# A Waveform and Velocity Ambiguity Resolution Method for Corner Radar
###### Abstract  
Millimeter-wave radar is experiencing an increasing demand for higher resolution and elevation measurement, necessitating its evolution from 3D millimeter-wave radar systems to 4D millimeter-wave radar. Unlike front automotive radar, corner radar is particularly interested in close-range targets. This article proposes a composite waveform tailored for automotive corner radar, employing different waveform schemes for various distances. This allows millimeter-wave angle radar to achieve superior range resolution and velocity resolution in the close and medium ranges. However, enhancing velocity resolution inevitably results in a reduction in the maximum unambiguous velocity. Consequently, a velocity ambiguity resolution method based on target parameter matching for front and rear frames is proposed to address this issue. The feasibility of the composite waveform and method are verified through simulation. Finally, a radar designed with the ALPS PRO chip is employed to test the designed waveform and velocity ambiguity resolution method, yielding results that are largely consistent with the simulation outcomes. The findings indicate a notable enhancement in resolution for medium distances ranging from 60 to 100 m when employing the proposed waveform. Moreover, the velocity ambiguity resolution method effectively resolves velocity ambiguity, leading to enhanced accuracy in velocity measurements. This suggests that the composite waveform and algorithm are well suited for current automotive angle radar applications.  
millieter wave radar; multi-mode waveform; maximum unambiguous velocity; velocity ambiguity resolution method +
Footnote †: journal: Applied  
0000-0002-4000-0000-0000-0000-0000-0000-0000-0000-0000-0000-0000-0000-00000-0000-00000-00000-00000-00000-00000-00000-00000-00000-000000  
velocity ambiguities through energy matching, as well as a velocity disambiguation method based on Doppler phase offset compensation. [PERSON] proposed a stepped chirp design aimed at enhancing range resolution [11]. While the literature has demonstrated success in disambiguating target velocity, reference [8] is applicable solely to single-transmitter and multiple-receiver radar systems and is not compatible with the prevalent multi-transmitter and multiple-receiver radar systems. The target matching method outlined in reference [9] is effectively applicable in TI's first-generation TDMA (Time Division Multiple Access) radar; however, for DDMA (Doppler Division Multiple Access) transmission systems, TI (Texas Instruments) offers only one method in its subsequent product lines. The waveform described in reference [11] can enhance resolution without necessitating bandwidth expansion but introduces complex motion phase compensation challenges [12; 13]. Furthermore, this waveform generation method necessitates chip hardware support, which is currently available from TI and NXP (NXP Semiconductors) but remains unattainable for Chinese automotive radar chips.  
This paper builds upon FMCW radar technology within the framework of TDMA-MIMO [14] and introduces a multi-mode waveform tailored specifically for corner radar systems featuring four transmitters and four receivers. Additionally, the paper presents a corresponding velocity ambiguity resolution method. Notably, this methodology extends its applicability to radars operating under the DDMA system and has been validated using the Alps pro chip. Alps Pro is a radar chip launched by Calterah at the end of 2022.