RF Intermodulation Suppression Branches for SV-LTE Interference
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Solution Overview
Problem
Mobile terminals face interference issues due to third-order intermodulation (IM3) products generated by nonlinear electronic components, which degrade performance and prevent simultaneous voice/LTE (SV-LTE) operation, as these products are difficult to attenuate with simple low-pass filters and often fall within the pass bands of receivers.
Innovation Solution
An RF system with parallel branches, each comprising a positive phase shift network, a negative phase shift network, and nonlinear components, where phase offsets are strategically applied to cancel IM3 products, utilizing a null offset branch and series stacked field effect transistors (FETs) to manage signal phases and reduce interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If two cellular front ends operate simultaneously for SV-LTE, then simultaneous voice and data communication is enabled, but third-order intermodulation products are generated that degrade receiver performance
Solution Approach 1:
The RF system is divided into multiple parallel branches, each containing nonlinear components. By segmenting the signal path into separate branches with different phase characteristics, the system can process multiple signals simultaneously while managing intermodulation products through controlled phase relationships between branches.
Solution Approach 2:
The patent converts the harmful IM3 products generated by nonlinear components into a beneficial cancellation mechanism. By introducing multiple branches with specific phase offsets, the IM3 products from different branches interfere destructively with each other, transforming the harmful intermodulation into a useful suppression effect.
2Device complexity
If simple low-pass filters are used to attenuate IM3 products, then filter complexity is reduced, but IM3 products within receiver pass bands cannot be effectively suppressed
Solution Approach 1:
The patent introduces phase shift networks as intermediary elements between the nonlinear components and the receiver. These phase shift networks modify the phase of signals passing through different branches, creating the conditions necessary for IM3 product cancellation without requiring complex filtering structures.
3Object-affected harmful factors
If phase shift networks with different magnitudes are used in different branches, then IM3 product cancellation is achieved, but system complexity increases
Solution Approach 1:
The patent systematically varies the phase offset parameters across different branches to achieve IM3 product cancellation. By carefully selecting specific phase offset values for each branch, the system creates destructive interference patterns for IM3 products while maintaining proper signal transmission, resolving the contradiction between suppression effectiveness and system complexity.
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
Substantially cancels IM3 products, improving receiver sensitivity and enabling SV-LTE operation by reducing IM3 products by approximately 30-36 dB, thus enhancing the performance of mobile terminals in dual-band operations.
Implementation Method 1
Phase offsets provided by the positive phase shift network and the negative phase shift network of each of the plurality of branches have the same magnitude but opposite polarities
Implementation Method 2
cause at least some of the IM3 products generated by and propagating through the RF system to substantially cancel
Data Source
AI summary
An RF system for suppressing third-order intermodulation (IM3) products is disclosed. The RF system is made up of a plurality of branches coupled in parallel. Each of the plurality of branches includes a positive phase shift network, a negative phase shift network, and nonlinear components, wherein the nonlinear components are coupled between the positive phase shift network and the negative phase shift network. The RF system also includes a null offset branch with nonlinear components that are coupled in parallel with the plurality of branches. In one embodiment, the nonlinear components are series stacked field effect transistors (FETs) that comprise an RF switch having a switch segment for the null offset branch and a switch segment for each of the plurality of branches. The RF switch further includes a control terminal for turning the FETs on and off.