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 (11, 11A) having at least a second waveguide (115A, 115B) 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 (17, 17A) positioned within the housing, wherein the circuit board has a receiving pin (172, 172A) configure to receive microwave signals propagating in the second waveguide (115A, 115B), 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 (115A, 115B); 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 (115A, 115B) in the housing, wherein the second waveguide (115A, 115B) 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 (115A, 115B), 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 (11, 11A) having at least a second waveguide (115A, 115B) 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 (17, 17A) positioned within the housing, wherein the circuit board has a receiving pin (172, 172A) configure to receive microwave signals propagating in the second waveguide (115A, 115B), 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 (115A, 115B); 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 (115A, 115B) in the housing, wherein the second waveguide (115A, 115B) 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 (115A, 115B), the first transforming structure has a first portion in the feed horn structure and a second portion in the depression.