RF Front-End Filtering for Passive Intermodulation Distortion
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Solution Overview
Problem
Concurrent transmission of multiple radio-frequency signals with different frequency bands in wireless communication systems often generates passive intermodulation distortion (PIMD), which can desensitize receivers by producing frequencies within the receive frequency band, leading to communication interference and increased maintenance costs.
Innovation Solution
A filter is positioned between the transmit antenna feed and other components in the transmitter, with a frequency response that passes multiple transmit frequency bands while attenuating frequencies associated with one or more receive frequency bands, thereby mitigating PIMD by using separate antenna feeds for transmission and reception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple radio-frequency transmit signals with different frequency bands are transmitted concurrently, then communication productivity and data transmission capability are improved, but passive intermodulation distortion is generated that desensitizes the receiver and causes communication interference
Solution Approach 1:
The antenna system is segmented into separate transmit and receive feeds, physically isolating the transmission and reception paths. This segmentation prevents the intermodulation distortion generated during transmission from affecting the receiver, allowing concurrent multi-band transmission while protecting receiver sensitivity.
Solution Approach 2:
A filter is introduced as an intermediary component in the transmit feed path. This filter selectively attenuates the intermodulation distortion frequencies while allowing the desired transmit signals to pass through, thereby mitigating the harmful effects of PIMD without compromising transmission productivity.
2Reliability
If a filter is added to attenuate passive intermodulation distortion frequencies, then receiver sensitivity is improved, but device complexity increases
Solution Approach 1:
The filter is placed locally in the transmit feed path, specifically at the point where intermodulation distortion is generated. This localized filtering approach addresses the PIMD problem at its source without requiring system-wide complexity increases, maintaining receiver sensitivity while minimizing added device complexity.
Solution Approach 2:
The filter serves as an intermediary component that selectively removes harmful frequencies from the transmit path. By positioning this single filter component in the transmit feed, the system achieves improved receiver sensitivity without substantial increases in overall device complexity.
3Object-affected harmful factors
If separate antenna feeds are used for transmission and reception, then passive intermodulation distortion is reduced, but device complexity and manufacturing cost increase
Solution Approach 1:
The antenna system is divided into separate transmit and receive feeds, creating distinct transmission and reception paths. This segmentation effectively reduces passive intermodulation distortion by preventing the mixing of high-power transmit signals with the sensitive receive path, while the added complexity is minimized through efficient feed network design.
Solution Approach 2:
While maintaining separate feeds for transmit and receive functions, the system merges the feed networks at strategic points to share common components and structures. This combining approach reduces the overall device complexity and manufacturing cost that would otherwise result from completely separate antenna systems.
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 solution effectively reduces passive intermodulation distortion, improving the sensitivity of the receiver and reducing maintenance costs by minimizing interference and the need for expensive passive components or complex compensation techniques.
Implementation Method 1
The filter has a frequency response that passes frequencies associated with multiple transmit frequency bands and attenuates frequencies associated with one or more receive frequency bands
Data Source
AI summary
An apparatus is disclosed for passive intermodulation distortion filtering. The apparatus includes a radio-frequency front-end circuit. The radio-frequency front-end circuit includes a transmit filter circuit and a receive filter circuit. The transmit filter circuit includes a passive circuit configured to combine at least two radio-frequency transmit signals associated with different transmit frequency bands. The transmit filter circuit also includes a filter coupled between the passive circuit and a first feed of an antenna. The filter is configured to attenuate frequencies associated with a receive frequency band. The receive filter circuit is coupled to a second feed of the antenna and is configured to pass the frequencies associated with the receive frequency band.