Switchable Frequency Selective Surface for Indoor mmWave Coverage
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Solution Overview
Problem
The challenge is to enhance the communication service coverage and signal quality for millimeter wave (mmWave) signals incident from outdoors to indoors, as these signals are significantly attenuated by building structures and windows, leading to shadow areas and increased installation and operating costs due to the need for multiple repeaters.
Innovation Solution
A frequency selective surface (FSS) is designed with a dielectric substrate, loop gaps, patches, cross strips, and a PIN diode. The FSS is arranged to induce broadband frequency passing characteristics and control the opening and closing of frequency bands by using the PIN diode between the patch and microstrip line.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mmWave signals are transmitted from outdoors to indoors through windows, then signal transmission is enabled, but the signal magnitude decreases due to impedance mismatch and transmission loss
Solution Approach 1:
The patent changes the electromagnetic parameters (impedance, phase) of the window surface by integrating an FSS structure with specific geometric patterns (patches, loops, crosses) that resonate at mmWave frequencies. This transforms the window from a signal-blocking barrier to a signal-enhancing surface by adjusting the electrical parameters at the interface between free space and glass.
Solution Approach 2:
The invention creates a composite structure combining the existing glass window material with an FSS patterned layer. This composite surface integrates the transparency and mechanical properties of glass with the electromagnetic wave manipulation capabilities of the FSS pattern, achieving both optical and RF performance.
2Reliability
If multiple mmWave repeaters are installed indoors to overcome signal loss, then communication coverage is improved, but installation and operating costs increase
Solution Approach 1:
The patent extracts the signal amplification and coverage extension function from indoor repeater devices and relocates it to the window surface itself. The FSS structure performs the function of signal enhancement at the boundary (window) rather than requiring separate active repeater units inside the building.
Solution Approach 2:
The FSS-patterned window acts as an intermediary surface between the outdoor mmWave environment and the indoor space. It mediates the signal transmission by providing impedance matching and constructive interference patterns, eliminating the need for additional repeater intermediaries indoors.
3Ease of manufacture
If conventional windows are used for mmWave transmission, then structural simplicity is maintained, but signal magnitude decreases due to impedance difference between free space and glass
Solution Approach 1:
The patent segments the window surface into discrete FSS unit cells (patches, loops, crosses) arranged in periodic patterns. Each unit cell is designed to resonate at specific mmWave frequencies, and the collective array provides the desired impedance matching and signal enhancement across the window surface.
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 FSS effectively expands the frequency bandwidth for signal transmission, allowing for improved signal quality and communication service coverage indoors, while also reducing the need for multiple repeaters and associated costs.
Implementation Method 1
A frequency selective surface (FSS) may include a dielectric having an arbitrary permittivity and a thickness, a loop gap including a gap and arranged on an upper surface of the dielectric, a patch arranged inside the loop gap, and a cross strip arranged on a lower surface of the dielectric
Implementation Method 2
a PIN diode arranged between the microstrip line and the patch. When the PIN diode is in an off state, the dielectric may pass a signal in all operating frequency bands and when the PIN diode is in an on state, the dielectric may block a signal in all operating frequency bands
Data Source
AI summary
A frequency selective surface (FSS) is provided. The FSS includes a dielectric having an arbitrary permittivity and a thickness, a loop gap including a gap and arranged on an upper surface of the dielectric, a patch arranged inside the loop gap, and a cross strip arranged on a lower surface of the dielectric.