Patent ID: 7983626

Claim:
A device for matching an antenna impedance in a portable radio telephone having a folder casing, an antenna, and a transmission/reception circuit, comprising: a folder sensor configured to sense one of a folded state and an unfolded state of the folder casing; a transmission/reception sensor configured to sense one of a transmitting state and a receiving state of the portable radio telephone; an antenna sensor configured to sense one of an extracted state and a retracted state of the antenna; a controller configured to control a voltage according to the states sensed by the folder sensor, antenna sensor, and the transmission/reception sensor; and a matching circuit having a variable capacitance diode for matching the antenna impedance and an impedance of the transmission/reception circuit according to the voltage of the controller; wherein the controller includes: a memory for storing data for an optimal antenna impedance matching for the folded state and the opened state of the folder casing, the extracted state and the retracted state of the antenna, and the transmitting state and the receiving state of the portable radio telephone; a central processing unit (CPU) for reading the data from the memory according to at least one of the sensing signal from the folder sensor, the transmission/reception sensor, and the antenna sensor; and a digital-to-analog converter (DAC) for converting the voltage from the CPU into an analog voltage and providing the analog voltage to the matching circuit, wherein the controller adjusts the matching circuit with a reference to the voltage.