Compact Bi-Directional RF Coupler Using Lumped Inductors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional directional couplers require quarter-wave lengths of transmission lines, leading to significant signal loss and increased IC area, making them unsuitable for integration with other circuitry on a single IC substrate, and complicating design and assembly.
Innovation Solution
A bi-directional coupler architecture using lumped component elements, specifically spiral secondary inductors electromagnetically coupled to a shared primary signal line, allowing for compact integration and reduced signal loss, with dual spiral inductors providing separate couplers for each signal direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If quarter-wave length transmission lines are used to implement directional couplers, then the desired system characteristic impedance matching is achieved, but the signal loss on the primary transmission line increases significantly and the IC area required increases
Solution Approach 1:
The patent transforms the transmission line structure from distributed quarter-wave sections into lumped element equivalents, changing the physical parameters from wavelength-dependent dimensions to compact circuit elements. This parameter transformation enables the coupler to achieve the same electrical length and impedance matching function with dramatically reduced physical size and lower signal loss.
Solution Approach 2:
The patent replaces the mechanical/transmission line-based quarter-wave structure with an equivalent lumped element circuit model consisting of discrete inductors and capacitors. This substitution eliminates the need for long physical transmission lines while maintaining the directional coupling function, thereby reducing both IC area and signal loss.
2Adaptability or versatility
If quarter-wave length transmission lines are used to implement directional couplers, then the desired coupling function is achieved, but the IC area required increases
Solution Approach 1:
The patent changes the physical implementation parameters from wavelength-scale transmission lines to compact lumped elements, enabling the same coupling function to be realized in a fraction of the IC area while maintaining adaptability for different coupling coefficients and impedance values through component selection.
Solution Approach 2:
The patent segments the continuous transmission line into discrete lumped inductance and capacitance elements, allowing independent optimization of each component's value to achieve the desired coupling function. This segmentation enables compact layout while preserving the directional coupling capability.
3Adaptability or versatility
If separate directional coupler devices are used instead of integrated circuits, then the coupler function is achieved, but the signal loss increases and parasitic circuit elements are introduced
Solution Approach 1:
The patent merges the directional coupler function with the IC substrate, integrating the lumped element coupler circuit directly into the chip alongside other RF circuitry. This integration eliminates the need for separate coupler devices and their associated interconnect parasitics, reducing overall signal loss while maintaining full coupler functionality.
Solution Approach 2:
The patent uses the IC substrate itself as the intermediary medium to implement the coupler, replacing external discrete components. The substrate's distributed capacitance and trace inductance are utilized as part of the lumped element model, eliminating the need for separate devices and reducing parasitic effects from interconnections.
4Adaptability or versatility
If separate directional coupler devices are used, then the coupler function is achieved, but the design and assembly complexity increases
Solution Approach 1:
The patent combines the directional coupler with other RF circuitry into a single integrated IC device, eliminating separate components and their associated design, assembly, and testing complexities. The lumped element implementation allows the coupler to be designed using standard IC fabrication processes, further simplifying manufacturing.
Solution Approach 2:
The patent creates a universal integrated RF circuit platform where the lumped element coupler can coexist with other RF functions (amplifiers, mixers, filters) on the same IC. This multi-functional integration reduces overall system complexity by replacing multiple discrete devices with a single versatile IC module.
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 approach enables a compact, low-loss, and highly customizable bi-directional coupler design that can be fully integrated with other IC circuitry, reducing IC space requirements, minimizing signal perturbation, and enhancing directivity and isolation, while allowing for independent tuning of ports and impedance matching.
Implementation Method 1
spiral secondary inductors electromagnetically coupled to a shared primary signal line
Data Source
AI summary
A bi-directional coupler architecture that allows an entire radio frequency coupler to be fully integrated with other circuitry on a single IC substrate. Embodiments of the invention use a lumped component architecture instead of quarter-wave transmission lines to reduce area and limit loss on the primary signal line. In some embodiments, two directional couplers of opposite polarities are implemented at least in part using spiral secondary inductors electromagnetically coupled to a shared primary inductor signal line, thus providing a bi-directional coupler architecture.