RF Front-End Filter Switching for Low Pass-Band Loss
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Solution Overview
Problem
Radio frequency front-end circuits face a trade-off between size reduction and loss in the pass band, as semiconductor switches used in these circuits increase either size or insertion loss, depending on their on-resistance.
Innovation Solution
A radio frequency front-end circuit design incorporating a switch circuit with two switch elements and frequency variable filters, where the on-resistance of one switch is minimized to reduce size while maintaining low insertion loss, by using a configuration with a frequency varying circuit that shifts attenuation poles and includes multiple parallel arm resonators to manage insertion loss across the pass band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a switch with small on-resistance is used, then the loss in the pass band is reduced, but the switch size is increased and the overall size of the radio frequency front-end circuit is increased
Solution Approach 1:
The patent applies different on-resistance values to different switch elements based on their functional requirements. The first switch element (main switch) has a smaller on-resistance to minimize pass band loss, while the second switch element (frequency varying circuit switch) has a larger on-resistance since it only needs to shift attenuation poles. This localized differentiation of switch characteristics resolves the contradiction between size and loss by optimizing each switch for its specific function rather than using uniform switch specifications throughout the circuit.
2Area of moving object
If a small-sized switch is used, then the overall size of the radio frequency front-end circuit is reduced, but the on-resistance of the switch is increased and the loss in the pass band is increased
Solution Approach 1:
The patent segments the switching function into two separate switch elements: a first switch element for main signal routing and a second switch element for frequency variation. This segmentation allows each switch to be independently optimized - the first switch can be larger with lower on-resistance for minimal loss, while the second switch can be smaller with higher on-resistance since it only controls the frequency varying circuit. The segmentation principle resolves the size-loss contradiction by distributing switching functions across multiple specialized components rather than relying on a single switch.
3Area of moving object
If the on-resistance of the first switch element is increased, then the size of the first switch element is reduced, but the insertion loss in the radio frequency front-end circuit is increased in proportion to the increase of that on-resistance
Solution Approach 1:
The patent changes the on-resistance parameter of the first switch element to be smaller than that of the second switch element. This parameter differentiation ensures that the primary signal path switch (first switch) has optimized low on-resistance for minimal insertion loss, while the frequency control switch (second switch) can have higher on-resistance. The deliberate parameter change in on-resistance values resolves the contradiction by assigning different resistance characteristics to switches based on their functional importance in the signal path.
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 design achieves concurrent size reduction and minimized loss in the pass band by optimizing the on-resistance ratio of switch elements and using multiple parallel arm resonators to control insertion loss, improving the overall performance of the radio frequency front-end circuit.
Implementation Method 1
a first parallel arm resonator connected between a node on the path and a ground; and a frequency varying circuit that is a circuit including a first impedance element and a third switch element connected in parallel to each other, and that is connected in series to the first parallel arm resonator between the node and the ground, wherein the frequency varying circuit is able to shift a frequency of at least one attenuation pole of the first filter
Data Source
AI summary
A radio frequency front-end circuit includes a first filter that is a frequency variable filter connected to a first select terminal of a switching circuit, and a second filter connected to a second select terminal of the switching circuit. The switching circuit includes a first switch that switches over conduction and non-conduction between a common terminal and the second select terminal. The first filter includes a serial arm resonance circuit connected to the first select terminal, a parallel arm resonator, and a frequency varying circuit. The frequency varying circuit includes a capacitor and a third switch connected in parallel to each other, and is connected in series to the parallel arm resonator. The frequency varying circuit shifts a frequency of the first filter depending on conduction and non-conduction of the third switch.