Cosynthesis of a Filtering Antenna With Harmonic Suppression

To suppress the undesired signals at the front-ends of wireless systems, a codesign of a simple filtering antenna highly integrated with a slotline-based network is presented and studied in this letter. The proposed antenna integrated with the low-pass filter, the bandpass response is achieved, and impedance bandwidth is also enlarged due to the additional reflection pole contributed by the high integration, which has been evaluated and verified through numerical calculations and full-wave simulations. A design example of the filtering antenna working at 3.5 GHz is developed and fabricated for demonstration purposes. Measured results indicate that good filtering responses with a low insertion loss are achieved. Compared to the original patch antenna, the fractional impedance bandwidth of the proposed one is significantly enhanced, from 6.63% to 13.7%. Besides, harmonics of up to 15.5 GHz are well suppressed. The proposed scheme is simple and compact, exhibiting attractive performance for bandwidth enhancement and spurious suppression applications.