| 摘要 |
PURPOSE:To select an antenna having a larger reception output level at all times even at a weak electric field by controlling a switch in response to the comparison output. CONSTITUTION:In using a hybrid transistor transformer circuit as an example of a phase difference synthesizer 9, the reception strength of antennas 1, 2 is taken as A, B and the strengths C, D appearing at an output of the synthesizer 9 are expressed as C=(B+A)...(1) and D=(A-B)...(2). An instantaneous mean value to be compared is an instantaneous mean value of Equation (1) or (2), then if the output of the antenna having better sensitivity is decreased due to fading at a weak electric field, the antenna is switched to the other antenna with lower sensitivity, and since the reference level is not the moving means value of the fading output with the low sensitivity as in case of a conventional receiver, but the moving mean value of the signal expressed in Equation (1), then the instantaneous means value of the antenna with lower sensitivity is decreased less than the said moving mean value the moving mean value and the antenna is made possible to be switched to the antenna with better sensitivity. Moreover, even if the reception strength of each antenna is not detected at all times, the antenna having the larger reception strength is selected. |
