Abstract: The invention relates to an inductor, and particularly to an inductor for a transmitter circuit. The invention also concerns a transmitter including said inductor, a proximity detection system employing such a transmitter, and a method of making said inductor. The inductor of the invention includes a core having non-uniform permeability and a conductor winding arranged around the core. When used in a transmitter circuit, this allows an induced electromagnetic field to propagate through the core in a more efficient manner than otherwise possible, so resulting in a higher dynamic field strength for a given resonant circuit drive.

Abstract: The invention generally relates to a field regulator, particularly a field regulator for a resonant circuit, a transmitter including such a field regulator, a proximity detection system including such a transmitter, and a method of regulating a resonant circuit. In one aspect the invention provides a field regulator for a resonant circuit, the resonant circuit including an inductor coil around a core, the field regulator including a DC bias circuit configured to apply a DC bias current to the inductor coil for regulating an electromagnetic field generated by the inductor. The DC bias circuit can be used to selectively change the inductance of the inductor in the resonant circuit so as to maintain a consistent field strength in a changing environment, particularly to take into account the presence of large metal bodies which might otherwise adversely impact on operation.

Abstract: The invention relates to an inductor, and particularly to an inductor for a transmitter circuit. The invention also concerns a transmitter including said inductor, a proximity detection system employing such a transmitter, and a method of making said inductor. The inductor of the invention includes a core having non-uniform permeability and a conductor winding arranged around the core. When used in a transmitter circuit, this allows an induced electromagnetic field to propagate through the core in a more efficient manner than otherwise possible, so resulting in a higher dynamic field strength for a given resonant circuit drive.

Abstract: The invention generally relates to a field regulator, particularly a field regulator for a resonant circuit, a transmitter including such a field regulator, a proximity detection system including such a transmitter, and a method of regulating a resonant circuit. In one aspect the invention provides a field regulator for a resonant circuit, the resonant circuit including an inductor coil around a core, the field regulator including a DC bias circuit configured to apply a DC bias current to the inductor coil for regulating an electromagnetic field generated by the inductor. The DC bias circuit can be used to selectively change the inductance of the inductor in the resonant circuit so as to maintain a consistent field strength in a changing environment, particularly to take into account the presence of large metal bodies which might otherwise adversely impact on operation.