Orthogonal-mode junction coupler with dipole radiating structure
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Solution Overview
Problem
Orthogonal-mode junction couplers used in radiofrequency antennas suffer from poor isolation between inlet ports and asymmetry, leading to degradation of modal network purity and excitation of higher order modes, which existing compensating circuits cannot fully address.
Innovation Solution
A coupling method and coupler design that includes a conducting rod isolated from the waveguide, projecting inside and extending between a short circuit and a C-shaped or U-shaped conducting structure, with specific wavelength-based spacing and a virtual short circuit, eliminating the need for external compensating circuits by achieving weak coupling between ports.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional orthogonal-mode junction couplers use connectors, grooves or offset supply points along the waveguide axis, then the coupler can separate dual-polarization bands, but the isolation between inlet ports deteriorates
Solution Approach 1:
The patent employs asymmetric positioning of the dipole radiating structure relative to the waveguide axis, creating intentional asymmetry in the coupling mechanism. This asymmetric configuration, combined with specific spacing (λ/4 from short circuit), achieves improved port isolation by preventing symmetric coupling paths that would cause interference between adjacent ports.
Solution Approach 2:
The dipole radiating structure acts as an intermediary element between the waveguide and the outlet ports. This intermediate dipole structure, positioned at a specific distance from the waveguide wall, mediates the coupling process to achieve better isolation between inlet ports while maintaining effective signal transmission.
2Reliability
If traditional couplers use offset supply points along the axis, then dual-polarization separation is achieved, but asymmetry excites higher order modes degrading modal network purity
Solution Approach 1:
The patent changes the coupling parameter from direct contact (connectors/grooves) to capacitive coupling through a dipole at a specific distance (λ/4) from the waveguide wall. This parameter change in spacing and coupling mechanism suppresses higher order mode excitation while maintaining modal network purity for the fundamental modes.
Solution Approach 2:
The dipole radiating structure creates a localized capacitive coupling region with specific electrical characteristics. This local quality change in the coupling zone, with the dipole positioned at λ/4 from the short circuit, enables selective excitation of desired modes while suppressing higher order modes that would degrade purity.
3Reliability
If external compensating circuits are added to offset coupling between inlet ports, then some isolation improvement is achieved, but the circuits cannot eliminate all errors and increase device complexity
Solution Approach 1:
The coupler design achieves self-correction of coupling errors through the specific dipole configuration and spacing. The λ/4 spacing from the short circuit creates natural phase relationships that self-compensate for coupling errors between ports, eliminating the need for external compensating circuits and reducing overall device complexity.
Solution Approach 2:
The dipole radiating structure is pre-positioned at a specific distance (λ/4) from the waveguide wall and short circuit, establishing optimal coupling conditions before operation. This preliminary configuration of the capacitive coupling mechanism pre-compensates for potential errors, achieving good isolation without requiring additional corrective circuits.
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 provides effective separation of dual-polarization bands with improved modal network purity and reduced parasitic modes, achieving weak coupling without requiring external compensating circuits, suitable for medium to broad frequency bands.
Implementation Method 1
capacitively supplying a conducting structure integral with the waveguide through a connector projecting inside the waveguide and extending between a short circuit of the waveguide and the conducting structure
Data Source
AI summary
Orthogonal-mode junction coupler with a medium to broad bandwidth for a waveguide (1) operating at a wavelength λ, characterized in that it includes a connector (5) projecting from the waveguide (1) and extending between a short circuit (3) of the waveguide (1) and a conducting structure (6) acting as dipole radiating at a wavelength of approximately λ/2 excited at its central point by the connector.