This document describes techniques and systems for asymmetrical frequency-division multiplexing (FDM) for radar systems. In some examples, a radar system includes multiple transmitters, multiple receivers, multiple polyphase shifters, and a processor. The transmitters can transmit electromagnetic (EM) signals in an FDM scheme. The receivers can receive EM signals reflected by one or more objects that include multiple channels. The polyphase shifters can introduce at least four potential phase shifts. The processor can control the polyphase shifters to introduce phase shifts asymmetrically spaced in a frequency spectrum. The processor can determine, using residue estimation and subtraction, potential detections of the objects. In this way, the described asymmetrical FDM for radar systems can support many simultaneous MIMO channels, increase the dynamic range of the radar system, resolve Doppler ambiguities, and provide an efficient processing scheme.

A method for a radar system is presented, for detecting the surroundings using transmission means for emitting transmission signals which contain a sequence of at least approximately identical individual signals, the sequence of individual transmission signals being repeated cyclically, said method being characterized in that over the sequence of the individual signals the frequency position thereof—optionally apart from a varying and at least approximately mean value-free component—is changed at least approximately linearly and, in the process, the slope of the linear frequency position change over the individual transmission signals is at least sometimes varied from sequence to sequence, in particular in order to increase the radial distance and/or relative speed measurement accuracy and/or in order to be more robust in respect of interference with other radar systems.

A method for controlling a radar system is presented, for detecting the surroundings using transmission means for emitting transmission signals which contain a sequence of at least approximately identical individual signals, the sequence of individual transmission signals being repeated cyclically, said method being characterized in that over the sequence of the individual signals the frequency position thereof—optionally apart from a varying and at least approximately mean value-free component—is changed at least approximately linearly and, in the process, the slope of the linear frequency position change over the individual transmission signals is at least sometimes varied from sequence to sequence, in particular in order to increase the radial distance and/or relative speed measurement accuracy and/or in order to be more robust in respect of interference with other radar systems.

A method for operating a radar sensor system including multiple radar sensors operating independently of one another in a motor vehicle, wherein the radar sensors are synchronized with one another with respect to their transmission times and transmission frequencies in such a way that two radar signals whose frequency separation is smaller than a certain minimum frequency separation are at no point in time transmitted simultaneously.

A radar sensor system is provided. The radar sensor system includes: at least two radar sensors each having at least one transmitter and at least one receiver, detection regions of the two radar sensors overlapping at least partially. The two radar sensors are situated at a defined distance from one another. Transmit signals of the two radar sensors are synchronizable in such a way that radiation of one radar sensor that was emitted by the respective other radar sensor and reflected by an object is capable of being evaluated by an evaluation device.

In accordance with an embodiment, a method of operating a radar system includes activating a transmitter to transmit a radar signal during a first time period, receiving a reflection of the radar signal from a radar antenna, downconverting the reflected radar signal, and digitally processing the downconverted reflected radar signal within a first frequency bandwidth using a first signal path. The method also includes deactivating the transmitter during a second time period, receiving a second signal from the radar antenna during the second time period, downconverting the second signal, measuring a power of the downconverted second signal within a second frequency bandwidth using a second signal path different from the first signal path, and determining an interference metric based on measuring the power.

A detection method includes determining a first frequency point of N frequency points, transmitting a radio signal in a first frequency band in N frequency bands. One of the N frequency bands partially overlaps at least one frequency band in other N−1 frequency bands, and an absolute value of a difference between lowest frequencies of any two frequency bands of the N frequency bands is not less than a first threshold (F), or the N frequency bands have at least one second frequency band that partially overlaps the first frequency band, and an absolute value of a difference between a lowest frequency of each second frequency band and a lowest frequency of the first frequency band is not less than F.

A stepped frequency radar system is disclosed. The system includes components for performing stepped frequency scanning across a frequency range using frequency steps of a step size, the stepped frequency scanning performed using at least one transmit antenna and a two-dimensional array of receive antennas, changing at least one of the step size and the frequency range, and performing stepped frequency scanning using the at least one transmit antenna and the two-dimensional array of receive antennas and using the changed at least one of the step size and the frequency range.

A method of microwave motion detection with adaptive frequency control, for a microwave motion sensor, comprises suppressing output of the first detecting signal generated with a first frequency, determining whether a first interference signal is detected in the first frequency during the suppressing, responsive to that the first interference signal is detected in the first frequency, generating a second detecting signal with a second frequency, which is different from the first frequency, and suppressing output of the second detecting signal, determining whether a second interference signal is detected in the second frequency during the suppressing, and responsive to that the second interference signal is not detected in the second frequency, outputting the second detecting signal for motion detection. The microwave motion sensor is operated in a normal mode or in a detection mode according to the first detecting signal, a reflected signal, the second detecting signal and an interference signal.

A novel and useful system and method by which radar angle and range resolution are significantly improved without increasing complexity in critical hardware parts. A multi-pulse methodology is described in which each pulse contains partial angular and range information consisting of a portion of the total CPI bandwidth, termed multiband chirp. Each chirp has significantly reduced fractional bandwidth relative to monoband processing. Each chirp contains angular information that fills only a portion of the ‘virtual array’, while the full virtual array information is contained across the CPI. This is done using only a single transmission antenna per pulse, thus significantly simplifying MIMO hardware realization, referred to as antenna-multiplexing (AM). Techniques for generating the multiband chirps as well as receiving and generating improved fine range-Doppler data maps. A windowing technique deployed in the transmitter as opposed to the receiver is also disclosed.