Multimode Reflector Antenna Feed for Monopulse Error Extraction
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Solution Overview
Problem
Monopulse tracking systems for radar and satellite applications face challenges with complex and costly array feeds that result in inaccurate pointing due to phase differences, especially when reflectors are small or have multiple sub-reflectors, leading to decreased antenna performance.
Innovation Solution
A multimode feed system utilizing a horn with a conical waveguide that generates multiple higher-order propagation modes, including TM 01, TE 21, TE* 21, and TE 01, which are coupled and summed to provide accurate azimuth and elevation error signals, allowing for precise tracking with reduced complexity and size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an array of feeds is used to illuminate the reflector, then the tracking system can determine azimuth and elevation errors, but the device complexity and costs increase significantly
Solution Approach 1:
The patent combines multiple feed elements into a single integrated feed structure that generates multiple higher-order modes (TE01, TE21, TM01, TM21) simultaneously. This merging approach eliminates the need for separate feed arrays while maintaining the capability to generate all four quadrant signals needed for monopulse tracking, thereby reducing device complexity and costs while preserving measurement precision
Solution Approach 2:
The single feed structure is designed to perform multiple functions: it generates all four higher-order modes required for monopulse tracking (azimuth and elevation error signals) and illuminates the entire reflector surface. This multi-functional design replaces what would traditionally require multiple specialized feed elements, reducing overall system complexity while maintaining full tracking capability
2Illumination intensity
If an array of feeds is used to ensure efficient illumination, then tracking capability is improved, but the dimensions and costs of the system increase
Solution Approach 1:
The patent merges the illumination function of multiple feed elements into a single compact feed structure that generates multiple higher-order modes. This single structure provides efficient illumination across the entire reflector surface without requiring a large array of separate feed elements, thereby maintaining illumination intensity while reducing the physical size of the feed system
3Power
If a feed array is used to achieve high antenna gain, then tracking performance is improved, but the device complexity increases
Solution Approach 1:
The patent combines the high-gain capabilities of multiple feed elements into a single integrated structure that generates multiple higher-order modes with appropriate radiation patterns. This merging maintains the antenna gain required for high-performance tracking while eliminating the complexity of coordinating multiple independent feed elements
Solution Approach 2:
The patent changes the operational parameters of the feed by utilizing higher-order waveguide modes (TE01, TE21, TM01, TM21) instead of conventional fundamental modes. This parameter change enables a single feed to achieve the radiation characteristics and gain distribution that would traditionally require multiple feed elements, thereby maintaining antenna gain while reducing device complexity
4Area of stationary object
If the reflector size is reduced, then system dimensions are decreased, but the feed array becomes even more complex and costly
Solution Approach 1:
The patent applies the single multi-mode feed structure specifically to small reflectors, where it provides all necessary illumination and tracking functions in one compact unit. This merging approach is particularly beneficial for small reflectors as it eliminates the need for complex dense feed arrays that would be required to achieve adequate illumination and tracking precision on limited aperture surfaces
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 multimode feed system enhances tracking accuracy, reduces production costs, and maintains high performance even with small reflectors, ensuring efficient illumination and accurate pointing corrections.
Implementation Method 1
the reflector antenna comprises only one feed, of the multimode type, formed by a horn having an aperture that receives an electromagnetic wave and generates higher-order propagation modes within it, as a function of the orientation between the direction of propagation of the wave and the aperture of the horn
Data Source
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AI summary
The invention concerns a multimode feed (1) for a reflector antenna of a monopulse tracking system. The feed comprises: a receiving element (5) having an aperture (10), which receives an electromagnetic wave (3) and generates, from the electromagnetic wave, a waveguide signal comprising a plurality of higher-order modes, as a function of an incidence angle of the electromagnetic wave on the aperture; and a waveguide structure (8), coupled to the receiving element, which generates, from the plurality of higher-order modes, a first error signal (AZ_ERR) at a first output port and a second error signal (EL_ERR) at a second output port. The waveguide structure has: a first coupler (15) that extracts, from the waveguide signal, a first higher-order mode (TE01) and provides a first extracted signal (S_TE01); a second coupler (16) that extracts, from the waveguide signal, a second higher-order mode (TE21) and provides a second extracted signal (S_TE21); a third coupler (17) that extracts, from the waveguide signal, a third higher-order mode (TE*21) and provides a third extracted signal (S_TE*21); a fourth coupler (18) that extracts, from the waveguide signal, a fourth higher-order mode (TM01) and provides a fourth extracted signal (S_TM01); a first summing element (23) that sums the first extracted signal and the second extracted signal, thereby generating the first error signal at the first output port; and a second summing element (24) that sums the third extracted signal and the fourth extracted signal, thereby generating the second error signal at the second output port.