Wideband Circularly Polarized Active Heatsink Antenna Array

A wideband active circularly polarized (CP) heatsink antenna array is designed in this article. It consists of a 3-D printing metal structure and a low-temperature co-fired ceramic (LTCC) substrate. The metal structure is a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4\times 4$ </tex-math></inline-formula> waveguide array, serving dual purposes as both a heatsink and an electromagnetic radiator. The substrate is placed under the metallic array, with a feeding network layer inside and a chip circuit layer on the surface. To generate a CP radiation wave, the antipodal linearly tapered slot antenna (ALTSA) is used as the heatsink element, which is fed by the stripline in the substrate. Two ridges and a back cavity are designed in each element to realize the wideband energy conversion from the guided wave in the stripline to the rectangular waveguide. A prototype of the heatsink antenna array without a chip is fabricated, and the electromagnetic performance is tested. The measured results demonstrated that the proposed antenna array obtains an impedance bandwidth (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert {S}_{11}\vert \lt -10$ </tex-math></inline-formula> dB) of 50% and an axial ratio (AR) bandwidth (AR < 3 dB) of 33.6%, respectively. The peak gain is 19 dBi at 34.7 GHz. Furthermore, an active antenna array, with a power amplifier (PA) integrated on the bottom of the substrate is also measured, which can achieve an effective peak gain of 39.7 dBi. The measured thermal performance reveals that a significant temperature drop of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$80~^{\circ }$ </tex-math></inline-formula>C is achieved by loading the metal heatsink on the LTCC package, ensuring the normal operation of the PA.