Frequency Scanning Radar Doppler Normalization
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Solution Overview
Problem
Frequency scanning antennas in radar systems complicate velocity ambiguity resolution due to variations in Doppler frequencies caused by changes in carrier frequency, especially for targets with frequencies close to half the sampling frequency.
Innovation Solution
A frequency scanning radar system that adjusts the period of frequency sweeps in proportion to the carrier frequency to maintain a constant normalized Doppler frequency, using a controller to select signal rates and modify modulation patterns, ensuring the Doppler frequency remains consistent across variations in carrier frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If frequency scanning antennas are used to sweep across regions and avoid detection, then the radar system gains versatility in beam steering and frequency hopping, but the Doppler frequencies for given targets are modified, complicating velocity ambiguity resolution
Solution Approach 1:
The patent changes the parameter of sweep period in direct proportion to carrier frequency. By making the sweep period variable rather than fixed, the system compensates for frequency variations introduced by frequency scanning antennas, thereby normalizing Doppler frequencies and resolving velocity ambiguities while maintaining beam steering versatility
Solution Approach 2:
The controller monitors the carrier frequency and adjusts the sweep period accordingly. This feedback mechanism ensures that the sweep period is always in direct proportion to the carrier frequency, automatically compensating for frequency changes and maintaining normalized Doppler frequency measurements
2Adaptability or versatility
If the carrier frequency is varied for frequency hopping and beam steering, then the radar system can avoid detection and interference, but the Doppler frequency for a given target changes, making velocity interpretation difficult
Solution Approach 1:
The patent introduces a dependent relationship between sweep period and carrier frequency. When the carrier frequency changes during frequency hopping, the sweep period changes proportionally, which normalizes the Doppler frequency and preserves the ability to correctly interpret target velocity information
Solution Approach 2:
The controller pre-establishes the proportional relationship between sweep period and carrier frequency before frequency hopping occurs. This preliminary configuration ensures that regardless of which frequency is selected for hopping, the corresponding sweep period is already set to maintain normalized Doppler frequency measurements
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 normalizes Doppler frequencies, reducing ambiguity in velocity measurements and maintaining consistent radar system performance across different carrier frequencies, thereby enhancing the accuracy of target motion analysis.
Implementation Method 1
frequency scanning arrays, which, in response to input signals of varying frequencies, can steer a beam in an angular plane
Implementation Method 2
Radar systems are used to detect the presence of objects and to measure the location and movement of objects... Radar systems are commonly used to identify the Doppler frequency of targets so as to identify the magnitude and direction of movement thereof
Data Source
AI summary
A frequency scanning radar system includes a controller for controlling a frequency generator and a signal processor arranged to determine a Doppler frequency associated with a target. The frequency generator generates three or more sets of signals, each set of signals having a different characteristic frequency and including signals transmitted at a selected rate, and the radar controller selects the rate in substantially direct proportion to the characteristic frequency, whereby to normalize the Doppler frequency determined by the signal processor, such that the normalized Doppler frequency is substantially constant in relation to variation in the carrier frequency. In a frequency modulated radar system, each set of signals includes a sequence of modulation patterns, and the radar controller modifies a given modulation pattern in dependence on the characteristic frequency of the signal being modulated.