CRLH Diplexer Synthesis via Phase-Advance Delay Lines
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Solution Overview
Problem
Conventional diplexers require complex design optimization and additional circuit elements to achieve low insertion loss and high isolation, particularly in dual-band operations, which complicates the design process and increases complexity.
Innovation Solution
The use of composite right/left-handed (CRLH) phase-advance/delay lines combined with a hybrid coupler simplifies the design by engineering the dispersion relation, allowing for compact diplexers with improved channel isolation and reduced complexity, utilizing a single-band power divider and CRLH-based directional coupler instead of two bandpass filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional diplexers use two bandpass filters with additional circuit elements (tapped open stubs, lambda/4 microstrip lines) to enhance channel isolation, then isolation between bands is improved, but device complexity increases
Solution Approach 1:
The patent changes the fundamental parameter of transmission line behavior by using composite right/left-handed (CRLH) transmission lines that exhibit both right-handed and left-handed characteristics. This allows the transmission lines to provide both phase delay and harmonic suppression inherently, eliminating the need for additional circuit elements like tapped open stubs and lambda/4 microstrip lines while maintaining channel isolation
Solution Approach 2:
The CRLH transmission lines perform multiple functions simultaneously: they provide frequency selective filtering, phase delay control, and harmonic suppression within a single structure. This multi-functionality replaces the conventional approach requiring separate bandpass filters and isolation enhancement elements, thereby reducing device complexity while maintaining reliability
2Reliability
If waveguide filters are used in diplexers to achieve low insertion loss and high isolation, then performance is improved, but parametric optimization and performance tuning become time-consuming
Solution Approach 1:
The patent employs CRLH transmission lines with controllable dispersion characteristics that can be tuned through parameter selection during design rather than iterative optimization during manufacturing. The phase velocity and impedance characteristics can be controlled by adjusting the ratio of right-handed and left-handed elements, allowing rapid design adjustments without time-consuming re-optimization
Solution Approach 2:
The diplexer design using CRLH transmission lines incorporates predetermined phase delay characteristics and frequency response profiles through the initial selection of transmission line parameters. This preliminary configuration of dispersion relations eliminates the need for subsequent parametric optimization and performance tuning, saving significant development time while maintaining low insertion loss and high isolation
3Reliability
If stepped-impedance resonators (SIRs) are utilized to suppress higher-order harmonics, then spurious harmonic responses are controlled, but design complexity increases
Solution Approach 1:
The patent fundamentally changes the transmission line characteristics by using CRLH structures that inherently suppress harmonics through their dispersion properties. The left-handed characteristic below the transition frequency naturally attenuates higher-order harmonics without requiring additional harmonic suppression structures like SIRs, thereby maintaining reliability while reducing design complexity
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 achieves insertion loss less than 1 dB and isolation better than 20 dB between dual bands, with high agreement between simulated and measured response characteristics, reducing design complexities and enabling efficient dual-band operation.
Implementation Method 1
composite right/left-handed (CRLH) phase-advance/delay lines... CRLH-based transmission lines with desired phase responses at two arbitrary frequencies
Implementation Method 2
CRLH hybrid coupler which is excited so that signals at designated frequencies are separated to the corresponding output ports
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
A diplexing apparatus and method which utilizes composite right/left-handed (CRLH) phase-advance/delay lines combined with a coupler. By engineering CRLH- based transmission lines with desired phase responses at two arbitrary frequencies of interest, the connected CRLH delay line and/or CRLH coupler are excited in a manner such that signals at designated frequencies are separated to the corresponding output ports of the hybrid coupler. Benefits of the apparatus include elimination of design complexities such as optimization of the interconnection junctions and the harmonic spurious suppression involved in conventional filter-based diplexers. In addition, channel isolation is beneficially achieved from the isolation property of directional couplers. Measured insertion loss on the implementations was found to be less than 1 dB, with isolation greater than 20 dB in the dual bands. A high level of agreement was observed between simulated and measured results.