On-Chip Variable Delay Transmission Line With Fixed Impedance
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Solution Overview
Problem
Conventional on-chip transmission line structures have fixed impedance and delay, making it difficult to change delay without increasing signal loss or footprint, which is undesirable for applications like phased arrays where variable delay is necessary.
Innovation Solution
A transmission line structure with selectable ground return paths of different geometries and distances from the signal line, allowing for variable delay without changing the characteristic impedance by switching between grounded and floating states of capacitance shields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the delay of a transmission line is changed by adjusting capacitance and inductance, then the delay is improved, but the characteristic impedance changes and signal loss increases
Solution Approach 1:
The patent implements a transmission line with dynamically switchable ground return paths. Multiple ground return structures are provided with different geometries and distances from the signal line, allowing the system to switch between different delay characteristics while maintaining consistent characteristic impedance. This dynamic switching capability enables delay adjustment without the traditional trade-off of increased signal loss or impedance variation.
2Loss of time
If the delay of a transmission line is changed by adjusting capacitance and inductance, then the delay is improved, but the characteristic impedance changes
Solution Approach 1:
The transmission line is segmented into multiple parallel ground return paths with different geometries and configurations. Each ground return structure provides a different delay characteristic. By switching between these segmented paths, the system can adjust the overall delay while each segment is designed to contribute to maintaining a consistent characteristic impedance across different delay settings.
Solution Approach 2:
The patent changes geometric parameters of the ground return structures (such as distance from signal line, width, and configuration) to achieve different delay values. These parameter changes are carefully designed so that the ratio of inductance to capacitance remains relatively constant, thereby maintaining stable characteristic impedance while varying the delay parameter.
3Adaptability or versatility
If multiple transmission lines with different delays are provided for each phased array element, then variable delay is achieved, but the footprint and manufacturing complexity increase
Solution Approach 1:
The patent creates a universal transmission line structure that can provide multiple delay values through switching between different ground return paths. Instead of requiring separate transmission lines for each delay value, a single multi-functional transmission line structure is used that can be configured to provide different delays by switching which ground return path is active, thereby reducing the footprint required for phased array elements.
Data Source
AI summary
A design structure, structure, and method for providing an on-chip variable delay transmission line with a fixed characteristic impedance. A method of manufacturing a transmission line structure includes forming a signal line of the transmission line structure, forming a first ground return structure that causes a first delay and a first characteristic impedance in the transmission line structure, and forming a second ground return structure that causes a second delay and a second characteristic impedance in the transmission line structure. The first delay is different from the second delay, and the first characteristic impedance is substantially the same as the second characteristic impedance.