes, transforming a static cancellation approach into a dynamic one that maintains effectiveness under varying operating conditions without requiring overly complex control mechanisms.
Data Source
AI summary
System and methods for reducing nonlinearity in radio frequency (RF) circuitries (e.g., RF switch circuitry and/or RF amplifier circuitry) are provided. A high-linearity RF integrated circuit device includes an input port; an output port; nonlinear circuitry arranged on a signal path between the input port and the output port; a shunt path including signal adjustment circuitry; and adjustable nonlinearity generation circuitry coupled to the signal adjustment circuitry, the adjustable nonlinearity generation circuitry including one or more metal-oxide-semiconductor (MOS) devices; and at least one nonlinearity generation activation element connected in parallel with a source terminal and a drain terminal of a first MOS device of the one or more MOS devices and responsive to an activation control signal. The nonlinear circuitry may include at least one of switching circuitry or amplifier circuitry. The shunt path may be coupled to the input port or the output port.