Abstract: An anechoic chamber and a construction method thereof are provided, the anechoic chamber includes a top surface, being a polygon; trapezoid surfaces, corresponding to edges of top surface, upper edge lengths of trapezoid surface being equal to edge lengths of top surface, trapezoid surfaces being connected to edges of top surface through the upper edges, the trapezoid surfaces being sequentially connected along a circumferential direction of top surface, and being at angle to the top surface; rectangular surfaces, corresponding to the trapezoid surfaces, upper edge lengths of rectangular surface being equal to lower edge lengths of trapezoid surface, rectangular surfaces being connected to the trapezoid surfaces through the upper edges, the rectangular surfaces being sequentially connected along a circumferential direction of the lower edges of trapezoid surfaces, and being perpendicular to the top surface; and an absorbing material, disposed on the top surface, the trapezoid surfaces and the rectangular surf

Abstract: A four-terminal-pair AC quantum resistance dissemination bridge and related methods are provided. The bridge includes: a supply transformer IVD1, a Kelvin branch A1, a Wagner branch A0, the first and second current sources A2, A3, an injection inductive voltage divider A4, a ratio transformer IVD2, the first and second four-terminal AC resistor connection points Z1, Z2, chokes H, and null indicators D. An isolated inductive winding LO is wound along the ratio transformer IVD2 and supplies excitation current to primary winding of injection inductive voltage divider A4 to avoid the mutual influence among various balance networks and rapid balance of the bridge can be realized. By changing turn ratio of primary winding L3 and secondary winding L4 of the second inductive voltage divider T2, the phase shift can be realized through only one set of capacitors for imaginary part error compensation, the bridge with multiple frequency points can be obtained.