MIMO Radar STBC Coding for Cross-Correlation Noise Cancellation
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Solution Overview
Problem
Radar systems face challenges in distinguishing between signals from moving targets and stationary objects due to cross-correlation noise, which leads to false detections or missed targets, as reflected energy from stationary objects can interfere with the detection of moving targets.
Innovation Solution
The use of complementary complex sequences in space-time block codes for MIMO radar systems enables orthogonality between transmit antennas, allowing for the cancellation of cross-correlation noise and improving the dynamic range in range domain measurements by employing space-time block codes (STBC) and space-frequency block codes (SFBC), which do not use zeros in the transmitted signal code.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If cross-correlation processing is used to detect targets, then target detection capability is improved, but cross-correlation noise from stationary objects increases leading to false detections
Solution Approach 1:
The patent converts the harmful cross-correlation noise from stationary objects into a beneficial signal by using the same noise component in subsequent processing steps. The system transmits orthogonal waveforms that generate predictable cross-correlation patterns, then uses these patterns to identify and remove stationary clutter while preserving moving target signals. This transforms the harmful interference into a useful reference for noise cancellation.
Solution Approach 2:
The patent applies different signal processing treatments to different components of the received signal. Moving target signals and stationary clutter signals are separated and processed differently - the stationary components are identified through their characteristic cross-correlation properties and selectively removed, while moving target components are preserved. This local differentiation in signal treatment resolves the contradiction by targeting only the harmful noise while maintaining target detection capability.
2Productivity
If orthogonal waveforms are used on different transmit antennas, then fast illumination and high angular resolution are achieved, but nonzero cross-correlation side lobes cause energy leakage and increased noise level
Solution Approach 1:
The patent implements a feedback mechanism where the system first transmits orthogonal waveforms to illuminate the scene, then uses the received signals to estimate cross-correlation side lobe levels and stationary clutter characteristics. This information is fed back into the signal processing chain to adjust the cancellation filters and refine the separation between stationary and moving components. The feedback loop continuously optimizes the noise cancellation while preserving the benefits of fast illumination.
Solution Approach 2:
The patent segments the received signal into stationary clutter components and moving target components based on their different cross-correlation properties. By dividing the signal processing into separate channels - one for estimating and canceling stationary noise, another for detecting moving targets - the system achieves both fast illumination through orthogonal waveforms and low noise levels through selective cancellation of side lobe energy.
3Ease of operation
If conventional binary codes are used in MIMO radar, then transmit orthogonality is achieved, but cross-correlation energy leakage occurs between sequences
Solution Approach 1:
The patent uses composite signal structures that combine multiple orthogonal code sequences with carefully designed correlation properties. Instead of using simple binary codes, the system employs composite waveforms that maintain orthogonality for fast illumination while having minimized cross-correlation side lobes. These composite signals integrate multiple code families or modified code structures that suppress energy leakage between sequences, thereby maintaining both ease of operation and measurement precision.
Data Source
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Figure 3A~3B
AI summary
A radar system comprises a plurality of transmit antennas that transmit a radar signal toward a target, wherein each transmit antenna transmits its signal using a different space-time block code in a given transmission time slot. In one embodiment, no two transmit antennas transmit using the same space-time block code in the same transmission time slot.