| 摘要 |
An attenuator employing a digital-to-analog converter 10 has the switching of n successive stages of a bit weighting resistor network controlled by a first control signal 40 and the particular group of n successive stages from the total number N of the stages are selected by a second control signal 44. The attenuator comprises a 17-bit multiplying-type D/A converter 10 having an R/2R ladder network to set the bit weights, and controlled by a 6- bit remotely-generated command signal to vary the attenuation in steps of 1.5 dB through a range of 88 dB. The 1.5 dB steps are controlled by a 4-bit code signal responsive to two bits of the command signal. The 4-bit code signal is directed to four successive bit input terminals connected to digital lines 14 of the converter. Which four D/A converter input terminals are selected is controlled by a shifting matrix 50 which shifts the four bits along the D/A converter input terminals to a position determined by the other four bits of the command signal. <IMAGE> |
