Liquid Crystal Phase Shifter With Defected Ground Structure
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Solution Overview
Problem
Conventional phase shifters require high voltages for significant phase changes and have large dielectric thickness and insertion loss, limiting their ability to reduce microstrip transmission line length while maintaining electrical performance.
Innovation Solution
A phase shifter incorporating a thin liquid crystal layer between substrates with a defected ground structure, where a DC voltage is applied to change the dielectric constant, allowing for phase shifting with a small applied voltage and reducing signal loss, while the defected ground structure increases the electrical length without increasing physical length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a conventional phase shifter with large dielectric thickness is used, then a high voltage can be applied to achieve phase change, but the insertion loss increases and the device size increases
Solution Approach 1:
The patent changes the dielectric parameter by using liquid crystal material whose dielectric constant can be dynamically adjusted through voltage control. This allows optimization of the dielectric thickness to a minimal value while maintaining effective phase control, thereby reducing insertion loss while preserving voltage efficiency.
Solution Approach 2:
The patent employs a composite structure combining liquid crystal dielectric material with metallic electrodes and ground structures. This composite approach enables the thin liquid crystal layer to achieve the necessary dielectric effect for phase shifting without requiring large thickness, thus reducing insertion loss while maintaining voltage control efficiency.
2Loss of energy
If the dielectric thickness is reduced to lower insertion loss, then the phase shifting capability with small voltage becomes feasible, but the electrical length control becomes more difficult
Solution Approach 1:
The patent utilizes the voltage-dependent dielectric constant of liquid crystal to dynamically adjust the electrical length of the transmission line. By changing the dielectric parameter through applied voltage, the system achieves reliable phase control despite the reduced physical thickness of the dielectric layer.
Solution Approach 2:
The patent introduces dynamic control capability by using liquid crystal whose dielectric properties can be changed in real-time through voltage application. This dynamic characteristic enables the thin dielectric structure to provide sufficient electrical length adjustment range for reliable phase shifting operation.
3Adaptability or versatility
If a large voltage is applied to achieve 360 degrees phase change, then the phase shifting range is sufficient, but the device complexity and power consumption increase
Solution Approach 1:
The patent exploits the electric field-induced change in liquid crystal dielectric constant to achieve phase shifting. This parameter change mechanism allows the system to obtain a full 360-degree phase shifting range by applying relatively low voltages that simply modify the dielectric property rather than requiring high voltages for direct phase modulation.
Solution Approach 2:
The patent replaces the conventional approach of using high voltage for direct phase control with a field-effect mechanism where electric field modifies dielectric constant, which in turn controls phase. This substitution of control mechanism reduces the required voltage level while maintaining the full phase shifting range.
4Length of moving object
If the microstrip transmission line length is reduced using DGS, then the device size decreases, but the electrical performance may deteriorate
Solution Approach 1:
The patent merges the DGS structure with the liquid crystal phase shifter functionality. The DGS provides electrical length extension in a compact physical space, while the liquid crystal layer provides phase control. This merging allows the device to achieve both miniaturization and maintained electrical performance with additional phase shifting capability.
Solution Approach 2:
The patent creates a composite structure integrating DGS metallic patterns with liquid crystal dielectric material. This composite design enables the short physical transmission line to achieve the necessary electrical length through DGS while the liquid crystal provides adjustable phase control, maintaining overall electrical performance despite reduced physical dimensions.
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 enables phase shifting with low voltage, reduces signal loss, and miniaturizes the phase shifter, allowing for wider bandwidth and reduced production costs, thereby improving performance and design flexibility in electromagnetic-wave communication modules.
Implementation Method 1
a liquid-crystal layer disposed in a space between the first substrate and the second substrate, wherein a direct current (DC) voltage is applied to between the ground layer and the microstrip
Implementation Method 2
The phase shifter has dielectric between an upper electrode and a lower electrode and changes the phase of the transmission line by adjusting the dielectric constant of the dielectric under control of a voltage applied to the upper electrode and the lower electrode
Implementation Method 3
when the defect ground structure (DGS) is inserted into the transmission line, a length of the microstrip transmission line can be reduced
Implementation Method 4
a ground layer disposed above the microstrip and spaced from the microstrip, wherein the ground layer includes a defected ground structure (DGS) by forming a defected pattern therein
Data Source
AI summary
A phase shifter includes a first substrate; a microstrip formed on the first substrate so as to extend in a first direction; a ground layer disposed with a space on the upper surface of the microstrip and having a defected ground structure (DGS) with a defected pattern formed therein; a second substrate disposed on the ground layer; and a liquid crystal layer disposed in a space between the first substrate and the second substrate, wherein DC voltage is applied between the ground layer and the microstrip.