Over-Coupled Directional Coupler for Wideband Quadrature Signals
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Solution Overview
Problem
Existing RF signal generation circuits face limitations in producing wideband signals at millimeter-wave frequencies, requiring complex digital reconfiguration and separate designs for different frequency bands, which increase system complexity and cost.
Innovation Solution
The use of over-coupled directional couplers with conductive strips arranged in parallel on different metal layers of a silicon substrate, optimized for a wide range of frequencies, allowing for wideband differential quadrature signal generation without digital reconfiguration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional passive structures (couplers) are used to generate quadrature signals, then the circuit structure is simple, but the fractional bandwidth is limited to 10-15%
Solution Approach 1:
The patent changes the coupling parameter from conventional coupling to over-coupling, where the coupling coefficient exceeds unity. This parameter change enables the directional coupler to achieve fractional bandwidths of 30-50% while maintaining the simple passive structure, resolving the contradiction between structural simplicity and bandwidth adaptability
Solution Approach 2:
The patent introduces tunable elements (such as varactor diodes or MEMS switches) into the directional coupler structure, enabling dynamic adjustment of the coupling coefficient. This allows the system to adaptively optimize performance across different frequency bands and maintain wide bandwidth operation, transforming a static structure into a dynamically adjustable one
2Adaptability or versatility
If digital circuitry is added to adjust and reconfigure bandwidth output, then the fractional bandwidth can be increased, but system complexity, design area requirements, and design cost increase
Solution Approach 1:
The patent replaces digital reconfiguration circuitry with an analog/RF-based solution using over-coupled directional couplers with tunable elements. This substitution eliminates the need for complex digital control logic, reducing system complexity, chip area, and power consumption while maintaining the ability to adjust bandwidth output
Solution Approach 2:
The over-coupled directional coupler design serves multiple functions: it provides quadrature signal generation, bandwidth adjustment, and frequency band reconfiguration all within a single passive structure. This multi-functionality eliminates the need for separate digital control circuits, reducing overall system complexity
3Ease of manufacture
If conventional couplers are used, then the design is simple, but frequency band reconfiguration switches output signals between bands instead of increasing overall bandwidth range
Solution Approach 1:
By changing the coupling parameter to over-coupling (coupling coefficient > 1) and making it tunable, the directional coupler can continuously adjust its operating characteristics to cover a wide overall bandwidth range (30-50% fractional bandwidth). This allows the same simple structure to operate across multiple frequency bands without switching, maintaining design simplicity while expanding adaptability
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 achieves improved fractional bandwidth of approximately 30% while reducing the need for additional design resources and costs, enabling the same coupler design to be used across multiple frequency bands.
Implementation Method 1
an input end of a first conductive strip of a pair of strips and a coupled end of a second conductive strip of the pair of strips, that are electromagnetically coupled together, produce an over-coupling factor
Data Source
AI summary
Embodiments disclosed herein relate to the structure and operation of a quadrature signal generation circuit. An example quadrature signal generation circuit includes a first layer having a first conductive strip and a second conductive strip; and a second layer having a third conductive strip and a fourth conductive strip, the third conductive strip arranged in parallel with respect to the first conductive strip and the fourth conductive strip arranged in parallel with the second conductive strip. Each of the first conductive strip and the second conductive strip have an input port to be coupled to an oscillator. Each of the first conductive strip and the second conductive strip have a through port to be coupled to a first signal mixer. Each of the third conductive strip and the fourth conductive strip have a coupled port to be coupled to a second signal mixer. Each of the third conductive strip and the fourth conductive strip have an isolated port to be coupled together.