Patent ID: 8633735
Filing Date: 2014-01-21
Classification: H03B,H03G,H03L

Abstract:
1. A signal level adjusting device, comprising: a variable attenuator provided in a signal path of a frequency signal and in which an attenuation amount of the frequency signal is adjusted by a control voltage; a detector detecting a signal level of the frequency signal on an output side of said variable attenuator to output a detector voltage corresponding to the signal level; a control unit outputting a control voltage signal corresponding to the control voltage in a predetermined time interval, based on the detector voltage and the target voltage corresponding to a target signal level of the frequency signal on said output side of said variable attenuator; a digital/analog converter converting the control voltage signal into an analog voltage to output the result as the control voltage; and a low-pass filter provided between an output side of said digital/analog converter and said variable, attenuator; and wherein the control unit outputs a command value in a current cycle obtained by adding a first value or subtracting the first value to the command value in a cycle one cycle before depending on a plus or negative code of a difference between the detector voltage and the target voltage so as to lower an absolute value of the difference, when the absolute value of the difference is smaller than a predetermined tolerance value; wherein the control unit outputs the command value in the current cycle obtained by adding a second value larger than the first value or subtracting the second value to the command value in the cycle one cycle before depending on a plus or negative code of the difference between the detection voltage and the target voltage so as to lower the absolute value of the difference, when the absolute value of the difference is larger than the predetermined tolerance value; and wherein a period of time from when said control unit outputs the control voltage to when the control unit reads the signal level detected by said detector is set to a period of time longer than a time constant of said low-pass filter determined by a cut-off frequency of said low-pass filter.