Coupler with waveguide transition for an antenna in a radar-based level measurement system

Apparatus for coupling a coaxial waveguide with a circular waveguide having a TE11 waveguide mode of operation, said apparatus comprising:

• a coaxial waveguide port for receiving said coaxial waveguide, said coaxial waveguide having a coaxial waveguide impedance, and said circular waveguide having an associated impedance;
• an impedance transformer;
• a matching waveguide;
• said matching waveguide being coupled to said coaxial waveguide port, said matching waveguide having an impedance matching the impedance of said coaxial waveguide and said matching waveguide further comprising a rectangular waveguide having a TE10 waveguide mode of operation;
• said impedance transformer having a first port for receiving said matching waveguide, a port for coupling to said circular waveguide and a transition section, said transition section having one or more waveguide transitions, said transition section serving to match the associated impedance of said circular waveguide with the impedance of said matching waveguide;
• a stepped section, said stepped section receiving said impedance transformer, and said stepped section having one or more steps corresponding to said waveguide transitions.

Apparatus for coupling a coaxial waveguide with a circular waveguide having a TE11 waveguide mode of operation, said apparatus comprising:

• a coaxial waveguide port for receiving said coaxial waveguide, said coaxial waveguide having a coaxial waveguide impedance, and said circular waveguide having an associated impedance;
• an impedance transformer;
• a matching waveguide;
• said matching waveguide being coupled to said coaxial waveguide port, and said matching waveguide having an impedance matching the impedance of said coaxial waveguide and said matching waveguide further comprising a rounded rectangular waveguide having a TE10 waveguide mode of operation;
• said impedance transformer having a first port for receiving said matching waveguide, a port for coupling to said circular waveguide and a transition section, said transition section having one or more waveguide transitions, said transition section serving to match the associated impedance of said circular waveguide with the impedance of said matching waveguide;
• a stepped section, said stepped section receiving said impedance transformer, and said stepped section having one or more steps corresponding to said waveguide transitions.