Wide Half Power Beamwidth MIMO Antenna for Vehicular Radar System

This article proposes a new microstrip antenna-based MIMO design that offers a wide half-power beamwidth over a frequency range of 77–81 GHz. The single antenna element has a size of 7 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mo>×</mml:mo> </mml:math> 7 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mo>×</mml:mo> </mml:math> 0.254 mm 3 and is built on a Taconic substrate ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:msub> <mml:mi>ϵ</mml:mi> <mml:mi>r</mml:mi> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>2.2</mml:mn> </mml:math> ). Parasitics are used to enhance the beamwidths to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:msup> <mml:mn>152.6</mml:mn> <mml:mo>∘</mml:mo> </mml:msup> </mml:math> , <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:msup> <mml:mn>149.4</mml:mn> <mml:mo>∘</mml:mo> </mml:msup> </mml:math> , and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:msup> <mml:mn>139</mml:mn> <mml:mo>∘</mml:mo> </mml:msup> </mml:math> at 77 GHz, 79 GHz, and 81 GHz, respectively, with a maximum gain of 5.74 dBi. The <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mn>2</mml:mn> <mml:mo>×</mml:mo> <mml:mn>2</mml:mn> </mml:math> MIMO arrangement increases the overall gain of the system up to 12.2 dBi, with a slight reduction in the beamwidths to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:msup> <mml:mn>139.9</mml:mn> <mml:mo>∘</mml:mo> </mml:msup> </mml:math> , <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:msup> <mml:mn>142.7</mml:mn> <mml:mo>∘</mml:mo> </mml:msup> </mml:math> , and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:msup> <mml:mn>133.5</mml:mn> <mml:mo>∘</mml:mo> </mml:msup> </mml:math> at 77 GHz, 79 GHz, and 81 GHz, respectively. The single element and the MIMO configuration achieve side lobe level suppression by 10.9 dB. The different MIMO performance metrics, such as envelope correlation coefficient, channel capacity loss, diversity gain, mean effective gain, TARC, etc., are well within the industry standards.