Spurious free microstrip antennas with quasi-periodical loaded transmission line

The paper presents an integrated patch antenna for mode-control. The harmonics and spurious suppression are effectively achieved by adding modified periodic loads to the microstrip line. The proposed integrated microstrip antenna not only suppresses the harmonic resonances within the quad band, but also retains the impedance matching and radiation performance of the original antenna. The results suggest that the spurious control and design simplicity of an integrated microstrip antenna can be achieved simultaneously. The article presents simple design principles to control the harmonic resonances and spurious emission, and discusses the design and experimental results for the spurious-free integrated circular patch antenna.