Time-and-Frequency Hybrid Multiplexing for Flexible Ambiguity Controls of DFT-coded MIMO OFDM Radar

Abstract

A time-and-frequency hybrid multiplexing technique for a multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) radar is proposed. Discrete Fourier transform (DFT)-coded OFDM waveforms are introduced, which allow it to be free from range-dependent angle errors. These are readily used to provide both time-domain and frequency-domain multiplexings in the MIMO OFDM radar. The DFT-coded frequency-domain multiplexing shortens the maximum unambiguous range, while the DFT-coded time-domain multiplexing lowers the maximum Doppler ambiguity. A hybrid of both domain multiplexing techniques can mitigate the respective limitations by adaptively selecting the proper DFT matrix size in each multiplexing domain. This allows to solve the intrinsic range and Doppler ambiguity problems of MIMO radars by controlling the hybrid ratio of the two kinds of DFT-code based multiplexing methods. Range-Doppler and range-angle maps of four examples with different hybrid multiplexing ratios are simulated with a MIMO OFDM radar numerical platform.INDEX TERMS Discrete Fourier transform (DFT) code, hybrid multiplexing, multiple-input multipleoutput (MIMO) radar, orthogonal frequency-division multiplexing (OFDM) radar, range and Doppler ambiguities.

Range-Division Multiplexing for MIMO OFDM Joint Radar and Communications

“…Another interesting multiplexing technique is investigated in [23], which also shifts the signal components radiated by different Tx antennas within the RDM. This is achieved by transmitting the same data on all Tx antennas and on all subcarriers, and in addition, employing a discrete Fourier transform (DFT) matrix as precoding matrix.…”

“…This work focuses on a multiplexing technique denoted as RDMult 1 . This multiplexing technique shares some similarities with AC-CDM and with the approach in [23], however, there exist some distinct differences in the details and in the focus of the analysis as discussed later. The working principle of RDMult is sketched in Fig.…”

“…• In contrast to [22], the work at hand contains a comprehensive investigation of the impact of the multiplexing technique on the communication task. As already stated, RDMult is also related to the multiplexing technique investigated in [23], which shifts the signal components radiated by different Tx antennas along both dimensions of the RDM. The precoding matrix employed in [23] can be translated to a phase shift from subcarrier to subcarrier as utilized in this work.…”

“…As already stated, RDMult is also related to the multiplexing technique investigated in [23], which shifts the signal components radiated by different Tx antennas along both dimensions of the RDM. The precoding matrix employed in [23] can be translated to a phase shift from subcarrier to subcarrier as utilized in this work. It will be shown, that the design rule for choosing the phase shift in [23] differs from the one proposed in this work (cf.…”

“…The precoding matrix employed in [23] can be translated to a phase shift from subcarrier to subcarrier as utilized in this work. It will be shown, that the design rule for choosing the phase shift in [23] differs from the one proposed in this work (cf. Sec.…”