Radar Antenna Array Pitch Segmentation for Grating Lobe Suppression
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Solution Overview
Problem
Phase monopulse radar apparatuses face limitations in target direction detection range due to phase foldover, and electronic scanning with array antennas is hindered by grating lobes that reduce detection reliability.
Innovation Solution
A radar apparatus with an array transmitting antenna and multiple receiving antennas, where the pitch of both antenna types is predetermined to ensure that the difference between the main lobe and grating lobe directions is greater than the target detection range, preventing grating lobes from affecting target authentication and allowing for a wide detection range without phase foldover.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the pitch of receiving antennas is increased to widen the target detection range, then the detection range is improved, but phase foldover occurs causing detection reliability to deteriorate
Solution Approach 1:
The receiving antenna array is segmented into multiple sub-arrays with different pitch values. Specifically, the array is divided into a first sub-array with pitch d1 and a second sub-array with pitch d2, where d1 < d2. This segmentation allows different portions of the array to handle different angular ranges, with the finer pitch preventing phase foldover in critical regions while the coarser pitch extends the overall detection range.
Solution Approach 2:
Different regions of the receiving antenna array are assigned different local properties (pitch values) according to their functional requirements. The first sub-array with smaller pitch d1 is positioned to handle directions where high reliability is critical, while the second sub-array with larger pitch d2 extends coverage to broader angular ranges. This local differentiation optimizes both reliability and detection range.
2Device complexity
If electronic scanning with array transmitting antenna is used to compact the radar system, then device complexity is reduced, but grating lobes appear causing detection reliability to deteriorate
Solution Approach 1:
The invention changes the pitch parameter of the transmitting antenna array to a specific value that satisfies the condition d ≤ λ/2, where λ is the wavelength of the transmitted signal. This parameter selection suppresses the formation of grating lobes in the radiation pattern, thereby maintaining detection reliability while preserving the compactness benefits of electronic scanning.
3Power
If the pitch of transmitting antenna elements is increased to narrow the main lobe and increase gain, then power is improved, but grating lobes appear causing harmful effects
Solution Approach 1:
The pitch d of the transmitting antenna elements is optimized to a specific range (d ≤ λ/2) that prevents grating lobe formation. This parameter selection achieves an optimal balance between maintaining sufficient antenna gain and suppressing harmful grating lobes, ensuring clean radiation patterns for accurate target detection.
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 configuration enables reliable target authentication and high accuracy in direction detection over a wide range, suppressing the adverse effects of grating lobes and allowing for a compact, electronically scanned radar system.
Implementation Method 1
a transmitting antenna formed of an array of antenna elements spaced apart with a fixed pitch for transmitting a beam of electromagnetic waves
Implementation Method 2
a plurality of receiving antennas spaced apart with a fixed pitch for receiving resultant reflected waves from a target
Implementation Method 3
phase control circuitry for supplying respective transmission signals to the elements of the transmitting antenna, and applying phase control to the transmission signals for sequentially shifting the orientation direction of the transmitted beam
Data Source
AI summary
A radar apparatus has a plurality of receiving antennas and an array transmitting antenna controlled to successively vary the direction of a transmitted beam within a range which includes a target detection range of directions. The direction of any target within the target detection range is detected based on a phase difference between incident reflected waves of adjacent receiving antennas. To eliminate false targets resulting from aliasing, each detected target is authenticated based upon closeness of its detected direction to the current transmitted beam direction. The receiving antennas and transmitting antenna are configured to exclude directions of grating lobes of the transmitted beam from the detection range, and thereby suppress effects of received reflected waves that originate from grating lobes.