Split Band Duplexer Sub-Band Segmentation for Isolation
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Solution Overview
Problem
Full duplex RF communications systems face challenges in providing minimal insertion loss and required isolation between transmit and receive signals, especially in communications protocols with narrow guard bands, such as UMTS, due to manufacturing tolerances and frequency drift.
Innovation Solution
A split band duplexer is introduced, which splits the transmit and receive passbands into sub-bands, increasing separation and allowing for the use of standard filter components like SAW filters, with optional sub-band duplexers sharing a common antenna and utilizing switching circuitry for MEMS or other types of switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a single duplexer is used to provide full bandwidth transmit and receive passbands, then the bandwidth coverage is complete, but the isolation between transmit and receive signals is insufficient due to narrow guard bands
Solution Approach 1:
The patent divides the full bandwidth transmit and receive passbands into multiple sub-bands, with each sub-band duplexer handling a specific frequency range. This segmentation allows each sub-band to have adequate guard band separation, improving isolation between transmit and receive signals while collectively covering the full bandwidth through multiple sub-band duplexers operating in parallel.
2Ease of manufacture
If standard filter components are used, then manufacturing cost is reduced, but manufacturing tolerances and frequency drift cause degradation of isolation margins
Solution Approach 1:
By segmenting the bandwidth into sub-bands, the patent reduces the bandwidth requirement for each individual filter component. This allows standard filter components with typical tolerances to maintain adequate isolation margins within each narrower sub-band, while the overall system achieves full bandwidth coverage through multiple sub-band duplexers.
3Productivity
If the guard band is made narrower to increase bandwidth efficiency, then spectral efficiency is improved, but insertion loss and isolation requirements become more difficult to meet
Solution Approach 1:
The patent segments the frequency spectrum into multiple sub-bands, each with its own duplexer. This allows each sub-band to operate with optimized guard band width, achieving better insertion loss performance within each sub-band while the aggregate system maintains high bandwidth efficiency through parallel operation of multiple sub-band duplexers.
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 split band duplexer enhances isolation and insertion loss margins, enabling efficient operation across full bandwidths while accommodating manufacturing variations and frequency shifts, supporting UMTS bands with improved performance.
Implementation Method 1
allows use of standard filter components, such as surface acoustic wave (SAW) filters
Data Source
AI summary
The present invention is a split band duplexer, which increases the separation between a transmit passband and a receive passband by splitting the transmit and receive passbands into sub-bands. Each sub-band has a bandwidth that is less than the bandwidth of the full passband. The increased separation increases isolation margins and insertion loss margins, which allows use of standard filter components, such as surface acoustic wave (SAW) filters, and their accompanying manufacturing tolerances and drift characteristics. In one embodiment of the present invention, the split band duplexer includes a first sub-band duplexer and a second sub-band duplexer. The first sub-band duplexer may provide a full bandwidth transmit passband and a receive passband that is less than full bandwidth. The second sub-band duplexer may provide a full bandwidth receive passband and a transmit passband that is less than full bandwidth.