Radar Signal Processing for False Image Elimination
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Solution Overview
Problem
Conventional pulse compression radar systems often create false images on the indicator screen due to automatic response signals from transponders like SART and RACON, which are not adequately compressed and result in interference.
Innovation Solution
A radar apparatus and method that employs a pulse compression technique with a signal processing module to separate, eliminate, and compress signals, using a non-modulated or trigger pulse followed by a modulated pulse, and comparing consecutive cycles to eliminate discontinuous signal components, ensuring the modulated pulse is transmitted before the automatic transponder's dead time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a pulse compression technique is used to enhance far-range radar search ability, then the detection capability for distant targets is improved, but false images are created on the indicator screen due to automatic response signals from transponders
Solution Approach 1:
The patent segments the received signal into two separate frequency bands: one containing the radar echo signal and another containing the automatic response signal from transponders. By applying different signal processing techniques to each segment, the system can compress the radar echo for enhanced detection while preventing the automatic response signals from creating false images on the indicator screen.
Solution Approach 2:
The patent extracts and removes the automatic response signal components from the received signal before pulse compression processing. By identifying and separating these interfering signals based on their frequency characteristics, the system eliminates the source of false images while preserving the useful radar echo information for accurate target detection.
2Object-affected harmful factors
If conventional interference elimination techniques are applied to remove automatic response signals, then some interference is reduced, but expanded pulses in the range direction are not sufficiently eliminated
Solution Approach 1:
The patent employs dynamic signal processing by comparing receive signals from multiple consecutive transmit/receive cycles. By dynamically identifying signal components that exhibit discontinuity between cycles (characteristic of automatic response signals with dead time) and selectively eliminating only those components, the system achieves more effective interference removal while preserving continuous echo signals from actual targets.
Solution Approach 2:
The patent changes the timing parameters of pulse transmission by varying the first time interval between the non-modulated pulse and the modulated pulse across different transmit/receive cycles. This parameter variation ensures that automatic response signals fall outside the pulse compression processing window, preventing their expansion and false image creation while maintaining effective detection of reflected echo signals.
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
Prevents false images of automatic response signals on the radar indicator screen by effectively eliminating interference through targeted signal processing and timing adjustments, ensuring accurate representation of both near-range and far-range targets.
Implementation Method 1
an antenna (12) adapted to transmit a modulated pulse and to receive an echo from an echo source as well as an automatic response signal from an automatic transponder
Implementation Method 2
a receiver adapted to receive a receive signal including a reflected echo signal and an automatic response signal
Implementation Method 3
a signal separator adapted to separate, from the receive signal, a first separated receive signal having a frequency band corresponding to that of the modulated pulse
Implementation Method 4
a pulse compressor adapted to apply a pulse compression process to the first separated receive signal having undergone the interference elimination process
Data Source
Figure 1
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Figure 3(a)~3(f)
AI summary
A radar apparatus using a pulse compression technique, in which any automatic response signals are prevented from creating false radar images on the indicator screen of the radar apparatus. An antenna repeats a transmit/receive cycle at a second time interval while rotating, in which i) a non-modulated pulse is transmitted, ii) a modulated pulse is transmitted a first time interval after the transmission of the non-modulated pulse, and iii) an echo and/or an automatic response signal occurring after the pulse transmission is received. For each transmit/receive cycle, a first separated receive signal having a frequency band corresponding to that of the modulated pulse and a second separated receive signal having a frequency band corresponding to that of the non-modulated pulse are separated. An elimination process is applied to the first separated receive signal, in which respective first separated receive signals for two consecutive transmit/receive cycles are compared and any signal component having discontinuity between two consecutive transmit/receive cycles is eliminated from the first separated receive signal. A pulse compression process is applied to the first separated receive signal having undergone the elimination process. The first separated receive signal having undergone the pulse compression process is combined with the second separated receive signal.