A Compact Cavity-Backed Endfire Slot Antenna

A compact endfire slot antenna is presented in this letter, which employs two thin substrates on both the top and bottom broad walls of a metallic cavity. Three slots with different lengths at suitable positions etched out of the cavity walls are utilized to enhance the bandwidth and achieve endfire radiation with supergain. The designed antenna operates at the center frequency of 5.8 GHz. Simulated results show that the slot antenna has an impedance bandwidth (vertical bar S-11 vertical bar < -10 dB) from 5.51 to 6.08 GHz (9.8%) and a maximum gain of 8.4 dB in the endfire direction. The gain ripple is 0.9 dB over the bandwidth of interest. A prototype of the proposed antenna with an integrated rat-race feeding balun is fabricated and tested. Measured results are in good agreement with simulated ones.