Signal coupling device for associating a first signal in a first frequency band and a second signal in a second frequency band in a common waveguide and for distributing the first and second signals to two separate waveguides, wherein the first frequency band is different from the second frequency band, comprising: a first circular waveguide with a constant internal diameter and cylindrical interior; and a second circular waveguide (200, 200'), which is arranged inside the cylindrical interior of the first circular waveguide coaxially to the first circular waveguide in such a way that a first region exists, in which the first and the second circular waveguide are present jointly coaxially, and a second region exists, in which only the first circular waveguide is present, wherein: - the first circular waveguide comprises, only in the second region, a plurality of nubs (102, 103, 104, 105, 106, 107, 108), wherein: -- the plurality of nubs is arranged on the inner circumference of the first circular waveguide in the second region, -- the plurality of nubs projects radially inwards from the inner circumference of the first circular waveguide, and -- the plurality of nubs is configured to activate higher modes from a fundamental mode, and - the first circular waveguide, the second circular waveguide and the plurality of nubs are configured in such a way that the superposition of the fundamental mode and the higher modes produces a wave front, which i) has field components in the first frequency band only in a region of a cylinder ring between the outer circumference (210, 210') of the second circular waveguide and the inner circumference of the first circular waveguide and ii) has field components in the second frequency band only in a cylindrical interior (220, 220') of the second circular waveguide. a first circular waveguide with a constant internal diameter and cylindrical interior; and a second circular waveguide (200, 200'), which is arranged inside the cylindrical interior of the first circular waveguide coaxially to the first circular waveguide in such a way that a first region exists, in which the first and the second circular waveguide are present jointly coaxially, and a second region exists, in which only the first circular waveguide is present, wherein: - the first circular waveguide comprises, only in the second region, a plurality of nubs (102, 103, 104, 105, 106, 107, 108), wherein: -- the plurality of nubs is arranged on the inner circumference of the first circular waveguide in the second region, -- the plurality of nubs projects radially inwards from the inner circumference of the first circular waveguide, and -- the plurality of nubs is configured to activate higher modes from a fundamental mode, and - the first circular waveguide, the second circular waveguide and the plurality of nubs are configured in such a way that the superposition of the fundamental mode and the higher modes produces a wave front, which i) has field components in the first frequency band only in a region of a cylinder ring between the outer circumference (210, 210') of the second circular waveguide and the inner circumference of the first circular waveguide and ii) has field components in the second frequency band only in a cylindrical interior (220, 220') of the second circular waveguide. - the first circular waveguide comprises, only in the second region, a plurality of nubs (102, 103, 104, 105, 106, 107, 108), wherein: -- the plurality of nubs is arranged on the inner circumference of the first circular waveguide in the second region, -- the plurality of nubs projects radially inwards from the inner circumference of the first circular waveguide, and -- the plurality of nubs is configured to activate higher modes from a fundamental mode, and -- the plurality of nubs is arranged on the inner circumference of the first circular waveguide in the second region, -- the plurality of nubs projects radially inwards from the inner circumference of the first circular waveguide, and -- the plurality of nubs is configured to activate higher modes from a fundamental mode, and - the first circular waveguide, the second circular waveguide and the plurality of nubs are configured in such a way that the superposition of the fundamental mode and the higher modes produces a wave front, which i) has field components in the first frequency band only in a region of a cylinder ring between the outer circumference (210, 210') of the second circular waveguide and the inner circumference of the first circular waveguide and ii) has field components in the second frequency band only in a cylindrical interior (220, 220') of the second circular waveguide.