New Generalized Multi-Structured MIMO Radar Configuration With Increased Degrees of Freedom

Unlike traditional phased-array-radar, multiple-input multiple-output (MIMO) radar is capable of achieving more degrees-of-freedom (DOF) and larger virtual aperture (VA) for the direction-of-arrival (DOA) estimation. In this letter, a new universal antenna array approach employing a one-level transmitter (Tx) and generalized receiver (Rx) is presented for MIMO radar to enhance the DOA estimation performance. The proposed configuration significantly improves the DOF capacity and expands VA by utilizing difference co-array of sum co-array method. The first-level of the Rx and a Tx with increased inter-element spacing is constructed using the nested-coprime array with displaced sub-arrays structure. The proposed Rx is transformable, generic, and easier to realize. It exploits symmetrical array geometry, such that once the initial-level is designed, the remaining stages will be known. The Rx also reveals an inbuilt Tx. Moreover, it achieves increased DOF and enlarged VA, reflecting the multifaceted advantages of the new Rx approach. The configuration is also benefited with closed-form expressions for VA, sensor locations, and DOF. Simulation results demonstrate the superiority of the proposed MIMO radar.

I. Introduction

Multiple-input multiple-output (MIMO) radar has attracted great attention in the last decade, which allows the simultaneous transmission of independent waveforms from multiple antennas and receiving the reflected information via multiple antennas [1]. As a result, MIMO radar achieves more degrees-of-freedom (DOF) and virtual aperture (VA) than the phased-array-radar. Subsequently, it provides enhancement in parameter identifiability, direction-of-arrival (DOA) estimation accuracy and resolution [1], [2]. The DOF indicates the ability to resolve more sources than the number of physical antennas. Hence, an increment in DOF capacity advantageously reduces hardware cost and complexity. A MIMO radar with uniform linear arrays (ULAs) constructing the transmitter (Tx) and receiver (Rx) has used the sum co-array method to enlarge the array aperture [3]. However, the implementation of ULAs and sum co-array operation limits the DOF capacity.