Design and Analysis of Planar Phased MIMO Antenna for Radar Applications

Phased-multiple-input multiple-output (phased-MIMO) radar using one-dimensio- nal transmit arrays has been thoroughly investigated in the literature. In this paper, we consider two-dimensional phased-MIMO radar array which is called planar-phased-MIMO radar. This new technique aggregates the advantages of the linear-phased-MIMO radar without sacriflcing either the main advantage of the planar-phased-array radar, which is the coherent processing gain, or the main advantage of the planar MIMO array radar, which is the diversity processing gain. The essence of the proposed technique is to partition the planar transmit array into a number of planar subarrays that are allowed to overlap. Then, each subarray is used to coher- ently transmit a waveform which is orthogonal to the waveforms transmitted by other subarrays. Coherent processing gain can be achieved by designing a weight matrix for each subarray to form a beam towards a certain direction in space. Moreover, the subarrays are combined jointly to form a planar-MIMO radar resulting in higher angular resolution capabilities. Substantial im- provements is ofiered by the proposed planar-phased-MIMO radar technique with respect to the linear-phased-MIMO, planar-MIMO and planar-phased-array radar techniques. The achieved improvements are demonstrated analytically and by simulations through analyzing the corre- sponding beampatterns, the resultant peak side lobe level, mean side lobe level, and directivity. Both analytical and simulation results validate the efiectiveness of the proposed planar-phased- MIMO radar. Phased-array technique have been widely employed in difierent radars to provide electronic beam steering of radiated or received electromagnetic signals operating at the same frequency (1{3). Controlling the phase shifts across elements, the beam can be steered to the desired direction. Detecting/tracking weak target echoes and suppressing sidelobe interferences from other directions can be obtained due to its high directional gain. The desire for new more advanced antenna array technologies has been derived by the requirements of many emerging applications (4{8). Multiple input multiple output (MIMO) radar systems are next-generation radar systems with multiple transmit and receive apertures, equipped with the capability of transmitting arbitrary and difiering signals at each transmit aperture. The emerging MIMO radar literature can be broken into two broad areas. The flrst is characterized by spatially distributed assets that are not phase-coherent on transmitting or receiving, that takes advantage of spatial diversity to gain multiple views of a target and achieves improving in stability of statistical hypothesis tests for target detection. These approaches are often characterized as statistical MIMO. Fishler etal. (9) introduces the statistical MIMO radar concept which provides great improvements over other types of array radars. Haimovich etal. (10) reviews some recent work on MIMO radar with widely separated antennas and it is shown that with noncoherent processing, a target's RCS spatial variations can be exploited to obtain a diversity gain for target detection. Bliss etal. (11), describes the theory behind the improved surveillance radar performance and illustrates this with measurements from experimental MIMO radars. In contrast, there is a MIMO radar literature built around an assumption of colocated assets like one might flnd with an antenna array or phased-array radar. Much interesting work has been done in this arena by other researches (12{14) introduce perfor- mance advantages of colocated MIMO radars. A. Hassanien etal. (15) proposes a new technique for MIMO radar with colocated antennas which called linear phased-MIMO radar. This technique enjoys the advantages of the MIMO radar without sacriflcing the main advantage of the phased-array radar which is the coherent processing gain at the transmitting side. This paper studies the design of a new technique for partition the planar transmit array into a number of planar subarrays that are allowed to overlap. Each subarray is used to coherently transmit a waveform which is orthogonal to the waveforms transmitted by other subarrays. Then, compares this design with previous techniques through analyzing the corresponding beampatterns, and directivity. Signiflcant improvements ofiered by the planar-phased-MIMO radar technique.