RF Switch Harmonic Suppression via Tank Circuit Segmentation
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Solution Overview
Problem
Conventional RF switches face a performance tradeoff between insertion loss and harmonic distortion, making it difficult to achieve low insertion loss while maintaining high harmonic suppression, especially under large signal operations.
Innovation Solution
The RF switch circuit incorporates transistor switch circuits with harmonic suppression capacitors and inductors forming tank circuits, which block RF signals and redistribute large signal voltage swings across parasitic diodes, thereby improving harmonic suppression while maintaining low insertion loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional stacked switches are used to improve harmonic suppression, then harmonic distortion is reduced, but insertion loss increases
Solution Approach 1:
The switch is divided into multiple stacked transistor stages (first stacked switch stage, second stacked switch stage, third stacked switch stage), with each stage contributing to harmonic suppression. The segmentation allows distributed harmonic cancellation while maintaining signal transmission paths that minimize insertion loss.
Solution Approach 2:
Capacitors are introduced as intermediary elements connected to intermediate nodes between stacked transistors. These capacitors mediate the voltage swing distribution, redirecting large signal voltage swings away from parasitic diodes and enabling harmonic suppression without the full penalty of stacked switch insertion loss.
2Ease of operation
If large signal voltage swings are allowed to concentrate on parasitic diodes, then switching action is enhanced, but harmonic distortion increases
Solution Approach 1:
The circuit dynamically redistributes voltage swings during large signal operation. Capacitors are strategically placed to capture and redirect voltage excursions, ensuring that parasitic diodes do not experience excessive voltage swings that would generate harmonics, while switching transistors maintain adequate voltage for proper switching action.
Solution Approach 2:
The invention changes the voltage distribution parameters across different nodes in the stacked switch. By introducing capacitive elements, the voltage swing amplitude at parasitic diode nodes is reduced while maintaining sufficient voltage swing at switching nodes, thereby changing the operating parameters to simultaneously achieve good switching action and low harmonic distortion.
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
This configuration achieves over 20 dB improvement in harmonic suppression while keeping insertion loss under 1 dB, significantly better than conventional stacked switches, enhancing the efficiency and performance of RF switches.
Implementation Method 1
an inductor and a capacitor defining a tank circuit with the transistor in an off state that blocks RF signals
Implementation Method 2
The harmonic suppression capacitor may be tuned to distribute large signal voltage swings in the RF signal amongst parasitic diodes of the transistor
Data Source
AI summary
A radio frequency switch circuit with improved harmonic suppression and low insertion loss has an antenna port and a plurality of signal ports. A plurality of transistor switch circuits, are connected to a respective one of the plurality of signal ports and to the antenna port. Each of the transistor switch circuits has a transistor, which in an off state, together with a harmonic suppression capacitor and a parallel inductor both connected thereto, define a tank circuit that suppresses RF signals applied to the corresponding transistor switch circuit from a different one of the transistor switch circuits. The harmonic suppression capacitor is tuned to distribute large signal voltage swings in the RF signal amongst parasitic diodes of the transistor.