Frequency multiplexers are one of the important components in wireless systems. There are several literatures published for bandpass multiplexers. However, reconfigurable lowpass-bandpass multiplexers are less discussed. To this end, microstrip technology, packaged varactors, and distributed coupling technique are employed in this project to realize the proposed circuits. This project will investigate reconfigurable lowpass filter with fixed-frequency stopband or broadband stopband, reconfigurable lowpass-bandpass diplexer, and reconfigurable lowpass-bandpass multiplexer.