Filters including dual cross-couplings and related combiners

A filter, comprising:

• a housing having outer sidewalls that define a rectangle;
• first through fourth resonant cavities that are within the housing and positioned at the four corners of the rectangle defined by the outer sidewalls of the housing;
• an input that extends into the first resonant cavity;
• and
• an output that extends from the fourth resonant cavity,
• wherein the first resonant cavity is configured to couple with the second and third resonant cavities, the second resonant cavity is configured to couple with the third and fourth resonant cavities, and the third resonant cavity is configured to couple with the fourth resonant cavity, and
• wherein a magnitude of the coupling between the first and third resonant cavities is configured to be substantially equal to a second magnitude of the coupling between the second and fourth resonant cavities
• wherein the first and third resonant cavities are arranged at opposed corners of the rectangle defined by the outer sidewalls of the housing.

A filter, comprising:

• first through fourth resonant cavities;
• an input that extends into the first resonant cavity;
• and
• an output that extends from the fourth resonant cavity,
• wherein the first resonant cavity is configured to couple with the second and third resonant cavities, the second resonant cavity is configured to couple with the third and fourth resonant cavities, and the third resonant cavity is configured to couple with the fourth resonant cavity, and
• wherein a magnitude of the coupling between the first and third resonant cavities is configured to be substantially equal to a second magnitude of the coupling between the second and fourth resonant cavities
• further comprising a coupling element that comprises a first conductive line that extends between the first and third resonant cavities and a second conductive line that extends between the second and fourth resonant cavities.

A filter, comprising:

• first through fourth resonant cavities;
• first through fourth resonators mounted in the respective first through fourth resonant cavities, where the first resonator is closer to the second and fourth resonators than it is to the third resonator and the second resonator is closer to the first and third resonators than it is to the fourth resonator;
• an input that is configured to feed RF signals from a first external circuit element into the first resonant cavity;
• an output that is configured to pass RF signals from the fourth resonant cavity to a second external circuit element;
• and
• a coupling element that extends between the first and third resonant cavities and between the second and fourth resonant cavities.

A combiner, comprising:

• a first frequency selective port;
• a second frequency selective port;
• a common port;
• a termination;
• a first bandpass filter that is to the coupled to the first frequency selective port, the second frequency selective port and the common port;
• and
• a second bandpass filter that is to the coupled to the first frequency selective port, the second frequency selective port and the common port;
• a first hybrid coupler coupled between the first frequency selective port and the common port;
• and
• a second hybrid coupler coupled between the second frequency selective port and the termination,
• wherein the first and second bandpass filters are each coupled between the first hybrid coupler and the second hybrid coupler,
• wherein the first and second bandpass filters each include an input, an output and first through fourth resonant cavities, where the first resonant cavity is configured to couple with the input and the second and third resonant cavities, the second resonant cavity is configured to couple with the third and fourth resonant cavities, and the fourth resonant cavity is configured to couple with the third resonant cavity and the output, and
• wherein a first conductive coupling element extends between the first and third resonant cavities, and a second conductive coupling element extends between the second and fourth resonant cavities.