A branch line coupler comprising: • four resonators (201, 202, 203, 204) formed by a body and a grounded element, wherein each resonator among the four resonators (201, 202, 203, 204) comprises: ∘ a capacitor element with a first portion of the capacitor element comprising at least a portion of the body and with a second portion comprising at least a portion of the grounded element, and ∘ an inductor element connected to the capacitor element in parallel, with the inductor element comprising at least a portion of the body and extending to the grounded element, ▪ wherein a first resonator and a second resonator among the four resonators (201, 202, 203, 204) are coupled by a first coupling, the second resonator and a third resonator among the four resonators (201, 202, 203, 204) are coupled by a second coupling, the third resonator and a fourth resonator among the four resonators (201, 202, 203, 204) are coupled by a third coupling, and the fourth resonator and the first resonator are coupled by a fourth coupling, wherein each of the first coupling, the second coupling, the third coupling, and the fourth coupling comprises a corresponding capacitive coupling; the branch line coupler being characterized in that it further comprises: ▪ a metal case formed by a cover, walls and a bottom, ▪ an isolation component, ∘ wherein a first end of the isolation component is connected to the cover and a second end of the isolation component is connected to the bottom, ∘ wherein the isolation component is arranged in a central position among the four resonators (201, 202, 203,. • four resonators (201, 202, 203, 204) formed by a body and a grounded element, wherein each resonator among the four resonators (201, 202, 203, 204) comprises: ∘ a capacitor element with a first portion of the capacitor element comprising at least a portion of the body and with a second portion comprising at least a portion of the grounded element, and ∘ an inductor element connected to the capacitor element in parallel, with the inductor element comprising at least a portion of the body and extending to the grounded element, ▪ wherein a first resonator and a second resonator among the four resonators (201, 202, 203, 204) are coupled by a first coupling, the second resonator and a third resonator among the four resonators (201, 202, 203, 204) are coupled by a second coupling, the third resonator and a fourth resonator among the four resonators (201, 202, 203, 204) are coupled by a third coupling, and the fourth resonator and the first resonator are coupled by a fourth coupling, ∘ a capacitor element with a first portion of the capacitor element comprising at least a portion of the body and with a second portion comprising at least a portion of the grounded element, and ∘ an inductor element connected to the capacitor element in parallel, with the inductor element comprising at least a portion of the body and extending to the grounded element, ▪ wherein a first resonator and a second resonator among the four resonators (201, 202, 203, 204) are coupled by a first coupling, the second resonator and a third resonator among the four resonators (201, 202, 203, 204) are coupled by a second coupling, the third resonator and a fourth resonator among the four resonators (201, 202, 203, 204) are coupled by a third coupling, and the fourth resonator and the first resonator are coupled by a fourth coupling, ▪ wherein a first resonator and a second resonator among the four resonators (201, 202, 203, 204) are coupled by a first coupling, the second resonator and a third resonator among the four resonators (201, 202, 203, 204) are coupled by a second coupling, the third resonator and a fourth resonator among the four resonators (201, 202, 203, 204) are coupled by a third coupling, and the fourth resonator and the first resonator are coupled by a fourth coupling, wherein each of the first coupling, the second coupling, the third coupling, and the fourth coupling comprises a corresponding capacitive coupling; the branch line coupler being characterized in that it further comprises: ▪ a metal case formed by a cover, walls and a bottom, ▪ an isolation component, ∘ wherein a first end of the isolation component is connected to the cover and a second end of the isolation component is connected to the bottom, ∘ wherein the isolation component is arranged in a central position among the four resonators (201, 202, 203,. ▪ a metal case formed by a cover, walls and a bottom, ▪ an isolation component, ∘ wherein a first end of the isolation component is connected to the cover and a second end of the isolation component is connected to the bottom, ∘ wherein the isolation component is arranged in a central position among the four resonators (201, 202, 203,. ∘ wherein a first end of the isolation component is connected to the cover and a second end of the isolation component is connected to the bottom, ∘ wherein the isolation component is arranged in a central position among the four resonators (201, 202, 203,.