Dual-polarized MIMO radar
A radar system with a transmit pipeline transmitting radio signals, and with a receive pipeline receiving radio signals including radio signals transmitted by own transmitters and reflected from objects in an environment, and interfering radio signals transmitted by other radar systems. The receive pipeline provides interference immunity from interfering radio signals transmitted by other radar systems. The transmit pipeline and/or the receive pipeline avoid transmitting radio signals that interfere with the other radar systems. The receive pipeline includes dual polarization receive channels. The interfering radio signals are a different polarization than the radio signals transmitted by own transmitters and reflected from targets in the environment. The receive pipeline provides improved signal handling dynamic range to avoid receive channels saturating at A-to-D converter stage before the radio signal has reached the digital signal processing domain.
1 . A radar system comprising:
a transmit pipeline comprising a plurality of transmitters configured to transmit radio signals; and
a receive pipeline comprising a plurality of receivers configured to receive radio signals that include (i) first radio signals transmitted by the plurality of transmitters and reflected from objects in an environment, and (ii) other radio signals that include second radio signals transmitted by at least one external transmitter distinct from the plurality of transmitters, wherein the second radio signals are unknown to the receive pipeline;
wherein the receive pipeline comprises dual polarization receive channels configured to receive radio signals with corresponding polarizations, such that at least the first radio signals and the second radio signals are received with different respective polarizations;
a signal analysis module configured to predict anticipated receive channel radio signals to be received based upon previously received receive channel radio signals, wherein the anticipated receive channel radio signals are defined at least in part by the previously received second radio signals, wherein the signal analysis module is configured to generate an interference prediction signal defined at least in part by the second radio signals, and wherein the signal analysis module is configured to perform correlation transforms comprising a fast Fourier transform combined with a Walsh-Fourier transform on the received receive channel radio signals to predict the anticipated receive channel radio signals to be received, and wherein correlation transforms and beamforming transforms are performed for each polarization; and
a summing junction configured to subtract the interference prediction signal from the received radio signals to reduce interference from the second radio signals transmitted by the at least one external transmitter;
wherein the receive pipeline is configured to provide interference immunity from the second radio signals transmitted by the at least one external transmitter, such that interference from the second radio signals transmitted by the least one external transmitter is mitigated based at least in part upon polarization differences and the interference prediction signal.
2 . The radar system of claim 1 , wherein the first radio signals have a first polarization, and wherein the second radio signals have a second polarization that is different from the first polarity.
3 . The radar system of claim 2 , wherein the dual polarization receive channels of the receive pipeline are configured to process the first radio signals separately from the second radio signals.
4 . The radar system of claim 1 , wherein the at least one external transmitter is a transmitter in a chirp radar.
5 . The radar system of claim 1 , wherein the at least one external transmitter is part of another radar system, and wherein the transmit pipeline is configured to avoid transmitting radio signals that interfere with the other radar system.
6 . The radar system of claim 1 , wherein the receive pipeline is configured to increase a signal handling dynamic range, wherein the increase in signal handling dynamic range is defined by the range necessary to avoid receive channels of the receive pipeline saturating at a respective first analog-to-digital (A-to-D) converter stage for each receive channel before the radio signal has reached the digital signal processing domain.
7 . The radar system of claim 6 further comprising:
a coarse digital-to-analog (D-to-A) converter configured to D-to-A convert the predicted receive channel radio signals into analog predicted signals; and
the summing junction configured to subtract the analog predicted signals from the received radio signals to produce residual signals, wherein the residual signals presented to the respective first A-to-D converter stages are of a reduced amplitude but still filling the dynamic range of the first A-to-D converter stages.
8 . The radar system of claim 7 further comprising a re-addition module configured add a digital value to digital outputs of the first A-to-D converter stages, wherein the digital value is defined by the analog predicted signals which were subtracted by the summing junction.
9 . The radar system of claim 7 , wherein the summing junction is configured to receive downconverted radio signals, wherein the downconverted radio signals are downconverted to the (I,Q) baseband.
10 . The radar system of claim 1 , wherein the signal analysis module is configured to determine a spatial direction of at least a portion of the second radio signals, and wherein the interference prediction signal is defined at least in part by the determined spatial direction of at least a portion of the second radio signals.
11 . A method for receiving radio signals and mitigating received interference signals, the method comprising:
transmitting, with a transmit pipeline that comprises at least one transmitter, radio signals;
receiving, with a receive pipeline that comprises at least one receiver, radio signals that include (i) first radio signals transmitted by the at least one transmitter and reflected from objects in an environment, and (ii) other radio signals that include second radio signals transmitted by at least one external transmitter distinct from the at least one transmitter, wherein the receiver is a dual polarization receive channel configured to receive radio signals with corresponding polarizations, and wherein the second radio signals are unknown to the receive pipeline;
predicting anticipated receive channel radio signals to be received based upon previously received receive channel radio signals, wherein the anticipated receive channel radio signals to be received are defined at least in part by the previously received second radio signals, and further comprising generating an interference prediction signal defined at least in part by the second radio signals, and wherein predicting anticipated receive channel radio signals to be received based upon previously received receive channel radio signals comprises performing correlation transforms comprising a fast Fourier transform combined with a Walsh-Fourier transform on the received receive channel radio signals to predict the anticipated receive channel radio signals to predict the anticipated receive channel radio signals to be received, and wherein the correlation transforms and beamforming transforms are performed for each polarization;
subtracting the interference prediction signal from the received radio signals to reduce interference from the second radio signals transmitted by the at least one external transmitter; and
mitigating interference in the received radio signals by separately processing the first radio signals and the second radio signals, such that interference from the second radio signals transmitted by the at least one external transmitter is mitigated based at least in part upon polarization differences and the interference prediction signals.
12 . The method of claim 11 , wherein the first radio signals have a first polarization, and wherein the second radio signals have a second polarization that is different from the first polarity.
13 . The method of claim 11 , wherein separately processing the first and second radio signals comprises separately processing, with the dual polarization receiver, the first radio signals with the first polarization from the second radio signals with the second polarization.
14 . The method of claim 11 , wherein the at least one external transmitter is a transmitter of a chirp radar.
15 . The method of claim 11 further comprising increasing a signal handling dynamic range of the received radio signal as defined by the range necessary to avoid saturating receive channels of the receive pipeline at a first digital (A-to-D) converter stage.
16 . The method of claim 15 further comprising:
digital-to-analog converting the predicted receive channel radio signals into analog predicted signals; and
subtracting the analog predicted signals from the received radio signals to produce residual signals, wherein the residual signals presented to the first A-to-D converter stage are of a reduced amplitude but still filling the dynamic range of the first A-to-D converter stage.
17 . The method of claim 16 further comprising adding a digital value to digital outputs of the first A-to-D converter stage, wherein the digital value is defined by the analog predicted signals which were subtracted.
18 . The method of claim 16 , wherein the analog predicted signals are subtracted from the received radio signals which have been downconverted into the (I,Q) baseband.