Wideband Substrate-Integrated Waveguide-Fed Endfire Metasurface Antenna Array

A vertically polarized substrate-integrated waveguide (SIW)-fed endfire metasurface antenna array is proposed for wideband operation. Each of the metasurfaces consists of 3 x 3 rectangular patches and is printed on the two surfaces of a single-layered substrate with a thickness of 0.16 lambda(0) (where lambda(0) is the wavelength at 32.65 GHz in free space). The antenna is fed at one side of metasurface by an open-end SIW for wideband endfire radiation. The proximity-coupled interdigital strips are introduced between the SIW and metasurface for fault-tolerant coupling. The wideband operating mechanism is revealed by studying the propagation mode and multiple resonant modes of metasurface. To verify the proposed antenna, a 1 x 4 array is presented with uniform excitation including two SIW Y junctions and an SIWT junction. Moreover, the connected SIW Y junction improved the impedance matching at the low frequencies based on the cavity mode analysis. The proposed design shows that the measured impedance bandwidth (10 dB return loss) is 26.6-38.7 GHz (37%) with the achieved gain of 9.1-13.8 dBi.