A mobile communication device, comprising: a tuneable impedance matching system having a tuneable impedance matching circuit (408, 508, 708, 1002) coupled between a transmitter/receiver front-end and an antenna of the mobile communication device, voltage sensors for measuring magnitudes of voltages from at least three predefined nodes of the tuneable impedance matching circuit (408, 508, 708, 1002) having a predefined topology, predefined component values of its fixed electrical components and a predefined operating frequency, calculation means configured to solve an impedance of the antenna based at least on the measured voltages, on component values and on the operating frequency and to determine values for adjustable electrical components of the tuneable impedance matching circuit (408, 508, 708, 1002) based on the impedance of the antenna and on an impedance matching condition, wherein the calculation means are arranged to solve the impedance of the antenna using two or more mathematical expressions that are derived via a standard circuit analysis procedure and that are descriptive of a relationship between a voltage magnitude ratio of a respective pair of the measured voltages and the impedance of the antenna and that have a form that depends at least on said topology, on said component values of the fixed electrical components, on said operating frequency and on said locations of the nodes from which the respective pair of measured voltages are measured, and control means configured to tune the adjustable electrical components of the tuneable impedance matching circuit (408, 508, 708, 1002) in accordance with the determined values. a tuneable impedance matching system having a tuneable impedance matching circuit (408, 508, 708, 1002) coupled between a transmitter/receiver front-end and an antenna of the mobile communication device, voltage sensors for measuring magnitudes of voltages from at least three predefined nodes of the tuneable impedance matching circuit (408, 508, 708, 1002) having a predefined topology, predefined component values of its fixed electrical components and a predefined operating frequency, calculation means configured to solve an impedance of the antenna based at least on the measured voltages, on component values and on the operating frequency and to determine values for adjustable electrical components of the tuneable impedance matching circuit (408, 508, 708, 1002) based on the impedance of the antenna and on an impedance matching condition, wherein the calculation means are arranged to solve the impedance of the antenna using two or more mathematical expressions that are derived via a standard circuit analysis procedure and that are descriptive of a relationship between a voltage magnitude ratio of a respective pair of the measured voltages and the impedance of the antenna and that have a form that depends at least on said topology, on said component values of the fixed electrical components, on said operating frequency and on said locations of the nodes from which the respective pair of measured voltages are measured, and control means configured to tune the adjustable electrical components of the tuneable impedance matching circuit (408, 508, 708, 1002) in accordance with the determined values.