Multi-Target Detection Method Based on Variable Carrier Frequency Chirp Sequence

Abstract

Continuous waveform (CW) radar is widely used in intelligent transportation systems, vehicle assisted driving, and other fields because of its simple structure, low cost and high integration. There are several waveforms which have been developed in the last years. The chirp sequence waveform has the ability to extract the range and velocity parameters of multiple targets. However, conventional chirp sequence waveforms suffer from the Doppler ambiguity problem. This paper proposes a new waveform that follows the practical application requirements, high precision requirements, and low system complexity requirements. The new waveform consists of two chirp sequences, which are intertwined to each other. Each chirp signal has the same frequency modulation, the same bandwidth and the same chirp duration. The carrier frequencies are different and there is a frequency shift which is large enough to ensure that the Doppler frequencies for the same moving target are different. According to the sign and numerical relationship of the Doppler frequencies (possibly frequency aliasing), the Doppler frequency ambiguity problem is solved in eight cases. Theoretical analysis and simulation results verify that the new radar waveform is capable of measuring range and radial velocity simultaneously and unambiguously, with high accuracy and resolution even in multi-target situations.

An Elaborated Signal Model for Simultaneous Range and Vector Velocity Estimation in FMCW Radar

“…For correct use of the method of two-dimensional Fourier transform [ 19 , 20 , 21 ] and an unambiguous estimate of the velocity vector of a radar target, it is necessary that the phase change Φ V ( kT c ), calculated on the local time interval [0 ≤ t L ≤ T c ], does not exceed the value π. This requirement determines that the point θ belongs to the three-dimensional subspace Θ ( 3) 2 of the measured parameters { V R , V TR , R 2 } in the relation Equation (34).…”

“…The second method of simultaneous estimation of target speed and range is based on the use of two-dimensional (2D) Fourier transform [ 20 , 21 , 22 ]. It is easy to show that the dynamic range of measured velocities and distances using this method is proportional to the sampling rate f s of the analog IF signal: where R max and δR —maximum range and range resolution respectively, c —speed of light, V R max —maximum radial component of target velocity, f D max —Doppler frequency shift, that corresponds to maximum velocity V R max , and f 0 —the initial frequency of the radiated chirp radio signal.…”

Perception Sensors for Road Applications

“…There are several waveforms and the chirp sequence waveform has the ability to extract the range and velocity parameters of multiple targets. Reference [6] proposes a new waveform that follows the practical application requirements, high precision requirements, and low system complexity requirements. Theoretical analysis and simulation results verify that the new radar waveform is capable of measuring the range and radial velocity simultaneously and unambiguously, with high accuracy and resolution even in multi-target situations.…”

Millimeter Wave Radar for Intelligent Transportation Systems: a Case Study of Multi-Target Problem Solution

“…For solving such problems, sensor systems based on radar technology are currently widely used [15,16]. In this regard, the urgent task is to detect and filter false targets when using millimeter-wave radars [17][18][19][20]. Millimeter-wave radar systems for automotive application include pulse radar, frequency-modulated continuous-wave (FMCW) radar and spread spectrum radar.…”