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 method to create 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 the ground return structures.
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 ground return path is segmented into multiple sections with different geometries and distances from the signal line. Each segment contributes differently to capacitance and inductance, allowing independent control of delay and impedance characteristics through selective grounding.
Solution Approach 2:
The ground return structures are made dynamically switchable between grounded and floating states using switches. This dynamic configuration allows the transmission line to change its electrical characteristics (delay and impedance) without physical reconfiguration, enabling delay adjustment while maintaining constant characteristic impedance.
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 ground return path is divided into multiple segments with different geometries. By selectively grounding specific segments, the total capacitance and inductance can be adjusted independently, allowing delay change while maintaining constant characteristic impedance through proper segment selection.
Solution Approach 2:
The electrical parameters (capacitance and inductance) are changed by switching different ground return configurations, not by altering the physical geometry. This allows independent control of delay and characteristic impedance, as the switching action changes L and C values while maintaining their ratio constant.
3Ease of manufacture
If conventional transmission line structures are used with fixed impedance, then manufacturing is simplified, but adaptability for variable delay applications is reduced
Solution Approach 1:
The transmission line structure is designed to serve multiple functions: it can operate with different delay values while maintaining constant characteristic impedance. The same physical structure supports variable delay through switching different ground return configurations, eliminating the need for multiple dedicated transmission lines for different delay requirements.
Solution Approach 2:
The structure incorporates dynamically switchable ground return paths that allow the transmission line to adapt its electrical characteristics based on operational requirements. This dynamic capability is achieved through switches that connect or disconnect different ground return segments, providing variable delay without changing the physical layout.
4Ease of operation
If multiple transmission lines with different delays are provided for phased array elements, then phase control is achieved, but the footprint and manufacturing complexity increase
Solution Approach 1:
Instead of providing separate transmission lines for different delay values, the ground return path is segmented into multiple sections. Each segment can be selectively grounded to achieve different delay values, reducing the total number of transmission lines required and minimizing footprint while maintaining phase control capability.
Solution Approach 2:
Multiple delay functions are merged into a single transmission line structure by combining multiple ground return segments. This consolidation allows one transmission line to perform the function of multiple separate lines, reducing overall footprint and simplifying manufacturing while preserving phase control for phased array applications.
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.