Active Metamaterial Surface for Antenna Phase Control
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Solution Overview
Problem
Conventional antennas face efficiency reduction due to phase reversal of reflected waves from metal grounding plates, leading to offset issues and reduced flexibility, especially in compact designs like cell phone antennas, and existing High Impedance Surface (HIS) structures have limited adaptability and restricted surface impedance characteristics.
Innovation Solution
A reflection frequency conversion device using an active metamaterial surface with a variable capacitor coupled to a High Impedance Surface (HIS), where an arbitrary waveform generator provides a voltage waveform to continuously change the phase of reflected waves, allowing for flexible frequency conversion and phase adjustment by altering the capacitance of the variable capacitor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a metal grounding plate is used in conventional antenna design, then the antenna structure is simple and easy to manufacture, but the phase reversal of reflected waves causes efficiency reduction and offset issues
Solution Approach 1:
The patent changes the surface impedance parameter of the grounding plate by using High Impedance Surface (HIS) structures instead of conventional metal grounding plates. The HIS structure provides a surface impedance of infinity at resonance frequency, which changes the reflection coefficient from -1 (180 degree phase reversal) to +1 (0 degree phase shift), thereby eliminating the phase reversal issue while maintaining structural simplicity
Solution Approach 2:
The patent employs a composite structure combining dielectric materials with periodic metallic patterns to create the High Impedance Surface. This composite approach achieves the desired high surface impedance characteristic while maintaining structural simplicity and ease of manufacturing on PCB substrates
2Reliability
If a thick PCB substrate is used to minimize phase reversal effects, then the phase issue is reduced, but the antenna thickness increases and flexibility is reduced
Solution Approach 1:
Instead of increasing substrate thickness to mitigate phase reversal, the patent changes the surface impedance parameter by implementing HIS structures on the grounding plate. This allows achieving the desired phase characteristic (0 degree phase shift) with a thin substrate, thereby maintaining antenna compactness and flexibility while solving the phase reversal issue
3Reliability
If conventional HIS structures are used to achieve high surface impedance, then the phase of reflected wave is corrected to 0 degrees, but the surface impedance characteristic is restricted by the fixed metal structure shape
Solution Approach 1:
The patent introduces variable capacitors into the HIS structure, transforming it from a static to a dynamic system. The capacitance values can be adjusted to change the resonance frequency of the HIS structure, thereby providing adaptable surface impedance characteristics across different frequency bands while maintaining the 0 degree phase shift characteristic at resonance
Solution Approach 2:
The patent changes the electrical parameters of the HIS structure by incorporating variable capacitors with adjustable capacitance values. This allows tuning the resonance frequency and surface impedance characteristics to match different operational requirements, thereby achieving both phase control and 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
The solution enables efficient frequency conversion and phase adjustment of reflected waves, enhancing antenna performance by minimizing phase offset and allowing for compact, flexible designs, while also expanding the applicability of antennas in various military and communication applications.
Implementation Method 1
the capacitance of the variable capacitor is changed in accordance with applied voltage to change the phase of the reflected wave
Implementation Method 2
capable of converting the frequency of a reflected wave by providing a voltage waveform changed with time
Data Source
AI summary
A reflection frequency conversion device using an active metamaterial surface comprising: a plate-shaped active metamaterial surface which is configured to continuously convert a phase of a reflected wave by changing surface impedance characteristics in accordance with input voltage; and an arbitrary waveform generator which provides a voltage waveform capable of linearly changing the phase of the reflected wave in accordance with time to the metamaterial surface, where a reflection frequency generated on the metamaterial surface is converted in accordance with a frequency of the voltage waveform provided from the arbitrary waveform generator, where a plurality of metamaterial unit structures are periodically disposed on the metamaterial surface, and where the metamaterial unit structure is a high impedance surface (HIS) provided with a variable capacitor, and the capacitance of the variable capacitor is changed in accordance with applied voltage to change the phase of the reflected wave.