Single Receiver N-Path Filtering for Intra-Band Jammer Rejection
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Solution Overview
Problem
In wireless receivers, transmit leakage and jammers impose performance limitations on receive circuitry, particularly in carrier aggregation architectures, where high impedance nodes cause linearity issues and degrade noise figures due to large blocker swings.
Innovation Solution
A single receiver with an N-path filter and multiple local oscillators is used to filter out jammer signals in gaps between non-contiguous frequency bands, employing a sliding intermediate frequency (IF) or non-sliding IF configuration to mitigate the effects of blockers and improve linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single receiver is used for carrier aggregation, then device complexity is reduced, but linearity performance degrades due to high impedance nodes causing large blocker swings
Solution Approach 1:
The receiver signal path is segmented into multiple parallel paths (first path with first LNA, second path with second LNA). Each path processes a different frequency component independently, avoiding the high impedance node problem in single-path architectures while maintaining a unified receiver structure.
Solution Approach 2:
A coupling matrix is introduced as an intermediary component to combine signals from multiple parallel paths. The coupling matrix enables signal combination while maintaining proper impedance matching and isolation, preventing the high impedance node issue that degrades linearity in conventional single-path designs.
2Reliability
If multiple receivers are used for carrier aggregation, then linearity performance improves, but device complexity and power consumption increase
Solution Approach 1:
Multiple receive paths are merged into a single unified receiver architecture through a coupling matrix. The multiple LNAs operate in parallel but their outputs are combined within one receiver structure, achieving the linearity benefits of multiple receivers while maintaining the simplicity of a single receiver unit.
Solution Approach 2:
The single receiver is designed with multi-functional capability to handle multiple frequency components simultaneously through parallel signal paths. The coupling matrix enables the receiver to process multiple carriers and filter different frequency components, making a single receiver perform the work of multiple receivers.
3Device complexity
If conventional carrier aggregation is used without N-path filter, then device complexity is low, but jammer signals degrade signal quality
Solution Approach 1:
The N-path filter uses dynamic switching between different filtering modes (first filtering mode for first frequency component, second filtering mode for second frequency component). This dynamic adaptation allows the filter to effectively reject jammer signals at different frequencies while maintaining a relatively simple filter structure.
Solution Approach 2:
The filter parameters (center frequency, bandwidth) are changed based on the operating mode. In the first filtering mode, the filter is configured for the first frequency component; in the second filtering mode, it is reconfigured for the second frequency component. This parameter adaptation enables effective jammer rejection without requiring complex multi-band filtering structures.
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
The solution effectively reduces the impact of jammers on the receiver circuitry, enhancing linearity and noise figure performance in carrier aggregation operations without the need for multiple receivers, thereby improving signal processing efficiency.
Implementation Method 1
The N-path filter includes multiple mixers. The N-path filter filters out at least a portion of the jammer signal in one or more gaps between the non-contiguous wanted signals in a same frequency band
Data Source
AI summary
A single receiver to process multiple signals to achieve carrier aggregation includes a main path, an auxiliary path and one or more local oscillators. The main path has an input that receives an input signal. The input signal includes non-contiguous wanted signals and a jammer signal. The single receiver also includes an output coupled to a modem. The output provides the wanted signals to the modem. The auxiliary path is coupled to ground and includes an N-path filter. The N-path filter has multiple mixers. The N-path filter filters out at least a portion of the jammer signal in one or more gaps between the non-contiguous wanted signals in a same frequency band. The one or more local oscillators are coupled to the main path and/or the auxiliary path to provide a first reference signal to the main path and/or to the N-path filter of the auxiliary path.