Metal integrated suspended line (MISL) circuits

A metal-integrated suspended line, comprising:

• a plurality of metal substrates stacked from top to bottom and connected by rivets or screws to form a self-encapsulating structure;
• wherein the plurality of metal substrates comprise a top metal substrate located at a top of the plurality of metal substrates and a bottom metal substrate located at a bottom of the plurality of metal substrates;
• at least two metal substrates of the plurality of metal substrates except the top metal substrate and the bottom metal substrate are spaced apart from each other, and each of the at least two metal substrates defines an air-filled hollow cavity;
• and one of the plurality of metal substrates disposed between two hollow cavities of two of the at least two metal substrates is provided with a circuit structure;
• wherein the circuit structure comprises a plurality of coaxial line filters;
• and the plurality of the coaxial line filters are spaced apart from each other and disposed on a side of an additional air cavity defined on the one metal substrate;
• and
• wherein a feed waveguide is provided at a top of the top metal substrate.