A passive frequency multiplexer includes a beam forming network lens including a plurality of input terminals and a plurality of output terminals; a transmission line for transmitting a signal to the beam forming lens; and a plurality of couplers arranged in series along the transmission line, each of the plurality of couplers comprising an input terminal, an output terminal, and a coupled output terminal, each of the coupled output terminals of the plurality of couplers being coupled to a respective one of the input terminals of the beam forming network lens.