| 摘要 |
PURPOSE:To simplify a test and an adjustment of a modulation circuit by varying a level of a modulating signal by using a control signal which is applied through a data line and a clock line. CONSTITUTION:A data and a clock of a frequency division ratio corresponding to assigned transmitting frequency are impressed to a shift register 4 through a data line and a clock line, and the data of the register 4 is latched to a latching circuit 5 by a strobe signal STB, and set to the frequency division ratio which has been designated by a frequency deviding circuit 6. Next, an output of a VCO 7 is brought to a frequency division 6, brought to a phase comparison 8 with a reference wave from a frequency dividing circuit 9, and a voltage corresponding to a phase difference is applied to the VCO 7. In this case, by using the data line and the clock line after the data has been latched, one control signal among four kinds of control signals is applied to a variable attenuator 10, a level of a modulating signal is varired by controlling its attenuation quantity, a modulation of the VCO 7 is executed by its output, and the maximum frequency deviation is improved. |
