The invention discloses an adjustable
duplexer based on folded open-loop resonators. The adjustable
duplexer comprises an upper
microstrip structure layer, a middle
dielectric plate layer and a lower grounding
metal layer, wherein the upper
microstrip structure layer comprises three input / output feeder lines, three blocking capacitors, a pair of first channel adjustable open-loop resonators and a pair of second channel adjustable open-loop resonators. Each adjustable open-loop
resonator is composed of a folded
microstrip line, a termination varactor
diode, a center-loaded
capacitor and a
resistor, wherein the termination varactor
diode is used for adjusting the
center frequency of each channel; and the center-loaded
capacitor and the
resistor are used for restraining the
harmonic component of each channel. A first input port and a second output port form a first channel transmission path, the first input port and a third output port form a second channel transmission path, and the two channels are mutually little influenced. The adjustable
duplexer has the advantages that the
center frequency of each channel is independently adjustable, the isolation degree is high, the structure is simply designed, the electric performance is good, and circuit integration and
system packaging can be realized easily.