Double-Curved Metal in Multilayer Printed Circuit Boards for Bandwidth Enhancement of Millimeter-Wave Patch Antennas

Metal curving or metal denting is usually an unwanted phenomenon in the printed circuit board (PCB) process. However, curved metal could provide some benefits to enhance performance of radio frequency components. In this article, an approach is proposed to develop a double-curved metal (DCM) in a multilayer PCB process by allocating a metal upon an air cavity and then laminating with buffer layers under suitable pressure and temperature. This approach could increase the degree of freedom on radio frequency component design in PCB process. Based on this approach, a millimeter-wave (mmWave) aperture-coupled patch antenna is produced with the improved characteristics of high gain, wide bandwidth, and compact size. Prototypes of the proposed antenna are designed, manufactured, measured, analyzed, dissected, and observed under a metallographic microscope. The measurements and simulations are in good agreement and demonstrate that the proposed antenna achieves a maximum gain of 8 dBi over an operating bandwidth of 27.4-34.2 GHz. Compared with an aperture-coupled patch antenna with a flat metal, the fractional bandwidth of that with a double-curved metal is enhanced by a factor of two.