Patent ID: 7953136

Claim:
A transmission circuit transmitting a power signal using a frequency hopping system from an antenna connected to the transmission circuit through a transmission path, the transmission circuit comprising: a controller outputting an amplitude set value for each hopping frequency of the power signal before being transmitted according to a power level of the power signal at the antenna; a pre-driver controlling an amplitude of the power signal before being transmitted for each hopping frequency according to the amplitude set value; a power amplifier outputting the power signal to the transmission path according to a signal output from the pre-driver; and an antenna circuit, connected between the transmission path and the antenna, detecting a level of the transmission power, wherein the antenna circuit comprises: a dummy antenna circuit artificially reproducing intrinsic impedance of the antenna; a transmission power detection circuit detecting the power level occurred at the dummy antenna circuit based on the power signal input through the transmission path and outputs a level detection signal showing the power level of the power signal; and a switch selectively connecting the transmission path and one of the antenna and the dummy antenna circuit.