Tunable Receive Filter for Intermodulation Distortion Suppression
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Solution Overview
Problem
Mobile communication devices face intermodulation distortion (IMD) issues in uplink carrier aggregation (ULCA) mode due to nonlinear components, which impair the reception of downlink signals by creating IMD products that fall into adjacent frequency bands, leading to degraded user experiences.
Innovation Solution
The RF circuit is reconfigured to form an IMD shunt path using tunable reflection circuitry and control circuitry, allowing the receive filter to function as an IMD bandstop filter, thereby attenuating the IMD products in the uplink signal and improving desense performance without additional cost or battery life penalty.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If nonlinear components (power amplifier, filter, multiplexer, switch) are used in the transmission path to enable ULCA mode, then the device can simultaneously transmit in multiple uplink frequency bands, but intermodulation distortion products are generated that fall into adjacent downlink frequency bands, degrading receive signal quality
Solution Approach 1:
The patent segments the receive filter's functionality into two distinct modes: normal receive mode for downlink signals and IMD suppression mode for attenuating intermodulation products. This is achieved through a switch that separates the filter path into a main signal path and a shunt path, allowing the same filter to serve different purposes in different operational states without requiring separate dedicated components for each function.
Solution Approach 2:
The receive filter is designed to perform multiple functions: it normally receives downlink signals in the first frequency band, but when reconfigured through the tunable reflection circuitry, it also functions as an IMD bandstop filter to suppress intermodulation products. This multi-functionality eliminates the need for additional dedicated IMD suppression filters, reducing overall device complexity while maintaining ULCA capability.
2Object-affected harmful factors
If additional IMD suppression components are added to attenuate IMD products, then receive signal quality improves, but device complexity and cost increase
Solution Approach 1:
The patent merges the IMD suppression function with the existing receive filter by adding tunable reflection circuitry that can reconfigure the filter's impedance characteristics. Instead of adding a completely separate suppression component, the solution combines IMD attenuation capability into the existing filter structure, allowing one component to handle both normal reception and IMD suppression tasks through dynamic reconfiguration.
Solution Approach 2:
The receive filter serves itself by being reconfigured to suppress IMD products that would otherwise interfere with reception. Through the tunable reflection circuitry, the filter adjusts its own characteristics to create a notched response at IMD frequencies, eliminating the need for external suppression components and reducing overall system complexity while maintaining effective IMD attenuation.
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 effectively suppresses IMD products, enhancing the RF circuit's ability to receive downlink signals and improving desense performance in ULCA mode, achieving improved signal quality without increasing costs or impacting battery life.
Implementation Method 1
tunable reflection circuitry to form an IMD shunt path from the common node to a ground through the first receive filter and the tunable reflection circuitry
Data Source
AI summary
Embodiments of the disclosure relate to reducing intermodulation distortion (IMD) in a radio frequency (RF) circuit. In examples discussed herein, the RF circuit operates in an uplink carrier aggregation (ULCA) mode to transmit an RF uplink signal simultaneously in a first uplink band and a second transmit band. However, nonlinear components in the RF circuit can create an IMD product(s) that can fall into a downlink band of an RF downlink signal, thus impairing a receive filter's ability to receive the RF downlink signal in the downlink band. The receive filter can be opportunistically reconfigured to form an IMD shunt path to attenuate the IMD product. By reconfiguring the receiver filter to form the IMD shunt path, it is possible to suppress the IMD product in the RF uplink signal, thus leading to an improved desense performance in the ULCA mode without incurring additional cost and/or battery life penalty.