AESA Transmit Nulling Calibration for Ground Clutter Suppression
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Solution Overview
Problem
AESA radar systems face challenges in suppressing ground clutter, which overwhelms useful signals and requires computationally expensive and power-intensive methods like STAP, making them unsuitable for efficient weather and target detection near the ground.
Innovation Solution
A method for maximizing equivalent isotropic radiated power (EIRP) by identifying nulling locations and calibrating RF channels to align theoretical aperture patterns with desired nulls, using iterative bisection to converge on actual gain and phase settings, thereby reducing ground clutter while maintaining beam alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If Space-Time Adaptive Processing (STAP) is used to suppress ground clutter, then clutter suppression capability is improved, but computational cost and power consumption increase prohibitively
Solution Approach 1:
The patent segments the clutter suppression function into two parts: (1) beamforming with nulling at desired locations that can be implemented in hardware, and (2) post-processing of radar returns that can be performed computationally. This segmentation allows the computationally intensive STAP to be applied only to processed data rather than raw signals, dramatically reducing power consumption while maintaining clutter suppression effectiveness.
Solution Approach 2:
The patent performs preliminary beamforming and nulling operations before applying STAP. By pre-aligning the beam and creating nulls at known clutter locations through hardware beamforming, the subsequent computational processing requires significantly less effort to achieve the same clutter suppression result, thereby reducing overall computational cost and power consumption.
2Object-affected harmful factors
If Space-Time Adaptive Processing (STAP) is used to suppress ground clutter, then clutter suppression capability is improved, but hardware requirements become heavy and expensive
Solution Approach 1:
The patent divides the processing architecture into hardware-based beamforming/nulling components and software-based STAP processing components. This segmentation allows standard, less expensive hardware to perform the bulk of the clutter mitigation through beamforming, while sophisticated STAP algorithms are applied only to reduced-dimensional data, avoiding the need for expensive specialized hardware throughout the entire signal chain.
Solution Approach 2:
The patent introduces beamforming as an intermediary processing stage between the radar receiver and the STAP algorithm. This intermediary performs preliminary clutter mitigation and signal enhancement, transforming the raw radar data into a form that requires less complex hardware to process through subsequent STAP operations, thereby reducing overall hardware complexity and cost.
3Measurement precision
If transmit power is increased to improve detection capability near ground, then detection sensitivity is improved, but ground clutter overwhelms useful signals
Solution Approach 1:
The patent applies different signal characteristics to different spatial locations by creating directional beams with localized nulls. High power is transmitted only in directions away from the ground, while nulls are created at specific angular positions corresponding to ground clutter sources. This local quality approach allows high detection sensitivity in desired directions while suppressing clutter in ground directions, resolving the contradiction between detection capability and clutter interference.
Solution Approach 2:
The patent creates nulls in the transmit beam pattern at anticipated clutter locations before the radar pulse is transmitted. This preliminary anti-action prevents ground clutter from being strongly illuminated in the first place, reducing the clutter return at its source. By combining this with high power transmission in non-ground directions, the system achieves both high detection sensitivity and effective clutter suppression.
Data Source
AI summary
A method is presented for maximizing equivalent isotropic radiated power (EIRP) of an active electronically scanned array (AESA) system. This AESA system includes a phased array of radio-frequency (RF) channels each having an associated emitter element. A desired nulling location is first identified, constituting a spatial location for transmission nulling relative to the phased array. Theoretical aperture patterns for the AESA system are computed to maximize radiated power while aligning a geographical null of a beam of the AESA system with the desired nulling location. These theoretical aperture patterns include nominal values of gain and a time-based parameter (e.g. phase or time delay) for each RF channel. From these theoretical aperture patterns, for each RF channel, actual gain is empirically calibrated to maximize EIRP, while actual time-based parameter is calibrated by iterative bisection of a time-based parameter table through successively narrower ranges of the time-based parameter converging upon a nominal gain value. Each RF channel is then driven according to its calibrated actual gain and time-based parameter.