This invention presents an alternative method of designing diplexer which is based upon transverse electric-magnetic mode of propagation in order to separate two different frequency spectrums. The invention has the advantages with low loss, high Q-factor and good selectivity. The significant contribution of this invention is to be implemented in any transceiver systems where demand for handling multiple separated frequencies in a single device is crucial such as in wireless backhaul systems. Therefore, the invention is considered beneficial to the community of microwave theory and technique as well as the possibility to upgrade the existing wireless communication systems and practically suitable for multichannel transceiver systems where the reduction of physical volume is very important, while maintaining its good performance.