wireless communications system for smart keyless entry system, receives certification request signal and transmits authentication response signal to vehicle equipment, after switching resonance circuit to resonant frequency

摘要

The system has electric field strength measurement unit that measures electric field strength of signal for electric field strength measurement. Resonance circuit (241) switches resonant frequency to multi step. Portable device (2) receives signal for electric field strength measurement transmitted from vehicle equipment (1). Portable device measures electric field strength of each level. Certification request signal is received and authentication response signal is transmitted to vehicle equipment, after switching resonance circuit to resonant frequency.