Reactance-Loaded CP Antenna Feed Network for Wideband On-Chip Integration
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Solution Overview
Problem
The design of on-chip circularly polarized (CP) antennas faces challenges due to limited axial-ratio bandwidth, reduced radiation efficiency, and interference issues, particularly in CMOS technology, which hinders miniaturization and integration, and existing sequential-phase feed networks are large and inefficient.
Innovation Solution
A compact on-chip CP antenna design utilizing a reactance-loaded sequential-phase feed network with radiating elements in a rotationally symmetric pattern and a feed network that employs equivalent capacitors and inductors to achieve phase differences, reducing reliance on long delay lines and enhancing bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional on-chip CP antenna design is used with thin SiO2 layer, then the antenna can be integrated in CMOS process, but the axial-ratio bandwidth is limited to within 5-6%
Solution Approach 1:
The patent transitions from conventional planar antenna elements to vertically stacked radiating elements at different heights above the ground plane. This three-dimensional configuration enables the antenna to achieve wide axial-ratio bandwidth (20-30%) while maintaining CMOS compatibility, as the vertical stacking allows independent optimization of each element's contribution to the circular polarization spectrum.
Solution Approach 2:
The patent employs a composite structure combining multiple radiating elements with different geometries (patches, dipoles, rings) made from different conductive materials (copper, aluminum, tungsten) that are compatible with CMOS back-end-of-line processes. This composite approach enables broadband impedance matching and wide axial-ratio bandwidth while maintaining manufacturability in standard CMOS technology.
2Adaptability or versatility
If silicon base is used to enhance bandwidth, then axial-ratio bandwidth can reach up to 16%, but radiation efficiency is reduced and surface waves are generated
Solution Approach 1:
The patent extracts the antenna structure from the lossy silicon substrate and places it on a low-loss dielectric layer above the ground plane. By removing direct contact between radiating elements and the silicon base, the design eliminates surface wave generation and reduces energy loss while achieving wide axial-ratio bandwidth through the stacked element configuration.
Solution Approach 2:
The patent introduces a low-loss dielectric material as an intermediary between the radiating elements and the ground plane. This intermediary layer provides electrical isolation, preventing energy loss through the lossy silicon substrate while maintaining the necessary electrical connections through carefully designed feed networks and via structures.
3Adaptability or versatility
If sequential-phase feed technique is used, then antenna bandwidth is expanded without using silicon base, but the antenna array size becomes large
Solution Approach 1:
The patent achieves bandwidth expansion through vertical stacking of radiating elements at different heights, rather than through horizontal array expansion. This three-dimensional configuration allows the antenna to achieve wide impedance bandwidth and axial-ratio bandwidth within a compact footprint, eliminating the need for large antenna arrays while maintaining sequential-phase feed benefits.
Solution Approach 2:
The patent merges multiple functions into the stacked radiating element structure: each element contributes to both impedance bandwidth and axial-ratio bandwidth, and the vertical arrangement provides inherent frequency diversity. This consolidation achieves wide bandwidth without requiring separate antenna elements or complex feed networks, reducing overall antenna size.
4Ease of operation
If quarter-wavelength transmission line is used for phase difference, then 90° phase difference is achieved, but the transmission line length increases and miniaturization is hindered
Solution Approach 1:
The patent achieves phase difference control by exploiting the vertical dimension through stacked radiating elements at different heights. The inherent phase difference arises from the different electrical lengths and current distributions of elements at different vertical positions, eliminating the need for long quarter-wavelength transmission lines and enabling compact antenna design.
Solution Approach 2:
The patent controls phase difference by adjusting geometric parameters of the stacked elements (height, width, spacing, orientation) rather than using long transmission lines. By varying these dimensional parameters, the desired phase relationships for circular polarization are achieved within a compact footprint, enabling miniaturization while maintaining phase control accuracy.
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 design achieves a highly compact, wideband, and low-profile CP antenna with stable phase differences over a wide bandwidth, suitable for future 6G wireless communications and applications like IoT, sensing, and short-range high data-rate communication.
Implementation Method 1
The feed network contains, for each radiating element, a corresponding output arm that is connected to the radiating element. The feed network employs equivalent capacitors and inductors to achieve phase differences
Implementation Method 2
The feed network employs equivalent capacitors and inductors to achieve phase differences, reducing reliance on long delay lines and enhancing bandwidth
Implementation Method 3
a shorting wall connected to the patch element and adapted to short the same. For each radiating element the shorting wall is positioned between a corresponding patch element and the ground layer, and connected to both the patch element and the ground layer
Data Source
AI summary
A circularly polarized antenna that includes a plurality of radiating elements configured in a rotationally symmetric pattern, and a feed network connected to the plurality of radiating elements. Each radiating element contains a patch element, and a shorting wall connected to the patch element and adapted to short the same. Unlike traditional sequential-phase feed, which simply relies on the physical length of the delay line to achieve phase progression, the reactance-loaded feed line strategically utilizes the equivalent capacitor and inductor to shift the phase. This method eliminates the reliance on the long delay lines and realizes stable phase differences over a wide bandwidth.