Microwave Backscatter Transponder Sidelobe Suppression via Tapered Modulation
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Solution Overview
Problem
Microwave backscatter transponders suffer from increased sidelobes, which lead to incorrect position determinations, reduced energy content in the mainlobe, and multipath propagation, causing interference.
Innovation Solution
The transponder employs a linear array of antenna elements with separate modulation units for inner and outer elements, using different duty cycles to create a taper effect, reducing sidelobes through selective pulse width modulation and bandpass filtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If uniform modulation is applied to all antenna elements, then the structure is simple and easy to implement, but sidelobes are increased leading to incorrect position determinations
Solution Approach 1:
The patent applies different modulation strategies to different groups of antenna elements. Outer antenna elements use one modulation scheme while inner antenna elements use another, creating local quality differences that suppress sidelobes and improve position determination accuracy without requiring complete system redesign
Solution Approach 2:
The antenna array is segmented into multiple groups (outer elements and inner elements) with different modulation characteristics. This segmentation allows independent optimization of each group's modulation parameters to achieve overall sidelobe suppression while maintaining manageable system complexity
2Device complexity
If uniform modulation is applied to all antenna elements, then the implementation is straightforward, but energy content in the mainlobe is reduced
Solution Approach 1:
Different modulation duty cycles are applied to outer and inner antenna elements. The inner elements use higher duty cycles (e.g., 50%) to maintain strong mainlobe energy, while outer elements use lower duty cycles to reduce sidelobe levels, optimizing the energy distribution locally across the array
3Device complexity
If uniform modulation is applied to all antenna elements, then the system is simple to operate, but multipath propagation and interference occur
Solution Approach 1:
The patent changes the modulation parameter (duty cycle) across different antenna element groups. By varying this parameter spatially, the radiation pattern is shaped to suppress sidelobes that cause multipath propagation and interference, while keeping the overall system operation relatively simple
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 suppresses sidelobes, enhancing the reliability and accuracy of position determination and reducing unwanted emissions in various applications, including aviation and radar systems.
Implementation Method 1
Backscatter transponders use the physical principle of modulated backscatter to respond to the incoming signal
Implementation Method 2
This switching changes the impedance of the antenna elements and thus their reflection behavior
Data Source
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AI summary
The invention relates to a microwave backscatter transponder with the following features: - it comprises a plurality of emitter elements (AE1-AE4) forming a 1- or 2-dimensional array (AR), - means (MOD1, MOD2, SPDT1-SPDT4) are provided to modulate the impedance of the emitter elements (AE1-AE4), - the emitter elements (AE1-AE4) are divided into several groups depending on their position within the array (AR), wherein a uniform impedance modulation, different from the modulations of the other groups, is applied to the emitter elements of each group (AE1, AE4; AE2, AE3), - wherein the assignment of a specific modulation to one of the groups is chosen such that tapering results, according to which the signal levels of the emitter elements (AE1, AE4) at the edges of the array (AR) are lower compared to the emitter elements (AE2, AE3) in the center of the array. Drop arrays to enable sidelobe suppression.