The invention discloses a
signal transmission line, a
duplexer, a
multiplexer and communication equipment. The
duplexer comprises an antenna, a transmitting filter, a receiving filter and an impedanceconverter, wherein the transmitting filter and the receiving filter are formed on the basis of acoustic resonators, and the
impedance converter is the
signal transmission line. The head end of a first
metal signal line layer of the signal
transmission line is connected with the antenna, and the
tail end of the second
metal signal line layer of the signal transmission line is connected with the antenna end of the receiving filter or the transmitting filter. According to the technical scheme, the signal transmission line has high
characteristic impedance, impedance conversion is achieved in theduplexer design, meanwhile, the
electrical length of the needed transmission line is shortened, the space occupied by the transmission line is reduced, and
miniaturization design of devices is facilitated. In addition, an
electromagnetic coupling path exists between the signal transmission line and a
coupling unit in the receiving filter and / or the transmitting filter, and the out-of-
band rejection characteristic and the isolation characteristic of the corresponding
frequency band can be improved by adjusting the
coupling mode and the
coupling strength of the
electromagnetic coupling path.