Diplexed TX Filter and RF Switch for IM3 Cancellation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current mobile terminal technologies face challenges in suppressing third-order intermodulation (IM3) products generated by nonlinear electronic components, which cause interference and degrade performance, especially in simultaneous voice/LTE (SV-LTE) operations, as these products are difficult to attenuate and can desense receivers.
Innovation Solution
A diplexed transmit (TX) filter and RF switch design that includes phase shift networks and power splitters/combiners to shift and cancel IM3 products, utilizing phase shift networks to impart specific offset angles to IM3 products, ensuring they cancel out before reaching the antenna or receiver, thereby reducing their impact.
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 strong interfering signals generate third-order intermodulation products that degrade receiver performance
Solution Approach 1:
The transmit path is segmented into multiple branches with separate RF switches and phase shift networks. Each branch processes signals independently and applies specific phase shifts to IM3 products, allowing selective cancellation of intermodulation products while maintaining simultaneous transmit/receive functionality across different bands
Solution Approach 2:
The patent converts harmful IM3 products into beneficial cancelled signals by applying phase shift networks that impart specific offset angles to IM3 products generated in different branches. The phase-shifted IM3 products are then combined in a way that causes destructive interference, transforming the harmful intermodulation products into cancelled signals that no longer degrade receiver performance
2Power
If nonlinear electronic components process high-power signals, then signal transmission is achieved, but compression and clipping generate third-order intermodulation products
Solution Approach 1:
The signal path is divided into multiple segments with separate nonlinear components (RF switches) in each branch. By segmenting the processing path, the patent reduces the IM3 products generated by each individual nonlinear component and enables selective cancellation of these products through phase shifting and combining
Solution Approach 2:
The patent applies phase shift networks to IM3 products generated by nonlinear components, imparting specific offset angles that enable destructive interference when branches are combined. This converts the harmful IM3 products into cancelled signals, effectively eliminating the harmful effects of nonlinear component compression and clipping
3Ease of manufacture
If simple low-pass filtering is applied to attenuate IM3 products, then frequency separation is simplified, but IM3 products close to original frequencies cannot be effectively attenuated
Solution Approach 1:
Instead of relying on frequency separation through filtering, the patent applies phase shift networks that impart specific offset angles to IM3 products. By controlling the phase relationships and combining branches appropriately, the patent causes destructive interference of IM3 products regardless of their frequency proximity to original signals, effectively canceling them without requiring complex frequency-selective filtering
Data Source
AI summary
Disclosed is a diplexed transmit (TX) filter and RF switch for suppressing third order intermodulation (IM3) products. Included are first and second duplexers each having a receive (RX) port, a TX port, and an RX/TX port. Also included are first and second power splitter/combiners each having first, second, and third terminals. Further included are first, second, and third phase shift networks. The first power splitter/combiner's first terminal is coupled to the first duplexer's TX port and a first switch segment is coupled between the first duplexer's RX/TX port and the first terminal of the second coupler. The first phase shift network is coupled to the second duplexer's TX port and a second switch segment in series with the second phase shift network is coupled between the second duplexer's RX/TX port and second coupler's second terminal. The third phase shift network is coupled to the second duplexer's RX terminal.