Combiner for electrical signals comprising at least one first element and a second element respectively connected to a first input port (P 1) and to a second input port (P 2), and a third element connected to an output port (Ps), the electrical signals being propagated between the input and output ports by bulk acoustic waves, wherein: - said first, second and third elements are bulk acoustic wave transducers, the waves being propagated at an acoustic wavelength λ; - said combiner comprising a propagation medium in which the input and output transducers are stacked, the propagation medium comprising at least one layer of piezoelectric material capable of allowing the propagation of bulk acoustic waves, each transducer comprising a stack of at least one layer of piezoelectric material and at least two electrodes located on either side of the layer of piezoelectric material, respectively; characterized in that: - said combiner comprises a structure for folding back the path of the signal propagating in the structure in an electrical and in an acoustic form simultaneously, the structure for folding back comprising three levels of bulk wave resonators that are stacked in the following order: ∘ a first level comprising a lower bulk acoustic wave transducer; ∘ a second level comprising, as a first element, a first intermediate bulk acoustic wave transducer connected to the first input port (P 1) and, as a second element, a second intermediate bulk acoustic wave transducer connected to the second port (P 2), said intermediate transducers being separated from the lower transducer by a first intermediate layer; ∘ a third level comprising, as a third element, an upper bulk acoustic wave transducer connected to the output port (Ps), separated from the intermediate transducers by a second intermediate layer; ∘ the total thicknesses of the upper transducer and of the second intermediate layer having a total thickness of (2k+1)λ/4 with k an integer greater than or equal to 0; ∘ the total thicknesses of the intermediate transducers and of the first intermediate layer having a total thickness of (2k'+2)λ/4 with k' an integer greater than or equal to 0; so as to, on the one hand, generate constructive interferences at the output port and, on the other hand, to isolate said first and second input ports by interference of destructive acoustic waves at said input ports. - said first, second and third elements are bulk acoustic wave transducers, the waves being propagated at an acoustic wavelength λ; - said combiner comprising a propagation medium in which the input and output transducers are stacked, the propagation medium comprising at least one layer of piezoelectric material capable of allowing the propagation of bulk acoustic waves, each transducer comprising a stack of at least one layer of piezoelectric material and at least two electrodes located on either side of the layer of piezoelectric material, respectively; - said combiner comprises a structure for folding back the path of the signal propagating in the structure in an electrical and in an acoustic form simultaneously, the structure for folding back comprising three levels of bulk wave resonators that are stacked in the following order: ∘ a first level comprising a lower bulk acoustic wave transducer; ∘ a second level comprising, as a first element, a first intermediate bulk acoustic wave transducer connected to the first input port (P 1) and, as a second element, a second intermediate bulk acoustic wave transducer connected to the second port (P 2), said intermediate transducers being separated from the lower transducer by a first intermediate layer; ∘ a third level comprising, as a third element, an upper bulk acoustic wave transducer connected to the output port (Ps), separated from the intermediate transducers by a second intermediate layer; ∘ the total thicknesses of the upper transducer and of the second intermediate layer having a total thickness of (2k+1)λ/4 with k an integer greater than or equal to 0; ∘ the total thicknesses of the intermediate transducers and of the first intermediate layer having a total thickness of (2k'+2)λ/4 with k' an integer greater than or equal to 0; so as to, on the one hand, generate constructive interferences at the output port and, on the other hand, to isolate said first and second input ports by interference of destructive acoustic waves at said input ports. ∘ a first level comprising a lower bulk acoustic wave transducer; ∘ a second level comprising, as a first element, a first intermediate bulk acoustic wave transducer connected to the first input port (P 1) and, as a second element, a second intermediate bulk acoustic wave transducer connected to the second port (P 2), said intermediate transducers being separated from the lower transducer by a first intermediate layer; ∘ a third level comprising, as a third element, an upper bulk acoustic wave transducer connected to the output port (Ps), separated from the intermediate transducers by a second intermediate layer; ∘ the total thicknesses of the upper transducer and of the second intermediate layer having a total thickness of (2k+1)λ/4 with k an integer greater than or equal to 0; ∘ the total thicknesses of the intermediate transducers and of the first intermediate layer having a total thickness of (2k'+2)λ/4 with k' an integer greater than or equal to 0; so as to, on the one hand, generate constructive interferences at the output port and, on the other hand, to isolate said first and second input ports by interference of destructive acoustic waves at said input ports.