Patent ID: 8358235

Claim:
A wireless sensor device comprising: a transmission signal generation unit configured to generate a frequency-spread high frequency transmission signal such that a transmission frequency is continuously increased and decreased with a predetermined period; a transmitter antenna configured to radiate the high frequency transmission signal generated by the transmission signal generation unit; a receiver antenna configured to receive a reflected wave from an object having received the high frequency transmission signal radiated from the transmitter antenna, and output a frequency-spread high frequency reception signal; a mixer circuit configured to receive a part of the high frequency transmission signal, which is input to the transmitter antenna, as a first frequency-spread high frequency signal, receive the high frequency reception signal, which is output from the receiver antenna, as a second frequency-spread high frequency signal, and output a DC beat signal by operating as a phase detector when a frequency of the first frequency-spread high frequency signal coincides with a frequency of the second frequency-spread high frequency signal; and a DC component extraction circuit configured to extract the DC beat signal from an output signal of the mixer circuit.