A simple design method for dual-band filtering antenna array using a transmission line

This paper presents a simple design method for dual-band patch antenna array using a novel feeding scheme to integrate bandpass response. The array has no filtering circuits but reveal high filtering performance. Only a microstrip transmission feed line is coupled to radiating patches and specific coupling regions are employed to obtain the desired current distribution on the radiating patches. In the operating band, the induced currents on the patches are in phase, resulting in high boresight gain. At the out-of-band frequencies, the patches are not excited or the induced currents on them are 180° out-of-phase, resulting in radiation suppression. Using this method, out-of-band radiation can be suppressed without degrading the in-band performance. For demonstration, a dual-band patch array is implemented. Dual-band bandpass response is observed and in-band gains are 12.6/13.0 dBi, whereas out-of-band suppression is more than 15 dB.