Interference of chirp sequence radars by OFDM radars at 77 GHz

Abstract

Abstract-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.

Radar Sensors for Autonomous Driving: Modulation Schemes and Interference Mitigation

“…In the baseband frequency spectrum the noise floor is raised compared to an interference-free frequency ramp. radars also leads to an increased overall noise level in both system types [74,75]. While an OFDM signal is affected by the full FMCW or chirp-sequence signal power, a linear frequency modulated radar is only disturbed by that part of the OFDM signal that falls into the receiver bandwidth, cf.…”

“…The interference power in the FMCW or chirp-sequence receiver is proportional to the area indicated by the gray parallelogram in Fig. 12 [75].…”

Mutual Interference of Automotive OFDM Radars—Analysis and Countermeasures

“…Furthermore, compressed-sensing techniques can be used to estimate missing signal parts [3], [4], and signal repairment based on linear prediction is possible [5]. In [6] the interference from OFDM to FMCW is studied theoretically with the conclusion that OFDM interference on chirp-sequence radars can be regarded as additional noise. A broad overview of automotive radar interference including a summary on mitigation possibilities is presented in [7].…”

Impact of Interference on OFDM based Radars

“…However, most of the active radars use different waveforms such as Frequency Modulated Continuous Wave (FMCW), instead of Orthogonal Frequency-Division Multiplexing (OFDM) modulation. In [5], the impact of interference between two active radars that use OFDM and FMCW waveforms is studied. It is concluded that an interfering OFDM waveform increases the noise floor of an FMCW radar.…”