To exactly decode a signal, which does not have a desired oscillation frequency, even when that signal is detected.
A vehicle 20 transfers signals with portable equipment 30 for remotely locking/unlocking a door with no contact. A receiving part 24 of the vehicle 20 is provided with a quadrature detecting circuit 52 for converting the frequency of a received signal to a DC voltage. The output terminal of the quadrature circuit 52 is connected to the input terminal of a coupling capacitor 64. The output terminal of the coupling capacitor 64 is connected to a base terminal 66b of a first transistor 66. A second transistor 76 having an emitter terminal 76e connected to an emitter terminal 66e of the first transistor 66 and grounded through a resistor 74 is provided. Resistors 72 and 82 are respectively provided between the bases and collectors of the first and second transistors 66 and 76. Collector terminals 66c and 76c of the first and second transistors 66 and 76 are respectively connected to the input terminal of a comparator 90.
OKUMURA RYOZO
NAGAI NOBUYOSHI
DENSO CORP