A compact planar bandpass filter is designed using a tapered slot resonator, which is formed using two tapered slot antennas connected in a face-to-face configuration. The tapering profile and dimensions of the resonator control the characteristics of the filter. The success of the method is demonstrated via full wave electromagnetic simulations and measurements. Passbands of 30-50% centred at about 6 GHz with an insertion loss of less than 1 dB and a peak-to-peak group delay of less than 0.5 ns are achieved in two filters having different tapering profiles and fabricated on RT6010 substrate with an overall dimension of 25 mm נ30 mm. The use of an open-ended series stub within the coplanar waveguide feeder of the filters extends their high stopband beyond 15 GHz.