| 摘要 |
PURPOSE:To detect a correct electric field even if the dynamic range of a receiver is deficient and to widen a electric field detecting range. CONSTITUTION:A high frequency amplifying part 2 amplifies a high frequency receiving signal inputted from an antenna 1 and a mixer circuit 3 converts an output from the amplifying part 2 into a 1st intermediate frequency signal (a). A variable attenuator 4 changes the quantity of pass attenuation in accordance with the quantity of attenuation set up to N stages and an intermediate frequency amplifying part 5 amplifies the output of the attenuator 4 and outputs a 2nd intermediate frequency signal (b). A limiter amplifier circuit 6 outputs analog voltage (c) corresponding to the level of the signal (b) and an analog/ digital (A/D) conversion circuit 7 converts the analog voltage (c) into digital voltage (d). A gate circuit 10 selects one of the 1st to N-th tables 81 to 8n in which the electric field intensity of the high frequency receiving signal is allowed to correspond to the digital voltage (d). |
