Multimode Reflector Antenna Feed for Accurate Monopulse Tracking
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Solution Overview
Problem
Monopulse tracking systems face challenges with complex design, high costs, and inaccurate pointing due to phase differences in feed arrays, especially in small reflectors or those with multiple sub-reflectors, leading to decreased antenna performance.
Innovation Solution
A multimode feed for a reflector antenna using a horn with a waveguide structure that generates multiple higher-order propagation modes, coupled with specific couplers and summing elements to generate accurate azimuth and elevation error signals, improving tracking accuracy and reducing complexity and size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If an array of feeds is used to illuminate the reflector, then the illumination efficiency is improved, but the device complexity and cost increase
Solution Approach 1:
The patent merges multiple feed functions into a single feed structure by utilizing higher-order propagation modes within one waveguide. Instead of using multiple separate feeds to illuminate different quadrants of the reflector, the invention uses a single feed that generates multiple higher-order modes (such as TE21, TE01, TM01) to achieve the same illumination and tracking functionality, thereby reducing device complexity and cost while maintaining illumination efficiency
Solution Approach 2:
The single feed structure is designed to perform multiple functions simultaneously by supporting multiple higher-order propagation modes. Each mode can be used for different purposes: some modes provide illumination while others generate the necessary error signals for monopulse tracking in both azimuth and elevation planes, making the feed universal and multi-functional
2Reliability
If an array of feeds is used to ensure high antenna gain and tracking pattern slope, then the tracking performance is improved, but the design complexity increases
Solution Approach 1:
The invention combines the tracking performance capabilities of multiple feeds into a single feed by strategically utilizing different higher-order propagation modes. The single feed generates modes that collectively provide the necessary error signals for accurate monopulse tracking, achieving the same reliability and tracking performance as a complex feed array would provide
Solution Approach 2:
The invention changes the operational parameters of the feed by exciting multiple higher-order propagation modes instead of using multiple physical feeds. By controlling the amplitude and phase of these higher-order modes, the system achieves the required tracking pattern slope and antenna gain characteristics without the complexity of a multi-feed array
3Measurement precision
If the frequency is increased to improve resolution, then the measurement precision is improved, but the pointing accuracy deteriorates due to phase differences
Solution Approach 1:
The invention replaces the mechanical/physical alignment precision requirements of multiple feeds with an electromagnetic field-based solution. By using higher-order propagation modes in a single feed, the system substitutes the need for precise mechanical positioning and phase alignment of multiple feeds with controlled electromagnetic mode generation and combination, thereby maintaining pointing accuracy at higher frequencies
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 solution enhances tracking accuracy and reduces the size and cost of reflector antennas by maximizing the extraction efficiency of higher-order modes, ensuring high performance even in small or multi-reflector configurations.
Implementation Method 1
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
AI summary
The invention concerns a multimode feed for a reflector antenna of a monopulse tracking system. The feed comprises: a receiving element having an aperture, which receives an electromagnetic wave 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, coupled to the receiving element, which generates, from the plurality of higher-order modes, a first error signal at a first output port and a second error signal at a second output port. The waveguide structure has: a first coupler that extracts, from the waveguide signal, a first higher-order mode and provides a first extracted signal; a second coupler that extracts, from the waveguide signal, a second higher-order mode and provides a second extracted signal; a third coupler that extracts, from the waveguide signal, a third higher-order mode and provides a third extracted signal; a fourth coupler that extracts, from the waveguide signal, a fourth higher-order mode and provides a fourth extracted signal; a first summing element 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 that sums the third extracted signal and the fourth extracted signal, thereby generating the second error signal at the second output port.