A miniaturized lowpass bandpass diplexer with high isolation

A new compact and wide band lowpass-bandpass diplexer with simple structure is designed and fabricated in this paper. T shaped and Z shaped resonators are used in the lowpass channel and two coupled open stubs are used in the bandpass channel. The designed diplexer has 3 dB cutoff frequency of 1 GHz in the lowpass channel and operating frequency of 2.4 GHz in the bandpass channel. The obtained insertion losses in the lowpass and bandpass channels are 0.25 dB and 0.58 dB, respectively. The obtained isolation between the two output ports is better than 35 dB. The overall size of the fabricated lowpass bandpass diplexer is obtained 45.6 mm × 28.6 mm, which shows good miniaturization, compared with other similar diplexers.