Jonathan Bechter

Analytical and Experimental Investigations on Mitigation of Interference in a DBF MIMO Radar

As driver assistance systems and autonomous driving are on the rise, radar sensors become a common device for automobiles. The high sensor density leads to the occurrence of interference, which decreases the detection capabilities. Here, digital beamforming (DBF) is applied to mitigate such interference. A DBF system requires a calibration of the different receiving channels. It is shown how this calibration completely changes the DBF beam pattern required to cancel interferences, if the system has no IQ receiver. Afterward, the application of DBF on a multiple-input multiple-output (MIMO) radar is investigated. It is shown that only the real aperture and not the virtual one can be used for interference suppression, leading to wide notches in the pattern. However, for any target the large virtual aperture can be exploited, even if interferers are blinded out. Moreover, the wide notches for interference suppression of the real aperture appear narrow in the virtual aperture for target localization. The results are verified by measurements with time-multiplexing MIMO radar.

Bats-inspired frequency hopping for mitigation of interference between automotive radars

It was reported for specific bats, that they use a certain scheme to shift the frequencies of their echo location calls to counteract interferences with conspecifics. As in road traffic, an increasing number of cars is equipped with radar sensors, there is also the problem of mutual interference. The available frequency bands are limited, so a randomized frequency hopping will not be the best solution. In this paper, we adapt the frequency hopping behavior of the bats reported in [1] to a radar system. We discuss the algorithm and show measurements of its performance in an anechoic chamber.

Blind Adaptive Beamforming for Automotive Radar Interference Suppression

Radar sensors offer enormous advantages as sensing devices for automated and autonomous driving. However, when multiple of such sensors are operated in a large number of cars, there is a high risk of the occurrence of mutual interference. In the currently widespread linearly frequency modulated sensors interference reduces the detection performance, especially for targets with a low radar cross section. In this paper the interference effects are suppressed with an adaptive beamforming scheme based on a mean square error minimization. The paper evaluates the algorithm with the help of a simulated and measured scenario, and discusses the occurring interference effects and the benefits of the beamforming approach.

Estimation and cancellation of interferences in automotive radar signals

Radar sensors become typical components for automotive driver assistance systems and autonomous driving. The widespread use of this sensor type leads to an increasing risk of unwanted interferences. Those interferences can severely degrade the detection performance and cause sensor blindness. To overcome this problem, this paper describes a method to estimate and remove interfering signals in data of chirp sequence modulated radars. The estimation is derived theoretically and applied on simulation and measurement data.

Ghost target identification by analysis of the Doppler distribution in automotive scenarios

In an automotive environment the presence of reflecting surfaces cannot be avoided. The electromagnetic wave returning from a target vehicle can get reflected on those surfaces causing a non existing so-called ghost target. For driver assistance systems ghost targets can lead to false decisions and, therefore, they should be detected and avoided. In this paper a model for describing those ghost targets and a procedure to distinguish them from real targets using the orientation and the motion state of a vehicle is presented.

Automotive radar interference mitigation using a sparse sampling approach

The application of radar sensors for driver assistance systems and autonomous driving leads to an increasing probability of radar interferences. Those interferences degrade the detection capabilities and can cause sensor blindness. This paper uses a realistic road scenario to address the problems of a common countermeasure that simply removes interference-affected parts of time domain radar signals and thereby introduces a gap. The paper solves the problem with the application of a sparse sampling signal recovery algorithm that is also used for compressed sensing problems. It is shown that the signal recovery can clearly overcome the shortcomings of just removing interfered signal parts. In the end of the paper, the applicability of the used algorithm is verified with measured radar data.

Compensation of motion-induced phase errors in TDM MIMO radars

For high-resolution direction of arrival estimation, a wide aperture is necessary. This can be achieved with multiple-input multiple-output radars, which offer a wide virtual aperture. However, the requirement of orthogonal transmit signals has to be satisfied for their operation. Although time division multiplexing of the transmit elements is an orthogonality realization with low hardware effort, phase errors occur in nonstationary scenarios. This letter briefly discusses the problem of the motion-induced phase errors and describes processing steps to mitigate them without additional effort. The proposed technique is demonstrated with simulation and measurement data.

Interference of chirp sequence radars by OFDM radars at 77 GHz

Radar sensors are common devices in daily traffic, especially for driver assistance and automotive safety systems. A high sensor density increases the probability of interferences, especially when the sensors occupy a large radar bandwidth. Many current sensors, e.g. chirp sequence radars, rely on frequency modulation schemes. A promising future radar concept applies orthogonal frequency division multiplexing (OFDM). This paper investigates the interference effect of an OFDM radar on a chirp sequence radar. Potential interference levels are derived and the influence of modulation parameters is evaluated with simulations.