Cross-Polarized FMCW Radar Antenna for Tx-Rx Isolation
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Solution Overview
Problem
Frequency modulated continuous wave (FMCW) radar systems face challenges in achieving isolation between transmit and receive antennas to reduce interference and enhance sensitivity, particularly in smaller applications like unmanned aerial vehicles (UAVs), where existing solutions like electronic band gap (EBG) structures may not be sufficient.
Innovation Solution
The implementation of orthogonally polarized transmit and receive antenna elements, with a polarizer layer to convert signals to co-polarized directions, reducing surface wave interference and allowing for a smaller antenna size while maintaining isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If EBG structures are used to stop surface wave propagation between transmit and receive antennas, then isolation between antennas is improved, but the antenna size increases
Solution Approach 1:
The patent changes the polarization parameter of antenna elements from parallel to orthogonal orientation. By making transmit elements horizontally polarized and receive elements vertically polarized (or vice versa), surface waves are naturally attenuated without requiring additional EBG structures, thus maintaining isolation while reducing antenna size
Solution Approach 2:
The patent extracts and removes the EBG isolation structures from the antenna design. By using orthogonally polarized elements instead, the harmful surface wave propagation is eliminated without the need for additional isolation components, thereby reducing overall antenna area
2Area of stationary object
If orthogonally polarized antenna elements are used to attenuate surface waves, then antenna size is reduced, but signal polarization alignment may be affected
Solution Approach 1:
The patent introduces a polarization dimension to solve the isolation problem. By utilizing orthogonal polarization states (horizontal vs vertical) as an additional degree of freedom, the system achieves spatial separation of transmit and receive signals without increasing physical separation distance, thus reducing antenna size while maintaining signal quality
Solution Approach 2:
The patent converts the potentially harmful effect of surface wave coupling into a beneficial isolation mechanism. Orthogonal polarization causes surface waves generated by transmit elements to be naturally rejected by receive elements, transforming the coupling problem into an isolation solution while enabling compact antenna design
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
This approach effectively attenuates surface waves, reduces antenna size, and improves isolation between transmit and receive signals, enabling better performance and increased range without increasing the overall size of the radar system.
Implementation Method 1
a polarizer configured to receive radar signals and output the received radar signals converted to an orthogonal polarization direction
Implementation Method 2
The cross-polarized antenna elements may cause attenuation of surface waves between the Tx and Rx antennae
Data Source
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AI summary
A frequency modulated continuous wave, FMCW, radar antenna (700) that may provide isolation between the transmit, Tx, antenna (728) and the receive, Rx, antenna (726) based on the arrangement of the transmit elements (724) and the receive elements. The transmit antenna elements may be orthogonally fed, e.g., different by 90 degrees, compared to the receive antenna elements. For example, for horizontally polarized receive antenna elements, the transmit elements may be vertically polarized, or vice versa. The cross-polarized antenna elements may cause attenuation of surface waves between the Tx and Rx antennae. A low insertion loss 90-degree polarizer layer (720) over one of the transmitter antenna, or the receiver antenna, to convert either the transmitted signals or the received reflections by 90-degrees so the reflected signal matches the polarization of the receiver antenna.