A broadband low profile microstrip filter-antenna with an omni-directional pattern

A broadband low profile microstrip filter-antenna with an omni-directional pattern is presented. A coupled line is used to connect a microstrip antenna and the second resonator of a filter as admittance inverter. In the design, the antenna performs as a radiator; meanwhile it is also the last resonator of the bandpass filter. Therefore, the loss is reduced between the filter and the microstrip antenna. The proposed filter-antenna can provide 15% impedance bandwidth, a low profile of 3.8mm, an omni-directional pattern and high suppression in the stopband. The proposed antenna simulated results are presented.