| 摘要 |
PROBLEM TO BE SOLVED: To quickly start communication when a communicable range is reached, while a power consumption is reduced, related to a receiver for a mobile narrow band communication using a radio antenna. SOLUTION: A receiver is provided with an NULL region sensing circuit (10), which outputs a trigger signal (w-up) for triggering a communication control part (108) of the receiver assuming that the distance between antenna approaches a communicable range, when a NULL region present between the main lobe and side lobe of the directional characteristics of the antenna is sensed, based on the fluctuation of a reception level signal (V1), which is a detection signal of the reception level of a transmission radio wave fluctuating, depending on the distance between the antennas. Here, the preparation for communication with the receiver is started, immediately prior to the distance between antenna of the transmitter, and the receiver reaches a communicable range. |
