COMMUNICATION DEVICE

摘要

A communication device which can perform a carrier sensing function without being affected by noise even in an environment where the noise level of radio communication greatly fluctuates. The carrier is sensed by amplifying received signals at a variable gain level and detecting the carrier on a transmission line by comparing the amplified received signals with a reference-level signal, and changing the gain level of the received signals based on the results of the detection of carrier. Therefore, the communication device can accurately receive a carrier without making erroneous detection of carrier due to noise. In a radio network system in which communication is carried out using a spread spectrum-modulation frequency hopping system, received signals are amplified at a variable gain level, the carrier is detected by comparing the amplified received signals with a reference-level signal, and the gain level of the received signals is changed based on the results of the detection of the carrier. A frequency hopping frame is transmitted to/from another communication device to synchronization of the frequency hopping, the received signal in the radio communication section after the synchronization is judged to be noise, the gain level at which the noise is amplified to the reference level is made a noise level, and the received signal is amplified at the noise level, thus sensing the carrier. Therefore, the radio network system which performs mutual communication using the spread spectrum-modulation frequency hopping system can accurately receive the carrier without making erroneous detection of the carrier due to noise.