Apparatus and system for splitting and combining signals in the frequency domain

An apparatus comprising:

• a first waveguide port for supporting a first signal, wherein the first waveguide port is configured to have a first frequency band of operation;
• a second waveguide port for supporting a second signal, wherein the second waveguide port is configured to have a second frequency band of operation that is a sub-band of the first frequency band of operation;
• a third waveguide port for supporting a third signal, wherein the third waveguide port is configured to have a third frequency band of operation that is a sub-band of the first frequency band of operation and that is higher than the second frequency band of operation;
• a waveguide structure, disposed between the first waveguide port and the second and third waveguide ports, configured to,
• split, in the frequency domain, the first signal into the second and third signals, and/or
• combine, in the frequency domain, the second and third signals into the first signal;
• wherein the waveguide structure comprises an asymmetric cross-sectional shape defining,
• a first aperture region having a first extent, and
• a second aperture region having a second extent less than the first extent;
• and
• wherein the waveguide structure is arranged relative to the second and third waveguide ports such that,
• the third waveguide port is predominantly adjacent the first aperture region, and
• the second waveguide port is predominantly adjacent the second aperture region.