This work presents a filtenna concept based on cascaded singlet filters, which inherits independent controllability of attenuation poles from the filter design and has high stopband performance. Two fourth-order filters with a center frequency of 270 GHz, a 14 GHz bandwidth, and in-band return losses of 15 dB and 18 dB, respectively, are manufactured and measured to verify the proposed concept. The filtennas with a single-slot and a double-slot configuration are fabricated by the silicon deep reactive ion etching technology and have the size of 3.65x2.6 mm2. Detailed explanations of the synthesis procedure, which was validated through EM simulation, and measurement results are provided. The measured single-slot and double-slot filtennas exhibit broadside radiation gains of approximately 4.5 dBi and 6.5 dBi at 270 GHz, respectively. Moreover, the challenges and details of silicon micromachining in fabricating the two filtering antennas are discussed.