Pass filter circuit arrangement

A pass filter circuit arrangement having (a) a first resonant circuit including a first inductive element and a first capacitance, (b) a second resonant circuit including a second inductive element and a second capacitance, and (c) a bilateral coupling between said inductive elements, said first inductive element being constituted by the impedance presented by a first port of a first gyrator circuit which has a third capacitance in parallel with its second port, said second inductive element being constituted by the impedance presented by a first port of a second gyrator circuit which has a fourth capacitance in parallel with its second port, and said bilateral coupling including a first substantially unilateral signal path from one port of the first gyrator circuit to one port of the second gyrator circuit and a second substantially unilateral signal path from the other port of the second gyrator circuit to the other port of the first gyrator circuit, said first signal path bypassing each of said other ports of said gyrator circuits and said second signal path bypassing each of said one ports of said gyrator circuits, whereby a loop is formed by said gyrator circuits and said first and second signal paths, each of said signal paths being devoid of elements having substantial reactance at the resonant frequency of either of said resonant circuits, characterized in that each of the gyrator circuits comprises a first and a second voltage-controlled current source, each of said first current sources having a first and a second input, which constitute a differential pair of inputs, and a first and a second output, which constitute a differential pair of outputs, the first input of each first current source being connected to the output of the second current source of the corresponding gyrator circuit and the input of each second current source being connected to the first output of the first current source of the corresponding gyrator circuit, one of the current sources of each gyrator circuit being inverting from the input thereof, which is connected to an output of the other current source of the corresponding gyrator circuit, to the output thereof, to which an input of the other current source of the corresponding gyrator circuit is connected, and the other of said current sources of each gyrator circuit being non-inverting from the input thereof, which is connected to an output of the one current source of the corresponding gyrator circuit, to the output thereof, to which an input of the one current source of the corresponding gyrator circuit is connected;

• said first signal path includes a coupling from the second output of the first current source of one gyrator circuit to the second input of the first current source of the other gyrator circuit, and said second signal path includes a coupling from the second output of the first current source of said other gyrator circuit to the second input of the first current source of said one gyrator circuit.