Frequency demultiplexer

A frequency demultiplexer comprising an input part with an input port, a low pass filter with an output port, and a band-pass filter with an output port, with the input part, the low-pass filter and the band-pass filter comprising open waveguide sections, and the band-pass filter comprising a plurality of gap-coupled resonators, with the input part and the low-pass filter both being connected at respective connection points to one and the same of said gap-coupled resonators, the connection point of the low-pass filter being located at a first maximum distance from a center point of the resonator and the connection point of the input part being located at a second maximum distance from said center point of the resonator, said center point corresponding to a wave node of a wavelength λ, where λ=2d/M, M is a positive integer value and d is the shortest end-to-end distance along the resonator, in which the first maximum distance from said center point of the resonator is d/8 and the second maximum distance from said center point of the resonator is d/4.