A low noise block down-converter with a waveguide transition structure for receiving satellite signals, comprising: a feed horn structure having at least a first waveguide extending along a first direction; a housing having at least a second waveguide extending along a second direction and communicating with the first waveguide , wherein the second direction is substantially not in parallel to the first direction; and a circuit board positioned within the housing, wherein the circuit board has a receiving pin configure to receive microwave signals propagating in the second waveguide , wherein the housing comprises: a base having an upper surface , a bottom surface , and a depression dented from the bottom surface towards the upper surface, and a metal layer disposed on the circuit board ; and a metal sheet substantially covering the depression to implement the second waveguide ; characterized in that the metal sheet has a concave , and the size of the circuit board is substantially the same as that of the concave , wherein an assembly of the metal sheet and the metal layer of the circuit board substantially covers the entire depression , thus implementing the second waveguide in the housing , wherein the second waveguide has a first end positioned at the depression and communicating with the first waveguide via a first transforming structure , and the circuit board is positioned substantially without overlapping the first end, wherein the second waveguide has a second end communicating with the circuit board , and the circuit board substantially overlaps the second end, wherein the first transforming structure is configured to guide the microwave signals from the first waveguide to the second waveguide , the first transforming structure has a first portion in the feed horn structure and a second portion in the depression . a feed horn structure having at least a first waveguide extending along a first direction; a housing having at least a second waveguide extending along a second direction and communicating with the first waveguide , wherein the second direction is substantially not in parallel to the first direction; and a circuit board positioned within the housing, wherein the circuit board has a receiving pin configure to receive microwave signals propagating in the second waveguide , wherein the housing comprises: a base having an upper surface , a bottom surface , and a depression dented from the bottom surface towards the upper surface, and a metal layer disposed on the circuit board ; and a metal sheet substantially covering the depression to implement the second waveguide ; characterized in that the metal sheet has a concave , and the size of the circuit board is substantially the same as that of the concave , wherein an assembly of the metal sheet and the metal layer of the circuit board substantially covers the entire depression , thus implementing the second waveguide in the housing , wherein the second waveguide has a first end positioned at the depression and communicating with the first waveguide via a first transforming structure , and the circuit board is positioned substantially without overlapping the first end, wherein the second waveguide has a second end communicating with the circuit board , and the circuit board substantially overlaps the second end, wherein the first transforming structure is configured to guide the microwave signals from the first waveguide to the second waveguide , the first transforming structure has a first portion in the feed horn structure and a second portion in the depression . <EOS>