Multiplexer-demultiplexer for a microwave antenna

A multiplexer-demultiplexer for a microwave antenna designed to transmit signals in first, second, third and fourth frequency bands respectively comprised between 3.6 and 4.2 kmc, 5.9 and 6.4 kmc, 6.4 and 7.1 kmc and 10.7 and 11.7 kmc, said multiplexer-demultiplexer comprising:

• a coupling arrangement for receiving vertical and horizontal polarization signals and having a first port for coupling to an antenna, and a second port;
• a first directional coupler having a first port coupled to said second port of said coupling arrangement, and second and third ports and a second directional coupler having a first port coupled to said third port of said first directional coupler, and second and third ports, one of said directional couplers being designed to transmit to its second port the whole of the vertically-polarized signals in said first frequency band applied to its first port, and the signals in said second, third, and fourth bands applied to its first port to its third port, and the other of said directional couplers being designed to transmit to its second port the whole of the horizontally-polarized signals in said first frequency band applied to its first port, and the signals in said second, third and fourth bands applied to its first port to its third port;
• a double directional coupler having a first port coupled to said third port of said second directional coupler, and second, third and fourth ports, said double directional coupler being designed to transmit to its second and third ports, respectively, the horizontally polarized signals and the vertically polarized signals in said fourth frequency band applied to its first port, and the signals in said second and third bands applied to its first port to its fourth port;
• and a polarizer having first and second polarization ports, and a further port coupled to said fourth port of said double directional coupler;
• said multiplexer-demultiplexer further comprising two waveguides each of which is provided with a stub, said two waveguides having respective first ends respectively coupled to said first and second polarization ports of said polarizer and respective second ends;
• first and second Y-junctions having respective first ports respectively coupled to the second ends of said two waveguides, each of said Y-junctions having two further ports;
• a first band-pass filter having a first port coupled to one of said further ports of said first Y-junction;
• and a second band-pass filter having a first port coupled to one of said further ports of said second Y-junction.