Design of selectable low- and bandpass filter for 2.4 GHz applications

A novel selectable low-and bandpass filter for 2.4 GHz wireless communication systems is proposed and realised by low temperature co-fired ceramic (LTCC) technology. The proposed filter consists of a lowpass filter (LPF), a bandpass filter (BPF), and a common matching network, which are fully embedded in the LTCC substrate. The suggested idea is that the filter can be selectively chosen and operated as either a 2 GHz LPF or a 2 GHz BPF, respectively, by simply making one of the output ports to be shorted to ground. The size of the fabricated filter is 2.3 x 2.3 x 0.44 mm. Insertion losses are less than 1.2 and 0.87 dB in BPF and LPF mode, respectively. The measured result of the implemented filter is in sufficiently good agreement with the simulated result.