Waveguide window/seal

1 . A satellite ground station antenna, comprising:

a hub comprising:

a first connecting member body,

a first circular waveguide extending through the hub coaxial with the first connecting member body and terminating at a first port at an end face of the first connecting member body,

a first window/seal to seal the first port, and

two or more pins extending radially from the first connecting member body; and

a front-side feed network comprising:

a second connecting member body comprising a cavity configured to fit over the first connecting member body, and two or more slots disposed around a perimeter of the cavity, each of the two or more slots configured to accept one of the two or more pins extending from the first connecting member body,

a second circular waveguide coaxial with the cavity and terminating at a second port within the cavity,

a second window/seal to seal the second port,

a cap configured to fit over the second connecting member body, the cap including two or more L-shaped slots, each L-shaped slot to engage one of the two or more pins extending from the first connecting member body through the slots of the second connecting member; and

a wave spring between an inside surface of the cap and a shoulder of the second connecting member body, the spring effective to urge the second port towards the first port when the two or more L-shaped slots of the cap are engaged with the two or more pins,

wherein the first and second window/seals each comprise:

a right-circular cylindrical window having an axis;

an annular rib surrounding and coaxial with the cylindrical window, an outer diameter of the annular rib configured to fit closely within an inside diameter of the respective circular waveguide; and

an annular recess between the cylindrical window and the annular rib.

2 . The antenna of claim 1 , wherein, for the first and second window/seals:

t1 is a length of the cylindrical window parallel to the axis,

t2 is a depth, parallel to the axis, of the annular recess,

t3 is a length, parallel to the axis of the annular rib, and

t2<t1<t3.

3 . The antenna of claim 1 , wherein

t1 is one-quarter wavelength at a frequency of operation.

4 . The antenna of claim 1 , each of the first and second window/seals further comprising:

a flange to locate the window/seal with respect to the respective circular waveguide.

5 . The antenna of claim 1 , each of the first and second window/seals further comprising:

a center conductor coaxial with the cylindrical window.

6 . The antenna of claim 1 , wherein

for each of the first and second window/seals, the cylindrical window and the annular rib comprise a dimensionally stable, low loss dielectric material suitable for outdoor use.

7 . The antenna of claim 1 , wherein

for each of the first and second window/seals, the cylindrical window and the annular rib comprise a cross-linked polystyrene plastic material.

8 . The antenna of claim 1 , wherein

for each of the first and second window/seals, inner and outer diameters of the annular recess, a depth of the annular recess, and a length of the annular rib are configured to provide an impedance transition region between the cylindrical waveguide and the cylindrical window.

9 . The antenna of claim 1 , wherein

for each of the first and second window/seals, inner and outer diameters of the annular recess, a depth of the annular recess, and a length of the annular rib are configured to tune frequencies of one or more resonances to not fall within an operating frequency range of a waveguide circuit comprising the cylindrical waveguide and the window/seal.

10 . The antenna of claim 1 , wherein

when the two or more L-shaped slots of the cap are engaged with the two or more pins, the first circular waveguide window/seal and the second circular waveguide window/seal are separated by a gap forming a radial waveguide, the radial waveguide terminated in a conductive seal and one or more choke grooves.