MIMO Radar Phase Modulation for Velocity Axis Spur Reduction
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Solution Overview
Problem
Inaccurate transmit phase shifters in MIMO radar systems lead to the generation of spurs along the velocity axis, limiting the number of transmitters that can be switched on simultaneously and causing confusion between actual targets and spurs.
Innovation Solution
A radar apparatus and method that employs a phase modulation scheme combining unique phase code sequences with a scrambling phase code sequence, distributing phase modulator errors evenly over the unit circle, allowing for improved separation of signals from multiple transmit channels using Doppler Division Multiplexing (DDM).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Doppler Division Multiplexing (DDM) is used to separate signals from multiple transmit channels, then signal separation capability is improved, but transmit phase shifter inaccuracy generates spurs along the velocity axis
Solution Approach 1:
The patent applies preliminary action by pre-modulating each transmit channel with a unique phase code sequence before transmission. This preliminary modulation embeds channel identification information into the transmitted signals, enabling the receiver to separate signals from different transmit channels even in the presence of phase shifter inaccuracies. The phase codes are assigned in advance to each transmit channel, creating a structured modulation pattern that facilitates later signal separation.
Solution Approach 2:
The patent changes the phase parameter of the transmitted FMCW chirps by modulating each transmit channel with different phase code sequences. This parameter change (phase modulation) transforms the signals in a way that makes them distinguishable at the receiver. By varying the phase parameter according to predefined codes, the system enables signal separation while the scrambling further distributes phase errors to reduce spur generation.
2Productivity
If more transmitters are switched on simultaneously to improve radar performance, then detection capability is improved, but phase shifter inaccuracy causes confusion between actual targets and spurs
Solution Approach 1:
The patent applies preliminary action by pre-modulating each transmit channel with a unique phase code sequence before transmission. This preliminary modulation embeds channel identification information into the transmitted signals, enabling the receiver to separate signals from different transmit channels even in the presence of phase shifter inaccuracies. The phase codes are assigned in advance to each transmit channel, creating a structured modulation pattern that facilitates later signal separation.
Solution Approach 2:
The patent introduces phase code sequences as an intermediary mechanism between the transmit channels and the received signals. These phase codes act as mediators that carry channel identification information through the transmission medium. At the receiver, these intermediary phase codes enable the separation and identification of signals from different transmit channels, preventing confusion between actual targets and spurs even when multiple transmitters operate simultaneously.
3Measurement precision
If unique phase code sequences are assigned to each transmit channel for signal separation, then channel identification is improved, but phase modulator errors are amplified without scrambling
Solution Approach 1:
The patent introduces phase code sequences as an intermediary mechanism between the transmit channels and the received signals. These phase codes act as mediators that carry channel identification information through the transmission medium. At the receiver, these intermediary phase codes enable the separation and identification of signals from different transmit channels, preventing confusion between actual targets and spurs even when multiple transmitters operate simultaneously.
Solution Approach 2:
The patent changes the phase parameter of the transmitted FMCW chirps by modulating each transmit channel with different phase code sequences. This parameter change (phase modulation) transforms the signals in a way that makes them distinguishable at the receiver. By varying the phase parameter according to predefined codes, the system enables signal separation while the scrambling further distributes phase errors to reduce spur generation.
Data Source
AI summary
A radar apparatus includes a transmitter circuit. The transmitter circuit is configured to transmit, via a first transmit channel, a first sequence of FMCW radar chirps, and to transmit, via at least a second transmit channel, a second sequence of FMCW radar chirps concurrently with the first sequence of FMCW radar chirps. The radar apparatus includes a control circuit configured to control the first and second transmit channels to set phases of the FMCW radar chirps of the first and second sequences in accordance with a phase modulation scheme that includes a first unique phase code sequence assigned to the first sequence of FMCW radar chirps, and a second unique phase code sequence assigned to the second sequence of FMCW radar chirps. The first unique phase code sequence is combined with a scrambling phase code sequence. The second unique phase code sequence is combined with the scrambling phase code sequence.