Vehicle Synthetic Aperture Radar Phase Correction
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Solution Overview
Problem
Vehicle radar systems face challenges in efficiently using antenna aperture and reliably compensating for phase shifts due to object movement, leading to potential angle distortion and limited Doppler Nyquist.
Innovation Solution
A vehicle radar system that generates and transmits two FMCW chirp signals with interleaved frequency ramps, calculating velocity compensation factors to correct phase shifts and maximize signal integration gain, thereby increasing antenna aperture and Doppler resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If two transmitting antenna arrays are activated with a time offset to produce a synthetic aperture, then the antenna aperture is increased, but angle distortion occurs due to object movement between activation of the antennas
Solution Approach 1:
The patent applies preliminary action by calculating and applying a Doppler phase correction factor before performing the azimuth FFT processing. The correction factor is computed based on the synthetic aperture configuration and object velocity, pre-compensating for the phase shifts that would otherwise cause angle distortion. This allows the synthetic aperture to be fully utilized while maintaining accurate angle measurement.
Solution Approach 2:
The patent implements feedback by using the measured Doppler velocity information to dynamically adjust the phase correction applied to the received signals. The system continuously monitors object velocity and uses this information to compute appropriate correction factors, creating a closed-loop system that adapts to changing conditions and maintains measurement accuracy.
2Device complexity
If a single Doppler correction factor is used for all targets in a Range-Doppler cell, then processing is simplified, but the correction is only accurate for targets with the exact same Doppler frequency
Solution Approach 1:
The patent applies local quality by computing separate Doppler correction factors for different azimuth angles rather than using a single uniform correction factor. Each azimuth bin receives a correction factor tailored to its specific characteristics and the expected velocity distribution in that direction. This allows accurate correction for targets with different Doppler frequencies while maintaining manageable processing complexity through the structured approach.
3Reliability
If the transmission time of an individual antenna is limited to maintain Doppler Nyquist, then Doppler aliasing is avoided, but the effective aperture and bearing quality are reduced
Solution Approach 1:
The patent applies dimensionality change by transitioning from a single-antenna time-domain limitation to a multi-antenna space-time solution. By activating multiple antennas in an interleaved manner and processing the combined signals through synthetic aperture techniques, the system effectively increases the time bandwidth product without violating the Doppler Nyquist criterion for any individual antenna transmission. This resolves the contradiction by utilizing the spatial dimension to compensate for temporal constraints.
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 solution effectively utilizes antenna aperture for improved bearing quality and doubles Doppler Nyquist frequency by selecting the azimuth angle with the highest signal integration gain, enhancing detection capabilities.
Implementation Method 1
A SAR is described in US 2014/0306840, where one example discloses a distance D between the phase centre of the outermost receiving antennas, and where the two transmitting antennas are arranged a distance D+dx apart, where dx is the distance between the phase centers of two adjacent receiving antennas. The resulting synthetic aperture has no overlapping antenna elements, presenting an efficient use of the antenna aperture.
Implementation Method 2
A vehicle radar system comprising at least one transceiver arrangement arranged to generate, transmit two FMCW (Frequency Modulated Continuous Wave) chirp signals, and to receive reflected signals.
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The present disclosure relates to a vehicle radar system (3) arranged to generate and transmit two FMCW chirp signal frequency ramps (4a, 4b). At least one transmitter antenna arrangement (10a) is arranged to transmit a first chirp signal (4a) at first times (t1(n)), and at least one other spatially separated transmitter antenna arrangement (10b) is arranged to be activated to transmit a second chirp signal (4b) at second times (t2(n)) in an interleaved and repeated manner. The system (3) is arranged to calculate: - a first velocity compensation factor VC1 according to: Vc1=4⋅π⋅vtarget⋅tr+tDλ, where vtarget is the object's speed, tr is the duration time for a frequency ramp and tD is a delay time between two consecutive frequency ramps; and - a second velocity compensation factor VC2 according to: Vc2=4⋅π⋅vtarget⋅tr+tDλ+π, and to choose the azimuth angle that has the highest signal integration gain. The present disclosure also relates to a corresponding method.