An approach to filter-antenna integration in SIW technology

An original filter-antenna module has been designed, manufactured and measured. The module can be viewed as a high order filter in which the last resonator has been replaced by a resonant antenna element. This antenna is coupled to the other resonators by means of two inter-cavity slots. The module was manufactured using the Substrate Integrated Waveguide technique, which allows the cavities to be fabricated by means of a standard printed circuit board process. Experimental results present good agreement with simulations. The measured return loss response of the filter-antenna module matches that of a second order bandpass filter, with a central frequency of 1.94GHz, a fractional bandwidth of 5.15% and a return loss of 7.5dB at the central frequency. The radiation function is incorporated to this filter´s response, with a maximum gain of 5.15dBi and a front-to-back ratio (FTBR) of 29.25dB.