Tx Beamformer Using SVD Spatial Codewords for Doppler Ambiguity
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Solution Overview
Problem
In MIMO radar systems, as the number of transmit antennas increases, the length of codewords and repetition interval also increase, leading to ambiguity in velocity estimation (Doppler frequency) due to the need for equal numbers of symbols in the sequence to separate transmission channels.
Innovation Solution
A method for transmit beamforming using a singular value decomposition (SVD) of a coding matrix to generate a transmit signal matrix with spatial codewords, allowing for beamforming over a desired field-of-view with fewer spatial codewords in each repetition sequence, reducing ambiguity in Doppler frequency estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of transmit antennas increases to improve spatial resolution and field-of-view coverage, then the measurement precision and adaptability improve, but the codeword length and repetition interval increase causing Doppler frequency estimation ambiguity
Solution Approach 1:
The patent segments the codeword transmission by dividing the field-of-view into multiple sectors, each handled by a different subset of transmit antennas. This allows shorter codewords to be transmitted in parallel across different spatial sectors, reducing the overall repetition interval while maintaining coverage of the entire field-of-view through the combined effort of all antenna segments.
Solution Approach 2:
The patent introduces a spatial dimension to the codebook design by assigning different spatial codewords to different angular sectors. This dimensional approach allows the system to multiplex transmissions across both time and space, enabling shorter repetition intervals while maintaining the ability to separate channels through spatial processing at the receiver.
2Adaptability or versatility
If the number of transmit antennas increases to improve field-of-view coverage, then the adaptability improves, but the codeword length increases leading to Doppler frequency ambiguity
Solution Approach 1:
The codebook is segmented into multiple spatial codewords, each optimized for a specific angular sector. This segmentation allows the system to cover a wide field-of-view using shorter individual codewords rather than requiring one long codeword to cover the entire angular range, thereby reducing Doppler frequency ambiguity while maintaining comprehensive coverage.
Solution Approach 2:
The patent creates a universal codebook structure where the same set of spatial codewords can be reused across multiple transmit antennas and different time intervals. This multi-functional codebook design allows the system to achieve wide field-of-view coverage without proportionally increasing codeword length, as the same codewords serve multiple spatial and temporal purposes.
3Measurement precision
If orthogonal waveforms are transmitted from multiple antennas to improve target detection, then the measurement precision improves, but the repetition interval increases causing velocity estimation ambiguity
Solution Approach 1:
The orthogonal waveform transmission is segmented across multiple spatial sectors, with each sector using a subset of antennas transmitting shorter codewords simultaneously. This segmentation maintains the orthogonality and detectability benefits of multiple waveforms while reducing the time required for each transmission sequence, thereby reducing repetition interval and Doppler ambiguity.
Solution Approach 2:
The patent enables continuous useful action by overlapping transmissions across different spatial sectors and time intervals. While one set of antennas transmits in one sector, other antennas simultaneously transmit in different sectors, ensuring that the radar system continuously collects useful echo data without waiting for complete sequences to finish, thus reducing effective repetition interval.
Data Source
AI summary
A method for transmit beamforming in a MIMO antenna for a radar system having N transmit antennas includes acquiring a coding matrix defining a desired field-of-view, generating a transmit signal matrix based on a singular value decomposition (SVD) of the coding matrix, wherein the columns of the transmit signal matrix are transmit signal vectors formed from the singular vectors corresponding to the maximal singular values of the coding matrix based on the SVD, the transmit signal vectors defining spatial codewords, and transmitting signals in sequences over the N transmit antennas according to the transmit signal matrix, the sequences correspond to the spatial codewords from the transmit signal vectors, wherein each sequence is defined by a number of spatial codewords transmitted in a single repetition sequence interval, and wherein transmitting the spatial codewords according to the transmit signal matrix enables beamforming of the transmitted signals to the desired field-of-view.