Active Radar Target Height Diversity Antenna Configuration
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Solution Overview
Problem
Current radar systems face challenges in accurately measuring the distance to complex targets, such as ships or oil rigs, due to diverse signal returns and interference from multiple signal paths, which complicates precise ranging and positioning applications.
Innovation Solution
An active radar target system with vertically displaced receive and transmit antennas, employing single sideband suppressed carrier modulation and frequency shift keying to reduce self-oscillation risks and enhance signal clarity, while allowing for data payload transmission and identity coding, thereby improving signal path diversity and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single antenna is used for radar signal transmission and reception, then the device complexity is reduced, but measurement precision deteriorates due to multi-path interference and inability to provide signal path diversity
Solution Approach 1:
The radar system is segmented into multiple antenna elements (at least two antennas) that are spatially separated. Each antenna receives signals through different propagation paths, allowing the system to distinguish between direct line-of-sight signals and reflected multi-path signals based on their different arrival characteristics.
Solution Approach 2:
The antennas are positioned at different vertical heights to create height diversity. This spatial separation in the vertical dimension ensures that signals propagating through different paths (direct vs. reflected) arrive at antennas with different phase and amplitude relationships, enabling the system to resolve multi-path interference by analyzing the dimensional differences in signal arrival.
2Reliability
If active radar target amplifies and retransmits the incoming signal, then the radar cross section is enhanced, but self-sustaining oscillation may occur due to frequency matching between transmitted and received signals
Solution Approach 1:
The system changes the frequency parameter of the retransmitted signal by applying a frequency shift (e.g., using a mixer to shift to a different frequency or applying a Doppler shift). This frequency differentiation ensures that the active target's retransmitted signal does not resonate with the incoming radar signal, preventing self-sustaining oscillation while maintaining enhanced signal detection capability.
3Measurement precision
If multiple signal paths are used for signal propagation, then signal path diversity is achieved, but destructive interference occurs due to phase differences between direct and reflected signals
Solution Approach 1:
The radar system uses feedback from multiple antennas receiving signals through different paths to identify and compensate for destructive interference patterns. By analyzing the phase and amplitude relationships of signals arriving at different antennas, the system can detect when destructive interference is occurring and adjust processing to select or combine signals that maintain measurement accuracy.
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 system achieves precise ranging and positioning capabilities by reducing interference and enhancing signal clarity, enabling accurate distance measurement to within a few meters, and allows for additional data transmission like GPS position and vessel dynamics.
Implementation Method 1
at least one amplifier and a modulator arranged to amplify and modulate an incoming signal prior to retransmitting it
Implementation Method 2
at least one amplifier and a modulator arranged to amplify and modulate an incoming signal prior to retransmitting it
Implementation Method 3
at least one antenna in a pair being vertically displaced with respect to at least one antenna in a different pair of antennas
Implementation Method 4
These two signal paths can interfere, either constructively or destructively depending on the relative path lengths
Implementation Method 5
the retransmitted signal is frequency shifted by a mixer or modulator so as to reduce the risk of self sustaining oscillation
Data Source
AI summary
An active radar target includes several receive antennas and several transmit antennas that are arrangeable into pairs of antennas. Each pair includes a transmit and a receive antenna. At least one antenna in a pair is at a different height relative to at least one other antenna in a different pair of antennas.