Active Radar Target With Single Sideband Modulator
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Solution Overview
Problem
Existing radar systems face challenges in achieving precise range measurements to complex targets, such as large ships or oil rigs, due to diverse radar returns, which are not useful for applications requiring accuracy to a few meters or less.
Innovation Solution
An active radar target system using an FMCW radar with a receive antenna, amplifier, transmit antenna, memory for identity code storage, and a single sideband modulator to modulate the radar signal with an identity code, employing frequency shift keying or phase shift keying for encoding, and providing additional data like GPS position and vessel dynamics, while using orthogonally polarized antennas to reduce self-oscillation risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional radar is used to measure distance to complex targets, then it can detect all reflecting surfaces, but it cannot achieve precise range measurement to a few meters or less
Solution Approach 1:
An active radar target is introduced as an intermediary device between the radar system and the complex structure (ship, oil rig, etc.). This active target carries a transponder that receives the radar signal, processes it, and returns a modulated signal with encoded identity information, enabling precise ranging while the complex structure remains passive
Solution Approach 2:
The active radar target is self-powered and autonomously processes the radar signal. The transponder on the active target receives the incoming radar pulse, amplifies it, modulates it with identity code, and retransmits it without requiring external control or power from the complex structure it is attached to
2Loss of information
If active radar reflectors are used to amplify the radar signal, then the signal return is enhanced, but the ability to transmit additional data beyond target identification is limited
Solution Approach 1:
The active radar target serves multiple functions: it acts as a high-visibility radar reflector for collision avoidance, provides precise ranging capability through FMCW modulation, and transmits data payloads including identity codes and additional information about the attached structure. This single device replaces multiple separate systems
3Reliability
If the receive and transmit antennas operate with the same polarization, then signal strength is maximized, but self-oscillation interference occurs
Solution Approach 1:
The receive and transmit antennas are designed with asymmetric polarization characteristics. The transmit antenna radiates with one polarization (e.g., horizontal), while the receive antenna is optimized for the orthogonal polarization (e.g., vertical). This asymmetric design prevents the transmitted signal from coupling back into the receive antenna, eliminating self-oscillation while maintaining adequate signal strength through the orthogonal polarization relationship
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 enables precise range measurement and data transmission, allowing for accurate identification and positioning of targets with improved signal processing, reducing interference and enhancing the ability to distinguish target returns from background noise, thereby achieving the required accuracy of 1 meter or less.
Implementation Method 1
a receive antenna for receiving a radar signal, an amplifier for amplifying the signal, and a transmit antenna for retransmitting the amplified signal
Implementation Method 2
wherein the receive and transmit antennas operate with orthogonally polarised radar signals
Implementation Method 3
a single sideband modulator for receiving the identity code and modulating the radar signal with at least the identity code prior to retransmission of the amplified signal
Data Source
Figure 1
Figure 2a~2b
Figure 3
AI summary
An active radar target comprising: a receive antenna for receiving a radar signal, an amplifier for amplifying the signal, and a transmit antenna for retransmitting the amplified signal, characterised in that the active radar target further includes a memory for storing an identity code or means for receiving an identity code, a modulator for receiving the identity code and modulating the radar signal with at least the identity code prior to retransmission of the amplified signal, and wherein the modulator is a single sideband modulator.