| 摘要 |
PURPOSE:To obtain the orthogonal modulating device which is stable against a fluctuation of a temperature and a power supply voltage by applying a digital signal for annihilating an equivalent offset of a same phase portion and an orthogonal portion generated in a modulator to the lower bit of an input of a converter. CONSTITUTION:Orthogonal base band data 1 and 1' pass through a digital filter 101 and 101', and are inputted to the upper bits of a digital-to-analog converter 102 and 102'. On the other hand, to the lower bit, an output 3 from a digital switch 103 for giving directly the DC offset quantity is connected with respect to the same phase side data, and as for the converter 102, an offset is superposed to the output as an analog voltage by the quantity designated by the lower bit. On the other hand, on the orthogonal side, in order to give necessary gain adjustment and a DC offset to the same phase side, a digital filter output 2' is shifted in the lower level direction by a shift register 105 by the quantity designated by a digital switch 104. The sum of an output 5 of the register 105 and an output 3' of a digital switch 103' for giving the DC offset quantity is taken by an adder 106, and its output 6 is connected as the lower bit of the converter 102'. |
