A 77GHz low-temperature cofired ceramic substrate integrated cavity circularly polarized antenna array

In this article, a low-temperature cofired ceramic (LTCC) substrate integrated cavity(SIC) circularly polarized(CP) antenna array operating in 77 GHz millimeter wave range is presented. This antenna employs LTCC and substrate integrated waveguide (SIW) technologies, utilizing a SIC as the radiating element and a T-type power divider as the feeding network, forming a 2 × 2 array. By increasing the cavity aperture size and adding metal parasitic patches on the cavity's upper surface to counteract the reverse electric field, the antenna operates in the high-order TM221-mode, achieving high-gain performance. At lower frequency, the parasitic patches inclined at 45° excites induced current with phase difference of 90° through a coupling slot to create CP performance. While at higher frequency, the equal amplitude and 90° phase difference of the TM211-mode and TM121-mode within the SIC together produce circular polarization. The combination of these two mechanisms achieves wideband circularly polarized performance. The simulation results show that the proposed array antenna achieves a 27.3% 3 dB gain bandwidth within the frequency range of 65 GHz to 86 GHz, with a peak gain of 14.2 dBi. The -10 dB impedance bandwidth and 3dB axial ratio bandwidth are 20.8% (68.1 GHz to 84.1 GHz) and 21.2% (69.9 GHz to 86.2 GHz), respectively.